Variability in transfusion practice for coronary artery bypass surgery persists despite national consensus guidelines: a 24-institution study. Institutions of the Multicenter Study of Perioperative Ischemia Research Group

Central/mixed venous oxygen saturation and lactate levels might be of limited use as physiologic transfusion triggers in cardiac surgery: Results of a retrospective analysis

BACKGROUND

Current guidelines differ in their recommendations regarding the use of physiologic transfusion triggers to guide transfusion practice. Data on the interaction between haemoglobin (Hb) and physiologic transfusion triggers, or their response to packed red blood cell (pRBC) transfusions are limited.

OBJECTIVES

This study aimed to evaluate the interactions between Hb, mixed/central venous oxygen saturation (SvO 2 ) and lactate levels as well as their changes (ΔSvO 2 , Δlactate) in response to pRBC transfusion in cardiac surgery patients.

DESIGN

Retrospective exploratory data analysis.

SETTING

A 22-bed intensive care unit (ICU) at a single tertiary academic centre and university hospital in Austria.

PATIENTS

Adult (age ≥ 18 years) patients who underwent cardiac surgery.

MAIN OUTCOME MEASURES

Pearson correlation coefficients ( r ) and coefficients of determination ( r2 ) between Hb, mixed/central venous oxygen saturation (SvO 2 ), and lactate levels. Pearson correlation coefficients ( r ) and coefficients of determination ( r2 ) between ΔSvO 2 , Δlactate and pretransfusion Hb.

RESULTS

A total of 5025 cardiac surgery patients, in whom 20 542 blood gas analyses were performed, were included in the final analysis. Correlations between Hb levels and SvO 2 ( r2  = 0.026, P  < 0.001) and between Hb and lactate levels ( r2  = 0.001, P  < 0.001) were statistically significant but weak overall. No correlations were found between ΔSvO 2 ( r2  = 0.002, P  = 0.13) or Δlactate ( r2  = 0.003, P  = 0.087) and pretransfusion Hb levels.

CONCLUSIONS

Hb, SvO 2 and lactate levels were only weakly correlated with each other, and changes in SvO 2 and lactate levels in response to pRBC transfusion did not correlate with pretransfusion Hb. Our findings question the usefulness of SvO 2 and lactate levels as physiologic transfusion triggers to guide transfusion practice in cardiac surgery patients.

TRIAL REGISTRATION

Johannes Kepler University Ethics Committee Study Reference Number 1063/2023.

Comparison of Perioperative Outcomes for Transfusion of Hemoconcentrated Bypass Versus Cell Saver Blood in Cardiac Surgical Patients

OBJECTIVE

Hemoconcentration and cell saver use are blood conservation techniques that are often used in cardiac surgery to salvage the patient's own blood to reduce autologous transfusion. The purpose of this study was to examine the perioperative outcomes including transfusion rates in cardiac surgical patients receiving hemoconcentrated blood versus cell saver blood via retrospective chart review. We hypothesized that hemoconcentration would have better patient outcomes, including reduced transfusion rates, compared to only cell salvage technique.

DESIGN

Single-center, retrospective chart review case-control study SETTING: Cardiac operating room of a tertiary care center PARTICIPANTS: Patients over 18 years old who underwent elective open-heart surgery with cardiopulmonary bypass between January 2015 to January 2018. Patients for emergencies, off-pump cases, transplants, and reoperations and with a need for second bypass were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The specific outcomes assessed include perioperative transfusion of packed red blood cells and blood products, intensive care unit (ICU) length of stay, hospital length of stay, and surgical site infections. Patient characteristics such as ejection fraction and comorbidities, pulmonary hypertension, atrial fibrillation history, and coagulation dysfunction were also analyzed. Propensity score matching was done to balance the covariates between the groups. The differences for each outcome outlined above were calculated. Of the 744 observations, 735 were used for analysis after propensity matching. Postoperative ICU red blood cell transfusions recorded a mean difference of -0.37 (95% CI: -0.78, 0.04). Postoperative ICU platelets and fresh frozen plasma recorded mean differences of -0.01 (95% CI: -0.11, 0.09) and -0.08 (95% CI: -0.19, 0.03), respectively. There were no significant differences in outcomes in bivariate- and covariate-adjusted models.

CONCLUSIONS

There is no significant difference in postoperative blood transfusion rates in hemoconcentrated versus cell saver blood usage in cardiac surgery patients. Further studies are needed to analyze specific quantities and ratios of hemoconcentrated and cell saver blood used in these patients for a more clinically relevant analysis. This would allow incorporation of hemoconcentration and cell saver techniques into better blood conservation processes and guide overall transfusion strategies to reduce transfusion rates of blood and blood products in cardiac surgical patients.

What drives variability in postoperative cardiac surgery transfusion rates?

OBJECTIVE

Wide interhospital variation exists in cardiac surgical postoperative transfusion rates. We aimed to compare transfusion rates at 2 hospitals and identify the institutional practice factors, unrelated to patient or operative characteristics, associated with postoperative transfusion rates.

METHODS

Records for adult patients undergoing routine cardiac surgery at 2 hospitals (H and L) from February 2020 to August 2022 were analyzed. Patient and operative characteristics, preoperative and intensive care unit hemoglobin values, and postoperative transfusion rates were compared. Transfusion indication was recorded prospectively. Propensity matching was completed to assess comparability of patient populations.

RESULTS

After propensity matching patients at H and L on age, procedure type, predicted morbidity or mortality, crossclamp time, preoperative hypertension, preoperative heart failure, and preoperative stroke, 2111 patients remained, with similar characteristics except hypertension. Matched results showed no significant differences in mortality, reoperation, or other major outcomes. Hospital H transfused 36% of patients (mean postoperative hemoglobin [Hb] 10.5) with 1483 units of packed red blood cells whereas hospital L transfused 12% of patients (mean postoperative Hb 9.4) with 198 units of packed red blood cells (P < .001). For all patients with a Hb >7.5, hospital H versus L transfused 27% versus 0.9% (P < .001). Hospital L's sole transfusion indication for pretransfusion hemoglobin trigger >7.5 was bleeding versus hospital H, which had multiple indications. When Hb concentration alone was the indication for transfusion, the threshold at hospital H was <7.5 g/dL versus <6 g/dL at hospital L.

CONCLUSIONS

Variation in transfusion rates between hospitals H and L resulted from strict adherence at hospital L to a transfusion trigger of <6 g/dL with narrow indications for transfusions above that Hb concentration.

