Preoperative anemia and perioperative outcomes in patients who undergo elective spine surgery

Study on the predictive model of delirium risk after surgery for elderly hip fractures based on meta-analysis

OBJECTIVE

To develop and validate a risk prediction model for postoperative delirium in elderly patients with hip fractures, aiming to identify high-risk patients and implement preventive measures.

METHODS

A systematic search of five authoritative medical databases was conducted, retrieving a total of 1368 relevant articles. After screening, 44 high-quality studies were included in the meta-analysis, analyzing 13 potential risk factors, such as age, gender, diabetes, and history of stroke. A risk prediction model was constructed and validated in a cohort of 189 elderly hip fracture patients. The model's predictive performance was evaluated using ROC curves, with calibration assessed through the Hosmer-Lemeshow test, and clinical utility examined via Decision Curve Analysis (DCA) and Clinical Impact Curves (CIC).

RESULTS

The meta-analysis identified the following as independent risk factors for postoperative delirium: age (≥ 70 years), male gender, diabetes, history of stroke, preoperative comorbidities (≥ 2), previous delirium, preoperative cognitive impairment, low preoperative albumin levels (≤ 40 g/L), prolonged preoperative waiting time (≥ 48 h), anemia (≤ 100 g/L), ASA classification (≥ 3), use of general anesthesia, and prolonged surgery duration (≥ 2 h). The prediction model demonstrated strong efficiency in the validation cohort, with an AUC of 0.956, sensitivity of 87.3%, specificity of 94.8%, and a Brier score of 0.144, indicating high predictive accuracy and calibration. DCA and CIC analyses showed the model to have strong clinical decision-making value and impact across most thresholds.

CONCLUSION

The risk prediction model developed in this study shows high predictive accuracy and clinical utility, making it valuable for identifying high-risk patients and implementing preventive measures in clinical practice. However, the study has limitations, such as potential retrospective bias, and further validation in larger, multicenter prospective studies is needed to confirm the model's broader applicability and stability.

Efficacy of Preoperative Autologous Blood Donation for Surgical Treatment of Thoracic Spinal Stenosis: A Propensity-Matched Cohort Study

OBJECTIVE

Thoracic spinal stenosis (TSS) surgeries necessitate a substantial amount of allogeneic blood resources. However, the efficacy of preoperative autologous blood donation (PABD) in TSS surgery has not been clearly evaluated. Therefore, we aimed to evaluate the efficacy of PABD for TSS surgery.

METHODS

This study is a retrospective study. Totally 397 patients who underwent TSS surgeries at our institution from January 2019 to June 2023 were included. Propensity score matching (PSM) was used to make the PABD and Non-PABD groups comparable at baseline. Regarding outcome measures, the incidence and amount of allogeneic blood transfusion, changes in postoperative hemoglobin and hematocrit levels, occurrence of postoperative complications, medical costs, drainage time, length of hospital stay, and postoperative neurological function were analyzed. The outcomes were compared between the matched PABD (n = 79) and Non-PABD (n = 79) groups. Univariate analysis methods were used for statistical analysis, including independent samples t-test, Wilcoxon rank-sum test, and chi-square test.

RESULTS

The incidence of allogeneic blood transfusion (8.9% vs. 25.3%, p = 0.006) and volume of intraoperative red blood cell (RBC) transfusion (10.12 ± 54.52 vs. 122.78 ± 275.00 mL, p < 0.001) in the PABD group were significantly lower than those in the Non-PABD group. The PABD group had significantly higher average postoperative hemoglobin and hematocrit levels than the Non-PABD group at 1, 3, and 5 days after surgery (p < 0.05). Similarly, the PABD group exhibited a smaller reduction in hemoglobin and hematocrit levels compared with the Non-PABD group on 1, 3, and 5 days postoperatively. There were no significant intergroup differences in terms of transfusion-related complications, medical expenses, neurological function, length of hospital stay, or drainage time. Notably, PABD was an independent protective factor of allogeneic transfusion in the multivariate regression analysis (OR = 0.334, 95%CI = 0.051-0.966).

CONCLUSIONS

PABD can effectively reduce the incidence of allogeneic blood transfusion and amount of allogeneic blood in TSS surgeries with safety. It also significantly improved the postoperative hemoglobin and hematocrit levels. Under the premise of clear indications, PABD is worth promoting for the surgical treatment of TSS.

Prevalence, Risk Factors, and Postoperative Infection Rates of Blood Transfusion in Lumbar Spinal Fusion Surgery: A Nationwide Population-Based Study

Study Design: Retrospective cohort study. Objectives: Effects of blood loss that requires blood transfusion after lumbar spinal fusion remain an important issue. Blood transfusions are used commonly in cases of significant blood loss in lumbar spinal fusion but are associated with adverse effects. The objective was to assess the rate of blood transfusion and the associated risk after lumbar spinal fusion from 2013 to 2018. Methods: In this nationwide population-based cohort study, the Korean Health Insurance Review and Assessment Service database was reviewed retrospectively from 2013 to 2018. Data were extracted from patients who underwent lumbar spinal fusion without history of lumbar spinal surgery in the preceding year. The primary outcome was the rate of blood transfusion within 1 week of surgery. In addition, the risk factors for blood transfusion and the rate of postoperative infection were evaluated. Results: A total of 188,581 patients underwent lumbar spinal fusion between 2013 and 2018. A significant decline in blood transfusions was observed during the study period (56.38-47.51%). The presence of comorbidities was associated with an increased risk of blood transfusion. Patients who underwent the posterior approach were more likely to receive blood transfusion than patients who underwent the anterior or anterior and posterior approach. Receiving blood transfusion was associated with postoperative infection. Conclusions: In the present study, the prevalence, risk factors, and postoperative infection rates associated with blood transfusion in lumbar spinal fusion were identified. Spine surgeons should consider these risk factors in patients at high risk of blood transfusion.

The Effect of Varying Preoperative Hemoglobin Levels on the Risk of Major Complications and Surgical Site Infections After Single Level Lumbar Fusion

INTRODUCTION

Blood transfusions are associated with an increased risk of complications after lumbar fusion, and current anemia hemoglobin thresholds are not surgery specific. We aimed to calculate single-level lumbar fusion-specific preoperative hemoglobin strata that observe the likelihood of 90-day transfusion and evaluate whether these strata are associated with increased risk of 90-day complications and 2-year infections.

METHODS

A national database identified patients undergoing primary single-level lumbar fusion with preoperative hemoglobin values (g/dL). Stratum-specific likelihood ratio analysis calculated sex-based hemoglobin strata associated with the risk of 90-day transfusion. Incidence and risk of 90-day major complications and 2-year infections were observed between strata.

RESULTS

Three female (hemoglobin strata, likelihood ratio [<10.9, 2.41; 11.0 to 12.4, 1.35; 12.5 to 17.0, 0.78]) and male (<11.9, 2.95; 12.0 to 13.4, 1.46; 13.5 to 13.9, 0.71) strata were associated with varying likelihood of 90-day blood transfusion. Increased 90-day complication risk was associated with two female strata (hemoglobin strata, relative risk [11.0 to 12.4, 1.52; <10.9, 3.40]) and one male stratum (<11.9, 2.02). Increased 2-year infection risk was associated with one female (<10.9, 3.67) and male stratum (<11.9, 2.11).

CONCLUSION

Stratum-specific likelihood ratio analysis established sex-based single-level lumbar fusion-specific hemoglobin strata that observe the likelihood of 90-day transfusion and the risk of 90-day major complications and 2-year infections. These thresholds are a unique addition to the literature and can assist in counseling patients on their postoperative risk profile and in preoperative patient optimization.

LEVEL OF EVIDENCE

Level III.

Increasing severity of preoperative anemia is associated with higher postoperative medical and surgical complications after primary shoulder arthroplasty

BACKGROUND

Anemia is a major cause of morbidity worldwide and compounds numerous medical conditions. Studies have found associations between anemia and both medical and surgical complications after shoulder arthroplasty (SA); however, most of these studies have used commercially available national databases with limited information on outcomes and typically short-term follow-up. Our study sought to evaluate the midterm outcomes of primary SA at a single institution when stratified by the degree of preoperative anemia.

METHODS

Between 2000 and 2020, 5231 primary SA (477 hemiarthroplasties, 2091 anatomic total SA, and 2335 reverse SA) with preoperative hematocrit values available and a minimum follow-up of 2 years were collected from a single-institution joint registry database. The severity of anemia was subclassified as no anemia (hematocrit >39% for males, >36% for females; n = 4194 [80.2%]), mild anemia (hematocrit 33%-39% for males, 33%-36% for females; n = 742 [14.2%]), and moderate-to-severe anemia (hematocrit <33% for both males and females; n = 295 [5.6%]). The mean follow-up time for the entire cohort was 5.9 years (range, 2-22 years). Medical and surgical complications, reoperations, revisions, and implant survivorship were assessed.

RESULTS

SA with moderate-to-severe anemia had the highest rate of nonfatal and nontransfusion medical complications (5.1%) relative to the nonanemic (1.2%; P < .001) and mild anemic groups (1.5%; P < .001). Similarly, SA with moderate-to-severe anemia had the highest rate of surgical complications (19.3%) compared with mild anemia (14.3%; P = .044) and no anemia (11.6%; P < .001). Postoperative transfusion was most frequent in the moderate-to-severe anemia cohort (40.3%) compared with the mild anemia (14.2%; P < .001) and nonanemic groups (2.5%; P < .001). Furthermore, SA who received postoperative transfusions had a higher risk of nonfatal medical complications (8.2% vs. 1.0%; P < .001), 90-day mortality (1.5% vs. 0.03%; P = .001), and surgical complications (19.5% vs. 12.0%; P < .001) when compared with those without transfusion.

