Agreement of surgical blood loss estimation methods

IN VITRO EVALUATION OF A NOVEL AUTOMATIC INTRAOPERATIVE BLOOD LOSS MONITOR

ABSTRACT

Introduction: Accurate and real-time monitoring of surgical blood loss is essential for ensuring intraoperative safety. However, there is currently no standard way to assess the amount of blood lost in patients during surgery. This study aims to evaluate the accuracy and precision of a new automatic intraoperative blood loss monitor, which can measure both free blood volume and blood content in sponges in real time. Methods: The monitor uses an integrated photoelectric probe to gauge hemoglobin levels in both free blood and blood taken from surgical sponges. These data, combined with initial hemoglobin levels, are processed using specific calculations to determine blood volume. We created 127 diverse free blood samples and 160 blood-containing sponge samples by using fresh pig blood and physiological saline. The monitor then measured these samples. We subsequently compared its measurements with actual values acquired through physical measurements, detecting both agreement and measurement errors. Repeated measurements were performed to calculate the coefficient of variation, thereby evaluating the monitor's precision. Results: The estimated blood loss percentage error of the monitor was 5.2% for free blood, -5.7% for small sponge, -6.3% for medium sponge, and -6.6% for large sponge. The coefficient of variation of free blood with different hemoglobin concentrations measured by the monitor was less than 10%. Bland-Altman analysis showed that the limits of agreement between the monitor and the reference method were all within the acceptable clinical range. Conclusion: The new automatic intraoperative blood loss monitor is an accurate and reliable device for monitoring both free blood and surgical sponge blood, and shows high performance under various clinical simulation conditions.

Prevalence of acute kidney injury following percutaneous nephrolithotomy

Background

The objective is to evaluate the prevalence of acute kidney injury (AKI) as an early complication of the percutaneous nephrolithotomy (PCNL) procedure.

Materials and Methods

From May 2022 to October 2022, we conducted a retrospective study on patients undergoing PCNL procedures in two of the tertiary medical centers affiliated with Isfahan University of Medical Sciences. Patients' baseline characteristics, laboratory values, perioperative data, and stone features were documented. AKI was defined either as a ≥0.3 mg/dL increase in the serum creatinine level within 2 days, or a ≥1.5-fold increase in baseline serum creatinine level within 7 days after the operation. Laboratory values were measured 1 day before PCNL and daily thereafter until discharge. Patients were followed 1 week later to detect all of the possible cases of AKI.

Results

The final analysis was performed on 347 individuals. AKI developed in 16 (4.61%) cases. The two groups were comparable regarding age (P = 0.887), gender (P = 0.566), and underlying comorbidities including diabetes mellitus (P = 0.577) and hypertension (P = 0.383). The mean body mass index (BMI) (P < 0.001) and both frequency and severity of hydronephrosis (P < 0.001) were significantly different. A higher mean PCNL duration (P < 0.001), period of hospitalization (P < 0.001), and blood loss volume (P < 0.001) were observed in those who developed AKI. Overall, 56.3% (9) of patients in the AKI group and 2.7% (9) in the non-AKI group required the establishment of more than one access tract, during the procedure (P < 0.001). A lower preoperative hemoglobin level was observed in the AKI group (P < 0.001). Those with AKI had significantly larger stones (3.08 ± 0.46 vs. 2.41 ± 0.23 cm, P < 0.001) and higher Hounsfield units (P < 0.001). In addition, in the AKI group, most of the calculi (81.3%, 13) were of staghorn type, whereas in the non-AKI group, calculi were most frequently located in the middle calyx (30.2%, 100), (P < 0.001).

Conclusion

The prevalence of post-PCNL AKI is approximately 4.61%. The mean BMI, preoperative hemoglobin level, PCNL duration, intraoperative blood loss volume, and hospitalization period were significantly higher among patients who developed AKI. Those with AKI had significantly larger stones with higher Hounsfield units and more frequently of staghorn type. The two groups were not statistically different regarding age, gender, and presence of comorbidities (hypertension and diabetes mellitus).

Hidden Blood Loss and Its Risk Factors for Oblique Lumbar Interbody Fusion

(1) Background: The amount of blood loss during oblique lumber interbody fusion (OLIF) surgery is often underestimated and may contribute to adverse postoperative outcomes. This study aims to evaluate hidden blood loss (HBL) in patients who underwent OLIF for degenerative lumbar spine disease and to analyze its risk factors. (2) Methods: The medical records of 179 patients who underwent OLIF surgery from 2015 to 2022 were reviewed. The HBL and total blood loss (TBL) were estimated using the Gross formula. Pearson correlation, Spearman correlation, and multivariate linear regression analyses were used to investigate risk factors for HBL. (3) Results: The mean HBL was 675.2 mL, and the mean hemoglobin loss was 1.7 g/dL during OLIF surgery. In the multivariate linear regression analysis, TBL (p < 0.001), estimated blood loss (p < 0.001), and pedicle screw fixation type (p = 0.039) were identified as independent risk factors of HBL. (4) Conclusions: The OLIF is associated with substantial perioperative HBL, for which we identified risk factors of TBL, EBL, and pedicle screw fixation type. Notably, OLIF with percutaneous pedicle screw fixation resulted in greater HBL than stand-alone OLIF or OLIF with open pedicle screw fixation.

Intravenous tranexamic acid for intracerebral meningioma resections: A randomized, parallel-group, non-inferiority trial

STUDY OBJECTIVES

Tranexamic acid (TXA) is an antifibrinolytic that is widely used to reduce surgical bleeding. However, TXA occasionally causes seizures and the risk might be especially great after neurosurgery. We therefore tested the hypothesis that TXA does not meaningfully increase the risk of postoperative seizures within 7 days after intracranial tumor resections.

DESIGN

Randomized, double-blind, placebo-controlled, non-inferiority trial.

SETTING

Beijing Tiantan Hospital, Capital Medical University.

PATIENTS

600 patients undergoing supratentorial meningioma resection were included from October 2020 to August 2022.

INTERVENTIONS

Patients were randomly assigned to a single dose of 20 mg/kg of TXA after induction (n = 300) or to the same volume of normal saline (n = 300).