Quality of registration and adherence to guidelines for blood management in CABG surgeries: a case study

In many hospitals, patients undergoing cardiac surgery receive a higher amount of blood products transfusions compared to other disciplines. Blood transfusion comes with risks and drawbacks, such as increased morbidity and mortality across different patient groups, and specifically patients undergoing cardiac surgery, and high costs. Patient Blood Management (PBM) practices focus on the application of evidence based medical and surgical concepts in order to preserve the patient's own blood. Unfortunately, studies suggest that only a small fraction of published guidelines are implemented and followed into daily clinical practicedue to clear guidance, concerns about risks, and lack of knowledge, interdisciplinary commitment or resources. The widespread adoption of electronic health record (EHR) offers the opportunity to improve clinical outcomes through use of decision support system to guide the healthcare providers through best practices and guidelines. Decision support systems can be active, data-based, patient-specific and act timely, and can be more useful that adding new clinical practice guidelines. This case study quantifies the quality of the data registration and provides the results for adherence to perioperative PBM guidelines for coronary artery bypass grafting (CABG) procedures during a three-year period (2018 to 2020), in the St. Antonius hospital, a single heart center that performs over 10% of the total number of heart operations in the Netherlands. With this case study we identify some of the possible improvement factors for PBM in our center. We also quantify the impact of the quality of the registration in the EHR on the analysis results and on possible implementation of decision support systems.

Reducing postoperative blood product usage and costs in cardiothoracic surgery: the implementation of a multispecialty perioperative care model incorporating a haemostasis checklist

Transfusion of blood products following cardiothoracic surgery represents a significant proportion of national blood product usage, has significant cost implications and is associated with increased 30-day mortality. Following identification of an increase in blood product use, we implemented a healthcare improvement initiative using a perioperative care model and establishment of a new multispecialty cardiothoracic surgery taskforce to further define and tackle the problem. The initiative incorporated a bundle of preoperative identification of high-risk patients, an intraoperative haemostasis checklist, a programme of unit education focussing on bleeding postbypass and use of thromboelastography and introduction of postoperative protocols for identification and escalation of bleeding. Following intervention, a 60% reduction in blood product use within the first 12 hours of cardiopulmonary bypass was observed. Red cell, cryoprecipitate and fresh frozen plasma usage were particularly reduced with 57%, 47% and 72% reductions, respectively, following intervention and similar results were maintained on repeat audit 1-year postintervention, with on average 84 fewer blood products used per 100 patients. This resulted in an estimated cost saving of AU$36 928 per 100 patients. This quality initiative was successful in overcoming traditional silos of care and describes how quality improvement methodology utilising a multispecialty and multidisciplinary approach can be applied to solve complex issues in the perioperative period. Here, we demonstrate a reproducible and sustainable model for reducing blood product use in the cardiothoracic perioperative population.

Advancing the Treatment Paradigm for Multivessel Coronary Artery Disease: Hybrid Coronary Revascularization

OBJECTIVE

The purpose of this study was to examine the longitudinal safety and efficacy of hybrid coronary revascularization (HCR) in a large cohort of patients with multivessel coronary artery disease (CAD).

METHODS

From 2009 to 2020, 561 consecutive patients (median age 64.0 years, predicted risk of mortality 1.3% ± 1.8%, 403 with 2-vessel disease and 158 with 3-vessel disease) underwent a planned HCR procedure with a robot-assisted off-pump left internal mammary artery to left anterior descending (LIMA-LAD) coronary artery bypass graft (CABG) combined with percutaneous coronary intervention (PCI) of non-LAD vessels. Multivariable regression analysis was used to identify risk factors for short-term and longer-term outcomes.

RESULTS

Operative mortality and stroke occurred in 4 (0.7%) and 5 patients (0.9%), respectively. Postoperative angiography revealed LIMA patency in 415 of 425 patients (98%). Median follow-up was 4.5 years and was 93% complete. Repeat revascularization occurred in 44 patients (8%) at a median of 2.7 years. Freedom from repeat revascularization and survival at 5 years was similar between patients with 2-vessel and 3-vessel disease (P = 0.73 and P = 0.19, respectively). Completely revascularized patients had 5-year survival of 91% versus 64% for incompletely revascularized patients (hazard ratio = 3.8, P < 0.001). Age (P = 0.03), renal failure (P < 0.001), and history of myocardial infarction (P = 0.01) were risk factors for late adverse events.

CONCLUSIONS

HCR is a safe and effective minimally invasive alternative to conventional CABG or multivessel PCI with a low incidence of late repeat revascularization and mortality. HCR can be safely applied to carefully selected patients with either 2-vessel or 3-vessel CAD; however, incomplete revascularization may result in lower long-term survival.

Biomarkers of inflammation and coagulation after minimally invasive mitral valve surgery: a prospective comparison to conventional surgery

OBJECTIVES

Minimally invasive cardiac surgery techniques are increasingly used but have longer cardiopulmonary bypass time, which may increase inflammatory response and negatively affect coagulation. Our aim was to compare biomarkers of inflammation and coagulation as well as transfusion rates after minimally invasive mitral valve repair and mitral valve surgery using conventional sternotomy.

DESIGN

A prospective non-randomized study was performed enrolling 71 patients undergoing mitral valve surgery (35 right mini-thoracotomy and 36 conventional sternotomy procedures). Blood samples were collected pre- and postoperatively to assess inflammatory response. Thromboelastometry (ROTEM) was performed to assess coagulation, and transfusion rates were monitored.

RESULTS

The minimally invasive group had longer cardiopulmonary bypass times compared to the sternotomy group: 127 min ([115-146] vs 79 min [65-112], p < 0.001) and were cooled to a lower temperature during cardiopulmonary bypass, 34 °C vs 36 °C (p = 0.04). IL-6 was lower in the minimally invasive group compared to the conventional sternotomy group when measured at the end of the surgical procedure, (38 [23-69] vs 61[41-139], p = 0.008), but no differences were found at postoperative day 1 or postoperative day 3. The transfusion rate was lower in the minimally invasive group (14%) compared to full sternotomy (35%, p = 0.04) and the chest tube output was reduced, (395 ml [190-705] vs 570 ml [400-1040], p = 0.04).

CONCLUSIONS

Our data showed that despite the longer use of extra corporal circulation during surgery, minimally invasive mitral valve repair is associated with reduced inflammatory response, lower rates of transfusion, and reduced chest tube output.

Evaluation of Red Blood Cell Biochemical Markers and Coagulation Profiles Following Cell Salvage in Cardiac Surgery: A Systematic Review and Meta-Analysis

Background: Individuals undergoing cardiac surgery face an increased risk of bleeding, as well as alterations in biochemical and coagulation patterns. Therefore, assessing the effectiveness of systems such as Cell Salvage is necessary to prevent potential surgical complications. Objective: To evaluate the efficacy of Cell Salvage in relation to the biochemical parameters of the red blood series and coagulation, as well as the risk of hemorrhage. Methods: A systematic review, accompanied by a meta-analysis, was executed via an extensive literature exploration encompassing Medline, CINAHL, Scopus, Web of Science, and the Cochrane Library. The inclusion criteria comprised studies in English or Spanish, without year restrictions, conducted in adults and with a randomized controlled trial design. Results: Twenty-six studies were included in the systematic review, involving a total of 2850 patients (experimental group = 1415; control group = 1435). Cell Salvage did not demonstrate superior outcomes compared to allogeneic transfusions in the management of post-surgical hemorrhage, as well as in total blood loss, platelet count, fresh frozen plasma, and fibrinogen. However, Cell Salvage showed a greater effectiveness for hemoglobin (moderate evidence), hematocrit (low evidence), post intervention D-dimer (low evidence), and some coagulation-related parameters (low evidence) compared to allogeneic transfusions. Finally, better results were found in the control group for INR parameters. Conclusions: The use of the Cell Salvage system holds high potential to improve the postoperative levels of biochemical and coagulation parameters. However, the results do not provide definitive evidence regarding its effectiveness for hemorrhage control, platelet count, fresh frozen plasma, and fibrinogen. Therefore, it is recommended to increase the number of studies to assess the impact of the Cell Salvage system on improvements in the red blood cell count and patient coagulation patterns. In addition, protocols should be homogenized, and variables such as the sex of the participants should be taken into account.