CONCLUSIONS

Moderate-to-severe anemia (hematocrit <33% for both males and females) was identified in approximately 5.6% of patients who underwent SA at a single institution and was associated with increased medical and surgical complications. Patients who received postoperative transfusions presented elevated rates of medical complications, 90-day mortality, and surgical complications. Health care teams should be aware of these risks in order to provide more individualized medical optimization and postoperative monitoring.

Response to Letter Regarding "Predictive Value of Preoperative Serum Albumin in Patients With Metastatic Spine Diseases: A Statistical Comment"

We thank the authors for their interest in and commentary on "Preoperative Serum Albumin Level Predicts Length of Stay and Perioperative Adverse Events Following Vertebral Corpectomy and Posterior Stabilization for Metastatic Spine Disease." We appreciate the opportunity to respond to their comments herein.

Postoperative Outcomes for Spinal Fusion Procedures in Pediatric Patients with Anemia: A Retrospective and Multivariate Analysis

BACKGROUND

Preoperative anemia is known to be associated with perioperative complications in many surgical interventions. Here, we examine the effects of preoperative anemia on peri-operative complications and postoperative outcomes in pediatric patients undergoing spinal fusion.

METHODS

Retrospective analysis was conducted using the American College of Surgeons Pediatric National Surgery Quality Improvement Program Database between 2012-2020. Current Procedural Terminology codes 22800, 22,802, 22,804, 22,840, 22,842, 22,843, and 22,844 were included to represent all primary spinal fusion procedures performed. Patients without preoperative hematocrit (HCT) levels were excluded. Classification of anemia was determined via age- and sex-adjusted HCT levels. Patient demographics, preoperative comorbidities and risk factors, and 30-day postoperative outcomes were compared between the 2 cohorts using univariate analysis. Multivariate logistic regressions were performed to determine if anemia severity was independently associated with worse postoperative outcomes.

RESULTS

A total of 30,243 pediatric patients were included in this study, with 26,621 not having preoperative anemia and 3622 having preoperative anemia. Pediatric patients with anemia have increased length of stay (LOS) (6.7 ± 9.6 vs. 5 ± 6, P < 0.001), 30-day unplanned reoperation rate (4% vs. 2.8%, P < 0.001), and total blood transfused (489.9 ± 497.8 vs. 423.4 ± 452.6, P < 0.001). Multivariate analysis supported anemia and degree of its severity as an independent predictor of increased length of stay (LOS), reoperation rate, and postoperative complications.

CONCLUSIONS

Preoperative anemia leads to worse outcomes in pediatric spinal fusion procedures. Utilizing HCT recordings could be factored into the equation for optimal patient selection and prevention of post-operative complications.

Effects of ferric derisomaltose on postoperative anaemia in adult spinal deformity surgery: a study protocol for a randomised controlled trial

INTRODUCTION

Postoperative anaemia is prevalent in adult spinal deformity (ASD) surgery in association with unfavourable outcomes. Ferric derisomaltose, a novel iron supplement, offers a promising solution in rapidly treating postoperative anaemia. However, the clinical evidence of its effect on patients receiving spinal surgery remains inadequate. This randomised controlled trial aims to evaluate the safety and efficacy of ferric derisomaltose on postoperative anaemia in ASD patients.

METHODS AND ANALYSIS

This single-centre, phase 4, randomised controlled trial will be conducted at Department of Orthopaedics at Peking Union Medical College Hospital and aims to recruit adult patients who received ASD surgery with postoperative anaemia. Eligible participants will be randomly assigned to receive ferric derisomaltose infusion or oral ferrous succinate. The primary outcome is the change in haemoglobin concentrations from postoperative days 1-14. Secondary outcomes include changes in iron parameters, reticulocyte parameters, postoperative complications, allogeneic red blood cell infusion rates, length of hospital stay, functional assessment and quality-of-life evaluation.

ETHICS AND DISSEMINATION

This study has been approved by the Research Ethics Committee of Peking Union Medical College Hospital and registered at ClinicalTrials.gov. Informed consent will be obtained from all participants prior to enrolment and the study will be conducted in accordance with the principles of the Declaration of Helsinki. The results of this study are expected to be disseminated through peer-reviewed journals and academic conferences.

TRIAL REGISTRATION NUMBER

NCT05714007.

The severity of preoperative anemia escalates risk of poor short-term outcomes after lumbar spine fusion

OBJECTIVE

To evaluate how preoperative anemia severity affects 90-day outcomes of spinal fusion surgery.

METHODS

A retrospective cohort study was conducted on adult lumbar fusion patients at a tertiary medical center. Patients were classified by World Health Organization anemia severity definitions for comparisons. Multivariate regression models were created to control for confounding variables, for all primary outcomes of transfusion requirements, non-home discharge, readmissions, complications, and length of stay.

RESULTS

A total of 2582 patients were included: 2.7% with moderate-severe anemia, 11.0% with mild anemia, and 86.3% without anemia. Moderate-severe patients had the longest hospital stay (5.03 days vs 4.14 and 3.59 days, p < 0.001) and highest risk of transfusion (52.2% vs 13.0% vs 2.69%, p < 0.001), non-home discharge (39.1% vs 27.8% vs 15.4%, p < 0.001), readmission (7.25% vs 5.99% vs 3.36%, p = 0.023), and complications (13.0% vs 9.51% vs 6.20%, p = 0.012). On multivariable logistic regression, both patients with mild and moderate-severe anemia had an increased risk of transfusion (OR: 37.3, p < 0.001; OR: 5.25, p < 0.001, respectively) and non-home discharge (OR: 2.00, p = 0.021; OR: 1.71, p = 0.001, respectively) compared to patients without anemia. Anemia severity was not independently associated with complications or 90-day readmission. On multivariable linear regression, mild anemia (β: 0.37, p = 0.001) and moderate-severe anemia (β: 1.07, p < 0.001) were independently associated with length of hospital stay.

CONCLUSION

Patients with moderate-severe preoperative anemia are at increased risk for longer length of stay, transfusions, and non-home discharge. Improved optimization of preoperative anemia may significantly reduce healthcare utilization, and surgeons should consider these risks in preoperative planning.

LEVEL OF EVIDENCE

III.

The Impact of Rocuronium and Sugammadex on Length of Stay in Patients Undergoing Open Spine Surgery: A Propensity Score-Matched Analysis

Enhanced Recovery After Surgery (ERAS), an all-encompassing perioperative care approach, has been demonstrated to enhance surgical results, mitigate postoperative issues, and decrease the length of hospital stay (LOS) in diverse surgical specialties. In this retrospective study, our objective was to examine the influence of muscle relaxant selection on LOS and perioperative results in adult patients undergoing open spine surgery. Specifically, we compared 201 patients who received cisatracurium and neostigmine with 201 patients who received rocuronium and sugammadex, after 1:1 propensity score matching. The utilization of the rocuronium and sugammadex combination in anesthesia for open spinal surgery did not lead to a reduction in the LOS but was associated with a decreased incidence of postoperative chest radiographic abnormalities, including infiltration, consolidation, atelectasis, or pneumonia (p = 0.027). In our secondary analysis, multivariate analysis revealed multiple determinants influencing the prolonged LOS (>7 days) during open spine surgery. Bispectral index-guided anesthesia emerged as a protective factor, while variables such as excessive intraoperative blood loss and fluid administration as well as postoperative chest radiographic abnormalities independently contributed to prolonged LOS.

Anemia and Its Severity Is Associated With Worse Postoperative Outcomes Following Open Reduction Internal Fixation of Ankle Fractures

BACKGROUND

Ankle fractures are often treated in a nonemergent fashion and therefore offer the chance for treatment of preoperative anemia. Although preoperative anemia has been associated with postoperative morbidity following certain types of orthopaedic procedures, its effect on postoperative outcomes following open reduction internal fixation (ORIF) of ankle fractures has not been evaluated. The purpose of this study was to determine the influence of preoperative anemia on 30-day postoperative outcomes following ankle fracture ORIF.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program (ASC-NSQIP) registry was queried from 2005 to 2019 for patients undergoing ankle fracture ORIF. Patients were stratified into nonanemic, mildly anemic, and moderately to severely anemic. Univariate analyses were used to assess differences in patient characteristics between cohorts. Multivariate logistic regressions adjusting for these differences were performed to assess the effect of preoperative anemia on 30-day postoperative outcomes.

RESULTS

We obtained data for 21 211 patients, of whom 14 931 (70.39%) were not anemic, 3982 (18.77%) were mildly anemic, and 2298 (10.83%) were moderately to severely anemic. After adjustment, mild preoperative anemia was associated with higher odds of any adverse event (P < .001), deep surgical site infections (SSIs; P = .013), sepsis (P = .001), 30-day readmission (P < .001), and extended length of stay (LOS) (P < .001). Similarly, moderate to severe anemia in these patients was also associated with increased odds of any adverse event (P < .001), deep SSIs (P = .003), sepsis (P = .001), readmission (P < .001), and extended LOS (P < .001). Both mild (P = .004) and moderate to severe (P < .001) anemia groups had higher odds of requiring a blood transfusion.

CONCLUSION

Preoperative anemia is associated with an increased risk of adverse postoperative outcomes in patients undergoing ORIF for ankle fractures. Future studies should evaluate whether optimization of hematocrit in these patients results in improved outcomes.

LEVEL OF EVIDENCE

Level III, comparative study.

Increased Severity of Anemia Is Associated with Postoperative Complications following a Adult Spinal Deformity Surgery

BACKGROUND

Anemia is a modifiable risk factor for postoperative complications following surgery. This study aimed to determine the impact of preoperative anemia severity on 30-day postoperative complications following adult spinal deformity (ASD) surgery.

