Factors affecting transfusion of fresh frozen plasma, platelets, and red blood cells during elective coronary artery bypass graft surgery

Development of a machine learning model to predict intraoperative transfusion and guide type and screen ordering

STUDY OBJECTIVE

To develop an algorithm to predict intraoperative Red Blood Cell (RBC) transfusion from preoperative variables contained in the electronic medical record of our institution, with the goal of guiding type and screen ordering.

DESIGN

Machine Learning model development on retrospective single-center hospital data.

SETTING

Preoperative period and operating room.

PATIENTS

The study included patients ≥18 years old who underwent surgery during 2019-2022 and excluded those who refused transfusion, underwent emergency surgery, or surgery for organ donation after cardiac or brain death.

INTERVENTION

Prediction of intraoperative transfusion vs. no intraoperative transfusion.

MEASUREMENTS

The outcome variable was intraoperative transfusion of RBCs. Predictive variables were surgery, surgeon, anesthesiologist, age, sex, body mass index, race or ethnicity, preoperative hemoglobin (g/dL), partial thromboplastin time (s), platelet count x 109 per liter, and prothrombin time. We compared the performances of seven machine learning algorithms. After training and optimization on the 2019-2021 dataset, model thresholds were set to the current institutional performance level of sensitivity (93%). To qualify for comparison, models had to maintain clinically relevant sensitivity (>90%) when predicting on 2022 data; overall accuracy was the comparative metric.

MAIN RESULTS

Out of 100,813 cases that met study criteria from 2019 to 2021, intraoperative transfusion occurred in 5488 (5.4%) of cases. The LightGBM model was the highest performing algorithm in external temporal validity experiments, with overall accuracy of (76.1%) [95% confidence interval (CI), 75.6-76.5], while maintaining clinically relevant sensitivity of (91.2%) [95% CI, 89.8-92.5]. If type and screens were ordered based upon the LightGBM model, the predicted type and screen to transfusion ratio would improve from 8.4 to 5.1.

CONCLUSIONS

Machine learning approaches are feasible in predicting intraoperative transfusion from preoperative variables and may improve preoperative type and screen ordering practices when incorporated into the electronic health record.

Systematic review highlights high risk of bias of clinical prediction models for blood transfusion in patients undergoing elective surgery

BACKGROUND

Blood transfusion can be a lifesaving intervention after perioperative blood loss. Many prediction models have been developed to identify patients most likely to require blood transfusion during elective surgery, but it is unclear whether any are suitable for clinical practice.

STUDY DESIGN AND SETTING

We conducted a systematic review, searching MEDLINE, Embase, PubMed, The Cochrane Library, Transfusion Evidence Library, Scopus, and Web of Science databases for studies reporting the development or validation of a blood transfusion prediction model in elective surgery patients between January 1, 2000 and June 30, 2021. We extracted study characteristics, discrimination performance (c-statistics) of final models, and data, which we used to perform risk of bias assessment using the Prediction model risk of bias assessment tool (PROBAST).

RESULTS

We reviewed 66 studies (72 developed and 48 externally validated models). Pooled c-statistics of externally validated models ranged from 0.67 to 0.78. Most developed and validated models were at high risk of bias due to handling of predictors, validation methods, and too small sample sizes.

CONCLUSION

Most blood transfusion prediction models are at high risk of bias and suffer from poor reporting and methodological quality, which must be addressed before they can be safely used in clinical practice.

Prediction of perioperative transfusions using an artificial neural network

BACKGROUND

Accurate prediction of operative transfusions is essential for resource allocation and identifying patients at risk of postoperative adverse events. This research examines the efficacy of using artificial neural networks (ANNs) to predict transfusions for all inpatient operations.

METHODS

Over 1.6 million surgical cases over a two year period from the NSQIP-PUF database are used. Data from 2014 (750937 records) are used for model development and data from 2015 (885502 records) are used for model validation. ANN and regression models are developed to predict perioperative transfusions for surgical patients.

RESULTS

Various ANN models and logistic regression, using four variable sets, are compared. The best performing ANN models with respect to both sensitivity and area under the receiver operator characteristic curve outperformed all of the regression models (p < .001) and achieved a performance of 70-80% specificity with a corresponding 75-62% sensitivity.

CONCLUSION

ANNs can predict >75% of the patients who will require transfusion and 70% of those who will not. Increasing specificity to 80% still enables a sensitivity of almost 67%. The unique contribution of this research is the utilization of a single ANN model to predict transfusions across a broad range of surgical procedures.

Leukodepleted Packed Red Blood Cells Transfusion in Patients Undergoing Major Cardiovascular Surgical Procedure: Systematic Review and Meta-Analysis

Background

Leukocytes contained in the allogeneic packed red blood cell (PRBC) are the cause of certain adverse reactions associated with blood transfusion. Leukoreduction consists of eliminating leukocytes in all blood products below the established safety levels for any patient type. In this systematic review, we appraise the clinical effectiveness of allogeneic leukodepleted (LD) PRBC transfusion for preventing infections and death in patients undergoing major cardiovascular surgical procedures.