A precise blood transfusion evaluation model for aortic surgery: a single-center retrospective study

Cardiac aortic surgery is an extremely complicated procedure that often requires large volume blood transfusions during the operation. Currently, it is not possible to accurately estimate the intraoperative blood transfusion volume before surgery. Therefore, in this study, to determine the clinically precise usage of blood for intraoperative blood transfusions during aortic surgery, we established a predictive model based on machine learning algorithms. We performed a retrospective analysis on 4,285 patients who received aortic surgery in Beijing Anzhen Hospital between January 2018 and September 2022. Ultimately, 3,654 patients were included in the study, including 2,557 in the training set and 1,097 in the testing set. By utilizing 13 current mainstream models and a large-scale cardiac aortic surgery dataset, we built a novel machine learning model for accurately predicting intraoperative red blood cell transfusion volume. Based on the transfusion-related risk factors that the model identified, we also established the relevant variables that affected the results. The results revealed that decision tree models were the most suitable for predicting the blood transfusion volume during aortic surgery. In particular, the mean absolute error for the best-performing extremely randomized forest model was 1.17 U, while the R2 value was 0.50. Further exploration into intraoperative blood transfusion during aortic surgery identified erythrocytes, estimated operation duration, body weight, sex, red blood cell count, and D-dimer as the six most significant risk factors. These factors were subsequently analyzed for their influence on intraoperative blood transfusion volume in relevant patients, as well as the protective threshold for prediction. The novel intraoperative blood transfusion prediction model for cardiac aorta surgery in this study effectively assists clinicians in accurately calculating blood transfusion volumes and achieving effective utilization of blood resources. Furthermore, we utilize interpretability technology to reveal the influence of critical risk factors on intraoperative blood transfusion volume, which provides an important reference for physicians to provide timely and effective interventions. It also enables personalized and precise intraoperative blood usage.

Red Blood Cell Transfusion Prior to Lung Transplantation: Impact on Patient Outcomes

There is an established association between red blood cell (RBC) transfusion and increased mortality and morbidity in cardiac surgery; however, there is little data demonstrating the influence of blood transfusion while awaiting lung transplantation. Therefore, our study compared the impact of pretransplant RBC transfusion on patient survival and post-transplantation adverse events. Adult lung transplant patient data were extracted retrospectively using the United Network for Organ Sharing thoracic database. Patients were stratified into two groups based on pretransplant transfusion status. In total, 28,217 patients were analyzed in our study (transfused: n = 1,415 and not transfused: n = 26,802). There was an increasing trend in pretransplant transfusion rates from 2006 to 2020. Transfused patients had a higher incidence of adverse events post-transplantation, including dialysis, stroke, and acute organ rejection before discharge. Multivariable survival analysis found an increased mortality risk in patients who required pretransplant transfusion(s) compared to those who did not have a transfusion (hazard ratio [HR]: 1.27; 95% confidence interval [CI]: 1.17-1.41; p < 0.001). There was no significant difference in bronchiolitis obliterans syndrome development between groups (HR: 0.92; 95% CI: 0.82-1.04; p = 0.185). To conclude, our study provides data to suggest that RBC transfusion(s) before lung transplantation are associated with increased patient morbidity and mortality, but have no association with chronic graft rejection development.

Association of blood donor's biological characteristics on outcomes of cardiac surgery patients receiving red blood cells transfusion

OBJECTIVES

This study aimed to assess the association of blood donor variables on the outcome of patients undergoing cardiac surgery.

STUDY DESIGN AND METHODS

A retrospective observational study was conducted on patients who had cardiac surgery between January 2018 and December 2020. Blood donor characteristics such as age (≤ or >30 years), sex, and body mass index (BMI) (≤ or >25 kg/m²) were analyzed for association with patient outcomes (length of hospital stay (LOS), mortality, and readmission). Sex matching was done as fully match, fully mismatch, and partial mismatch. Cox regression and Linear regression models were used to study the association with mortality and readmission, and LOS.

RESULTS

During the study period, 5788 patients had cardiac surgery; receiving a total of 20,348 red cell units. Of which, 522 (9%) died, 531 (9.2%) re-admitted and median LOS was 11 days (IQR 7-18). BMI >25 kg/m² (β, 2.96; p = 0.000), female to male transfusion (partial mismatch: β, 4.42; p = 0.001; fully mismatch: β, 9.0; p = 0.02) negatively affected LOS. BMI >25 kg/m² (HR, 2.07; p = 0.00) and partial mismatch transfusion to male patients (HR, 1.60; p = 0.01) increased mortality. Fully mismatch transfusion to female patients (HR, 1.24; p = 0.01) and partial mismatch to male patients (HR, 1.86; p = 0.01) increased readmission. No association of donor age on patient outcome was observed.

DISCUSSION

Blood donor sex, and BMI can influence mortality and LOS in cardiac surgery patients. The use of computer tools to match the patient's and donor's characteristics can assist to eliminate these types of adverse consequences.

Morbidity and Mortality associated with Blood Transfusions in Elective Adult Cardiac Surgery

OBJECTIVES

Perioperative transfusion thresholds have garnered increasing scrutiny as restrictive strategies have been shown to be noninferior. The study authors used data from a statewide academic collaborative to test the association between transfusion and 30-day mortality.

DESIGN

All adult patients undergoing coronary artery bypass grafting (CABG) and/or valve surgeries between 2013 and 2019 in the authors' Academic Cardiac Surgery Consortium were examined. The relationship between the number of overall packed red blood cell (pRBC) and coagulation product (CP) (fresh frozen plasma, cryoprecipitate, platelets) transfusions on 30-day mortality was evaluated. Multivariate regression was used to evaluate predictors of transfusion and study endpoints. Machine learning (ML) models also were developed to predict 30-day mortality and rank transfusion-related features by relative importance.

SETTING

At an Academic Cardiac Surgery Consortium of 5 institutions.

PARTICIPANTS

Patients ≥18 years old undergoing CABG and/or valve surgeries.