METHODS

Adults undergoing spinal fusion for ASD from 2012 to 2018 were identified in the National Surgical Quality Improvement Program database. Patients were substratified into 3 cohorts-non-anemia, mild anemia, and moderate-to-severe anemia-based on World Health Organization definitions. We assessed 30-day wound, cardiac, pulmonary, renal, and thromboembolic complications, as well as sepsis, mortality, postoperative transfusions, extended length of stay, and reoperation. Bivariate analyses and multivariable logistic regression were performed.

RESULTS

Of 2173 patients, 1694 (78%) had no anemia, 307 (14%) had mild anemia, and 172 (8%) had moderate or severe anemia. Following adjustments, patients with mild anemia were more likely to have postoperative blood transfusions (odds ratio [OR] 1.80, P < 0.001) and extended length of stay (OR 1.43, P < 0.001). Patients with moderate-to-severe anemia were at increased risk of organ space infection (OR 3.27, P = 0.028), death (OR 13.15, P = 0.001), postoperative blood transfusion (OR 2.81, P < 0.001), and extended length of stay (OR 3.02, P < 0.001).

CONCLUSIONS

We found a stepwise and approximately two-fold increase in the odds ratio of postoperative transfusion and length of stay with increasing severity of anemia. Moderate-to-severe anemia was associated with increased odds of death and organ space infection. Patients with moderate-to-severe anemia should be medically optimized before ASD surgery.

Preoperative anemia and deep vein thrombosis in patients with perioperative bone trauma: a cohort study

Background

In current active prevention (including physical and drug prevention), the incidence of perioperative deep vein thrombosis (DVT) of the lower extremities remains high in patients with bone trauma. Risk factors need to be further optimized, and high-risk patients must be identified early. Preoperative comorbidities, especially preoperative anemia, and DVT in patients with perioperative bone trauma are not clear. The purpose of this study was to explore the causal relationship between preoperative anemia and DVT in patients with perioperative bone trauma, and further reduce the incidence of DVT in patients with bone trauma.

Objectives

To analyze the relationship between preoperative anemia and perioperative DVT in patients with femoral and pelvic fractures and provide a reference for the optimization of risk factors for DVT.

Methods

The clinical data of 1049 patients with femoral and pelvic fractures who received surgical treatment from May 2018 to June 2021 were retrospectively analyzed. Propensity score matching (PSM) was performed for the covariates of DVT. Modified Poisson regression was used to analyze the relationship between preoperative anemia and DVT.

Results

After matching 1:1 propensity scores in 1049 patients included in this study, there were 258 patients in the anemic and non-anemic groups. Preoperative anemia was statistically significant for the formation of DVT in patients with perioperative bone trauma (P = 0.000, RR = 1.567 [95% CI 1.217–2.017]). This conclusion remained true after PSM (P = 0.009, RR = 1.500 [95% CI 1.105–2.036]). Preoperative anemia has some predictive value for perioperative DVT, with DVT-associated preoperative anemia thresholds of 125 g/L and area under the receiver operating characteristic curve of 0.5877 (95% CI 0.5345 to 0.6408). On this basis, sensitivity and specificity were 89.2 and 30.3%, respectively, with a Youden index of 0.195. In addition, we conducted an E-value determination of the propensity score; the E-value analysis showed robustness to unmeasured confounding.

Conclusions

Preoperative anemia is highly correlated with perioperative DVT in patients with bone trauma, which is the cause of perioperative DVT in these patients.

Analysis of risk factors for perioperative complications in spine surgery

Complications in spine surgery can arise in the intraoperative or the immediate postoperative period or in a delayed manner. These complications may lead to severe or even permanent morbidity if left undiagnosed and untreated. We prospectively interviewed 526 patients out of 1140 patients who consecutively underwent spinal surgery in our department between November 2017 and November 2018 and analysed the outcome and complication rates. A 12 months follow-up period was also adopted. We analysed the patients' clinical characteristics, comorbidities, surgical management, survival rates, and outcomes. Risk factor analyses for the development of complications were also performed. Patients' median age was 67 years (range: 13-96). The main diagnoses were as follows: degenerative in 50%, tumour in 22%, traumatic fractures in 13%, infections in 10%, reoperations in 3%, and others in 2%. Surgeries were emergency procedures (within 24 h) in 12%. Furthermore, 59% required instrumentation. The overall postoperative complication rate was 26%. Revision surgery was required in 12% of cases within 30 postoperative days (median time to revision 11 days [IQR 5-15 days]). The most frequent complications included wound healing disorders, re-bleeding, and CSF leakage. Thereby, the risk factor analysis revealed age-adjusted CCI (p = 0.01), metastatic tumour (p = 0.01), and atrial fibrillation (p = 0.02) as significant risk factors for postoperative complications. Additionally, postoperative KPS (p = 0.004), postoperative anaemia (p = 0.001), the length of hospital stay (p = 0.02), and duration of surgery (p = 00.002) were also identified as associated factors. Complication rates after spinal surgeries are still high, especially in patients with metastatic tumour disease and poor clinical status (KPS), requiring revision surgeries in several cases. Therefore, specific risk factors should be determined to carefully select surgery groups.

Enhanced recovery after surgery (ERAS) protocol in spine surgery

Enhanced recovery after surgery (ERAS) protocols are a set of interventions which are carried out in the preoperative and perioperative period. They are aimed to decrease the harmful effects of surgery on the body and help the patient recover better post-surgery. The effectiveness of ERAS has been well established in various other surgical specialities. Earlier spine surgery was thought to be very complex for application of ERAS protocols. However, this has changed over the last decade with (ERAS) protocols gaining widespread popularity in spine surgery. Initial studies involving ERAS in spine surgery were limited to lumbar spine. However, over the years the horizon of ERAS has expanded to include anterior cervical surgeries, spine deformity, spinal tumors and spine surgery in the elderly. ERAS has been shown to reduce the length of hospital stay, overall hospital costs, opioid consumption in perioperative and postoperative period and to lower complication rates in spine surgery. In this narrative review, we discuss various aspects of ERAS in spine surgery including the benefits of ERAS in spine surgery, the various components of preoperative, intraoperative and postoperative measures of ERAS protocol.

Is preoperative S-albumin associated to postoperative complications and readmission in patients with adult spinal deformity: a prospective analysis of 128 patients using the Spine AdVerse Event Severity (SAVES) system

PURPOSE

To assess the association between preoperative S-albumin and postoperative outcome following adult spinal deformity (ASD) surgery.

METHODS

All patients undergoing ASD surgery from February 1, 2017 and January 31, 2018 at a single quaternary referral center were prospectively included. Adverse events (AE) during admission were assessed using the Spine AdVerse Events Severity (SAVES) system. Based on preoperative S-albumin, patients were categorized as "normal" or "abnormal" and compared regarding postoperative outcome, adverse events (AEs), 30- and 90-day readmission, revision surgery, and mortality.

RESULTS

A total of 128 patients aged ≥ 18 years were included, and S-albumin was available in 88%. Of these, 73% (n = 93) were classified as "normal", 16% (n = 20) as "abnormal", and 12% (n = 15) as "missing". The "normal" albumin group had less comorbidity burden [ASA score 2 (2, 3) vs 3 (2, 3), p = 0.011], higher hemoglobin levels (8.4 (± 0.9) mmol/L vs 7.4 (± 1.1) mmol/L, p < 0.001), and higher S-albumin (38.9 (± 2.7) g/L vs 31.9 (± 4.4) g/L, < 0.001). The rate of 90-day readmission was significantly increased in the "abnormal" group (65% vs 36%), corresponding to a relative risk increase of 1.25 (95% CI 1.02-1.52, p = 0.029). Similar increased risks were found in subsequent logistic regression analyses, although results were not significant in multivariable analysis (p = 0.102). Comparing remaining outcome parameters, point estimates revealed increased AEs, 30-day readmission, and revision in the "abnormal" albumin group, although effects did not reach statistical significance.

CONCLUSIONS

In a prospective, consecutive, single-center cohort of 128 patients undergoing ASD surgery, we found a significant association between "abnormal" preoperative S-albumin and increased 90-day readmission. Furthermore, although the findings were not statistically significant, we did find that AEs, 30-day readmission, and revision were numerically more frequent in the "abnormal" group, suggesting an expected tendency that should be further investigated. We conclude that nutritional status prior to ASD surgery could be important to consider and suggest validation in larger prospective cohorts.

LEVEL OF EVIDENCE

Prognostic II.

Prediction of Long-Term Recovery From Disability Using Hemoglobin-Based Models: Results From a Cohort of 1,392 Patients Undergoing Spine Surgery

Hemoglobin and its associated blood values are important laboratory biomarkers that mirror the strength of constitution of patients undergoing spine surgery. Along with the clinical determinants available during the preadmission visit, it is important to explore their potential for predicting clinical success from the patient's perspective in order to make the pre-admission visit more patient-centered. We analyzed data from 1,392 patients with spine deformity, disc disease, or spondylolisthesis enrolled between 2016 and 2019 in our institutional Spine Registry. Patient-reported outcome measure at 17 months after surgery was referred to the Oswestry disability index. High preoperative hemoglobin was found to be the strongest biochemical determinant of clinical success along with high red blood cells count, while low baseline disability, prolonged hospitalization, and long surgical times were associated with poor recovery. The neural network model of these predictors showed a fair diagnostic performance, having an area under the curve of 0.726 and a sensitivity of 86.79%. However, the specificity of the model was 15.15%, thus providing to be unreliable in forecasting poor patient-reported outcomes. In conclusion, preoperative hemoglobin may be one of the key biomarkers on which to build appropriate predictive models of long-term recovery after spine surgery, but it is necessary to include multidimensional variables in the models to increase the reliability at the patient's level.