Methods

We searched randomized controlled trials (RCT), enrolling patients undergoing a major cardiovascular surgical procedure and transfused with LD-PRBC. Data were extracted, and risk of bias was assessed according to Cochrane guidelines. In addition, trial sequential analysis (TSA) was used to assess the need of conducting additional trials. Quality of the evidence was assessed using the GRADE approach.

Results

Seven studies met the eligibility criteria. Quality of the evidence was rated as moderate for both outcomes. The risk ratio for death from any cause comparing the LD-PRBC versus non-LD-PRBC group was 0.69 (CI 95% = 0.53 to 0.90; I² = 0%). The risk ratio for infection in the same comparison groups was 0.77 (CI 95% = 0.66 to 0.91; I² = 0%). TSA showed a conclusive result in this outcome.

Conclusions

We found evidence that supports the routine use of leukodepletion in patients undergoing a major cardiovascular surgical procedure requiring PRBC transfusion to prevent death and infection. In the case of infection, the evidence should be considered sufficient and conclusive and hence indicated that further trials would not be required.

Risk of massive blood product requirement in cardiac surgery: A large retrospective study from 2 heart centers

Cardiac surgery under cardiopulmonary bypass (CPB) accounts for most consumption of red blood cells (RBCs). Identifying risk factors for massive red blood cell transfusion (MRT) in cardiac surgery may help to reduce this consumption.We retrospectively analyzed 8238 patients who underwent valve surgery and/or coronary artery bypass grafting (CABG) under CPB at 2 major heart centers in China. Uni- and multivariate logistic regression was carried out to assess whether risk factors for MRT (defined as receiving at least 4 units RBCs) varied with type of cardiac surgery.A total of 1691 patients (21%) received at least 4 units RBCs (6.77 ± 4.78 units per person). This MRT group consumed 70% of the total units of allogeneic RBCs in the study. MRT incidence was 2-fold higher among patients undergoing CABG with or without valve surgery than among patients undergoing valve surgery alone. Multivariate logistic analysis identified the following MRT risk factors common to valve surgery alone, CABG alone, and their combination: female sex, older age, renal dysfunction, lower body mass index, lower preoperative hemoglobin, and longer CPB. Several independent MRT risk factors were also identified specific to valve surgery: active endocarditis, nonatrial fibrillation, smaller left atrium diameter, abnormal international normalized ratio, and repeat surgery.Different types of cardiac surgery share several, but not all, MRT risk factors. This study may help guide the prediction and management of patients at higher MRT risk.

Big data modeling to predict platelet usage and minimize wastage in a tertiary care system

In modern hospital systems where complicated, severely ill patient populations are the norm, there is currently no reliable way to forecast the use of perishable medical resources to enable a smart and economic way to deliver optimal patient care. We here demonstrate a statistical model using hospital patient data to quantitatively forecast, days in advance, the need for platelet transfusions. This approach can be leveraged to significantly decrease platelet wastage, and, if adopted nationwide, would save approximately 80 million dollars per year. We believe our approach can be generalized to all other aspects of patient care involving timely delivery of perishable medical resources.

Maintaining a robust blood product supply is an essential requirement to guarantee optimal patient care in modern health care systems. However, daily blood product use is difficult to anticipate. Platelet products are the most variable in daily usage, have short shelf lives, and are also the most expensive to produce, test, and store. Due to the combination of absolute need, uncertain daily demand, and short shelf life, platelet products are frequently wasted due to expiration. Our aim is to build and validate a statistical model to forecast future platelet demand and thereby reduce wastage. We have investigated platelet usage patterns at our institution, and specifically interrogated the relationship between platelet usage and aggregated hospital-wide patient data over a recent consecutive 29-mo period. Using a convex statistical formulation, we have found that platelet usage is highly dependent on weekday/weekend pattern, number of patients with various abnormal complete blood count measurements, and location-specific hospital census data. We incorporated these relationships in a mathematical model to guide collection and ordering strategy. This model minimizes waste due to expiration while avoiding shortages; the number of remaining platelet units at the end of any day stays above 10 in our model during the same period. Compared with historical expiration rates during the same period, our model reduces the expiration rate from 10.5 to 3.2%. Extrapolating our results to the ∼2 million units of platelets transfused annually within the United States, if implemented successfully, our model can potentially save ∼80 million dollars in health care costs.

Factors influencing transfusion requirement in patients undergoing first-time, elective coronary artery bypass graft surgery

CONTEXT

Coronary artery bypass graft (CABG) operation is associated with high frequency of allogeneic blood transfusion due to the acquired hemostatic challenges in patients undergoing CABG. However, allogeneic blood transfusion carries risks of infection, adverse reaction, and mortality as well as prolonged hospital stay and increased hospital cost. It is important to identify patients who require blood transfusion to mitigate their risk factors and reduce the chance of exposure to allogeneic blood.

AIMS

This study was conducted to evaluate factors that influence the decision to transfuse red cell in first-time elective CABG patients.

SETTINGS AND DESIGN

This was a cross-sectional study based on a retrospective record review. The study was done in the National Heart Institute.

MATERIALS AND METHODS

All patients who underwent first-time elective CABG were included in this study. Variables analyzed include age, gender, body weight, preoperative hemoglobin (Hb) level, patients' comorbidities, and other clinical parameters.