MEASUREMENTS AND MAIN RESULTS

Of the 7,762 patients (median hematocrit [HCT] 39%, IQR 35%-43%) who were included in the final study cohort, >40% were transfused at least 1 unit of pRBC or CP. In adjusted analyses, higher preoperative HCT was associated with reduced odds of mortality (adjusted odds ratio [aOR] 0.95, 95% CI 0.92-0.98), renal failure (aOR 0.95, 95% CI 0.92-0.98), and prolonged mechanical ventilation (aOR 0.97, 95% CI 0.95-0.99). In contrast, perioperative transfusions were associated with increased 30-day mortality after adjustment for preoperative HCT and other baseline features. The ML models were able to predict 30-day mortality with an area under the curve of 0.814-to-0.850, with perioperative transfusions displaying the highest feature importance.

CONCLUSIONS

The present analysis found increasing HCT to be associated with a lower incidence of mortality. The study authors also found a direct dose-response association between transfusions and all study endpoints examined.

Cardiac Surgery and Blood-Saving Techniques: An Update

Cardiac surgery is typically attributed with a significant risk of intraoperative blood loss and allogeneic blood transfusions. Intraoperative blood loss, allogenic blood transfusions, high dose anticoagulation requirement, and interactions with cardiopulmonary bypass (CPB) have all been linked to cardiac surgeries. To reduce unnecessary transfusions and their negative effects, it is recommended to follow evidence-based multidisciplinary strategies, which are collectively termed patient blood management (PBM). This review highlights the most recent blood conservation strategies in adult cardiac surgery, which can be employed pre-operatively, intra-operatively, and postoperatively, to enhance red cell mass and attenuate the utilization of packed red blood cells (PRBCs) and other blood products.

Transfusion in Elective Proximal Aortic Reconstruction: Where Do We Currently Stand?

Aortic procedures are associated with higher risks of bleeding, yet data regarding perioperative transfusion in this patient population are lacking. We evaluated transfusion patterns in patients undergoing proximal aortic surgery to provide a benchmark against which future standards can be assessed. Between June 2014 and July 2017, 247 patients underwent elective aortic reconstruction for aneurysm. Patients with acute aortic syndrome, endocarditis, and/or prior cardiac surgery were excluded. Transfusion data were analyzed by type of operation: ascending aorta replacement ± aortic valve procedure (group 1, n  = 122, 49.4%); aortic root replacement with a composite valve-graft conduit ± ascending aorta replacement (group 2, n  = 93, 37.7%); valve-sparing aortic root replacement (VSARR) ± ascending aorta replacement (group 3, n  = 32, 13.0%). Thirty-day mortality for the entire cohort was 2.02% (5 deaths). Overall, 75 patients (30.4%) did not require any transfusion of blood or other products. Patients in groups 1 and 3 were significantly more likely to avoid transfusion than those in group 2. Mean transfusion volume for any individual patient was modest; those who underwent VSARR (group 3) required less intraoperative red blood cells (RBC) than others. Intraoperative transfusion of RBC was independently associated with an increased risk of death at 30 days. Elective proximal aortic reconstruction can be performed without the need for excessive utilization of blood products. Composite root replacement is associated with a greater need for transfusion than either VSARR or isolated replacement of the ascending aorta.

Surgical volume reduction and the announcement of triage during the 1st wave of the COVID-19 pandemic in Japan: a cohort study using an interrupted time series analysis

Purpose

The coronavirus disease (COVID-19) pandemic has caused unprecedented challenges for surgical staffs to minimize exposure to COVID-19 or save medical resources without harmful patient outcomes, in accordance with the statement of each surgical society. No research has empirically validated declines in surgical volume in Japan, based on the usage of surgical triage. We aimed to identify whether the announcement of surgical priorities by each Japanese surgical society may have affected the surgical volume decline during the 1st wave of this pandemic.

Methods

We extracted 490,719 available cases of patients aged > 15 years who underwent elective major surgeries between July 1, 2018, and June 30, 2020. After the categorization of surgical specialities, we calculated descriptive statistics to compare the year-over-year trend and conducted an interrupted time series analysis to validate the decline of each surgical procedure.

Results

Monthly surgical cases of eight surgical specialities, especially ophthalmology and ear/nose/throat surgeries, decreased from April 2020 and reached a minimum in May 2020. An interrupted time series analysis showed no significant trends in oncological and critical surgeries.

Conclusion

Non-critical surgeries showed obvious and statistically significant declines in case volume during the 1st wave of the COVID-19 pandemic according to the statement of each surgical society in Japan.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00595-021-02286-6.

Machine learning models to predict red blood cell transfusion in patients undergoing mitral valve surgery

Background

Red blood cell (RBC) transfusion therapy has been widely used in surgery, and has yielded excellent treatment outcomes. However, in some instances, the demand for RBC transfusion is assessed by doctors based on their experience. In this study, we use machine learning models to predict the need for RBC transfusion during mitral valve surgery to guide the surgeon's assessment of the patient's need for intraoperative blood transfusion.

Methods

We retrospectively reviewed 698 cases of isolated mitral valve surgery with and without combined tricuspid valve operation. Seventy percent of the database was used as the training set and the remainder as the testing set for 13 machine learning algorithms to build a model to predict the need for intraoperative RBC transfusion. According to the characteristic value of model mining, we analyzed the risk-related factors to determine the main effects of variables influencing the outcome.

Results

A total of 166 patients of the cases considered had undergone intraoperative RBC transfusion (24.52%). Of the 13 machine learning algorithms, CatBoost delivered the best performance, with an AUC of 0.888 (95% CI: 0.845-0.909) in testing set. Further analysis using the CatBoost model revealed that hematocrit (<37.81%), age (>64 y), body weight (<59.92 kg), body mass index (BMI) (<22.56 kg/m²), hemoglobin (<122.6 g/L), type of surgery (median thoracotomy surgery), height (<160.61 cm), platelet (>194.12×10⁹/L), RBC (<4.08×10¹²/L), and gender (female) were the main risk-related factors for RBC transfusion. A total of 204 patients were tested, 177 of whom were predicted accurately (86.8%).

Conclusions

Machine learning models can be used to accurately predict the outcomes of RBC transfusion, and should be used to guide surgeons in clinical practice.

Efficacy, Safety, and Strategies for Recombinant-Activated Factor VII in Cardiac Surgical Bleeding: A Narrative Review

As perioperative bleeding continues to be a major source of morbidity and mortality in cardiac surgery, the search continues for an ideal hemostatic agent for use in this patient population. Transfusion of blood products has been associated both with increased costs and risks, such as infection, prolonged mechanical ventilation, increased length of stay, and decreased survival. Recombinant-activated factor VII (rFVIIa) first was approved for the US market in 1999 and since that time has been used in a variety of clinical settings. This review summarizes the existing literature pertaining to perioperative rFVIIa, in addition to society recommendations and current guidelines regarding its use in cardiac surgery.

