Predictors of excessive blood use after coronary artery bypass grafting

Consensus Statement: Hemostasis Trial Outcomes in Cardiac Surgery and Mechanical Support

BACKGROUND

Research evaluating hemostatic agents for the treatment of clinically significant bleeding has been hampered by inconsistency and lack of standardized primary clinical trial outcomes. Clinical trials of hemostatic agents in both cardiac surgery and mechanical circulatory support, such as extracorporeal membrane oxygenation and ventricular assist devices, are examples of studies that lack implementation of universally accepted outcomes.

METHODS

A subgroup of experts convened by the National Heart, Lung, and Blood Institute and the US Department of Defense developed consensus recommendations for primary outcomes in cardiac surgery and mechanical circulatory support.

RESULTS

For cardiac surgery the primary efficacy endpoint of total allogeneic blood products (units vs mL/kg for pediatric patients) administered intraoperatively and postoperatively through day 5 or hospital discharge is recommended. For mechanical circulatory support outside the perioperative period the recommended primary outcome for extracorporeal membrane oxygenation is a 5-point ordinal score of thrombosis and bleeding severity adapted from the Common Terminology Criteria for Adverse Events version 5.0. The recommended primary endpoint for ventricular assist device is freedom from disabling stroke (Common Terminology Criteria for Adverse Events AE ≥ grade 3) through day 180.

CONCLUSIONS

The proposed composite risk scores could impact the design of upcoming clinical trials and enable comparability of future investigations. Harmonizing and disseminating global consensus definitions and management guidelines can also reduce patient heterogeneity that would confound standardized primary outcomes in future research.

Microvascular reactivity measured by vascular occlusion test is an independent predictor for postoperative bleeding in patients undergoing cardiac surgery

The purpose of the study is to investigate the relationship between microvascular reactivity and postoperative bleeding in cardiac surgery. The authors retrospectively analyzed a prospectively collected registry of cardiac surgery patients. Data from 154 patients enrolled in the registry were analyzed. A linear mixed model was performed to evaluate the association between the amount of postoperative chest tube output (CTO, milliliter, repeatedly measured at 0-8, 8-24, and 24-48 h) and tissue oxygen saturation (StO₂₎ recovery slope (%/s) measured by vascular occlusion test (VOT) at skin closure. A logistic regression was carried out to see the relationship between StO₂ recovery slope and packed red blood cell (PRBC) transfusion during the 48-h postoperative period. In the multivariable adjusted model, the effect of StO₂ recovery slope on postoperative CTO (log-transformed) was statistically significant, and the degree of StO₂ recovery slope was inversely related to the amount of CTO (exp(estimate) = 0.935; exp(95% CI) 0.881-0.992; p = 0.027). StO₂ recovery slope was also inversely associated with postoperative PRBC transfusion possibility (OR = 0.795; 95% CI 0.633-0.998; p = 0.048). Microvascular reactivity measured by VOT is independently and inversely associated with postoperative bleeding in patients undergoing cardiac surgery.

Blood Conservation Strategies in Cardiac Surgery

Perioperative bleeding in cardiac surgery is related to both surgical trauma of blood vessels and defects in the hemostatic mechanism caused, in part, by cardiopulmonary bypass. Blood transfusion therefore remains a significant risk of cardiac surgery with important health and economic consequences. Blood conservation strategies for cardiac surgery have advanced over the years and the following discussion will focus on the current practices at Toronto General Hospital.

A novel chest packing technique for intractable bleeding after open heart surgical procedures

Intractable bleeding after cardiac surgical procedures is a life-threatening complication. In most cases, the main bleeding site is present in the retrosternal space, not the pericardial space. Packing the chest may be a useful technique for achieving hemostasis. Herein, we describe a novel and effective procedure for the treatment of intractable bleeding in the retrosternal space using a sheet of oxidized regenerated cellulose and sponges after cardiac surgical procedures.

[Haemorrhage and morbidity associated with the use of tranexamic acid in cardiac surgery: a retrospective, multicentre cohort study]

INTRODUCTION

Postoperative bleeding is common complication, affecting up to 20% of patients, after cardiac bypass surgery. Fibrinolysis is one of the causes of this excessive bleeding, and for this reason the use of tranexamic acid is recommended. The problem with using this is that there are numerous guidelines and differences in the dose to be administered. Our aim was to evaluate whether there were any differences in postoperative bleeding and morbidity after cardiac surgery with the administering of different tranexamic acid doses in three university hospitals.