MEASUREMENT

The primary outcome was postoperative seizures occurring within 7 days after surgery, analyzed in both the intention-to-treat and per-protocol populations. Non-inferiority was defined by an upper limit of the 95% confidence interval for the absolute difference being <5.5%. Secondary outcomes included incidence of non-epileptic complication within 7 days, changes in hemoglobin concentration, estimated intraoperative blood loss. Post hoc analyses included the types and timing of seizures, oozing assessment, and a sensitivity analysis for the primary outcome in patients with pathologic diagnosis of meningioma.

MAIN RESULTS

All 600 enrolled patients adhered to the protocol and completed the follow-up for the primary outcome. Postoperative seizures occurred in 11 of 300 (3.7%) of patients randomized to normal saline and 13 of 300 (4.3%) patients assigned to tranexamic acid (mean risk difference, 0.7%; 1-sided 97.5% CI, -∞ to 4.3%; P = 0.001 for noninferiority). No significant differences were observed in any secondary outcome. Post hoc analysis indicated similar amounts of oozing, calculated blood loss, recurrent seizures, and timing of seizures.

CONCLUSION

Among patients having supratentorial meningioma resection, a single intraoperative dose of TXA did not significantly reduce bleeding and was non-inferior with respect to postoperative seizures after surgery.

REGISTRY INFORMATION

This trial was registered at clinicaltrials.gov (NCT04595786) on October 22, 2020, by Dr.Yuming Peng.

Mechanism-Based Modeling of Perioperative Variations in Hemoglobin Concentration in Patients Undergoing Laparoscopic Surgery

BACKGROUND

Hemoglobin concentration ([Hb]) in the perioperative setting should be interpreted in the context of the variables and processes that may affect it to differentiate the dilution effects caused by changes in intravascular volume. However, it is unclear what variables and processes affect [Hb]. Here, we modeled the perioperative variations in [Hb] to identify the variables and processes that govern [Hb] and to describe their effects.

METHODS

We first constructed a mechanistic framework based on the main variables and processes related to the perioperative [Hb] variations. We then prospectively studied patients undergoing laparoscopic surgery, divided into 2 consecutive cohorts for the development and validation of the model. The study protocol consisted of serial measurements of [Hb] along with recordings of hemoglobin mass loss, blood volume loss, fluid infusion, urine volume, and inflammatory biomarkers measurements, up to 96 hours postoperatively. Mathematical fitting was performed using nonlinear mixed-effects. Additionally, we performed simulations to explore the effects of blood loss and fluid therapy protocols on [Hb].

RESULTS

We studied 154 patients: 118 enrolled in the development group and 36 in the validation group. We characterized the perioperative course of [Hb] using a mass balance model that accounted for hemoglobin losses during surgery, and a 2-compartment model that estimated fluid kinetics and intravascular volume changes. During model development, we found that urinary fluid elimination represented only 24% of the total fluid elimination, and that total fluid elimination was inhibited after surgery in a time-dependent manner and influenced by age. Also, covariate evaluation showed a significant association between the type of surgery and proportion of fluid eliminated via urine. In contrast, neither the type of infused solution, blood volume loss nor inflammatory biomarkers were found to correlate with model parameters. In the validation analysis, the model demonstrated a considerable predictive capacity, with 95% of the predicted [Hb] within -4.4 and +5.5 g/L. Simulations demonstrated that hemoglobin mass loss determined most of the postoperative changes in [Hb], while intravascular volume changes due to fluid infusion, distribution, and elimination induced smaller but clinically relevant variations. Simulated patients receiving standard fluid therapy protocols exhibited a hemodilution effect that resulted in a [Hb] decrease between 7 and 15 g/L at the end of surgery, and which was responsible for the lowest [Hb] value during the perioperative period.

CONCLUSIONS

Our model provides a mechanistic and quantitative understanding of the causes underlying the perioperative [Hb] variations.

More than 30 Years of POSSUM: Are Scoring Systems Still Relevant Today for Colorectal Surgery?

BACKGROUND

The Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM) weights the patient's individual health status and the extent of the surgical procedure to estimate the probability of postoperative complications and death of general surgery patients. The variations Portsmouth-POSSUM (P-POSSUM) and colorectal POSSUM (CR-POSSUM) were developed for estimating mortality in patients with low perioperative risk and for patients with colorectal carcinoma, respectively. The aim of the present study was to evaluate the significance of POSSUM, P-POSSUM, and CR-POSSUM in two independent colorectal cancer cohorts undergoing surgery, with an emphasis on laparoscopic procedures.

METHODS

For each patient, an individual physiological score (PS) and operative severity score (OS) was attributed to calculate the predicted morbidity and mortality, respectively. Logistic regression analysis was used to evaluate the possible correlation between the subscores and the probability of postoperative complications and mortality.

RESULTS

The POSSUM equation significantly overpredicted postoperative morbidity, and all three scoring systems considerably overpredicted in-hospital mortality. However, the POSSUM score identified patients at risk of anastomotic leakage, sepsis, and the need for reoperation. Logistic regression analysis demonstrated a strong correlation between the subscores and the probability of postoperative complications and mortality, respectively.

CONCLUSION

Our results suggest that the three scoring systems are too imprecise for the estimation of perioperative complications and mortality of patients undergoing colorectal surgery in the present day. Since the subscores proved valid, a revision of the scoring systems could increase their reliability in the clinical setting.

"Parenchyma transection-first" strategy is superior to "tunnel-first" strategy in robotic spleen-preserving distal pancreatectomy with conservation of splenic vessels

BACKGROUND

Creating a tunnel between the pancreas and splenic vessels followed by pancreatic parenchyma transection ("tunnel-first" strategy) has long been used in spleen-preserving distal pancreatectomy (SPDP) with splenic vessel preservation (Kimura's procedure). However, the operation space is limited in the tunnel, leading to the risks of bleeding and difficulties in suturing. We adopted the pancreatic "parenchyma transection-first" strategy to optimize Kimura's procedure.

METHODS

The clinical data of consecutive patients who underwent robotic SPDP with Kimura's procedure between January 2017 and September 2022 at our center were retrieved. The cohort was classified into a "parenchyma transection-first" strategy (P-F) group and a "tunnel-first" strategy (T-F) group and analyzed.