Restrictive Transfusion Strategy after Cardiac Surgery

BACKGROUND

Recent guidelines on transfusion in cardiac surgery suggest that hemoglobin might not be the only criterion to trigger transfusion. Central venous oxygen saturation (Svo2), which is related to the balance between tissue oxygen delivery and consumption, may help the decision process of transfusion. We designed a randomized study to test whether central Svo2-guided transfusion could reduce transfusion incidence after cardiac surgery.

METHODS

This single center, single-blinded, randomized controlled trial was conducted on adult patients after cardiac surgery in the intensive care unit (ICU) of a tertiary university hospital. Patients were screened preoperatively and were assigned randomly to two study groups (control or Svo2) if they developed anemia (hemoglobin less than 9 g/dl), without active bleeding, during their ICU stay. Patients were transfused at each anemia episode during their ICU stay except the Svo2 patients who were transfused only if the pretransfusion central Svo2 was less than or equal to 65%. The primary outcome was the proportion of patients transfused in the ICU. The main secondary endpoints were (1) number of erythrocyte units transfused in the ICU and at study discharge, and (2) the proportion of patients transfused at study discharge.

RESULTS

Among 484 screened patients, 100 were randomized, with 50 in each group. All control patients were transfused in the ICU with a total of 94 transfused erythrocyte units. In the Svo2 group, 34 (68%) patients were transfused (odds ratio, 0.031 [95% CI, 0 to 0.153]; P < 0.001 vs. controls), with a total of 65 erythrocyte units. At study discharge, eight patients of the Svo2 group remained nontransfused and the cumulative count of erythrocyte units was 96 in the Svo2 group and 126 in the control group.

CONCLUSIONS

A restrictive transfusion strategy adjusted with central Svo2 may allow a significant reduction in the incidence of transfusion.

EDITOR’S PERSPECTIVE

Intra-operative autologous blood donation for cardiovascular surgeries in Japan: A retrospective cohort study

Intra-operative autologous blood donation is a blood conservation technique with limited evidence. We evaluated the association between intra-operative autologous blood donation and decrease in peri-operative transfusion in cardiovascular surgery based on evidence from a Japanese administrative database. We extracted the data of patients who had undergone cardiovascular surgery from the Diagnosis Procedure Combination database in Japan (2016–2019). Based on the surgery type, we examined the association of intra-operative autologous blood donation with the transfusion rate and amount of blood used in cardiac and aortic surgeries using multilevel propensity score matching. We enrolled 32,433 and 4,267 patients who underwent cardiac and aortic surgeries and received 5.0% and 6.7% intra-operative autologous blood donation with mean volumes of 557.68 mL and 616.96 mL, respectively. The red blood cell transfusion rates of the control and intra-operative autologous blood donation groups were 60.6% and 38.4%, respectively, in the cardiac surgery cohort (p < .001) and 91.4%, and 83.8%, respectively, in the aortic surgery cohort (p = .037). The transfusion amounts for the control and intra-operative autologous blood donation groups were 5.9 and 3.5 units of red blood cells, respectively, for cardiac surgery patients (p < .001) and 11.9 and 7.9 units, respectively, for aortic surgery patients (p < .001). Intra-operative autologous blood donation could reduce the transfusion rate or amount of red blood cells and fresh frozen plasma for patients undergoing index cardiovascular surgery and could be an effective blood transfusion strategy in cardiovascular surgery for Japanese patients.

Impact of body weight on hemoglobin increments in adult red blood cell transfusion

BACKGROUND

Though weight is a major consideration when transfusing blood in pediatric patients, it is generally not considered when dosing transfusions in adults. We hypothesized that the change in hemoglobin (Hb) concentration is inversely proportional to body weight when transfusing red blood cells (RBC) in adults.

METHODS

A total of 13,620 adult surgical patients at our institution were assessed in this retrospective cohort study (2009-2016). Patients were stratified based on total body weight (kg): 40-59.9 (16.6%), 60-79.9 (40.4%), 80-99.9 (28.8%), 100-119.9 (11.3%), and 120-139.9 (2.9%). The primary outcome was the change in Hb per RBC unit transfused. Subgroup analyses were performed after stratification by sex (male/female) and the total number of RBC units received (1/2/≥3 units). Multivariable models were used to assess the association between weight and change in Hb.

RESULTS

As patients' body weight increased, there was a decrease in the mean change in Hb per RBC unit transfused (40-59.9 kg: 0.85 g/dL, 60-79.9 kg: 0.73 g/dL, 80-99.9 kg: 0.66 g/dL, 100-119.9 kg: 0.60 g/dL, 120-139.9 kg: 0.55 g/dL; p < .0001). This corresponded with a 35% difference in the change in Hb between the lowest and highest weight categories on univariate analysis. Similar trends were seen after subgroup stratification. On multivariable analysis, for every 20 kg increase in patient weight, there was a ~6.5% decrease in the change in Hb per RBC unit transfused (p < .0001).

CONCLUSIONS

Patient body weight differentially impacts the change in Hb after RBC transfusion. These findings justify incorporating body weight into the clinical decision-making process when transfusing blood in adult surgical patients.

Long-term Impact of Perioperative Red Blood Cell Transfusion on Patients Undergoing Cardiac Surgery

BACKGROUND

There is a known association between need for transfusion and short-term outcomes in patients undergoing cardiac surgery. However long-term data are lacking in the contemporary literature.

METHODS

All patients who underwent open cardiac surgery from 2010 to 2018 were included, except those undergoing transplant, with a ventricular-assist device, and requiring circulatory arrest. Primary outcome included short- and long-term mortality. Secondary outcomes included postoperative complications and hospital readmissions.

RESULTS

The total patient population included 14,281 patients with a median follow-up of 4.03 years (range, 2.25-6.1). Outcomes were stratified into patients with (n = 6239) or without (n = 8042) packed red blood cell (PRBC) use. Patients with PRBC transfusions had significantly (P < .001) worse postoperative outcomes compared with those without PRBC use, including higher operative mortality (6.89% vs 0.98%), return to the operating room (17.8% vs 1.61%), pneumonia (7.84% vs 0.98%), stroke (3.22% vs 1.51%), sepsis (2.66% vs 0.20%), renal failure (8.42% vs 1.12%), and dialysis (5.74% vs 0.42%). On multivariate analysis PRBC transfusion was an independent predictor of mortality (hazard ratio [[HR], 2.39; 95% confidence interval [CI], 2.08-2.64; P < .001) and hospital readmission (HR, 1.15; 95% CI, 1.09-1.21; P < .001). Total units of PRBCs were directly associated with mortality (HR, 1.09; 95% CI, 1.08-1.09; P < .001) and hospital readmissions (HR, 1.02; 95% CI, 1.01-1.03; P < .005).

CONCLUSIONS

Patients with perioperative PRBC transfusions have increased operative and long-term mortality and hospital readmissions. Total units of PRBCs transfused were directly associated with mortality and readmissions.