STATISTICAL ANALYSIS USED

Data were analyzed using SPSS software version 20.

RESULTS

A total of 463 patients underwent first-time elective CABG during the period of the study. Three hundred and eighty-six (83.4%) patients received red cell transfusion. From multiple logistic regression analysis, only age (odds ratio [OR] = 1.040, 95% confidence interval [CI]: 1.003, 1.077, P = 0.032), body weight (OR = 0.951, 95% CI: 0.928, 0.974, P < 0.001), Hb level (OR = 0.500, 95% CI: 0.387, 0.644, P < 0.001), and cardiopulmonary bypass time (OR = 1.013, 95% CI: 1.004, 1.023, P < 0.001) were the significant independent predictors of red cell transfusion.

CONCLUSIONS

By stratifying patients according to their risk factor for red cell transfusion, the high-risk patients could be recognized and should be enrolled into effective patient blood management program to minimize their risk of exposure to allogeneic blood transfusion.

Influencia del polimorfismo rs11549465 de HIF-1α en los niveles de hemoglobina y lactato en pacientes de cirugía cardiovascular

Introducción. La anemia perioperatoria es una complicación común de la cirugía cardiovascular. Pacientes con el alelo T del polimorfismo rs11549465 de HIF-1α podrían tener niveles alterados de hemoglobina y lactato antes, durante y después de la cirugía, en comparación con los del ancestral. Esto, por un aumento en la estabilidad de HIF-1α causado por este.Objetivo. Describir la frecuencia del alelo T en pacientes de cirugía cardiovascular programada y su relación con los niveles de hemoglobina y lactato.Materiales y métodos: Se aisló ADN de 84 pacientes de cirugía cardiovascular para genotipificación por secuenciación de Sanger y se recolectaron características demográficas y clínicas.Resultados. La frecuencia del alelo T fue 0.066 (IC95%: 0.037-0.114). No hubo diferencias significativas en los niveles de hemoglobina y lactato preoperatorios, intraoperatorios y posoperatorios entre pacientes con alelo T y aquellos con alelo ancestral.Conclusión. La frecuencia del alelo T fue menor que la esperada, de acuerdo con otros estudios en poblaciones similares de voluntarios sanos y no mostró diferencias significativas con algunas poblaciones asiáticas, ni con un grupo de pacientes con infarto agudo de miocardio. Parece que la genotipificación de rs11549465 en pacientes de cirugía cardiovascular no representó un método de estratificación de riesgo de anemia en este grupo.

Benchmarking the use of blood products in cardiac surgery to stimulate awareness of transfusion behaviour : Results from a four-year longitudinal study

Introduction

Cardiac operations account for a large proportion of the blood transfusions given each year, leading to high costs and an increased risk to patient safety. Therefore, it is important to explore initiatives to reduce transfusion rates. This study aims to provide a benchmark for transfusion practice by inter-hospital comparison of transfusion rates, blood product use and costs related to patients undergoing coronary artery bypass grafting (CABG), valve surgery or combined CABG and valve surgery.

Methods

Between 2010 and 2013, patients from four Dutch hospitals undergoing CABG, valve surgery or combined CABG and valve surgery (n = 11,150) were included by means of a retrospective longitudinal study design.

Results

In CABG surgery the transfusion rate ranged between 43 and 54%, in valve surgery between 54 and 67%, and in combined CABG and valve surgery between 80 and 88%. With the exception of one hospital, the trend in transfusion rate showed a significant decrease over time for all procedures. Hospitals differed significantly in the units of blood products given to each patient, and in the use of specific transfused combinations of blood products, such as red blood cells (RBCs) and a combination of RBCs, fresh frozen plasma (FFP) and platelets.

Conclusion

This study indicates that benchmarking blood product usage stimulates awareness of transfusion behaviour, which may lead to better patient safety and lower costs. Further studies are warranted to improve awareness of transfusion behaviour and increase the standardisation of transfusion practice in cardiac surgery.

BMI Is an Independent Preoperative Predictor of Intraoperative Transfusion and Postoperative Chest-Tube Output

Background An increasing obese population in the United States focuses attention on perioperative management of obese and overweight patients. Objective We sought to determine if obesity, determined by body mass index (BMI), was a preoperative indicator of bleeding in coronary artery bypass graft (CABG) surgery as measured by intraoperative packed red blood cell transfusion frequency and 24-hour chest-tube output amount. Methods A retrospective chart review examined 290 consecutive patients undergoing single-surgeon off-pump or on-pump CABG surgery between November 2003 and April 2009. Preoperative variables of age, gender, hematocrit, platelet count, and BMI, chest tube output during the immediate 24-hour postoperative period, and the type of procedure (on-pump vs. off-pump) were analyzed. Logistic regression analysis was used to evaluate the likelihood of intraoperative transfusion. Linear regression analysis was used to evaluate 24-hour chest-tube output. Results Preoperative variables that significantly increased the likelihood of intraoperative transfusions were older age and low hematocrit; a significant decrease in likelihood was found with male gender, overweight BMI, and off-pump procedures. Preoperative variables that significantly increased 24-hour chest-tube output were low hematocrit, high hematocrit, and low platelets while a significant decrease in output was seen with overweight BMI and obese BMI. Conclusion Overweight and obese BMI are significant independent predictors of decreased intraoperative transfusion and decreased postoperative blood loss.