RESULTS

A total of 91 patients were enrolled in this cohort, with 49 in the T-F group and 42 in the P-F group. Compared with the T-F group, the P-F group had significantly shorter operative time (146.1 ± 39.2 min vs. 174.9 ± 46.6 min, P < 0.01) and lower estimated blood loss [40.0 (20.0-55.0) mL vs. 50.0 (20.0-100.0) mL, P = 0.03]. Failure of splenic vessel preservation occurred in 10.2% patients in the T-F group and 2.4% in the P-F group (P = 0.14). The grade 3/4 complications were similar between the two groups (P = 0.57). No differences in postoperative pancreatic fistula, abdominal infection or hemorrhage were observed between the two groups.

CONCLUSIONS

The pancreatic "parenchyma transection-first" strategy is safe and feasible compared with traditional "tunnel-first strategy" in SPDP with Kimura's procedure.

Postoperative Hemodynamics of Total Knee Arthroplasty Unaffected by Cementless Approach under Contemporary Patient Blood Management Protocol: A Propensity Score-Matched Study

(1) Background: A cementless total knee arthroplasty (TKA) is a recent and an increasingly popular innovation that enhances porous fixation surfaces. However, the lack of cemented sealing of an exposed resected bone has raised concerns about the potential for greater blood loss. The goals of this study were to determine if a cementless approach impacts post-TKA hemodynamics and to identify risk factors for blood loss in instances of cementless (vs. cemented) TKAs under a contemporary patient blood management (PBM) protocol. (2) Methods: We recruited 153 consecutive patients undergoing unilateral TKAs between 2019 and 2023. All enrollees received cementless or cemented prostheses of the same design (cementless, 87; cemented, 66). After propensity score matching for demographics, there were 46 patients in each group. We then compared blood loss metrics (total [TBL] and estimated [EBL]), drainage volumes, hemoglobin (Hb) levels, and transfusion rates by group. (3) Results: Post-TKA hemodynamics (i.e., TBL, EBL, drainage, Hb level, and transfusion rate) of cementless (n = 46) and cemented (n = 46) TKA groups did not differ significantly. In addition, the proportions of patients with Hb drops > 3.0 g/dL were similar for the two groups. A logistic regression analysis revealed that only preoperative Hb and EBL during the early postoperative period were predictive of a substantial fall in Hb levels. The fixation method was not associated with Hb decline > 3.0 g/dL by postoperative Day 3. (4) Conclusion: The cementless TKA has no impact on customary post-TKA hemodynamics and is not associated with greater TKA-related blood loss when implementing a contemporary PBM protocol.

A novel mini-open transforaminal lumbar interbody fusion for lumbar degenerative diseases: technical note and preliminary results

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF) is an effective and popular surgical procedure for the management of various spinal pathologies, especially degenerative diseases. Surgeons have been pursuing minimally invasive technology as soon as TLIF was appeared. Currently, TLIF can be performed with transforaminal approaches by open surgery, minimally invasive surgery or percutaneous endoscope. We provide a detailed description of a new modified open TLIF with percutaneous pedicle screws, which we refer to as mini-open TLIF. The objective of this study was to present feasibility of this procedure and the preliminary results.

METHODS

The study is a prospective study. From January 2021 to March 2022, 96 patients (43 males and 53 females) with neurological symptoms due to degenerative lumbar spine diseases were enrolled. Operation time, blood loss, ambulatory time, hematocrit and complications were recorded during perioperative period. Clinical symptoms were evaluated 1 week, 3 months and 12 months after surgery. Visual analogue scale (VAS) scores for lower back pain and leg pain and Oswestry disability index (ODI) were assessed. Magnetic resonance imaging was performed preoperatively and 12 months postoperatively to emulate cross-sectional area of paraspinal muscles. The lumbar interbody fusion rate was evaluated by CT scanning.

RESULTS

The mean operation time of single level was 112.6 min, and the mean operation time of multilevel was 140.1 min. Intraoperative blood loss of single level was 64.5 ml and was 116.3 ml of multilevel. The VAS and ODI scores before and after surgery were significantly different (P < 0.0001) and reached minimal clinically important difference. Atrophy rate of paraspinal muscles was 2.5% for symptomatic side and 1.2% for asymptomatic side. The cross-sectional area before and after the operation and atrophy rate had no statistically significant difference (P > 0.05).

CONCLUSION

Mini-open TLIF is effective and feasible for the treatment of lumbar degenerative diseases especially in multilevel disease, with minor damage to muscle and shorter operation time.

TRIAL REGISTRATION

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of the Second Affiliated Hospital of Soochow University (No. JD-LK2023045-I01).

Closed Suction Drainage May Not be Beneficial in Revision Total Hip Arthroplasty: A Propensity Score-Matched Cohort Study

Background

Many studies on closed suction drainage (CSD) in primary total hip arthroplasty (THA) have demonstrated that it has no definite benefit. However, evidence of the clinical benefits of CSD in revision THA has not yet been established. Therefore, this retrospective study aimed to investigate the benefits of CSD in revision THA.

Materials and Methods

We reviewed 107 hips of patients who underwent revision THA between June 2014 and May 2022, excluding cases of fracture and infection. We compared perioperative blood test results, calculated total blood loss (TBL), and postoperative complications, including allogenic blood transfusion (ABT), wound complications, and deep venous thrombosis (DVT), between the groups with and without CSD. Propensity score matching was conducted to balance patients' demographics and surgical factors.

Results

ABT, wound complications, and DVT were observed in 10.3% (n = 11), 5.6% (six), and 5.6% (six) of patients, respectively. There were no significant differences in ABT, calculated TBL, wound complications, and DVT between all patients and propensity score-matched patients with or without CSD. The calculated TBL was approximately 1200 mL and showed no significant difference between the two groups in the matched cohort (p = 0.40) but tended to have a greater volume in the drain group than in the non-drain group.

Conclusion

The routine use of CSD in revision THA for aseptic loosening may not be useful in clinical practice.

Intraoperative Blood Loss Estimation in Hepato-pancreato-biliary Surgery- Relevant, Not Reported, Not Standardized: Results From a Systematic Review and a Worldwide Snapshot Survey

OBJECTIVE

To provide an overview of the current practice of intraoperative blood loss (BL) estimation in hepato-pancreato-biliary (HPB) surgery.

BACKGROUND

Intraoperative BL is a major quality marker in HPB surgery and a predictor of perioperative outcomes. However, the method for BL estimation is not standardized.

METHODS

A systematic review was performed of original studies published between 2006 and 2021 reporting the intraoperative BL of patients undergoing pancreatic or hepatic resections. A web-based snapshot survey was distributed globally to all members of the International Hepato-Pancreato-Biliary Association (IHPBA).