Prospective study of preoperative autologous blood donation for patients with high risk of allogeneic blood transfusion in lumbar fusion surgery: a study protocol of a randomised controlled trial

INTRODUCTION

Preoperative autologous blood donation (PABD) can be used to reduce the exposure of allogeneic blood transfusion in patients undergoing elective surgery. Better blood management to avoid anaemia and reduce allogeneic blood transfusion after spine surgery become increasingly important with development of enhanced recovery after surgery. We present here the design of a randomised controlled trial with three groups to verify the clinical effectiveness of PABD in patients at high risk of transfusion for lumbar fusion surgery and explore the optimal timing of autologous blood donation.

METHOD AND ANALYSIS

Patients (age 18-70 years) who will receive lumbar fusion surgery for degenerative disease with haemoglobin over 110 g/L and 'high risk' of allogeneic blood transfusion are eligible, unless they refuse participation or are diagnosed with malignant metastases, infection, cardiovascular and cerebrovascular diseases, haematological disorders or relevant drug history and critical illnesses. A total of 1200 patients will be recruited and randomised into three groups. Patients in group A will not receive PABD and be regarded as control group. PABD will be performed for patients in groups B and C. Blood donation will be finished at 1 week (±3 day) before surgery in group B and 2 weeks (±3 day) before surgery in group C. Primary outcome measures will include haemoglobin decline, incidence and amount of allogeneic blood transfusion. Secondary outcome measures will include days of hospitalisation after surgery, haematocrit level and incidence of complications. This study is a single-centre and open-label randomised controlled trial. The sample size is calculated with reference to the retrospective data and previous studies.

ETHICS AND DISSEMINATION

This trial has been approved by the Peking University Third Hospital Medical Science Research Ethic Committee (no: 2020-262-02). Results of the trial will be submitted for publication in a peer-reviewed journal and as conference presentations.

TRIAL REGISTRATION NUMBER

ChiCTR2000039824, preresults.

Design and Implementation of an Enhanced Recovery After Surgery Protocol in Elective Lumbar Spine Fusion by Posterior Approach: A Retrospective, Comparative Study

STUDY DESIGN

Retrospective, comparative.

OBJECTIVE

The aim of this study was to design an enhanced recovery after surgery (ERAS) protocol for elective lumbar spine fusion by posterior approach, and to compare the results after ERAS implementation in patients undergoing elective lumbar spine fusion with conventional perioperative care.

SUMMARY OF BACKGROUND DATA

Despite wide adoption in other surgical disciplines, ERAS has only been recently implemented in spine surgery. The integrated multidisciplinary approach of ERAS aims to reduce surgical stress to achieve better outcomes.

METHODS

Hospital records of adult patients who underwent one- to three-level elective lumbar spine fusion by posterior approach at a single center were retrospectively studied. An ERAS protocol was designed based on the prevalent hospital practices, local resources and supportive evidence from literature. The ERAS protocol was implemented at our institute in December 2016-dividing patients into pre-ERAS and post-ERAS groups. The outcome measures for comparison were: length of hospital stay (LOS), postoperative complications, 60-day readmission rate, 60-day reoperation rate, and patient-reported outcome measures (visual analogue scale [VAS] and Oswestry Disability Index [ODI] score) at stipulated time intervals.

RESULTS

A total of 812 patients were included - 496 in the pre-ERAS group and 316 in the post-ERAS group. There was no significant difference between the two groups in baseline demographic, clinical, and surgery-related variables. Patients in the post-ERAS group had a significantly shorter LOS (2.94 vs. 3.68 days). The rate of postoperative complications (13.5% vs. 11.7%), 60-day readmission (1.8% vs. 2.2%), and 60-day reoperation (1.2% vs. 1.3%) did not differ significantly between the pre-ERAS and post-ERAS groups. The VAS and ODI scores, similar at baseline, were significantly lower in the post-ERAS group (VAS: 49.8 ± 12.0 vs. 44 ± 10.8, ODI: 31.6 ± 14.2 vs. 28 ± 12.8) at 4 weeks after surgery. This difference however was not significant at intermediate-term follow-up (6 months and 12 months).

CONCLUSION

Implementation of an ERAS protocol is feasible for elective lumbar spine fusion, and leads to shorter LOS and improved early pain and functional outcome scores.Level of Evidence: 3.

Short term outcomes associated with patients requiring blood transfusion following elective laminectomy and fusion for lumbar stenosis: A propensity-matched analysis

Perioperative blood transfusion has been associated with poor outcomes but the impacts of transfusion after fusion for lumbar stenosis have not been well-described. We assessed this effect in a large cohort of patients from 2012 to 2018 in the National Surgical Quality Improvement Program (NSQIP). We evaluated baseline characteristics including demographics, comorbidities, hematocrit, and operative characteristics. We generated propensity scores using baseline characteristics and patients were matched to approximate randomization. We assessed odds of 30-day outcomes including prolonged length-of-stay (LOS), complications, discharge to facility, readmission, reoperation, and death using logistic regression. We identified 16,329 eligible patients who underwent lumbar fusion for stenosis; 1,926 (11.8%) received a transfusion. Before matching, there were multiple differences in baseline covariates including age, gender, BMI, ASA class, medical comorbidities, hematocrit, coagulation indices, platelets, operative time, fusion technique, number of levels fused, and osteotomy. However, after matching, no significant differences remained. In the matched cohorts, transfusion was associated with increased prolonged LOS (OR 1.66, 95% CI 1.45-1.91, p < 0.001), minor complication (OR 1.60, 95% CI 1.20-2.12, p = 0.001), major complication (OR 1.51, 95% CI 1.16-1.98, p = 0.003), any complication (OR 1.54, 95% CI 1.24-1.92, p < 0.001), discharge to facility (OR 1.70, 95% CI 1.48-1.95, p < 0.001), 30-day readmission (OR 1.56, 95% CI 1.23-1.99, p < 0.001), and 30-day reoperation (OR 1.85, 95% CI 1.35-2.53, p < 0.001). Although transfusion is performed based on perceived clinical need, this study contributes to growing evidence that it is important to balance the risks of perioperative blood transfusion with its benefits.

Prevalence and intervention of preoperative anemia in Chinese adults: A retrospective cross-sectional study based on national preoperative anemia database

BACKGROUND

Preoperative anemia is an important pillar of perioperative patient blood management. However, there was no literature comprehensively described the current situation of preoperative anemia in China.

METHODS

We conducted a national retrospective cross-sectional study to assess the prevalence and intervention of preoperative anemia in Chinese adults. Data were from the National Preoperative Anemia Database based on hospital administration data from January 1, 2013 to December 31, 2018.

FINDINGS

A total of 797,002 patients were included for analysis. Overall, 27.57% (95% CI 27.47-27.67) of patients had preoperative anemia, which varied by gender, age, regions, and type of operation. Patients who were female, age over 60 years old, from South China, from provinces with lower per capita GDP, underwent operations on the lymphatic and hematopoietic system, with laboratory abnormalities were more likely to have a high risk of preoperative anemia. Among patients with preoperative anemia, 5.16% (95% CI 5.07-5.26) received red blood cell transfusion, 7.79% (95% CI 7.67-7.91) received anemia-related medications such as iron, erythropoietin, folic acid or vitamin B12, and 12.25% (95% CI 12.10-12.40) received anemia-related therapy (red blood cell transfusion or anemia-related medications) before operation. The probability of preoperative RBC transfusion decreased by 54.92% (OR 0.46, 95% CI 0.46-0.47) as each 10-g/L increase in preoperative hemoglobin. Patients with preoperative hemoglobin less than 130 g/L was associated with longer hospital stay and more hospital costs. Patients with severe preoperative anemia given iron preoperatively had lower intra/post-operative RBC transfusion rate, shorter length of stay and less hospitalization costs, but no similar correlation was found in patients with mild and moderate preoperative anemia and patients given erythropoietin preoperatively.

INTERPRETATION

Our present study shows that preoperative anemia is currently a relatively prevalent problem that has not been fully appreciated in China. More researches will be required to optimize the treatment of preoperative anemia.

FUNDING

National Natural Science Foundation of China and the Logistics Support Department of the Central Military Commission.

Consensus statement for perioperative care in lumbar spinal fusion: Enhanced Recovery After Surgery (ERAS®) Society recommendations

BACKGROUND

Enhanced Recovery After Surgery (ERAS) evidence-based protocols for perioperative care have led to improvements in outcomes in numerous surgical areas, through multimodal optimization of patient pathway, reduction of complications, improved patient experience and reduction in the length of stay. ERAS represent a relatively new paradigm in spine surgery.

PURPOSE

This multidisciplinary consensus review summarizes the literature and proposes recommendations for the perioperative care of patients undergoing lumbar fusion surgery with an ERAS program.

STUDY DESIGN

This is a review article.

METHODS

Under the impetus of the ERAS® society, a multidisciplinary guideline development group was constituted by bringing together international experts involved in the practice of ERAS and spine surgery. This group identified 22 ERAS items for lumbar fusion. A systematic search in the English language was performed in MEDLINE, Embase, and Cochrane Central Register of Controlled Trials. Systematic reviews, randomized controlled trials, and cohort studies were included, and the evidence was graded according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Consensus recommendation was reached by the group after a critical appraisal of the literature.