MATERIAL AND METHODS

A retrospective, multicentre cohort study was conducted. A total of 146 patients who were subjected to elective cardiac bypass surgery according to the anaesthetic-surgical protocol of each hospital were included in the study. The clinical histories were reviewed, and they were divided into two groups according to the tranexamic acid dose: Group A (high doses), initial dose of 20mg/kg and continuous infusion of 4 mg/kg/hour until closure of the sternotomy. A further 100mg was added to prime the bypass machine. Group B (low doses), initial dose of 10mg/kg followed by a continuous infusion of 2mg/kg/hour until closure of the sternotomy. A further 50mg was added to prime the bypass machine. Variables, such as age, sex, weight, height, type of surgical procedure (valvular, coronary or mixed), haematocrit, INR, and preoperative platelet count, time and temperature of the bypass machine, and haematocrit on sternum closure, were recorded. Among the post-operative variables collected were: debit due to drainage at 6, 12 and 24 hours after surgery, number and type of blood products transfused in the first 24 hours, need for further surgery due to haemorrhage, CVA, TIA, or a new acute myocardial infarction, convulsions, and mortality.

RESULTS

The incidence of increased bleeding (patients in the 90 percentile) was higher in Group B at all the study evaluation times (P<.05). The incidence of further surgery due to bleeding, and the need for transfusion of ≥ 3 units of packed red cells was lower in Group A (5.56%) than in Group B (13.89%). There were no significant differences in the requirements for blood products transfusions between the groups. As regards associated morbidity, there was one isolated case of convulsion and a perioperative AMI in another case in Group A, and three cases of perioperative AMI in Group B.

CONCLUSIONS

Elevated doses of tranexamic acid in cardiac bypass surgery appear to significantly reduce bleeding in the first hours after surgery compared to low doses. However, this decrease did not lead to a reduction in the needs for blood products.

An operational research approach to identify cardiac surgery patients at risk of severe post-operative bleeding

Severe post-operative bleeding can lead to adverse outcomes for cardiac surgery patients and is a relatively common complication of cardiac surgery. One of the most effective drugs to prevent such bleeding, aprotinin, has been withdrawn from the market due to concerns over its safety. Alternative prophylactic drugs which can be given to patients to prevent bleeding can result in significant side effects and are expensive. For this reason it is difficult to make a clinical or economic case for administering these drugs to all cardiac surgery patients, and the prevailing view is that their use should be targeted at patients considered to be at relatively high risk of post-operative bleeding. However, there is currently no objective method for identifying such patients. Over the past 7 years, a team of clinicians and researchers at Papworth Hospital has collected data concerning post-operative blood loss for each cardiac surgery patient, totalling 11,592 consecutive records. They approached a team of operational researchers (MU, ACP, BR) with extensive experience of developing clinical risk models with the aim of devising a risk stratification scheme that could potentially be used to identify a cohort of higher risk patients. Such patients could be treated with the available prophylactic drugs or recruited to studies to evaluate new interventions. This paper is intended to describe the Operational Research process adopted in the development of this scheme. A concise description of the scheme and its clinical interpretation is published elsewhere.

Perioperative Coagulopathy, Bleeding, and Hemostasis During Cardiac Surgery

Cardiac surgery patients use 10%-25% of the blood products transfused annually in the United States. The transfusion of red blood cells or blood products has been the subject of intense scrutiny over the past 10 years. Bleeding after cardiac surgery can be surgical or nonsurgical and lead to hemodynamic compromise and surgical reexploration. Because hemorrhage and blood product transfusions are associated with multiple negative outcomes, including increased mortality, it is prudent to understand the mechanisms responsible for nonsurgical bleeding. This review focuses on the physiology of the normal coagulation and fibrinolysis, risk factors associated with patients presenting for cardiac surgery, impairments of normal hemostasis associated with cardiac surgery and cardiopulmonary bypass (CPB), and potential interventions to reduce perioperative blood loss and blood transfusion.

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.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.

Does the Use of Preoperative Aspirin Increase the Risk of Bleeding in Patients Undergoing Coronary Artery Bypass Grafting Surgery? Systematic Review and Meta-Analysis

BACKGROUND

The traditional recommendation has been to stop Aspirin seven to 10 days prior to coronary artery bypass surgery to reduce the potential risk of bleeding. A few reports have shown that Aspirin did not increase the risk of bleeding and may be beneficial to be continued until the time of surgery. The objective of this review was to evaluate the effect of preoperative Aspirin on bleeding in patients undergoing elective bypass surgery.