RESULTS

A total of 806 studies were included; 480 (60%) had BL as their primary outcome, and 105 (13%) had BL as their secondary outcome. However, 669 (83%) did not specify how BL estimation was performed, and 9 different methods were found among the remaining 136 (17%) studies.The survey was completed by 252 surgeons. Most of the responders (94%) declared that they systematically performed BL estimation and considered BL predictive of postoperative complications after pancreatic (73%) and liver (74%) resection. All methods previously identified in the literature were used by responders with different frequencies. A calculation based on suction fluid amounts, operative gauze weight, and irrigation was the most used method in the literature (7%) and among responders (51%). Most responders (83%) felt that BL estimation in HPB surgery needs improved standardization.

CONCLUSIONS

Standardization of intraoperative BL estimation is urgently needed in HPB surgery to ensure the consistency of reporting and reproducibility.

Preoperative Fibrinogen Level and Bleeding in Liver Transplantation for End-stage Liver Disease: A Cohort Study

BACKGROUND

Liver transplantation is a high-risk surgery associated with important perioperative bleeding and transfusion needs. Uncertainties remain on the association between preoperative fibrinogen level and bleeding in this population.

METHODS

We conducted a cohort study that included all consecutive adult patients undergoing a liver transplantation for end-stage liver disease in 1 center. We analyzed the association between the preoperative fibrinogen level and bleeding-related outcomes. Our primary outcome was intraoperative blood loss, and our secondary outcomes were estimated perioperative blood loss, intraoperative and perioperative red blood cell transfusions, reinterventions for bleeding and 1-y graft and patient survival. We estimated linear regression models and marginal risk models adjusted for all important potential confounders. We used restricted cubic splines to explore potential nonlinear associations and reported dose-response curves.

RESULTS

We included 613 patients. We observed that a lower fibrinogen level was associated with a higher intraoperative blood loss, a higher estimated perioperative blood loss and a higher risk of intraoperative and perioperative red blood cell transfusions (nonlinear effects). Based on an exploratory analysis of the dose-response curves, these effects were observed below a threshold value of 3 g/L for these outcomes. We did not observe any association between preoperative fibrinogen level and reinterventions, 1-y graft survival or 1-y patient survival.

CONCLUSIONS

This study suggests that a lower fibrinogen level is associated with bleeding in liver transplantation. The present results may help improving the selection of patients for further studies on preoperative fibrinogen administration in liver transplant recipients with end-stage liver disease.

Intravenous Tranexamic Acid Reduces Blood Loss in Multilevel Spine Surgeries

INTRODUCTION

Complex spine surgeries are associated with notable blood loss requiring numerous strategies to preserve blood volume. Tranexamic acid (TXA) is efficacious in reducing blood loss when used topically during surgery, intravenously with or without postoperative maintenance treatment. We aimed to evaluate the effect of preoperative weight-independent intravenous administration of 1 g intravenous TXA on perioperative blood loss in lumbar microdiskectomy, single-level lumbar spinal fusion, and multilevel lumbar decompression (two or more levels).

METHODS

This is a retrospective cohort study comparing patients who underwent microdiskectomy, single-level lumbar fusion, and multilevel laminectomies with and without preoperative IV TXA administration between 2016 and 2020.

RESULTS

Two hundred ten patients underwent spine surgery without preoperative IV TXA administration between 2016 and 2018 compared with 109 patients who received preoperative 1 g of IV TXA between 2018 and 2020. Preoperative IV TXA treatment did not change blood loss after microdiskectomy, 77.2 ± 53.9 mL and 77.2 ± 95.2 mL, respectively ( P = 0.792). Preoperative IV TXA treatment reduced blood loss after multilevel lumbar laminectomy and lumbar posterior spinal fusion with a transforaminal intervertebral fusion (PSF and TLIF) ( P = 0.004 and P = 0.0001, respectively). The same effect was found for intraoperative blood loss and postoperative drainage, with preoperative TXA administration reducing intraoperative blood loss and postoperative drainage for the multilevel lumbar laminectomy and lumbar PSF and TLIF cohorts. No IV TXA treatment adverse events were registered in all cohorts.

CONCLUSION

A routine administration of preoperative weight-independent 1 g intravenous TXA protocol is efficacious and safe in reducing perioperative blood loss for lumbar multilevel laminectomies and PSF and TLIFs.

Transfusion Rates in the Operative Treatment of Prosthetic Hip and Knee Infection

Surgery for prosthetic joint infection (PJI) can often lead to significant blood loss, necessitating allogeneic blood transfusion (ABT). The use of ABT is associated with higher rates of morbidity and death in revision total joint arthroplasty, particularly in the treatment of PJI. We compared ABT rates by procedure type among patients treated for PJI. We retrospectively reviewed 143 operative cases of hip and knee PJI performed at our institution between 2016 and 2018. Procedures were categorized as irrigation and debridement (I&D) with modular component exchange (modular component exchange), explantation with I&D and placement of an antibiotic spacer (explantation), I&D with antibiotic spacer exchange (spacer exchange), or antibiotic spacer removal and prosthetic reimplantation (reimplantation). Rates of ABT and the number of units transfused were assessed. Factors associated with ABT were assessed with a multilevel mixed-effects regression model. Of the cases, 77 (54%) required ABT. The highest rates of ABT occurred during explantation (74%) and spacer exchange (72%), followed by reimplantation (36%) and modular component exchange (33%). A lower preoperative hemoglobin level was associated with higher odds of ABT. Explantation, reimplantation, and spacer exchange were associated with greater odds of ABT. Antibiotic spacer exchange and explantation were associated with greater odds of multiple-unit transfusion. Rates of ABT remain high in the surgical treatment of PJI. Antibiotic spacer exchange and explantation procedures had high rates of multiple-unit transfusions, and additional units of blood should be made available. Preoperative anemia should be treated when possible, and further refinement of blood management protocols for prosthetic joint infection is necessary. [Orthopedics. 2022;45(6):353-359.].