RESULTS

Two hundred fifty-six articles were included to develop the consensus statements for 22 ERAS items; one ERAS item (prehabilitation) was excluded from the final summary due to very poor quality and conflicting evidence in lumbar spinal fusion. From these remaining 21 ERAS items, 28 recommendations were included. All recommendations on ERAS protocol items are based on the best available evidence. These included nine preoperative, eleven intraoperative, and six postoperative recommendations. They span topics from preoperative patient education and nutritional evaluation, intraoperative anesthetic and surgical techniques, and postoperative multimodal analgesic strategies. The level of evidence for the use of each recommendation is presented.

CONCLUSION

Based on the best evidence available for each ERAS item within the multidisciplinary perioperative care pathways, the ERAS® Society presents this comprehensive consensus review for perioperative care in lumbar fusion.

Associations between preoperative anaemia and hospital costs following major abdominal surgery: cohort study

Background

Determining the cost-effectiveness and sustainability of patient blood management programmes relies on quantifying the economic burden of preoperative anaemia. This retrospective cohort study aimed to evaluate the hospital costs attributable to preoperative anaemia in patients undergoing major abdominal surgery.

Methods

Patients who underwent major abdominal surgery between 2010 and 2018 were included. The association between preoperative patient haemoglobin (Hb) concentration and hospital costs was evaluated by curve estimation based on the least-square method. The in-hospital cost of index admission was calculated using an activity-based costing methodology. Multivariable regression analysis and propensity score matching were used to estimate the effects of Hb concentration on variables related directly to hospital costs.

Results

A total of 1286 patients were included. The median overall cost was US $18 476 (i.q.r.13 784–27 880), and 568 patients (44.2 per cent) had a Hb level below 13.0 g/dl. Patients with a preoperative Hb level below 9.0 g/dl had total hospital costs that were 50.6 (95 per cent c.i. 14.1 to 98.9) per cent higher than those for patients with a preoperative Hb level of 9.0–13.0 g/dl (P < 0.001), 72.5 (30.6 to 128.0) per cent higher than costs for patients with a Hb concentration of 13.1–15.0 g/dl (P < 0.001), and 62.4 (21.8 to 116.7) per cent higher than those for patients with a Hb level greater than 15.0 g/dl (P < 0.001). Multivariable general linear modelling showed that packed red blood cell (PRBC) transfusions were a principal cost driver in patients with a Hb concentration below 9.0 g/dl.

Conclusion

Patients with the lowest Hb concentration incurred the highest hospital costs, which were strongly associated with increased PRBC transfusions. Costs and possible complications may be decreased by treating preoperative anaemia, particularly more severe anaemia.

Assessing the Impact of Neurogenic Claudication on Outcomes Following Decompression With Lumbar Interbody Fusions in Patients With Lumbar Spinal Stenosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To conduct the first comprehensive national-level study examining specific risks, outcomes, and costs surrounding surgical treatment of lumar spinal stenosis (LSS) in patients with and without neurogenic claudication (NC).

METHODS

Data for patients with or without NC who underwent decompression with a lumbar interbody fusion approached anteriorly (ALIF), posteriorly (PLIF), or laterally (LLIF) for LSS was collected from the 2013-2014 National Inpatient Sample using International Classification of Disease codes.

RESULTS

A total of 121 025 LSS cases without NC and 20 095 cases with NC were included in this study. The most significant complications associated with NC status by organ system included renal (P = .0030) and hematological complications (P = .0003). Multivariate regression controlling for key demographic and comorbidity variables showed that patients with NC did not have significantly higher odds of complication, non-home discharge, or extended hospitalization compared to patients without NC regardless of fusion type. Interestingly, NC patients had comparatively lower total charges for their hospitalization following PLIFs (P = .0001) and LLIFs (P < .0001), but not ALIFs (P = .6121).

CONCLUSION

NC does not appear to significantly increase odds of adverse outcomes following fusion in LSS. Given the large prevalence of LSS and coincidental NC, these findings may carry important implications in managing this challenging patient population and justifies future prospective investigation of this topic.

Hypoalbuminemia Increased the Length of Stay in the Treatment of Postoperative Acute Surgical Site Infection in Spinal Surgery

STUDY DESIGN

Multicenter retrospective study.

OBJECTIVE

The aim of this study was to identify specific risk factors for increased length of stay (LOS) in the management of acute surgical site infection (SSI) following spinal surgery.

SUMMARY OF BACKGROUND DATA

Postoperative SSI is a serious complication of spinal surgery and is known to be associated with increased LOS and additional cost. Although many risk factors contribute to the development of SSI following spinal surgery, little is known about risk factors associated with the treatment of SSI that contribute to increased LOS.

METHODS

Patients at two institutions experiencing deep SSI following spinal surgery between January 2009 and December 2016 were identified. The patients were divided into two groups depending upon the median LOS attributable to SSI. The effects of patient characteristics, comorbidities, disease history, and invasiveness of the elective surgery on the risk of increased LOS were determined using univariate analyses and multivariate logistic regression.

RESULTS

Of the 1656 spinal surgery cases, 40 (2.4%) experienced deep SSI. The median LOS was 67 days. Multivariate logistic regression analysis revealed that hypoalbuminemia during hospitalization was associated with increased LOS (odds ratio 0.042, confidence interval 0.005-0.342; P = 0.003). We determined the appropriate diagnostic cutoff of hypoalbuminemia during hospitalization using receiver-operating characteristic curves. A serum albumin level <3.1 g/dL (sensitivity, 86.4%; specificity, 75.0%; area under the curve, 0.84) was indicative of a longer hospital stay.

CONCLUSION

Low serum albumin level during hospitalization was an independent risk factor for increased LOS in the treatment of SSI following spinal surgery. When the serum albumin level is <3.1 g/dL in patients with SSI, we should consider interventions aimed at correcting this hypoalbuminemia.

LEVEL OF EVIDENCE

4.

Prolonged length of stay and discharge disposition to rehabilitation facilities following single-level posterior lumbar interbody fusion for acquired spondylolisthesis

Background

Acquired lumbar spondylolisthesis is often treated with interbody fusion. However, few studies have evaluated predictors for prolonged length of stay (LOS) and disposition to rehabilitation facilities after posterior single-level lumbar interbody fusion for acquired spondylolisthesis.

Methods

The American College of Surgeons National Quality Improvement Program database was queried for adults with acquired spondylolisthesis who underwent single-level lumbar interbody fusion through a posterior approach (posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion [TLIF]). We utilized multivariate logistic regression analysis to identify predictors of prolonged LOS and disposition in this patient population.

Results

Among 2080 patients identified, 700 (33.7%) had a prolonged LOS (≥4 days), and 306 (14.7%) were discharged postoperatively to rehabilitation facilities. Predictors for prolonged LOS included: American Society of Anesthesiologist (ASA) class ≥3, anemia, prolonged operative time, perioperative blood transfusion, pneumonia, urinary tract infections, and return to the operating room. The following risk factors predicted discharge to postoperative rehabilitation facilities: age ≥65 years, male sex, ASA class ≥3, modified frailty score ≥2, perioperative blood transfusion, and prolonged LOS.

Conclusion

Multiple partial-overlapping risk factors predicted prolonged LOS and discharge to rehabilitation facilities after single-level TLIF/PLIF performed for acquired spondylolisthesis.

Risks associated with perioperative anaemia and perioperative blood transfusion in patients undergoing neurosurgical operation

OBJECTIVE

To investigate the prevalence of preoperative anaemia and the risks associated with perioperative anaemia and blood transfusion in patients who underwent neurological surgery.

BACKGROUND

Perioperative anaemia has an important impact on neurosurgery patients. The prevalence and risks of perioperative anaemia and blood transfusion in Chinese patients are still unknown.

METHODS

Logistic regression was used to predict adverse outcomes of red blood cell (RBC) transfusion and different levels of anaemia. Anaemia and transfusion were compared as independent variables by using a 1:1 match on propensity score.

RESULTS

The prevalence of preoperative anaemia in neurosurgical patients was 20.05%; 10.33% patients received RBC transfusion. Perioperative RBC and plasma transfusion rates (P < .001) and average hospital costs (P = .0365) were higher in preoperative moderate-to-severe anaemia patients than in no anaemia patients. Perioperative RBC transfusion patients had longer hospital length of stay (LOS) (P < .001) and higher average hospital costs (P < .001) than no-transfusion patients. The rates of return to the operating room (OR) within 30 days and intensive care unit stay did not demonstrate any significant difference in anaemia and transfusion cohorts, respectively.

CONCLUSION

The status of preoperative anaemia in Chinese neurosurgical patients is associated with increased transfusion rates and hospital costs. Perioperative RBC transfusion is associated with increased length and cost of hospitalisation.

Postoperative Anemia Predicts Length of Stay for Geriatric Patients Undergoing Minimally Invasive Lumbar Spine Fusion Surgery

Introduction:

We hypothesize that postoperative anemia will predict length of stay (LOS) for geriatric patients undergoing minimally invasive (MIS) lumbar spine fusions.

Materials and Methods:

Patients who underwent MIS lateral and transforaminal lumbar interbody fusion between January 2017 and March 2018 at an academic tertiary care referral center were selected. Eighty-one patients were included. The primary outcome variable was LOS, measured in days. The predictors studied were preoperative hemoglobin (Hgb), postoperative day 1 Hgb, postoperative nadir Hgb, intraoperative Hgb decrement (preoperative Hgb-postoperative day 1 Hgb), perioperative Hgb decrement (preoperative Hgb-postoperative nadir Hgb), age, American Society of Anesthesiologists–Physical Status (ASA-PS) score, volume of perioperative intravenous (IV) fluids (IVFs), and number of levels fused. Simple linear regression and analysis of variance were used for statistical analysis.