Variation of blood transfusion in patients undergoing major noncardiac surgery

OBJECTIVE

To examine the hospital variability in use of red blood cells (RBCs), fresh-frozen plasma (FFP), and platelet transfusions in patients undergoing major noncardiac surgery.

BACKGROUND

Blood transfusion is commonly used in surgical procedures in the United States. Little is known about the hospital variability in perioperative transfusion rates for noncardiac surgery.

METHODS

We used the University HealthSystem Consortium database (2006-2010) to examine hospital variability in use of allogeneic RBC, FFP, and platelet transfusions in patients undergoing major noncardiac surgery. We used regression-based techniques to quantify the variability in hospital transfusion practices and to study the association between hospital characteristics and the likelihood of transfusion.

RESULTS

After adjusting for patient risk factors, hospital transfusion rates varied widely for patients undergoing total hip replacement (THR), colectomy, and pancreaticoduodenectomy. Compared with patients undergoing THR in average-transfusion hospitals, patients treated in high-transfusion hospitals have a greater than twofold higher odds of being transfused with RBCs [adjusted odds ratio (AOR) = 2.41; 95% confidence interval (CI), 1.89-3.09], FFP (AOR = 2.81; 95% CI, 2.02-3.91), and platelets (AOR = 2.52; 95% CI, 1.95-3.25), whereas patients in low-transfusion hospitals have an approximately 50% lower odds of receiving RBCs (AOR = 0.45; 95% CI, 0.35-0.57), FFP (AOR = 0.37; 95% CI, 0.27-0.51), and platelets (AOR = 0.42; 95% CI, 0.29-0.62). Similar results were obtained for colectomy and pancreaticoduodenectomy.

CONCLUSIONS

There was dramatic hospital variability in perioperative transfusion rates among patients undergoing major noncardiac surgery at academic medical centers. In light of the potential complications of transfusion therapy, reducing this variability in hospital transfusion practices may result in improved surgical outcomes.

Predictors of transfusion of packed red blood cells in coronary artery bypass grafting surgery

OBJECTIVES

Finding predictors of blood transfusion may facilitate the most efficient approach for the use of blood bank services in coronary artery bypass grafting procedures. The aim of this retrospective study is to identify preoperative and intraoperative patient characteristics predicting the need for blood transfusion during or after CABG in our local cardiac surgical service.

METHODS

435 patients undergoing isolated first-time CABG were reviewed for their preoperative and intraoperative variables and analyzed postoperative data. Patients were 255 males and 180 females, with mean age 62.01 ± 10.13 years. Regression logistic analysis was used for identifying the strongest perioperative predictors of blood transfusion.

RESULTS

Blood transfusion was used in 263 patients (60.5%). The mean number of transfused blood products units per patient was 2.27 ± 3.07 (0-23) units. The total number of transfused units of blood products was 983. Univariate analysis identified age >65 years, weight <70 Kg, body mass index <25 Kg/m2, hemoglobin <13mg/dL, hematocrit < 40% and ejection fraction <50%, use of cardiopulmonary bypass (CPB), not using an internal thoracic artery as a bypass, and multiple bypasses as significant predictors. The strongest predictors using multivariate analysis were hematocrit < 40% (OR 2.58; CI 1.62-4.15; P<0.001), CPB use (OR 2.00; CI 1.27-3.17; P=0.003) and multiple bypasses (OR 2.31; CI 1.31-4.08; P=0.036).

CONCLUSIONS

The identification of these risk factors leads to better identification of patients with a greater probability of using blood, allocation blood bank resources and cost-effectiveness use of blood products.

[Transfusion requirements, morbidity and mortality in cardiac surgery and the use of antifibrinolytic agents: a comparison of aprotinin and tranexamic acid]

OBJECTIVE

To evaluate transfusion requirements, morbidity and mortality when 2 antifibrinolytic agents (aprotinin and tranexamic acid) were used in patients undergoing cardiac surgery.

PATIENTS AND METHODS

Comparison of the effects of 2 antifibrinolytic agents in 243 patients undergoing cardiac surgery between December 2006 and June 2008. We recorded the surgical procedures used, blood product transfusions required, complications (particularly renal), mortality, and length of hospital stay.

RESULTS

The patients were distributed into 2 groups to receive tranexamic acid (n = 144) or aprotinin (n = 99). The incidence of transfusion in the tranexamic acid group (31.94%) was nonsignificantly lower than in the aprotinin group (38.38%) (PF = .31). The mean (SD) number of units of packed red blood cells transfused was 0.67 (1.18) in the tranexamic acid group and 1.01 (1.54) in the aprotinin group (P = .07). The mean preoperative hemoglobin concentration in the tranexamic acid group (11.79 [1.71] mg/dL) was significantly lower than in the aprotinin group (12.35 [1.70] mg/dL) (P < .01). Incipient postoperative renal failure tended to occur more frequently in the aprotinin group (19.6% compared to 16%; P = .47). Mortality at 1 year was 9.02% in the tranexamic acid group (compared to 14.14% in the aprotinin group; PF-.21); the trend for mortality related to postoperative renal failure was similar (7.6% in the tranexamic acid group compared to 12.4% in the aprotinin group; P = .22). No significant differences were observed in postoperative complications or length of hospital stay. However, the lack of randomization and the small sample size do not allow for definitive conclusions.