Blood Loss and Transfusion in a Pediatric Scoliosis Surgery Cohort in the Antifibrinolytic Era

Children and adolescents undergoing posterior spinal fusion for scoliosis experience high rates of bleeding and blood product transfusion. Antifibrinolytic therapy is one key strategy to decrease blood loss and transfusion in pediatric scoliosis surgery. Here we review 172 pediatric scoliosis patients (birth to 21 y) who underwent posterior spinal fusion at our institution from 2017 to 2018. We reported rates of blood loss and transfusion, compared patients receiving tranexamic acid to a ε-aminocaproic acid, and evaluated antifibrinolytic agent and laboratory parameters as predictors of blood loss and transfusion. Intraoperatively, 62% received tranexamic acid and 38% received ε-aminocaproic acid. Overall, blood loss (mean intraoperative estimated blood loss=14.9±9.7 mL/kg, 22% with clinically significant blood loss [>20 mL/kg], and mean calculated hemoglobin mass loss=175.9±70.1 g) and transfusion rates (15% with intraoperative allogeneic red blood cell transfusion and mean intraoperative allogeneic red blood cell transfusion volume=12.5±7.1 mL/kg) were similar to previous cohorts studying intraoperative antifibrinolytics. There was no difference in intraoperative estimated blood loss, clinically significant blood loss, calculated hemoglobin mass loss, or transfusion rates between the antifibrinolytic groups. Antifibrinolytic choice was not predictive of blood loss or transfusion. Routine hematologic laboratory parameters and antifibrinolytic choice were insufficient to predict blood loss or other outcomes. Future prospective laboratory-based studies may provide a more comprehensive model of surgical-induced coagulopathy in scoliosis surgery and provide a better tool for predicting blood loss and improving outcomes.

Estimating blood loss during cesarean delivery: A comparison of methods

Objectives

Obstetrical hemorrhage contributes significantly to maternal morbidity and mortality. Assessment of blood loss while undergoing cesarean sections (CS) is essential in lowering the morbidity and mortality, however this amount is commonly underestimated by the surgeon and probably the anesthetist too.

Methods

This study addresses this issue by comparing three separate ways of assessing blood loss during cesarean sections. For each of 97 full-term pregnant women undergoing elective CS, blood loss was measured by the following: visual estimation by both the obstetrician and the anesthetist, weighing surgical pads pre operatively and post operatively and by calculations (multiplying the difference of pre-operative and postoperative hemoglobin values by the patient's estimated blood volume).

Results

The results of this study indicated that the lowest estimated value for blood loss came from visual estimation, while the highest value came from the mathematical formula. Anesthetists were more accurate in their visual estimation of blood loss than were obstetricians.

Conclusion

This study found the amount of blood loss during CS to be overestimated by the mathematical calculation and underestimated by obstetricians. However, the estimate given by anesthetists was close to that obtained by weighing pads. This underscores the need for more accurate methods of blood loss estimation in cesarean sections to be adopted.

Effect of tranexamic acid on the prognosis of patients with traumatic brain injury undergoing craniotomy: study protocol for a randomised controlled trial

INTRODUCTION

Abnormal coagulation function aggravates the prognosis of patients with traumatic brain injury (TBI). It was reported that the antifibrinolytic drug tranexamic acid (TXA) could reduce intracranial haemorrhage and mortality in non-operative patients with TBI. However, there is a lack of evaluation of TXA in patients with TBI undergoing craniotomy.

METHODS AND ANALYSIS

This is a single-centre randomised controlled, double-blind, parallel study aiming to investigate the effectiveness and safety of TXA in patients with TBI during the perioperative period. Blood loss and transfusion, neurological function, adverse events, mortality and serum immune-inflammatory cytokines will be collected and analysed.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Medical Ethics Committee of Beijing Tian Tan Hospital, Capital Medical University (reference number KY 2020-136-03). The results of this study will be disseminated through presentations at scientific conferences and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2100041911.

Surgical Outcomes of Obese Patients With Adolescent Idiopathic Scoliosis From Endemic Areas of Obesity in the United States

BACKGROUND

Obesity rates continue to rise among children and adolescents across the globe. A multicenter research consortium composed of institutions in the Southern US, located in states endemic for childhood obesity, was formed to evaluate the effect of obesity on pediatric musculoskeletal disorders. This study evaluates the effect of body mass index (BMI) percentile and socioeconomic status (SES) on surgical site infections (SSIs) and perioperative complications in patients with adolescent idiopathic scoliosis (AIS) treated with posterior spinal fusion (PSF).

METHODS

Eleven centers in the Southern US retrospectively reviewed postoperative AIS patients after PSF between 2011 and 2017. Each center contributed data to a centralized database from patients in the following BMI-for-age groups: normal weight (NW, 5th to <85th percentile), overweight (OW, 85th to <95th percentile), and obese (OB, ≥95th percentile). The primary outcome variable was the occurrence of an SSI. SES was measured by the Area Deprivation Index (ADI), with higher scores indicating a lower SES.

RESULTS

Seven hundred fifty-one patients were included in this study (256 NW, 235 OW, and 260 OB). OB and OW patients presented with significantly higher ADIs indicating a lower SES (P<0.001). In addition, SSI rates were significantly different between BMI groups (0.8% NW, 4.3% OW, and 5.4% OB, P=0.012). Further analysis showed that superficial and not deep SSIs were significantly different between BMI groups. These differences in SSI rates persisted even while controlling for ADI. Wound dehiscence and readmission rates were significantly different between groups (P=0.004 and 0.03, respectively), with OB patients demonstrating the highest rates. EBL and cell saver return were significantly higher in overweight patients (P=0.007 and 0.002, respectively).

CONCLUSION

OB and OW AIS patients have significantly greater superficial SSI rates than NW patients, even after controlling for SES.

LEVEL OF EVIDENCE

Level III.

Evaluating the efficacy of bimanual compression of abdomen-flank to control postoperative bleeding after percutaneous nephrolithotomy: A randomized clinical trial

PURPOSE

To investigate the influence of bimanual compression of abdomen-flank to control bleeding after completion of percutaneous nephrolithotomy (PCNL) including tubeless PCNL.

MATERIALS AND METHODS

This study is a parallel-group randomized clinical trial with 1:1:1 randomization. Ninety patients who were candidates for PCNL during July to October 2019 were enrolled. After completion of PCNL operation, patients were randomized into three groups to receive bimanual abdomen-flank compression for 0, 3, and 7 min by the operating surgeon with the opening of sealed envelopes (groups 0, 3, and 7 min afterwards). Preoperative, 24, and 48 h postoperative hemoglobin (Hb) and electrolytes were collected. The primary endpoint of interest was the comparison of 48-h blood loss across study groups. Secondary endpoints included the percent drop in 24- and 48-h Hb, transfusion rates, and operation complications. This trial is registered at www.irct.ir with the following number: IRCT20190618043925N1 on 18 July 2019.