Results:

In the present study, preoperative anemia was not associated with longer LOS (P = .15). Postoperative anemia was associated with longer LOS as both postoperative day 1 Hgb (P = .05*) and postoperative nadir Hgb (P < .0001*) predicted longer LOS. Greater intraoperative Hgb decrement did not predict longer LOS (P = .36); however, greater perioperative Hgb decrement predicted longer LOS (P < .0001*). Older age (P = .01*) and greater number of levels fused (P = .03*) predicted longer LOS; however, a greater ASA-PS classification did not predict longer LOS. Greater IVF administration was associated with longer LOS (P < .0001*).

Discussion:

Postoperative nadir Hgb (P < .0001*) was more predictive of longer LOS than postoperative day 1 Hgb (P = .05*). There is a perioperative Hgb decrement associated with longer LOS (P < .0001*). Geriatric patients may be more susceptible to the potential contributors to Hgb decrement, including occult bleeding post-op and hemodilution from IVF administration.

Conclusion:

Postoperative anemia, perioperative decrement in Hgb, older age, greater number of levels fused, and greater total IVFs administered predict longer LOS. Understanding the impact of these factors on LOS is critical as these procedures increasingly move to the outpatient setting.

High, As Well As Low, Preoperative Platelet Counts Correlate With Adverse Outcomes After Elective Posterior Lumbar Surgery

STUDY DESIGN

Retrospective cohort study of prospectively collected data.

OBJECTIVE

Assess correlation between preoperative platelet counts and postoperative adverse events after elective posterior lumbar surgery procedures.

SUMMARY OF BACKGROUND DATA

Preoperative low platelet counts have been correlated with adverse outcomes after posterior lumbar surgery. Nonetheless, the effect of varying platelet counts has not been studied in detail for a large patient population, especially on the high end of the platelet spectrum.

METHODS

Patients who underwent elective posterior lumbar surgery were identified in the 2011 to 2016 National Surgical Quality Improvement Program database. Preoperative platelet counts were considered relative to 30-day perioperative adverse outcomes. Patients were classified into platelet categories based on determining upper and lower bounds on when the adverse outcomes crossed a relative risk of 1.5. Univariate and multivariate analyses compared 30-day postoperative complications, readmissions, operative time, and hospital length of stay between those with low, normal, and high platelet counts.

RESULTS

In total, 137,709 posterior lumbar surgery patients were identified. Using the relative risk threshold of 1.5 for the occurrence of any adverse event, patients were divided into abnormally low (≤140,000/mL) and abnormally high (≥447,000/mL) platelet cohorts. The abnormally low and high platelet groups were associated with higher rates of any, major, minor adverse events, transfusion, and longer hospital length of stay. Furthermore, the abnormally low platelet counts were associated with a higher risk of readmissions.

CONCLUSION

The data-based cut-offs for abnormally high and low platelet counts closely mirrored those found in literature. Based on these definitions, abnormally high and low preoperative platelet counts were associated with adverse outcomes after elective posterior lumbar surgery. These findings facilitate risk stratification and suggest targeted consideration for patients with high, as well as low, preoperative platelet counts.

LEVEL OF EVIDENCE

3.

Prevalence of anemia and its relationship with neurological status in patients undergoing surgery for degenerative cervical myelopathy and radiculopathy: A retrospective study of 2 spine centers

Both degenerative cervical myelopathy (DCM) and anemia are common among older patients, however insufficient data exists evaluating their co-occurrence and the influence of anemia on baseline neurological status. To address this, we examined a retrospective multicenter series of patients treated for DCM or radiculopathy. Myelopathy was graded using the Nurick scale. Established criteria for diagnosing abnormalities were used to identify blood abnormalities, including macrocytic and microcytic anemia. Multivariable regression was used to determine the impact of hematological anomalies on Nurick grades. In our analysis, we included 725 patients (age of 57.1 ± 11.7), of whom 398 presented with myelopathy and 327 presented with radiculopathy alone. Twenty six percent of all patients were anemic at baseline and the mean preoperative Nurick grade across all patients was 2.09 ± 1.29; mean Nurick grade amongst those with DCM was 2.98 ± 1.12. Compared to those with myelopathy, patients with radiculopathy were significantly younger (53.8 ± 11.0 vs 59.8 ± 11.6, p < 0.001) and less likely to be anemic (16.8% vs 33.7%, p < 0.0001). Nurick grading was significantly higher in myelopathy patients with anemia (3.13 ± 1.19 vs 2.91 ± 1.07, p = 0.05) and macrocytic anemia (4.00 ± 1.41 vs 2.97 ± 1.11, p = 0.04). Multivariate regression demonstrated that anemia (p < 0.001), age (p < 0.0001), and posterior surgical approach (p < 0.0001) were related to worse preoperative Nurick grade. In sum, these data suggest that anemia and degenerative cervical spine pathologies commonly co-occur. Anemia, and macrocytic anemia specifically, is associated with poorer neurological status in myelopathic patients. These data suggest anemia may influence baseline neurological status and impact surgical recovery in patients treated for DCM or radiculopathy.

Preoperative Maximization to Reduce Complications in Spinal Surgery

STUDY DESIGN

Invited narrative review.

OBJECTIVES

The aim of this review was to summarize current literature regarding risk factors that surgeons can optimize in the preoperative setting in the spinal surgery patient, in order to reduce complications and improve patient-reported outcomes.

METHODS

Review of the relevant literature by the authors.

RESULTS

Modifiable risk factors identified relative to the patient include obesity, malnutrition/nutrient deficiency, diabetes/hyperglycemia, preoperative anemia, vitamin D/DEXA (dual-energy radiograph absorptiometry), nicotine use/smoking, and opioid use/psychosocial factors.

CONCLUSION

By maximizing a patient's physiological and psychological status prior to elective spine surgery, we may move closer to achieving the goals of value-based care: improving patient-reported outcomes while decreasing the cost of care.

Predicting In-Hospital Complications After Anterior Cervical Discectomy and Fusion: A Comparison of the Elixhauser and Charlson Comorbidity Indices

OBJECTIVE

The objective of this study was to determine the ability of the Elixhauser Comorbidity Index (ECI) and Charlson Comorbidity Index (CCI) to predict postoperative complications after anterior cervical discectomy and fusion (ACDF).

METHODS

This was a retrospective study of ACDF hospitalizations in the National Inpatient Sample from 2013 to 2014. The ECI and CCI were calculated, and patients who experienced postoperative complications were identified. The ability of these indexes to predict complications was compared using the c statistic (area under the receiver operating characteristic curve [AUC]). In addition, the CCI and ECI were compared with a base model that included age, sex, race, and primary payer.

RESULTS

A total of 261,780 patients were included. Patients who experienced a complication were more often male (P < 0.0001) and older (P < 0.0001). They also had a higher comorbidity burden as assessed by both the ECI (P < 0.0001) and the CCI (P < 0.0001). The ECI was superior in predicting airway complications (AUC, 0.81 vs. 0.75; P < 0.0001), hemorrhagic anemia (AUC, 0.67 vs. 0.63; P = 0.0015), pulmonary embolism (AUC, 0.91 vs. 0.77; P < 0.0001), wound dehiscence (AUC, 0.80 vs. 0.55; P = 0.0080), sepsis (AUC, 0.87 vs. 0.82; P = 0.0001), and septic shock (AUC, 0.94 vs. 0.83; P < 0.0001). The CCI was not found to be superior to the ECI for predicting any complications. Both were excellent for predicting mortality (ECI AUC, 0.87; CCI AUC, 0.90).

CONCLUSIONS

The ECI was superior to the CCI in predicting 6 of 15 complications in this study. Both are excellent tools for predicting mortality after ACDF.

Lack of Prognostic Model Validation in Low Back Pain Prediction Studies: A Systematic Review

OBJECTIVE

The objective of this study was to investigate the frequency with which prediction studies for low back pain outcomes utilize prospective methods of prognostic model validation.

METHOD

Searches of Medline and Embase for terms "predict/predictor," "prognosis," or "prognostic factor." The search was limited to studies conducted in humans and reported in the English language. Included articles were all those published in 2 Spine specialty journals (Spine and The Spine Journal) over a 13-month period, January 2013 to January 2014. Conference papers, reviews, and letters were excluded. The initial screen identified 55 potential studies (44 in Spine, 11 in The Spine Journal); 34 were excluded because they were not primary data collection prediction studies; 23 were not prediction studies and 11 were review articles. This left 21 prognosis papers for review, 19 in Spine, 2 in The Spine Journal.

RESULTS

None of the 21 studies provided validation for the predictors that they documented (neither internal or external validation). On the basis of the study designs and lack of validation, only 2 studies used the correct terminology for describing associations/relationships between independent and dependent variables.

DISCUSSION

Unless researchers and clinicians consider sophisticated and rigorous methods of statistical/external validity for prediction/prognostic findings they will make incorrect assumptions and draw invalid conclusions regarding treatment effects and outcomes. Without proper validation methods, studies that claim to present prediction models actually describe only traits or characteristics of the studied sample.

The use of tranexamic acid in adult spinal deformity: is there an optimal dosing strategy?

BACKGROUND CONTEXT

ASD (Adult spinal deformity) surgery often entails complex osteotomies and realignment procedures, particularly in the setting of rigid deformities. Although previous studies have established the efficacy of tranexamic acid (TXA), data evaluating the widely variable dosing regimens remains sparse.

PURPOSE

To improve understanding of blood loss and transfusion requirements for low-dose and high-dose TXA regimens for adult spinal deformity (ASD) surgery.

STUDY DESIGN/SETTING

This is a retrospective cohort study of 318 ASD patients who received TXA. Outcome measures include estimated blood loss (EBL), perioperative transfusion requirement, and complications.