CONCLUSIONS

This study, subject to the aforementioned limitations, shows that tranexamic acid is as effective as aprotinin for reducing transfusion requirements in cardiac surgery in Spain.

Safety of cardiac surgery without blood transfusion: a retrospective study in Jehovah's Witness patients

The aim of this retrospective study was to compare the utilisation of blood products and outcomes following cardiac surgery for 123 Jehovah's Witnesses and 4219 non-Jehovah's Witness patient controls. The study took place over a 7-year period at the Amphia Hospital in Breda, the Netherlands. A specific protocol was used in the management of Jehovah's Witness patients, while the control group received blood without restriction according to their needs. Patients' characteristics were comparable in both groups. Pre-operatively, the mean (SD) Euro Score was higher in the Jehovah's Witness group (3.2 (2.6) vs 2.7 (2.5), respectively; p < 0.02). Pre-operative haemoglobin concentration was higher in the Jehovah's Witness group (8.9 (0.7) vs 8.6 (0.9) g.dl(-1), respectively; p < 0.001). The total cardiopulmonary bypass time did not differ between groups. The requirement for allogenic blood transfusion was 0% in the Jehovah's Witness group compared to 65% in the control group. Postoperatively, there was a lower incidence of Q-wave myocardial infarction (2 (1.8%) vs 323 (7.7%), respectively; p < 0.02), and non Q-wave infarction (11 (9.8%) vs 559 (13.2%), respectively; p < 0.02) in the Jehovah's Witness group compared with controls. Mean (SD) length of stay in the intensive care unit (2.3 (3.2) vs 2.6 (4.2) days; p = 0.26), re-admission rate to the intensive care unit (5 (4.5%) vs 114 (2.7%); p = 0.163), and mortality (3 (2.7%) vs 65 (1.5%); p = 0.59), did not differ between the Jehovah's Witness and control groups, respectively.

Hospital variation in transfusion and infection after cardiac surgery: a cohort study

BACKGROUND

Transfusion practices in hospitalised patients are being re-evaluated, in part due to studies indicating adverse effects in patients receiving large quantities of stored blood. Concomitant with this re-examination have been reports showing variability in the use of specific blood components. This investigation was designed to assess hospital variation in blood use and outcomes in cardiac surgery patients.

METHODS

We evaluated outcomes in 24,789 Medicare beneficiaries in the state of Michigan, USA who received coronary artery bypass graft surgery from 2003 to 2006. Using a cohort design, patients were followed from hospital admission to assess transfusions, in-hospital infection and mortality, as well as hospital readmission and mortality 30 days after discharge. Multilevel mixed-effects logistic regression was used to calculate the intrahospital correlation coefficient (for 40 hospitals) and compare outcomes by transfusion status.

RESULTS

Overall, 30% (95 CI, 20% to 42%) of the variance in transfusion practices was attributable to hospital site. Allogeneic blood use by hospital ranged from 72.5% to 100% in women and 49.7% to 100% in men. Allogeneic, but not autologous, blood transfusion increased the odds of in-hospital infection 2.0-fold (95% CI 1.6 to 2.5), in-hospital mortality 4.7-fold (95% CI 2.4 to 9.2), 30-day readmission 1.4-fold (95% CI 1.2 to 1.6), and 30-day mortality 2.9-fold (95% CI 1.4 to 6.0) in elective surgeries. Allogeneic transfusion was associated with infections of the genitourinary system, respiratory tract, bloodstream, digestive tract and skin, as well as infection with Clostridium difficile. For each 1% increase in hospital transfusion rates, there was a 0.13% increase in predicted infection rates.

CONCLUSION

Allogeneic blood transfusion was associated with an increased risk of infection at multiple sites, suggesting a system-wide immune response. Hospital variation in transfusion practices after coronary artery bypass grafting was considerable, indicating that quality efforts may be able to influence practice and improve outcomes.

Predictors of packed red cell transfusion after isolated primary coronary artery bypass grafting--the experience of a single cardiac center: a prospective observational study

Background

Preoperative patients' characteristics can predict the need for perioperative blood component transfusion in cardiac surgical operations. The aim of this prospective observational study is to identify perioperative patient characteristics predicting the need for allogeneic packed red blood cell (PRBC) transfusion in isolated primary coronary artery bypass grafting (CABG) operations.

Patients and Methods

105 patients undergoing isolated, first-time CABG were reviewed for their preoperative variables and followed for intraoperative and postoperative data. Patients were 97 males and 8 females, with mean age 58.28 ± 10.97 years. Regression logistic analysis was used for identifying the strongest perioperative predictors of PRBC transfusion.