METHODS

A meta-analysis of 10 randomized and nonrandomized studies reporting comparisons between Aspirin and control was undertaken. The primary outcome was the total amount of postoperative chest tube drainage. Secondary outcomes were the number of units of packed red blood cell transfusion, platelet transfusion, fresh frozen plasma transfusion, and number of patients reexplored for bleeding.

RESULTS

Ten studies, involving 1748 patients, met the inclusion criteria for this review of whom 913 were in the Aspirin group and 835 were in the control group. Pooling the results of all studies showed a significant increase in blood loss and transfusion of red blood cells and fresh frozen plasma in the Aspirin group (p < 0.05). There was no significant difference between the two groups in the rate of platelet transfusion, or the incidence of reexploration (p > 0.05). Included studies were heterogeneous and of low methodological quality.

CONCLUSION

Aspirin is associated with increased chest tube drainage and may be associated with a greater requirement for blood products. High-quality prospective studies are warranted to reassess the effect of Aspirin on important postoperative outcomes.

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.

Trauma Associated Severe Hemorrhage (TASH)-Score: probability of mass transfusion as surrogate for life threatening hemorrhage after multiple trauma

BACKGROUND

To develop a simple scoring system that allows an early and reliable estimation for the probability of mass transfusion (MT) as a surrogate for life threatening hemorrhage following multiple trauma.

METHODS

Potential clinical and laboratory variables documented in the Trauma Registry of the German Trauma Society (DGU) (1993-2003; n=17,200) were subjected to univariate and multivariate logistic regression analysis to predict the probability for MT.

RESULTS

Clinical and laboratory variables available from data sets were screened for their association with mass transfusion. MT was defined by transfusion requirement of >or=10 units of packed red blood cells from emergency room (ER) to intensive care unit admission. Seven independent variables were identified to be significantly correlated with an increased probability for MT: systolic blood pressure (<100 mm Hg=4 pts, <120 mm Hg=1 pt), hemoglobin (<7 g/dL=8 pts, <9 g/dL=6 pts, <10 g/dL=4 pts, <11 g/dL=3 pts, and <12 g/dL=2 pts), intra-abdominal fluid (3 pts), complex long bone and/or pelvic fractures (AIS 3/4=3 pts and AIS 5=6 pts), heart rate (>120=2 pts), base excess (<-10 mmol/L=4 pts, <-6 mmol/L=3 pts, and <-2 mmol/L=1 pt), and gender (male=1 pt). These variables were incorporated into a risk score, the Trauma Associated Severe Hemorrhage Score (TASH-Score, 0-28 points). Performance of the score was tested with respect to discrimination, precision, and calibration. Increasing TASH-Score points were associated with an increasing probability for MT.

CONCLUSION

The TASH-Score is an easy-to-use scoring system that reliably predicts the probability for MT after multiple trauma. Taken as a surrogate for life threatening bleeding calculation may focus attention on relevant variables indicative for risk and impact strategies to stop bleeding and stabilize coagulation in acute trauma care.

Development and validation of Transfusion Risk Understanding Scoring Tool (TRUST) to stratify cardiac surgery patients according to their blood transfusion needs

BACKGROUND

Allogeneic blood transfusion is associated with transfusion reactions, infection transmission, and postoperative morbidity and mortality. The objective of this study was to develop and validate an accurate and simple clinical index to stratify cardiac surgery patients according to their blood transfusion needs.

METHODS AND RESULTS

Data on consecutive adult patients who underwent cardiac surgery at Toronto General Hospital (n = 11,113) and Sunnybrook and Women's College Health Sciences Center (n = 5316) between May 1999 and June 2004 were collected for the development, validation, and external validation of the index. Primary outcome was the exposure to blood transfusion in the operative and first postoperative days. Multivariable logistic regression modeling techniques were used to determine the relationship between each independent variable and the exposure to allogeneic blood transfusion. Score assignment for each predictor variable was based on its regression coefficient. The predicted probabilities at each total score were compared to the observed proportions of patients exposed to blood transfusion. The clinical tool consists of eight preoperative variables: preoperative hemoglobin, weight, female sex, age, nonelective procedure, preoperative creatinine, previous cardiac surgical procedure, and nonisolated procedure.

CONCLUSIONS

Based on the standards of measurement in clinical research, a valid clinical tool was developed for predicting the need for blood transfusion in patients undergoing cardiac surgery. The clinical tool was internally and externally validated, and the results suggest that it should perform well at other institutions.