METHODS

A retrospective review was conducted on 318 ASD patients: 258 patients received a low-dose regimen of TXA (10 or 20 mg/kg loading dose with a 1 or 2 mg/kg/h maintenance dose) and 60 patients received a high-dose regimen of TXA (40 mg/kg loading dose with a 1 mg/kg/h maintenance dose, 30 mg/kg loading dose with a 10 mg/kg/h maintenance dose, or 50 mg/kg loading dose with a 5 mg/kg/h maintenance dose).

RESULTS

Compared with the low-dose TXA group, the high-dose TXA group had significantly decreased EBL (1402 vs. 1793 mL, p=.009), blood volume lost (30.3 vs. 39.4%, p=.01), intraoperative packed red blood cell (pRBC) transfusion (0.9 vs. 1.6 U, p<.0001), and intraoperative platelet transfusion (0 vs. 0.1 U, p<.0001). High-dose TXA was predictive of 515 cc less EBL (p=.002), 11.4% less blood volume lost (p=.004), and 1 U pRBC less transfused intraoperatively (p<.0001) than the low-dose TXA group. The high-dose TXA group had a higher incidence of postop atrial fibrillation (5 vs. 0%, p<.0001) and myocardial infarction (1.7 vs. 0%, p=.04).

CONCLUSIONS

Varying dosing regimens of TXA are utilized for ASD surgery, with a prevailing theme of dosing ambiguity. These data demonstrate that high-dose TXA is more effective than low-dose TXA in reducing blood loss and blood product transfusion requirement in ASD surgery. Importantly, rates of MI and postop AF were higher in the high-dose TXA group.

The Role of Potentially Modifiable Factors in a Standard Work Protocol to Decrease Complications in Adult Spinal Deformity Surgery: A Systematic Review, Part 1

STUDY DESIGN

Structured Literature Review.

OBJECTIVES

We sought to evaluate the peer-reviewed literature for potentially modifiable patient and surgical factors that could be incorporated into a Standard Work protocol to decrease complications in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

Lean Methodology uses Standard Work to improve efficiency and decrease waste and error. ASD is known to have a high surgical complication rate. Several patient and surgical potentially modifiable factors have been suggested to affect complications, including preoperative hemoglobin, bone density, body mass index (BMI), age-appropriate realignment, preoperative albumin/prealbumin, and smoking status. We sought to evaluate the literature for evidence supporting these factors to include in a Standard Work protocol to decrease complications.

METHODS

Each of these six factors was developed into an appropriate clinical question that included the patient population, surgical intervention, a comparison group, and outcomes measure (PICO question). A comprehensive literature search was then performed. The authors reviewed abstracts and analyzed data from included studies. From 456 initial citations with abstract, 173 articles underwent full-text review. The best available evidence for clinical questions regarding the influence of these factors was provided by 93 included studies.

RESULTS

We found fair evidence supporting a low preoperative hemoglobin level associated with increased transfusion rates and decreased BMD and increased BMI associated with increased complication rates. Fair evidence supported low albumin/prealbumin associated with increased complications. There was fair evidence associating smoking exposure to increased reoperations, but conflicting evidence associating it with increased complications. There was no evidence in the literature evaluating age-appropriate realignment and complications.

CONCLUSION

Preoperative hemoglobin, bone density, body mass index, preoperative albumin/prealbumin, and smoking status all are potentially modifiable risk factors that are associated with increased complications in the adult spine surgery population. Developing a Standard Work Protocol for patient evaluation and optimization should include these factors.

LEVEL OF EVIDENCE

Level II.

Red blood cell transfusion associated with increased morbidity and mortality in patients undergoing elective open abdominal aortic aneurysm repair

BACKGROUND

Red blood cell (RBC) transfusions are associated with increased mortality and morbidity. The aim of this analysis was to examine the association between RBC transfusions and long-term survival for patients undergoing elective open infrarenal abdominal aortic aneurysm (AAA) repair with up to 15 years of follow-up.

METHODS

Prospective cohort study using data from The Danish Vascular Registry from 2000-2015. Primary endpoint was all-cause mortality. Secondary endpoints were in-hospital complications. Transfused patients were divided into subgroups based on received RBC transfusions (1, 2-3, 4-5 or > 5). Using Cox regression multi-adjusted analysis, non-transfused patients were compared to transfused patients (1, 2-3, 4-5, >5 transfusions) for both primary and secondary endpoints.

RESULTS

There were 3 876 patients included with a mean survival of 9.1 years. There were 801 patients who did not receive transfusions. Overall 30-day mortality was 3.1% (121 patients) and 3.6% (112) for all transfused patients. For the five subgroups 30-day mortality was: No transfusions 1.1% (9 patients), 1 RBC 1.2% (4 patients), 2-3 RBC 2.2% (26 patients), 4-5 RBC 1.9% (14 patients) and > 5 RBC 7.9% (68 patients). After receiving RBCs, the hazard ratio for death was 1.54 (95% CI 1.27-1.85) compared to non-transfused patients. There was a significant increase in mortality when receiving 2-3 RBC: HR 1.32 (95% CI 1.07-1.62), 4-5 RBC: 1.64 (1.32-2.03) and >5 RBC: 1.96 (1.27-1.85) in a multi-adjusted model.

CONCLUSION

There is a dose-dependent association between RBC transfusions received during elective AAA repair and an increase in short- and long-term mortality. Approximately 25% of included patients had preoperative anemia. These findings should raise awareness regarding potentially unnecessary and harmful RBC transfusions.

Development and implementation of a comprehensive spine surgery enhanced recovery after surgery protocol: the Cleveland Clinic experience

Enhanced recovery after surgery (ERAS) protocols have been shown to be effective at reducing perioperative morbidity and costs while improving outcomes. To date, spine surgery protocols have been limited in scope, focusing only on specific types of procedures or specific parts of the surgical episode. The authors describe the creation and implementation of one of the first comprehensive ERAS protocols for spine surgery. The protocol is unique in that it has a comprehensive perioperative paradigm encompassing the entire surgical period that is tailored based on the complexity of each individual spine patient.

Patient Blood Management: Recommendations From the 2018 Frankfurt Consensus Conference

IMPORTANCE

Blood transfusion is one of the most frequently used therapies worldwide and is associated with benefits, risks, and costs.

OBJECTIVE

To develop a set of evidence-based recommendations for patient blood management (PBM) and for research.

EVIDENCE REVIEW

The scientific committee developed 17 Population/Intervention/Comparison/Outcome (PICO) questions for red blood cell (RBC) transfusion in adult patients in 3 areas: preoperative anemia (3 questions), RBC transfusion thresholds (11 questions), and implementation of PBM programs (3 questions). These questions guided the literature search in 4 biomedical databases (MEDLINE, EMBASE, Cochrane Library, Transfusion Evidence Library), searched from inception to January 2018. Meta-analyses were conducted with the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology and the Evidence-to-Decision framework by 3 panels including clinical and scientific experts, nurses, patient representatives, and methodologists, to develop clinical recommendations during a consensus conference in Frankfurt/Main, Germany, in April 2018.

FINDINGS

From 17 607 literature citations associated with the 17 PICO questions, 145 studies, including 63 randomized clinical trials with 23 143 patients and 82 observational studies with more than 4 million patients, were analyzed. For preoperative anemia, 4 clinical and 3 research recommendations were developed, including the strong recommendation to detect and manage anemia sufficiently early before major elective surgery. For RBC transfusion thresholds, 4 clinical and 6 research recommendations were developed, including 2 strong clinical recommendations for critically ill but clinically stable intensive care patients with or without septic shock (recommended threshold for RBC transfusion, hemoglobin concentration <7 g/dL) as well as for patients undergoing cardiac surgery (recommended threshold for RBC transfusion, hemoglobin concentration <7.5 g/dL). For implementation of PBM programs, 2 clinical and 3 research recommendations were developed, including recommendations to implement comprehensive PBM programs and to use electronic decision support systems (both conditional recommendations) to improve appropriate RBC utilization.

CONCLUSIONS AND RELEVANCE

The 2018 PBM International Consensus Conference defined the current status of the PBM evidence base for practice and research purposes and established 10 clinical recommendations and 12 research recommendations for preoperative anemia, RBC transfusion thresholds for adults, and implementation of PBM programs. The relative paucity of strong evidence to answer many of the PICO questions supports the need for additional research and an international consensus for accepted definitions and hemoglobin thresholds, as well as clinically meaningful end points for multicenter trials.

Platelet count abnormalities and peri-operative outcomes in adults undergoing elective, non-cardiac surgery

BACKGROUND

Anemia and transfusion of blood in the peri-operative period have been shown to be associated with increased morbidity and mortality across a wide variety of non-cardiac surgeries. While tests of coagulation, including the platelet count, have frequently been used to identify patients with an increased risk of peri-operative bleeding, results have been equivocal. The aim of this study was to assess the effect of platelet level on outcomes in patients undergoing elective surgery.

MATERIALS AND METHODS

Retrospective cohort analysis of prospectively-collected clinical data from American College of Surgeons National Surgical Quality Improvement Program (NSQIP) between 2006-2016.

RESULTS

We identified 3,884,400 adult patients who underwent elective, non-cardiac surgery from 2006-2016 at hospitals participating in NSQIP, a prospectively-collected, national clinical database with established reproducibility and validity. After controlling for all peri- and intraoperative factors by matching on propensity scores, patients with all levels of thrombocytopenia or thrombocytosis had higher odds for perioperative transfusion. All levels of thrombocytopenia were associated with higher mortality, but there was no association with complications or other morbidity after matching. On the other hand, thrombocytosis was not associated with mortality; but odds for postoperative complications and 30-day return to the operating room remained slightly increased after matching.