Results

PRBC transfusion was used in 71 patients (67.6%); 35 patients (33.3%) needed > 2 units and 14 (13.3%) of these needed > 4 units. Univariate analysis identified female gender, age > 65 years, body weight ≤ 70 Kg, BSA ≤ 1.75 m², BMI ≤ 25, preoperative hemoglobin ≤ 13 gm/dL, preoperative hematocrit ≤ 40%, serum creatinine > 100 μmol/L, Euro SCORE (standard/logistic) > 2, use of CPB, radial artery use, higher number of distal anastomoses, and postoperative chest tube drainage > 1000 mL as significant predictors. The strongest predictors using multivariate analysis were CPB use, hematocrit, body weight, and serum creatinine.

Conclusion

The predictors of PRBC transfusion after primary isolated CABG are use of CPB, hematocrit ≤ 40%, weight ≤ 70 Kg, and serum creatinine > 100 μmol/L. This leads to better utilization of blood bank resources and cost-efficient targeted use of expensive blood conservation modalities.

Risks and predictors of blood transfusion in pediatric patients undergoing open heart operations

BACKGROUND

Blood transfusion in adults is associated with increased mortality and morbidity after cardiac operations. The aim of this study was to identify the main predictors of blood transfusion and explore the relationship between blood transfusion and adverse outcomes in a pediatric population.

METHODS

We retrospectively analyzed a prospectively collected database (January 2002 to December 2003) of 657 consecutive pediatric patients undergoing open heart procedures in a tertiary pediatric cardiac center. Risk models were calculated for each blood product and for the total amount of blood transfused during the operation and in the first 24 hours. Postoperative adverse events were investigated after propensity score adjustment.

RESULTS

During the postoperative period, 30 patients (4.6%) died, 80 (12.2%) sustained nonvascular pulmonary complications, and 113 (17.2%) had infection. The risk model for the total amount of blood transfusion included weight, preoperative creatinine clearance, preoperative mechanical ventilation, duration of operation and cross-clamp, surgeon, delayed chest closure, inotropic dose, and nitric oxide administration. Univariate analyses demonstrated significant associations between blood transfusion and occurrence of every complication except of neurologic events. After adjustment for propensity score and disease severity, the total amount of blood transfusion was independently associated with an increased risk for infections (odds ratio, 1.01; 95% confidence interval, 1.002 to 1.02; p = 0.01). Transfusion of platelets was associated with lower incidence of nonvascular pulmonary complications (odds ratio, 0.89; 95% confidence interval, 0.79 to 0.99; p = 0.049).

CONCLUSIONS

The amount of blood transfusion is independently associated with infections but not with mortality.

Risk factors for red cell transfusion in adults undergoing coronary artery bypass surgery: a systematic review

BACKGROUND AND OBJECTIVE

Identifying factors that can predict adults at high risk of receiving red blood cell transfusion during coronary artery bypass graft (CABG) surgery may aid in more efficient blood banking practices and may tailor blood conservation strategies for these adult patients. The objective was to identify clinical factors associated with increased red cell transfusion in adults undergoing CABG surgery.

METHODS

A systematic review of the MEDLINE and HealthSTAR databases from 1966 to December 2005 was conducted. Citations containing the medical subject heading or textwords 'coronary artery bypass graft', 'CABG' and 'cardiovascular surgery' were combined with the medical subject headings or textwords 'transfusion' and 'blood transfusion'.

RESULTS

A total of 2461 abstracts were retrieved. Twenty-one studies met the inclusion/exclusion criteria. Transfusion rates ranged from 7 to 97%. Several variables were identified that were associated with increased red cell transfusion rates including older age, female sex, low haemoglobin concentration or haematocrit value, renal insufficiency and urgent/emergent surgery. The strongest risk factor was the urgency of surgery (urgent or emergent surgery), which was associated with a 4x to 8x increase in transfusion rates compared to elective surgery. Increasing age and female sex increased the likelihood of transfusion by 1x to 3x and 2x, respectively.

CONCLUSIONS

Increasing patient age, female sex, lower preoperative haemoglobin levels, as well as the urgency of the CABG surgery were associated with higher transfusion rates. Identifying risk factors for transfusion may allow for targeted use of blood conservation strategies, improved efficiency in blood utilization and informing adults at risk of transfusion.

Prediction of massive blood transfusion in cardiac surgery

PURPOSE

In cardiac surgery with cardiopulmonary bypass (CPB), excessive blood loss requiring the transfusion of multiple red blood cell (RBC) units is a common complication that is associated with significant morbidity and mortality. The objective of this study was to develop a prediction rule for massive blood transfusion (MBT) that could be used to optimize the management of, and research on, at-risk patients.

METHODS

Data were collected prospectively over the period from 2000 to 2005, on patients who underwent surgery with CPB at one hospital. Patients who received > or = five units of RBC within one day of surgery were classified as MBT. Logistic regression was used to appropriately select and weigh perioperative variables in the prediction rule, which was developed on the initial 60% of the sample and validated on the remaining 40%.

RESULTS

Of the 10,667 patients included, 925 (8.7%) had MBT. The clinical prediction rule included 12 variables (listed in order of predictive value: CPB duration, preoperative hemoglobin concentration, body surface area, nadir CPB hematocrit, previous sternotomy, preoperative shock, preoperative platelet count, urgency of surgery, age, surgeon, deep hypothermic circulatory arrest, and type of procedure) and was highly discriminative (c-index = 0.88). In the validation set, those classified as low-, moderate-, and high-risk by a simple risk score derived from the prediction rule had a 5%, 27%, and 58% chance of MBT, respectively.