RESULTS

There was no statistically significant difference in study groups regarding stone mass, stone location, access location, and patients' age (all p > 0.05). The medians (IQR) of 48-h blood loss were 490 mL (105-916), 338 mL (160-933), and 413 mL (71-650) in groups of 0, 3, and 7 min. The percent drop in 24-h postoperative Hb relative to preoperative Hb were 11.5 ± 8.6% versus 9.2 ± 7.3% versus 9.3 ± 6.8% (p = 0.44) and relative values for the percent drop in 48-h Hb relative to preoperative Hb were 8.6 ± 8.7% versus 9.5 ± 9.9% versus 7.2 ± 9.6% (p = 0.63) in groups of 0, 3, and 7 min respectively. Transfusion was needed in four patients in group 0 min, five patients in group 3 min, and three patients in group 7 min.

CONCLUSIONS

The results of this study reveal that postoperative bimanual compression of abdomen-flank has no statistically significant influence on the control of bleeding after PCNL operations.

Does autotransfusion from a contaminated trauma laparotomy field increase the risk of complications?

BACKGROUND

Autotransfusion (AT) in trauma laparotomy is limited by concern that enteric contamination (EC) increases complications, including infections. Our goal was to determine if AT use increases complications in trauma patients undergoing laparotomy with EC.

METHODS

Trauma patients undergoing laparotomy from October 2011-November 2020 were reviewed. Patients were excluded if they did not receive blood in the operating room, did not have a full thickness hollow viscus injury, or died <24 h from admission. AT and non-AT patients were matched. Outcomes were compared.

RESULTS

185 patients were included, 60 received AT, and 46 pairs were matched. After matching, demographics were similar. No differences were noted in septic complications (33 vs 41%, p = 0.39), overall complications (59% vs 54%, p = 0.67), or mortality (13 vs 6%, p = 0.29).

CONCLUSIONS

AT use in contaminated trauma laparotomy fields was not associated with a higher rate of complications.

[Tranexamic acid for bleeding prophylaxis in orthopedic surgery and trauma-standard or customized therapy?]

The use of tranexamic acid (TXA) is established in the treatment of bleeding, especially of bleeding due to hyperfibrinolysis. In recent years the prophylactic use of TXA in trauma and orthopedic surgery has increased leading to open questions regarding potentially associated risks and a possible classification as off label use. The available literature provides a sound basis for the recommendation that TXA can be used in these indications provided that an individual risk assessment is done in patients with increased risks for thromboembolic complications. Although the prophylactic use of TXA in orthopedic surgery and trauma is not explicitly listed in the product characteristics, it should not be regarded as an off label use.

Optimal protamine dosing after cardiopulmonary bypass: The PRODOSE adaptive randomised controlled trial

BACKGROUND

The dose of protamine required following cardiopulmonary bypass (CPB) is often determined by the dose of heparin required pre-CPB, expressed as a fixed ratio. Dosing based on mathematical models of heparin clearance is postulated to improve protamine dosing precision and coagulation. We hypothesised that protamine dosing based on a 2-compartment model would improve thromboelastography (TEG) parameters and reduce the dose of protamine administered, relative to a fixed ratio.

METHODS AND FINDINGS

We undertook a 2-stage, adaptive randomised controlled trial, allocating 228 participants to receive protamine dosed according to a mathematical model of heparin clearance or a fixed ratio of 1 mg of protamine for every 100 IU of heparin required to establish anticoagulation pre-CPB. A planned, blinded interim analysis was undertaken after the recruitment of 50% of the study cohort. Following this, the randomisation ratio was adapted from 1:1 to 1:1.33 to increase recruitment to the superior arm while maintaining study power. At the conclusion of trial recruitment, we had randomised 121 patients to the intervention arm and 107 patients to the control arm. The primary endpoint was kaolin TEG r-time measured 3 minutes after protamine administration at the end of CPB. Secondary endpoints included ratio of kaolin TEG r-time pre-CPB to the same metric following protamine administration, requirement for allogeneic red cell transfusion, intercostal catheter drainage at 4 hours postoperatively, and the requirement for reoperation due to bleeding. The trial was listed on a clinical trial registry (ClinicalTrials.gov Identifier: NCT03532594). Participants were recruited between April 2018 and August 2019. Those in the intervention/model group had a shorter mean kaolin r-time (6.58 [SD 2.50] vs. 8.08 [SD 3.98] minutes; p = 0.0016) post-CPB. The post-protamine thromboelastogram of the model group was closer to pre-CPB parameters (median pre-CPB to post-protamine kaolin r-time ratio 0.96 [IQR 0.78-1.14] vs. 0.75 [IQR 0.57-0.99]; p < 0.001). We found no evidence of a difference in median mediastinal/pleural drainage at 4 hours postoperatively (140 [IQR 75-245] vs. 135 [IQR 94-222] mL; p = 0.85) or requirement (as a binary outcome) for packed red blood cell transfusion at 24 hours postoperatively (19 [15.8%] vs. 14 [13.1%] p = 0.69). Those in the model group had a lower median protamine dose (180 [IQR 160-210] vs. 280 [IQR 250-300] mg; p < 0.001). Important limitations of this study include an unblinded design and lack of generalisability to certain populations deliberately excluded from the study (specifically children, patients with a total body weight >120 kg, and patients requiring therapeutic hypothermia to <28°C).

CONCLUSIONS

Using a mathematical model to guide protamine dosing in patients following CPB improved TEG r-time and reduced the dose administered relative to a fixed ratio. No differences were detected in postoperative mediastinal/pleural drainage or red blood cell transfusion requirement in our cohort of low-risk patients.

TRIAL REGISTRATION

ClinicalTrials.gov Unique identifier NCT03532594.

Estimation of blood volume and blood loss in primary total hip and knee replacement: An analysis of formulae for perioperative calculations and their ability to predict length of stay and blood transfusion requirements

Introduction

Blood loss continues to be a common surgical risk in total hip (THR) and knee replacements (TKR). Accurate prediction of blood loss permits appropriate counselling of risks to patients, target optimisation and forecasting future transfusion requirements. We compared blood volume formulae of Moore and Nadler, and blood loss formulae of Liu, Mercuriali, Bourke, Ward, Gross, Lisander and Meunier, to assess associations between calculated values with length of stay and transfusion requirements and determine which are useful in contemporary practice.