CONCLUSIONS

These findings may guide surgeons in the appropriate use and appreciation of the utility of pre-operative screening of the platelet count prior to an elective, non-cardiac surgery.

Optimizing Preoperative Anemia to Improve Patient Outcomes

Anemia is a decrease in red blood cell mass, which hinders oxygen delivery to tissues. Preoperative anemia has been shown to be associated with mortality and morbidity following major surgery. The preoperative care clinic is an ideal place to start screening for anemia and discussing potential interventions in order to optimize patients for surgery. This article (1) reviews the relevant literature and highlights consequences of preoperative anemia in the surgical setting, and (2) suggests strategies for screening and optimizing anemia in the preoperative setting.

Risk Factors for Adverse Cardiac Events After Lumbar Spine Fusion

Background

To determine the incidence and risk factors for adverse cardiac events after lumbar spine fusion.

Methods

A total of 50 495 patients were identified through the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database who underwent lumbar spine fusion between 2005 and 2015. The 30-day postoperative data were analyzed to assess for the incidence of adverse cardiac events including cardiac arrest or myocardial infarction. Of those who experienced an event, patient- and surgery-specific parameters were evaluated to assess for risk factors.

Results

A total of 240 cardiac events occurred in the studied cohort (4.76 events/1000 patients). Factors that were associated with an increased cardiac risk were age (odds ratio [OR] = 1.039, 95% confidence interval [CI] = 1.03, 1.05, P < .001), male sex (OR = 1.51, 95% CI = 1.17, 1.94, P = .001), insulin-dependent diabetes (OR = 1.83, 95% CI = 1.29, 2.6, P = .001), American Society of Anesthesiologists (ASA) score >3 (OR = 1.92, 95% CI = 1.00, 3.65, P = .048), absolute hematocrit different from 45 (OR = 1.07, 95% CI = 1.04, 1.10, P < .001), and smoking (OR = 1.39, 95% CI = 1.02, 1.90, P = .04). The impact of sustaining a cardiac event in the setting of single-level lumbar fusion is catastrophic as the 30-day postoperative mortality rate for those sustaining an event was 24.6% (59/240 patients), compared to 0.2% (87/50 255) for those not sustaining an event (P < .001).

Conclusions

Cardiac events after lumbar fusion are a rare but devastating series of complications. Several risk factors were identified, including insulin-dependent diabetes mellitus, smoking, advanced age, male sex, ASA score of >3, and anemia/polycythemia. Considering the severity of these consequences, appropriate risk stratification is imperative, and optimization of modifiable risk factors may mitigate this risk.

Systematic Changes in the National Surgical Quality Improvement Program Database Over the Years Can Affect Comorbidity Indices Such as the Modified Frailty Index and Modified Charlson Comorbidity Index for Lumbar Fusion Studies

STUDY DESIGN

Retrospective cohort study of prospectively collected data.

OBJECTIVE

The aim of this study was to investigate the influence of changes in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database over the years on the calculation of the modified Frailty Index (mFI) and the modified Charlson Comorbidity Index (mCCI) for posterior lumbar fusion studies.

SUMMARY OF BACKGROUND DATA

Multiple studies have utilized the mFI and/or mCCI and showed them to be predictors of adverse postoperative outcomes. However, changes in the NSQIP database have resulted in definition changes and/or missing data for many of the variables included in these indices. No studies have assessed the influence of different methods of treating missing values when calculating these indices on such studies.

METHODS

Elective posterior lumbar fusions were identified in NSQIP from 2005 to 2014. The mFI was calculated for each patient using three methods: treating conditions for which data was missing as not present, dropping patients with missing values, and normalizing by dividing the raw score by the number of variables collected. The mCCI was calculated by the first two of these methods. Mean American Society of Anesthesiologists (ASA) scores used for comparison.

RESULTS

In total, 19,755 patients were identified. Mean ASA score increased between 2005 and 2014 from 2.27 to 2.50 (+10.1%). For each of the methods of data handling noted above, mean mFI over the years studied increased by 33.3%, could not be calculated, and increased by 183.3%, respectively. Mean mCCI increased by 31.2% and could not be calculated respectively.

CONCLUSION

Systematic changes in the NSQIP database have resulted in missing data for many of the variables included in the mFI and the mCCI and may affect studies utilizing these indices. These changes can be understood in the context of ASA trends, and raise questions regarding the use of these indices with data available in later NSQIP years.

LEVEL OF EVIDENCE

3.

Determinants of perioperative transfusion risk in patients with adult spinal deformity

OBJECTIVE

To determine predictors of perioperative allogeneic packed red blood cell (pRBC) transfusion requirement (total units transfused) in patients with adult spinal deformity (ASD).

METHODS

The authors retrospectively analyzed records of patients aged 18 years or older who underwent surgical correction of ASD that involved 4 or more spinal levels by the same spine surgeon between 2010 and 2016. Data regarding patient characteristics, comorbidities, surgical factors, and perioperative transfusions (up to 10 days after surgery) were analyzed using a linear regression model. Significance was set at p < 0.05.

RESULTS

The authors analyzed 165 patients (118 women) with a mean (± SD) age of 61 ± 12 years. Three-column osteotomies were associated with a mean intraoperative transfusion volume of 1.74 additional units of pRBCs. Each unit of intraoperatively salvaged blood used was associated with a mean 0.39-U increase in postoperative transfusion volume (p = 0.031). Every unit of allogeneic blood transfused intraoperatively was associated with a mean 0.23-U decrease in postoperative transfusion volume (p = 0.001). A preoperative hemoglobin concentration of 11.5 g/dl or more was associated with significantly fewer units transfused intraoperatively; a preoperative hemoglobin concentration of 14.0 g/dl or more was associated with fewer units transfused postoperatively. A history of smoking and intraoperative antifibrinolytic use were associated with increased and decreased numbers of units transfused postoperatively, respectively.

CONCLUSIONS

Effective blood management is key to perioperative care of patients with ASD. Three-column osteotomies were associated with a greater number of units of blood transfused. When considering postoperative transfusion requirements, surgeons should note that intraoperative blood salvage might be inferior to intraoperative allogeneic blood transfusion. Using antifibrinolytics and increasing the preoperative hemoglobin concentration to 11.5 g/dl or more are strategies for decreasing the need for perioperative transfusion. A history of smoking is a risk factor for postoperative transfusion requirement (total units transfused).

Blood Transfusion and Postoperative Infection in Spine Surgery: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

Allogeneic blood transfusion-related immunomodulation may relatively suppress the immune system, heightening the risk of infection following spine surgery. This systematic review seeks to determine whether allogeneic blood transfusion increases the risk of postoperative infection and whether there are any factors that modify this association.

METHODS

PubMed, Cochrane Central Register of Controlled Trials, and reference lists from included studies were searched from inception to April 20, 2017 to identify studies examining the risk of infection following allogeneic blood transfusion in adult patients receiving surgery for degenerative spine disease.

RESULTS

Eleven retrospective cohort or case-control studies, involving 8428 transfusion patients and 43 242 nontransfusion patients, were identified as meeting the inclusion criteria. Regarding surgical site infection (SSI), the results were mixed with roughly half reporting a significant association. There was an association between allogeneic transfusion and urinary tract infection (UTI) and any infection, but not respiratory tract infection. There was no statistical modifying effect of lumbar versus thoracic surgery on the association of allogeneic transfusion and SSI, though subgroup analyses in 3 of 4 studies reported a statistical association between transfusion and postoperative infections, including SSI, UTI, and any infection within the lumbar spine.

CONCLUSIONS

This systematic review failed to find a consistent association between allogeneic transfusion and postoperative infection in spine surgery patients. However, these studies were all retrospective with a high or moderately high risk of bias. To properly examine this association an observational prospective study of sufficient power, estimated as 2400 patients, is required.

Red blood cell antibody-induced anemia causes differential degrees of tissue hypoxia in kidney and brain

Moderate anemia is associated with increased mortality and morbidity, including acute kidney injury (AKI), in surgical patients. A red blood cell (RBC)-specific antibody model was utilized to determine whether moderate subacute anemia could result in tissue hypoxia as a potential mechanism of injury. Cardiovascular and hypoxic cellular responses were measured in transgenic mice capable of expressing hypoxia-inducible factor-1α (HIF-1α)/luciferase activity in vivo. Antibody-mediated anemia was associated with mild intravascular hemolysis (6 h) and splenic RBC sequestration ( day 4), resulting in a nadir hemoglobin concentration of 89 ± 13 g/l on day 4. At this time point, renal tissue oxygen tension (P_tO₂) was decreased in anemic mice relative to controls (13.1 ± 4.3 vs. 20.8 ± 3.7 mmHg, P < 0.001). Renal tissue hypoxia was associated with an increase in HIF/luciferase expression in vivo ( P = 0.04) and a 20-fold relative increase in renal erythropoietin mRNA transcription ( P < 0.001) but no increase in renal blood flow ( P = 0.67). By contrast, brain P_tO₂ was maintained in anemic mice relative to controls (22.7 ± 5.2 vs. 23.4 ± 9.8 mmHg, P = 0.59) in part because of an increase in internal carotid artery blood flow (80%, P < 0.001) and preserved cerebrovascular reactivity. Despite these adaptive changes, an increase in brain HIF-dependent mRNA levels was observed (erythropoietin: P < 0.001; heme oxygenase-1: P = 0.01), providing evidence for subtle cerebral tissue hypoxia in anemic mice. These data demonstrate that moderate subacute anemia causes significant renal tissue hypoxia, whereas adaptive cerebrovascular responses limit the degree of cerebral tissue hypoxia. Further studies are required to assess whether hypoxia is a mechanism for acute kidney injury associated with anemia.