CONCLUSION

A clinical prediction rule was developed that accurately identified patients at low-risk or high-risk for MBT. Studies are needed to determine the external generalizability and clinical utility of the prediction rule.

Morbidity and mortality risk associated with red blood cell and blood-component transfusion in isolated coronary artery bypass grafting

OBJECTIVE

Our objective was to quantify incremental risk associated with transfusion of packed red blood cells and other blood components on morbidity after coronary artery bypass grafting.

DESIGN

The study design was an observational cohort study.

SETTING

This investigation took place at a large tertiary care referral center.

PATIENTS

A total of 11,963 patients who underwent isolated coronary artery bypass from January 1, 1995, through July 1, 2002.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among the 11,963 patients who underwent isolated coronary artery bypass grafting, 5,814 (48.6%) were transfused. Risk-adjusted probability of developing in-hospital mortality and morbidity as a function of red blood cell and blood-component transfusion was modeled using logistic regression. Transfusion of red blood cells was associated with a risk-adjusted increased risk for every postoperative morbid event: mortality (odds ratio [OR], 1.77; 95% confidence interval [CI], 1.67-1.87; p<.0001), renal failure (OR, 2.06; 95% CI, 1.87-2.27; p<.0001), prolonged ventilatory support (OR, 1.79; 95% CI, 1.72-1.86; p<.0001), serious infection (OR, 1.76; 95% CI, 1.68-1.84; p<.0001), cardiac complications (OR, 1.55; 95% CI, 1.47-1.63; p<.0001), and neurologic events (OR, 1.37; 95% CI, 1.30-1.44; p<.0001).

CONCLUSIONS

Perioperative red blood cell transfusion is the single factor most reliably associated with increased risk of postoperative morbid events after isolated coronary artery bypass grafting. Each unit of red cells transfused is associated with incrementally increased risk for adverse outcome.

Effect of Clopidogrel Premedication in Off-Pump Cardiac Surgery

Background— Premedication with clopidogrel has reduced thrombotic complications after percutaneous coronary revascularization procedures. However, because of the enhanced and irreversible platelet inhibition by clopidogrel, patients requiring surgical revascularization have a higher risk of bleeding complications and transfusion requirements. A principal benefit of surgical coronary revascularization without cardiopulmonary bypass is its lower hemorrhagic sequelae. The purpose of this study was to evaluate the effect of preoperative clopidogrel administration in the incidence of hemostatic reexploration, blood product transfusion rates, morbidity, and mortality in patients undergoing off-pump coronary artery bypass graft surgery using a large patient sample and a risk-adjusted approach.

Methods and Results— Two hundred eighty-one patients (17.9%) did and 1291 (82.1%) did not receive clopidogrel before their surgery, for a total of 1572 patients undergoing isolated off-pump coronary artery bypass graft surgery between January 2000 and June 2002. Risk-adjusted logistic regression analyses and a matched pair analyses by propensity scores were used to assess the association between clopidogrel administration and reoperation as a result of bleeding, intraoperative and postoperative blood transfusions received, and the need for multiple transfusions. Hemorrhage-related preoperative risk factors identified in the literature and those found significant in a univariate model were used. The clopidogrel group had a higher likelihood of hemostatic reoperations (odds ratio [OR], 5.1; 95% confidence interval [CI], 2.47 to 10.47; P <0.01) and an increased need in overall packed red blood cell (OR, 2.6; 95% CI, 1.94 to 3.60; P <0.01), multiple unit (OR, 1.6; 95% CI, 1.07 to 2.48; P =0.02), and platelet (OR, 2.5; 95% CI, 1.77 to 3.66; P <0.01) transfusions. Surgical outcomes and operative mortality (1.4% versus 1.4%; P =1.00) were not statistically different.

Conclusions— Clopidogrel administration in the cardiology suite increases the risk for hemostatic reoperation and the requirements for blood product transfusions during and after off-pump coronary artery bypass graft surgery.

Clinical use of plasma and plasma fractions

The use of plasma and plasma-derived products has always involved a careful balance of anticipated benefit versus risk. Risk reduction through pathogen-inactivated products has been successful, but the expense of manufacture does not warrant widespread use. Although plasma has always had limited indications for use, these are often misunderstood or ignored in favor of received knowledge and tradition. Solid evidence from multiple trials support the limited indications for FFP described here and support products that target specific coagulation defects.

Transfusion rates vary significantly amongst Canadian medical centres

PURPOSE

To document variation of transfusion practice following repair of hip fracture or cardiac surgery, as well as those requiring intensive care following a surgical intervention or multiple trauma (high risk patients).

METHODS

We documented rates of allogeneic red cell transfusion in 41,568 patients admitted to 11 hospitals across Canada between August 1998 and August 2000 as part of a retrospective observational cohort study. In the subgroup of 7,552 patients receiving red cells, we also compared mean nadir hemoglobin concentrations from centre to centre.