Methods

We retrospectively studied patients undergoing primary THR and TKR. We collected data on patient demographics, surgical interventions, pre- and postoperative haemoglobin and haematocrit values, length of stay and blood transfusion requirements. Spearman correlation tests and least squares multiple linear regression were performed.

Results

149 THRs and 90 TKRs in 239 patients were analysed over four months. There was a very strong correlation between blood volume formulae. There were multiple very strong and strong associations between blood loss formulae. Bourke correlated significantly to length of stay, and Liu, Mercuriali, Lisander and Meunier correlated for incidence of transfusion.

Conclusion

Accurate estimation of perioperative blood loss is increasingly important as demand for joint replacement surgery increases in an ageing population. If the primary interest is the association of blood loss and length of stay, Bourke's formula should be preferred. If the primary interest is calculating risk of transfusion, the formulae of Liu or Meunier should be preferred. The formulae of Mercuriali and Lisander are becoming redundant in contemporary practice.

The visually estimated blood volume in scaled canisters based on a simulation study

BACKGROUND

The most common technique used worldwide to quantify blood loss during an operation is the visual assessment by the attending intervention team. In every operating room you will find scaled suction canisters that collect fluids from the surgical field. This scaling is commonly used by clinicians for visual assessment of intraoperative blood loss. While many studies have been conducted to quantify and improve the inaccuracy of the visual estimation method, research has focused on the estimation of blood volume in surgical drapes. The question whether and how scaling of canisters correlates with actual blood loss and how accurately clinicians estimate blood loss in scaled canisters has not been the focus of research to date.

METHODS

A simulation study with four "bleeding" scenarios was conducted using expired whole blood donations. After diluting the blood donations with full electrolyte solution, the sample blood loss volume (SBL) was transferred into suction canisters. The study participants then had to estimate the blood loss in all four scenarios. The difference to the reference blood loss (RBL) per scenario was analyzed.

RESULTS

Fifty-three anesthetists participated in the study. The median estimated blood loss was 500 ml (IQR 300/1150) compared to the RBL median of 281.5 ml (IQR 210.0/1022.0). Overestimations up to 1233 ml were detected. Underestimations were also observed in the range of 138 ml. The visual estimate for canisters correlated moderately with RBL (Spearman's rho: 0.818; p < 0.001). Results from univariate nonparametric confirmation statistics regarding visual estimation of canisters show that the deviation of the visual estimate of blood loss is significant (z = - 10.95, p < 0.001, n = 220). Participants' experience level had no significant influence on VEBL (p = 0.402).

CONCLUSION

The discrepancies between the visual estimate of canisters and the actual blood loss are enormous despite the given scales. Therefore, we do not recommend estimating the blood loss visually in scaled suction canisters. Colorimetric blood loss estimation could be a more accurate option.

Palatal pre-suturing for perioperative hemostasis at free gingival graft donor sites-A randomized controlled clinical trial

BACKGROUND

The palatal suture has been well known in literature as a method for palatal hemostasis but has not been validated for its efficacy. The aim of this parallel-arm randomized controlled clinical trial was to evaluate the efficacy of palatal pre-suturing using the greater palatine compression suture (GPCS) in reducing the perioperative hemorrhage associated with the palatal free gingival graft (FGG) procedure.

METHODS

Twenty-four patients requiring the FGG procedure for recession coverage or augmentation of keratinized tissue were recruited in the study and randomized to the GPCS group and the control group. The GPCS was placed using a previously described protocol by a single operator in all the participants in the GPCS group. Perioperative blood loss was estimated by weighing the gauze used to mop the palatal hemorrhage, before and after the procedure. The time required for the surgery was also recorded by an independent observer.

RESULTS

Significantly lesser blood loss was observed in the GPCS group (4.33 ± 0.89 g) as compared with the control group (8.91 ± 4.16 g). The difference in the time taken for the surgical procedure for the GPCS group (73.25 ± 22.35 minutes) was not significantly different from that required for the control group (76.08 ± 14.47 minutes).

CONCLUSION

This study demonstrates that pre-suturing of the palate using the GPCS is an effective technique to reduce the perioperative blood loss associated with the palatal FGG procedure.

Techniques for blood loss estimation in major non-cardiac surgery: a systematic review and meta-analysis

PURPOSE

Estimated blood loss (EBL) is an important tool in clinical decision-making and surgical outcomes research. It guides perioperative transfusion practice and serves as a key predictor of short-term perioperative risks and long-term oncologic outcomes. Despite its widespread clinical and research use, there is no gold standard for blood loss estimation. We sought to systematically review and compare techniques for intraoperative blood loss estimation in major non-cardiac surgery with the objective of informing clinical estimation and research standards.

SOURCE

A structured search strategy was applied to Ovid Medline, Embase, and Cochrane Library databases from inception to March 2020, to identify studies comparing methods of intraoperative blood loss in adult patients undergoing major non-cardiac surgery. We summarized agreement between groups of pairwise comparisons as visual estimation vs formula estimation, visual estimation vs other, and formula estimation vs other. For each of these comparisons, we described tendencies for higher or lower EBL values, consistency of findings, pooled mean differences, standard deviations, and confidence intervals.

PRINCIPLE FINDINGS

We included 26 studies involving 3,297 patients in this review. We found that visual estimation is the most frequently studied technique. In addition, visual techniques tended to provide lower EBL values than formula-based estimation or other techniques, though this effect was not statistically significant in pooled analyses likely due to sample size limitations. When accounting for the contextual mean blood loss, similar case-to-case variation exists for all estimation techniques.

CONCLUSIONS

We found that significant case-by-case variation exists for all methods of blood loss evaluation and that there is significant disagreement between techniques. Given the importance placed on EBL, particularly for perioperative prognostication models, clinicians should consider the universal adoption of a practical and reproducible method for blood loss evaluation.

TRIAL REGISTRATION

PROSPERO (CRD42015029439); registered: 18 November 2015.PROSPERO (CRD42015029439); registered: 18 November 2015.