Association Between Post-Operative Infection and Blood Transfusion in Cardiac Surgery

Background

Blood transfusion is a commonly used therapy in cardiac surgery, whether it is given during the surgery or in the intensive care unit. It is important to evaluate the risks and benefits of exposure to blood transfusion. The use of blood transfusions can influence patient outcome. Previous studies have implicated blood transfusion as a causative factor in post-operative infection.

Objectives

We aim to determine the effect of blood transfusion on post-operative infection in cardiac surgery patients at the King Faisal Cardiac Center, Jeddah, Saudia Arabia, from January 2017 to January 2019.

Methods

The regular six-week follow-up of cardiac surgery patients allowed us to maintain a six-week infection span. The main variables included patient characteristics, operative characteristics, pre-operative hemoglobin, six-week infection, blood transfusion, and clinical outcomes. A logistic regression model was developed to identify patient and procedure variables that were associated with blood transfusion and infection. The baseline variables were entered into the model. Variables with p-value less than 0.05 were considered significant.

Results

The incidence of transfusion out of 197 patients was 93.4% (n = 184). The occurrence of infection was 31.82% (n = 63). There was no difference in post-operative infection for patients who received blood transfusions compared with those who did not receive blood transfusions (p = 0.902). In comparing patients receiving 1-2 units of red blood cells (RBCs) (48%) and those receiving >2 units of RBCs (52%), there was no significance (p = 0.549).

Conclusions

There was no association between the incidence of infection and blood transfusion. While there are other reasons for withholding blood, it would not be recommended to do so based on the concern of infection.

Evolution of perioperative blood transfusion practice after coronary artery bypass grafting in the past two decades

BACKGROUND AND AIM OF THE STUDY

Transfusion of blood products after coronary artery bypass grafting (CABG) is associated with increased morbidity and mortality. We evaluated the perioperative use of blood products in patients undergoing CABG in our institution over the past two decades.

METHODS

The study included 18 992 patients who underwent isolated CABG at our hospital between 1998 and 2017. Baseline characteristics of patients and the number of perioperative transfusions during their hospital stay (including red blood cells [RBCs], platelets, and fresh frozen plasma [FFP]) were assessed. Logistic regression models were used to identify risk factors for perioperative transfusion.

RESULTS

The rates of perioperative RBC transfusion decreased for all patients undergoing isolated CABG (52.1% in 1998 vs 18.6% in 2017) in our institution. The mean number of transfused RBC units was significantly higher in women than in men (1.57 ± 2.2 vs 0.68 ± 1.84; P < .005); this difference remained significant over the years. After adjusting the results for other risk factors, female sex was a significant independent risk factor for perioperative RBC transfusion. The platelet transfusion rate increased over the past two decades (1.4% in 1998 vs 9.7% in 2017). The number of FFP transfusions remained unchanged.

CONCLUSIONS

Over the past two decades, we observed a decrease in the incidence of perioperative RBC transfusions in patients undergoing isolated CABG, whereas platelet transfusions increased. Female sex was an independent predictor of perioperative RBC transfusion.

Society of Cardiovascular Anesthesiologists Clinical Practice Improvement Advisory for Management of Perioperative Bleeding and Hemostasis in Cardiac Surgery Patients

Bleeding after cardiac surgery is a common and serious complication leading to transfusion of multiple blood products and resulting in increased morbidity and mortality. Despite the publication of numerous guidelines and consensus statements for patient blood management in cardiac surgery, research has revealed that adherence to these guidelines is poor, and as a result, a significant variability in patient transfusion practices among practitioners still remains. In addition, although utilization of point-of-care (POC) coagulation monitors and the use of novel therapeutic strategies for perioperative hemostasis, such as the use of coagulation factor concentrates, have increased significantly over the last decade, they are still not widely available in every institution. Therefore, despite continuous efforts, blood transfusion in cardiac surgery has only modestly declined over the last decade, remaining at ≥50% in high-risk patients. Given these limitations, and in response to new regulatory and legislature requirements, the Society of Cardiovascular Anesthesiologists (SCA) has formed the Blood Conservation in Cardiac Surgery Working Group to organize, summarize, and disseminate the available best-practice knowledge in patient blood management in cardiac surgery. The current publication includes the summary statements and algorithms designed by the working group, after collection and review of the existing guidelines, consensus statements, and recommendations for patient blood management practices in cardiac surgery patients. The overall goal is creating a dynamic resource of easily accessible educational material that will help to increase and improve compliance with the existing evidence-based best practices of patient blood management by cardiac surgery care teams.

MIECT: How did it start?

Transiently assuming the functions of both heart and lungs as surgeons repair critical valves and vessel lesions can be achieved by mechanical circulatory support has its origins in cardiopulmonary bypass (CPB). However, CPB technologies induce also some unintended adverse effects. During the 90s, a mayor trend pushed many physicians to reconsider the place of coronary artery bypass grafting (CABG) and challenged the surgical reference treatment by less invasive catheter-based angioplasties. Nevertheless, best long-term patient outcomes were related to surgery. Therefore, a small number of multidisciplinary teams in Regensburg and Paris started to develop a minimally invasive CPB system. The basic concept relied on a closed-loop perfusion circuit with a non-occlusive pump. Moreover, the team in Paris pushed the concept further and developed a complete fully integrated CPB system allowed first closed-heart and later open-heart surgery with aortic cross-clamping and efficient cardioprotection. Those were the initial steps towards the future developments of minimally invasive extracorporeal circulation technologies. Initial clinical results were clearly positive in terms of overall morbimortality. Moreover, several preliminary results pointed out the biological benefits that decreased hemodilution, improved preservation of the immune reactions and more stable anticoagulation could bring to the field of ECT.

The effect of perioperative blood transfusion on kidney functions in total knee Arthroplasty

Objective:

Various studies have examined the effects of perioperative blood transfusion on kidney functions. In this study, we investigated the effects of blood transfusion on the kidney functions of patients undergoing total knee arthroplasty.

Methods:

: This retrospective study was carried out on 216 patients who had undergone total knee arthroplasty between January 2016 and January 2017. The patients were divided into two groups according to the level of blood transfusion used during surgery. Group-1 comprised 157 patients (72.7%) needing a blood transfusion of less than three units, while the 59 (27.3) patients in Group-2 required three or more than three units.

Results:

No statistical difference was found between the two groups regarding hypertension before surgery, diabetes mellitus, chronic kidney failure, smoking habits or lung disease (p> 0.05). Likewise, there was no significant difference related to pulmonary and other complications or mortality (p> 0.05). When the groups were compared according to their blood parameters, no statistical differences in postoperative renal or other system functions were found (p> 0.05).

Conclusions:

Blood transfusion does not have a negative effect on postoperative blood urea nitrogen (BUN) and creatinine levels, or glomerular filtration rate in total knee arthroplasty.

Perioperative use of blood products is associated with risk of morbidity and mortality after surgery

BACKGROUND

Administration of blood products may be associated with increased morbidity and perioperative mortality in surgical patients.