RESULTS

The overall rate of red cell transfusion was 38.7%, and ranged from 23.8% to 51.9% across centres among the 41,568 perioperative and critically ill patients. Women were more likely to be transfused (43.7% vs 35.3%, P < 0.0001), with higher rates of transfusion in eight of 11 centres. Compared to a chosen reference hospital having a crude transfusion rate near the median, the adjusted odds of transfusion ranged from 0.44 to 1.53 overall, from 0.42 to 1.22 in patients undergoing a hip fracture repair, from 0.72 to 3.17 in cardiac surgical patients undergoing cardiac surgery, and from 0.27 to 1.11 in critically ill and trauma patients. In the 7,552 transfused patients, the mean adjusted nadir hemoglobin was 74.0 +/- 4.83 g x L(-1) overall, and ranged from 66.9 +/- 1.7 g x L(-1) to 84.5 +/- 1.6 g x L(-1) across centres. Similar differences among centres were observed amongst hip fracture patients (71.2 +/- 2.9 g x L(-1) to 82.8 +/- 1.7 g x L(-1)), cardiac surgical patients (65.7 +/- 1.1 g x L(-1) to 77.3 +/- 1.0 g x L(-1)) and critically ill and trauma patients (66.1 +/- 3.04 g x L(-1) to 87.5 +/- 2.5 g x L(-1)).

CONCLUSION

We noted significant differences in the rates of red cell transfusion and nadir hemoglobin concentrations in various surgical and critical care settings.

Hemodilution during cardiopulmonary bypass is an independent risk factor for acute renal failure in adult cardiac surgery

BACKGROUND

This observational study sought to determine whether the degree of hemodilution during cardiopulmonary bypass is independently related to perioperative acute renal failure necessitating dialysis support.

METHODS

Data were prospectively collected on consecutive patients undergoing cardiac operations with cardiopulmonary bypass from 1999 to 2003 at a tertiary care hospital. The independent relationship was assessed between the degree of hemodilution during cardiopulmonary bypass, as measured by nadir hematocrit concentration, and acute renal failure necessitating dialysis support. Multivariate logistic regression was used to control for variables known to be associated with perioperative renal failure and anemia.

RESULTS

Of the 9080 patients included in the analysis, 1.5% (n = 134) had acute renal failure necessitating dialysis support. There was an independent, nonlinear relationship between nadir hematocrit concentration during cardiopulmonary bypass and acute renal failure necessitating dialysis support. Moderate hemodilution (nadir hematocrit concentration, 21%-25%) was associated with the lowest risk of acute renal failure necessitating dialysis support; the risk increased as nadir hematocrit concentration deviated from this range in either direction (P = .005). Compared with moderate hemodilution, the adjusted odds ratio for acute renal failure necessitating dialysis support with severe hemodilution (nadir hematocrit concentration <21%) was 2.34 (95% confidence interval, 1.47-3.71), and for mild hemodilution (nadir hematocrit concentration >25%) it was 1.88 (95% confidence interval, 1.02-3.46).

CONCLUSIONS

Given that there is an independent association between the degree of hemodilution during cardiopulmonary bypass and perioperative acute renal failure necessitating dialysis support, patient outcomes may be improved if the nadir hematocrit concentration during cardiopulmonary bypass is kept within the identified optimal range. Randomized clinical trials, however, are needed to determine whether this is a cause-effect relationship or simply an association.

Clopidogrel administration prior to coronary artery bypass grafting surgery: the cardiologist's panacea or the surgeon's headache?

AIMS

Thrombotic complications after percutaneous coronary intervention procedures have decreased in past years mainly due to the use of clopidogrel antiplatelet therapy. However, the risk of bleeding due to enhanced and irreversible platelet inhibition in patients who will require surgical coronary revascularization instead has not been adequately addressed in the literature. The purpose of this study was to evaluate the effect of pre-operative clopidrogel exposure in haemorrhage-related re-exploration rates, peri-operative transfusion requirements, morbidity, and mortality in patients undergoing coronary artery bypass grafting (CABG) surgery.

METHODS AND RESULTS

A study population of 2359 patients undergoing isolated CABG between January 2000 and June 2002 was reviewed. Of these, 415 (17.6%) received clopidogrel prior to CABG surgery, and 1944 (82.4%) did not. A risk-adjusted logistic regression analysis was used to assess the association between clopidogrel pre-medication (vs. no) and haemostatic re-operation, intraoperative and post-operative blood transfusion rates, and multiple transfusions received. Haemorrhage-related pre-operative risk factors identified from the literature and those found significant in a univariate model were used. Furthermore, a sub-cohort, matched-pair by propensity scores analysis, was also conducted. The clopidogrel group had a higher likelihood of haemostatic re-operation [OR = 4.9, (95% CI, 2.63-8.97), P < 0.01], an increase in total packed red blood cell transfusions [OR = 2.2, (95% CI, 1.70-2.84), P < 0.01], multiple unit blood transfusions [OR = 1.9, (95% CI, 1.33-2.75), P < 0.01] and platelet transfusions [OR = 2.6, (95% CI, 1.95-3.56), P < 0.01]. Surgical outcomes and operative mortality [OR = 1.5, (95% CI, 0.36-6.51), P = 0.56] were not significantly different.

CONCLUSION

Pre-operative clopidogrel exposure increases the risk of haemostatic re-operation and the requirements for blood and blood product transfusion during, and after, CABG surgery.