Estimating Surgical Blood Loss Volume Using Continuously Monitored Vital Signs

Background: There are currently no effective and accurate blood loss volume (BLV) estimation methods that can be implemented in operating rooms. To improve the accuracy and reliability of BLV estimation and facilitate clinical implementation, we propose a novel estimation method using continuously monitored photoplethysmography (PPG) and invasive arterial blood pressure (ABP). Methods: Forty anesthetized York Pigs (31.82 ± 3.52 kg) underwent a controlled hemorrhage at 20 mL/min until shock development was included. Machine-learning-based BLV estimation models were proposed and tested on normalized features derived by vital signs. Results: The results showed that the mean ± standard deviation (SD) for estimating BLV against the reference BLV of our proposed random-forest-derived BLV estimation models using PPG and ABP features, as well as the combination of ABP and PPG features, were 11.9 ± 156.2, 6.5 ± 161.5, and 7.0 ± 139.4 mL, respectively. Compared with traditional hematocrit computation formulas (estimation error: 102.1 ± 313.5 mL), our proposed models outperformed by nearly 200 mL in SD. Conclusion: This is the first attempt at predicting quantitative BLV from noninvasive measurements. Normalized PPG features are superior to ABP in accurately estimating early-stage BLV, and normalized invasive ABP features could enhance model performance in the event of a massive BLV.

Do we visually estimate intra-operative blood loss better with white or green sponges and is the deviation from the real blood loss clinically acceptable? Results from a simulated scenario study

BACKGROUND

The intraoperative blood loss is estimated daily in the operating room and is mainly done by visual techniques. Due to local standards, the surgical sponge colours can vary (e.g. white in US, green in Germany). The influence of sponge colour on accuracy of estimation has not been in the focus of research yet.

MATERIAL AND METHODS

A blood loss simulation study containing four "bleeding" scenarios each per sponge colour were created by using expired whole blood donation samples. The blood donations were applied to white and green surgical sponges after dilution with full electrolyte solution. Study participants had to estimate the absorbed blood loss in sponges in all scenarios. The difference to the reference blood loss was analysed. Multivariate linear regression analysis was performed to investigate other influence factors such as staff experience and sponge colour.

RESULTS

A total of 53 anaesthesists participated in the study. Visual estimation correlated moderately with reference blood loss in white (Spearman's rho: 0.521; p = 3.748*10-16) and green sponges (Spearman's rho: 0.452; p = 4.683*10-12). The median visually estimated blood loss was higher in white sponges (250ml IRQ 150-412.5ml) than in green sponges (150ml IQR 100-300ml), compared to reference blood loss (103ml IQR 86-162.8). For both colour types of sponges, major under- and overestimation was observed. The multivariate statistics demonstrates that fabric colours have a significant influence on estimation (p = 3.04*10-10), as well as clinician's qualification level (p = 2.20*10-10, p = 1.54*10-08) and amount of RBL to be estimated (p < 2*10-16).

CONCLUSION

The deviation of correct blood loss estimation was smaller with white surgical sponges compared to green sponges. In general, deviations were so severe for both types of sponges, that it appears to be advisable to refrain from visually estimating blood loss whenever possible and instead to use other techniques such as e.g. colorimetric estimation.

Comparison of common perioperative blood loss estimation techniques: a systematic review and meta-analysis

Estimating intraoperative blood loss is one of the daily challenges for clinicians. Despite the knowledge of the inaccuracy of visual estimation by anaesthetists and surgeons, this is still the mainstay to estimate surgical blood loss. This review aims at highlighting the strengths and weaknesses of currently used measurement methods. A systematic review of studies on estimation of blood loss was carried out. Studies were included investigating the accuracy of techniques for quantifying blood loss in vivo and in vitro. We excluded nonhuman trials and studies using only monitoring parameters to estimate blood loss. A meta-analysis was performed to evaluate systematic measurement errors of the different methods. Only studies that were compared with a validated reference e.g. Haemoglobin extraction assay were included. 90 studies met the inclusion criteria for systematic review and were analyzed. Six studies were included in the meta-analysis, as only these were conducted with a validated reference. The mixed effect meta-analysis showed the highest correlation to the reference for colorimetric methods (0.93 95% CI 0.91–0.96), followed by gravimetric (0.77 95% CI 0.61–0.93) and finally visual methods (0.61 95% CI 0.40–0.82). The bias for estimated blood loss (ml) was lowest for colorimetric methods (57.59 95% CI 23.88–91.3) compared to the reference, followed by gravimetric (326.36 95% CI 201.65–450.86) and visual methods (456.51 95% CI 395.19–517.83). Of the many studies included, only a few were compared with a validated reference. The majority of the studies chose known imprecise procedures as the method of comparison. Colorimetric methods offer the highest degree of accuracy in blood loss estimation. Systems that use colorimetric techniques have a significant advantage in the real-time assessment of blood loss.

Perioperative blood loss: estimation of blood volume loss or haemoglobin mass loss?

BACKGROUND

Perioperative blood loss is an essential parameter in research into Patient Blood Management. However, currently there is no "gold standard" method to quantify it. Direct measurements of blood loss are considered unreliable methods, and the formulae to estimate it have proven to be significantly inaccurate. Given the need for better research tools, this study evaluated an estimation of haemoglobin mass loss as an alternative approach to estimate perioperative blood loss, and compared it to estimations based on blood volume loss.

MATERIAL AND METHODS

We studied one hundred consecutive patients undergoing urological laparoscopic surgery. Both haemoglobin mass loss and blood volume loss were directly measured during surgery, under highly controlled conditions for a reliable direct measurement of blood loss. Three formulae were studied: 1) a haemoglobin mass loss formula, which estimated blood loss in terms of haemoglobin mass loss, 2) the López-Picado's formula and 3) an empirical volume formula that estimated blood loss in terms of blood volume loss. The empirical volume formula was developed within the study with the aim of providing the best possible estimation of blood volume loss in the studied population. The formulae were evaluated and compared by assessing their agreements with their respective direct measurements of blood loss.

RESULTS

The haemoglobin mass loss formula met the predefined agreement criterion of ±71 g, with 95% limits of agreement ranging from 0.6 to 44.1 g and a moderate overestimation of 22.4. In comparison to both blood volume loss formulae, the haemoglobin mass loss formula was superior in every agreement parameter evaluated.

DISCUSSION

In this study, the estimation of haemoglobin mass loss was found to be a more accurate method to estimate perioperative blood loss. This estimation method could be a robust research tool, although more studies are needed to establish its reliability.