METHODS

Patients aged 18 + who underwent gastrointestinal surgery at the Ohio State University Wexner Medical Center 9/10/2015-5/9/2018 were identified. Multivariable logistic regression models were used to evaluate impact of blood product use on survival and complications, as well as to identify factors associated with receipt of transfusions.

RESULTS

Among 10,756 patients, 35,517 units of blood products were transfused. Preoperative nadir hemoglobin was associated with receipt of blood product transfusion (OR 0.55, 95% CI 0.53, 0.68). After adjusting for patient and procedural characteristics, patients undergoing transfusion of blood products had an increased risk of perioperative mortality (OR 7.80, 95% CI 6.02, 10.10).

CONCLUSIONS

The use of blood products was associated with increased risk of complication and death. Patient blood management programs should be implemented to provide rational criteria and guidance for the transfusion of blood products.

Off-Pump versus Conventional Coronary Artery Bypass Grafting: A Meta-Analysis and Consensus Statement from the 2004 ISMICS Consensus Conference

Background

The purpose of this evidence-based consensus statement is to systematically review and meta-analyze the randomized and nonrandomized evidence comparing off-pump (OPCAB) to conventional coronary artery bypass (CCAB) surgery and to provide consensus on the role of OPCAB in low- and high-risk surgical patients.

Methods and Results

This consensus conference was conducted according to the American College of Cardiology (ACC)/American Heart Association (AHA) standards for development of clinical practice guidelines. The Steering Committee collated all published studies of OPCAB versus CCAB through May 2004 and developed six questions central to controversies surrounding OPCAB surgery in mortality, morbidity, and resource utilization. For mixed-risk patient populations, meta-analysis of 37 randomized clinical trials (3,369 patients, Level A) reported across a total of 53 papers, and two meta-analyses of nonrandomized trials (Level B) comparing OPCAB versus CCAB were identified. For high-risk patient populations, we performed a meta-analysis of 3 randomized and 42 nonrandomized trials (26,349 patients, Level B).

Conclusion

Meta-analysis of Level A and B evidence provided the basis for the following consensus statements in patients undergoing surgical myocardial revascularization: (1) OPCAB should be considered a safe alternative to CCAB with respect to risk of mortality [Class I, Level A]; (2) With appropriate use of modern stabilizers, heart positioning devices, and adequate surgeon experience, similar completeness of revascularization and graft patency can be achieved [Class IIa, Level A]; (3) OPCAB is recommended to reduce perioperative morbidity [Class I, Level A]; (4) OPCAB may be recommended to minimize midterm cognitive dysfunction [Class IIa, Level A]; (5) OPCAB should be considered as an equivalent alternative to CCAB in regard to quality of life [Class I, Level A]; (6) OPCAB is recommended to reduce the duration of ventilation, ICU and hospital stay, and resource utilization [Class I, Level A]; (7) OPCAB should be considered in high-risk patients to reduce perioperative mortality, morbidity, and resource utilization [Class IIa, Level B].

A review of hybrid coronary revascularization

Purpose

Hybrid coronary revascularization is an emerging treatment strategy for coronary artery disease. We will review the reasons for the development of this strategy, describe surgical techniques, and review outcomes. Finally, we will discuss the future of hybrid revascularization and explain why it will grow as a treatment modality.

Methods

For this review, we conducted an unstructured review of the literature for articles related to hybrid coronary revascularization, bypass surgery, and percutaneous coronary interventions.

Results

Hybrid coronary revascularization has been shown in large series to have excellent results. These include fast recovery time, low mortality and rates of complications, and excellent surgical graft patency. There may be increased need for revascularization over conventional bypass surgery.

Conclusions

The combination improved surgical techniques including a robotic surgery platform, as well as the ever-improving efficacy and durability of coronary stents have made hybrid coronary revascularization an attractive option for many patients. It offers a minimally invasive approach to surgery while avoiding the poor patency of saphenous vein grafts. In appropriately selected patients, this may be an ideal treatment strategy that minimizes risks and maximizes short- and long-term benefits.

Gender and intraoperative blood transfusion: analysis of 54,122 non-reoperative coronary revascularization procedures

Background:

Previous studies have shown that women undergoing isolated coronary artery bypass graft (CABG) surgery have an increased risk for postoperative morbidity and mortality when compared to men. Additionally, recent evidence suggests that blood transfusions are independently associated with an increased risk of adverse outcome.

Methods:

We evaluated gender differences in the risk of intraoperative red blood cell (RBC) transfusion during CABG surgery. Consecutive, non-reoperative CABG procedures performed across 196 institutions between April 2012 and May 2015 were retrospectively reviewed. Gender differences for intraoperative transfusion were evaluated with a multi-variable binary logistic regression model, adjusting for age, blood volume (Nadler formula to normalize for height and weight), body mass index, procedure acuity, net extracorporeal circuit prime volume, use of autologous priming, first hematocrit (Hct) in the operating room (OR), nadir Hct on cardiopulmonary bypass (CPB), volume added on CPB, ultrafiltration volume, urine output on CPB and procedure duration.

Results:

Among 54,122 patients (25.3% female), 21.6% (n = 11,701) received a RBC transfusion. Compared to men, female patients were older (66 years vs. 64 years, p<0.001), had lower blood volumes (4.3L vs. 5.6L, p<0.001) and a lower preoperative Hct (32.9% vs. 37.2%, p<0.001). Transfusion rates were three-fold higher in women versus men (45.1% vs. 13.7%, p<0.001). After adjustment for independent predictors of intraoperative transfusion, women remained at increased risk versus men (OR = 1.30, 95%CI = 1.19−1.43).

Conclusions:

Women have an increased risk of intraoperative RBC transfusion versus men. After adjusting for height and weight, much of this risk is due to gender differences in preoperative Hct and blood volume; however, a residual significant risk remained after adjustment. Perfusion strategies aimed at gender differences may minimize unnecessary transfusions. Future study on the impact of gender on transfusion practice in cardiac surgery is warranted.

Intraoperative transit-time flow measurement in on-pump coronary artery bypass graft surgery: Single center experience

Background

This study aims to evaluate the effects of graft dysfunction detected by intraoperative transit-time flow measurement on the outcomes of on-pump coronary artery bypass graft surgery.

Methods

A total of 1,240 patients (856 males, 384 females; mean age 57.4±12.1 years; range, 47 to 74 years), who underwent isolated on-pump coronary artery bypass graft surgery via median sternotomy performed by the same surgical team, were reviewed retrospectively. With the introduction of transit-time flow measurement into practice at our clinic in 2006, all patients regularly underwent transit-time flow measurement during surgery in order to evaluate the graft patency. Interpretation of the data obtained using the transit-time flow measurement in patients who underwent surgery has directed our decision as to whether to perform graft revision. Patients were evaluated for early- and late-period mortality/ morbidity, perioperative and postoperative myocardial infarction, and intraaortic balloon requirement.

Results

A total of 3,596 grafts in the perioperative period was evaluated using transit-time flow measurement. Anastomosis/graft revision, new anastomosis/patch plasty to distal native artery or free left internal mammary artery graft was performed in 146 grafts of 143 patients in whom transittime flow measurement showed insufficient patency. Four of six patients who developed peri/postoperative myocardial infarction were found to have perioperative hypotension, ST elevation, and wall motion abnormality on transesophageal echocardiography before closure of the sternum. The flow was corrected by extending the short length of the grafts with insufficient flow after transit-time flow measurement and it was recorded that transit-time flow measurements were at normal values at these four grafts. Two patients developed acute myocardial infarction in the postoperative period and stent was applied in one vessel of each patient; however, one of these patients died. Sixteen patients were inserted intraaortic balloon pump, four of which being in the preoperative period. Revision surgery was performed due to bleeding in 56 patients and sternal infection in 12 patients. Of all patients, 28 (2.3%) died in the early postoperative period.

Conclusion

We believe that transit-time flow measurement may be an important tool in evaluating graft function and contribute to eliminate the causes of graft failure during surgery.

Preoperative anemia versus blood transfusion: Which is the culprit for worse outcomes in cardiac surgery?

BACKGROUND

Reducing blood product utilization after cardiac surgery has become a focus of perioperative care as studies have suggested improved outcomes. The relative impact of preoperative anemia versus packed red blood cells (PRBC) transfusion on outcomes remains poorly understood, however. In this study, we investigated the relative association between preoperative hematocrit (Hct) level and PRBC transfusion on postoperative outcomes after coronary artery bypass grafting (CABG) surgery.

METHODS

Patient records for primary, isolated CABG operations performed between January 2007 and December 2017 at 19 cardiac surgery centers were evaluated. Hierarchical logistic regression modeling was used to estimate the relationship between baseline preoperative Hct level as well as PRBC transfusion and the likelihoods of postoperative mortality and morbidity, adjusted for baseline patient risk. Variable and model performance characteristics were compared to determine the relative strength of association between Hct level and PRBC transfusion and primary outcomes.

RESULTS

A total of 33,411 patients (median patient age, 65 years; interquartile range [IQR], 57-72 years; 26% females) were evaluated. The median preoperative Hct value was 39% (IQR, 36%-42%), and the mean Society of Thoracic Surgeons (STS) predicted risk of mortality was 1.8 ± 3.1%. Complications included PRBC transfusion in 31% of patients, renal failure in 2.8%, stroke in 1.3%, and operative mortality in 2.0%. A strong association was observed between preoperative Hct value and the likelihood of PRBC transfusion (P < .001). After risk adjustment, PRBC transfusion, but not Hct value, demonstrated stronger associations with postoperative mortality (odds ratio [OR], 4.3; P < .0001), renal failure (OR 6.3; P < .0001), and stroke (OR, 2.4; P < .0001). A 1-point increase in preoperative Hct was associated with decreased probabilities of mortality (OR, 0.97; P = .0001) and renal failure (OR, 0.94; P < .0001). The models with PRBC had superior predictive power, with a larger area under the curve, compared with Hct for all outcomes (all P < .01). Preoperative anemia was associated with up to a 4-fold increase in the probability of PRBC transfusion, a 3-fold increase in renal failure, and almost double the mortality.

CONCLUSIONS

PRBC transfusion appears to be more closely associated with risk-adjusted morbidity and mortality compared with preoperative Hct level alone, supporting efforts to reduce unnecessary PRBC transfusions. Preoperative anemia independently increases the risk of postoperative morbidity and mortality. These data suggest that preoperative Hct should be included in the STS risk calculators. Finally, efforts to optimize preoperative hematocrit should be investigated as a potentially modifiable risk factor for mortality and morbidity.

Measurement of Blood Loss in Cardiac Surgery: Still Too Much

BACKGROUND

Cardiac surgery is associated with a significant decrease in hematocrit. It is unclear whether that occurs from hemodilution, loss of red cells, or both. Hematocrit is a major determinant of transfusion decisions although transfusion is associated with increased morbidity and mortality. Physicians must determine whether this anemia is the result of hemodilution or red blood cell loss as the former would be treated with packed red blood cell transfusions and the latter by diuresis. We hypothesize that the decrease in hematocrit observed in cardiac surgery is due to hemodilution.

METHODS

Blood volume (BV), plasma volume (PV), and red blood cell volume (RBCV) were measured in 54 patients undergoing coronary artery bypass graft surgery, valve surgery, or coronary artery bypass graft/valve surgery. Measurements were made preoperatively, immediately postoperatively, and 2 hours after surgery utilizing a dilution tracer method and hematocrit measurements.

RESULTS

Preoperative average BV was 6,094 mL (SD 1,904 mL), RBCV was 2,024 mL (SD 720 mL), and PV was 4,070 mL (SD 1,339 mL). Postoperative average BV was 4,834 mL (SD 1,432 mL), RBCV 1,226 mL (SD 527 mL), and PV 3,607 mL (SD 993 mL). Blood volume decreased 18% (p < 0.0001), RBCV decreased 38% (p < 0.001), and PV decreased 8% (p < 0.012). There were no significant changes between postoperative values and those 2 hours later in the cardiac surgery intensive care unit.

CONCLUSIONS

Decreases in hematocrit observed in cardiac surgery patients are due to significant red blood cell losses and not to hemodilution. Red blood cell losses averaged 38%. Plasma volume also decreased.

Blood Transfusion and Increased Perioperative Risk in Coronary Artery Bypass Grafts

OBJECTIVE

To correlate blood transfusions and clinical outcomes during hospitalization in coronary artery bypass grafting surgery (CABG).

METHODS

Transfusion, clinical and hematological data were collected for 1,378 patients undergoing isolated or combined CABG between January 2011 and December 2012. The effect of blood transfusions was evaluated through multivariate analysis to predict three co-primary outcomes: composite ischemic events, composite infectious complications and hospital mortality. Because higher risk patients receive more transfusions, the hospital mortality outcome was also tested on a stratum of low-risk patients to isolate the effect of preoperative risk on the results.

RESULTS

The transfusion rate was 63.9%. The use of blood products was associated with a higher incidence of the three coprimary outcomes: composite infectious complications (OR 2.67, 95% CI 1.70 to 4.19; P<0.001), composite ischemic events (OR 2.42, 95% CI 1.70 to 3.46; P<0.001) and hospital mortality (OR 3.07, 95% CI 1.53 to 6.13; P<0.001). When only patients with logistic EuroSCORE ≤ 2% were evaluated, i.e., low-risk individuals, the mortality rate and the incidence of ischemic events and infectious complications composites remained higher among the transfused patients [6% vs. 0.4% (P<0.001), 11.7% vs. 24,3% (P<0.001) and 6.5% vs. 12.7% (P=0.002), respectively].

CONCLUSION

The use of blood components in patients undergoing CABG was associated with ischemic events, infectious complications and hospital mortality, even in low-risk patients.