Factors predicting loss and gain of red cell volume in cardiac surgery patients

Haemoglobin may be a poor indicator of changes in red cell volume (RCV) because of factors such as haemodilution. This study has been designed to analyse what peri-operative variables may be associated with loss or gain in RCV due to bleeding or transfusion. Prospective observational study. Single centre study based in a regional cardiac surgery centre. Twenty-nine elective adult cardiac surgery patients. Loss and gain of RCV were measured in theatre and for the first 24 h post-operatively. Patient and operative factors analysed were age, sex, height, weight, body surface area (BSA), induction haematocrit (Hct), estimated pre-operative RCV and antiplatelet therapy taken less than 7 days before operation, cardiopulmonary bypass (CPB) time, aortic occlusion time, minimum and maximum CPB temperatures and fluid administered. Age, sex, height, weight, BSA and induction Hct were found to predict red cell transfusion but not RCV loss. The total number of red cells transfused was significantly associated with RCV lost when expressed as a percentage reduction in the estimated pre-operative RCV but not the absolute RCV lost. Pre-operative RCV, as predicted by the variables outlined above, is more important than RCV lost in triggering red cell transfusion.

Effect on platelet function of cilostazol, clopidogrel, and aspirin, each alone or in combination

Management of peripheral arterial disease (PAD) requires standard atherosclerotic risk management interventions. However, PAD is often complicated by walking pain (intermittent claudication [IC]), which requires symptom-specific therapies as well. Thus, all PAD patients are encouraged to take antiplatelet agents to reduce the associated risks of major cardiovascular events, and those with IC may also require treatment with cilostazol, an agent proven to increase exercise capacity and enhance quality of life in these patients. Although it was initially thought that cilostazol's antiplatelet properties might render it unsafe to use in combination with other platelet inhibitors because of possible additive effects, a recent study has dispelled such concerns. There is evidence that in a crossover trial of 21 patients with PAD and IC, aspirin alone, or clopidogrel alone, significantly increased bleeding times, but cilostazol alone did not. The combination of aspirin and clopidogrel had a greater effect on increasing bleeding time than either monotherapy, and no further bleeding time prolongation was observed, when cilostazol was added to any aspirin/clopidogrel regimen. These findings suggest that PAD patients with IC may be safely managed with both cilostazol and standard antiplatelet therapy, without increasing the risk of adverse bleeding effects.

Hemodilution and surgical hemostasis contribute significantly to transfusion requirements in patients undergoing coronary artery bypass

OBJECTIVE

We sought to determine the incidence of and risk factors for the development of low intraoperative hematocrit levels and of excessive postoperative bleeding in patients undergoing coronary artery bypass grafting, whether the risk factors are the same, and their effect on blood product transfusions.

METHODS

We performed a prospective cohort study of 613 adult patients who underwent coronary artery bypass grafting in 3 tertiary, university-affiliated hospitals during the period from October 1, 2000, to March 31, 2001.

RESULTS

Low intraoperative hematocrit levels (<19%) were found in 131 (24%) patients who had operations performed with extracorporeal circulation compared with in 3 (4%) patients with operations performed off pump. In multivariate analysis this was associated with older age, female sex, lower preoperative hemoglobin levels, lower body surface area, longer duration on bypass, and use of higher total volumes with more hydroxyethyl starch in the circuit. Low intraoperative hematocrit levels did not predict excessive postoperative hemorrhage (>1 L of mediastinal drainage in the first 12 hours). This occurred in 26% (n = 140) of patients undergoing on-pump operations and in 25% of patients undergoing off-pump operations and in multivariate analysis was associated with male sex, longer pump times, not receiving aprotinin, and operations performed by certain surgeons but not with total circuit or hydroxyethyl starch volume.

CONCLUSIONS

We observed that the risk factors for the development of a low intraoperative hematocrit level and excessive postoperative bleeding differed. Our results suggest that decreasing these outcomes in patients undergoing cardiac surgery requires a comprehensive approach, including limiting hemodilution, particularly in female subjects with lower preoperative hemoglobin levels, and careful attention to surgical hemostasis.

Artificial Neural Network Medical Decision Support Tool: Predicting Transfusion Requirements of ER Patients

Blood product transfusion is a financial concern for hospitals and patients. Efficient utilization of this dwindling resource is a critical problem if hospitals are to maximize patient care while minimizing costs. Traditional statistical models do not perform well in this domain. An additional concern is the speed with which transfusion decisions and planning can be made. Rapid assessment in the emergency room (ER) necessarily limits the amount of usable information available (with respect to independent variables available). This study evaluates the efficacy of using artificial neural networks (ANNs) to predict the transfusion requirements of trauma patients using readily available information. A total of 1016 patient records are used to train and test a backpropagation neural network for predicting the transfusion requirements of these patients during the first 2, 2-6, and 6-24 h, and for total transfusions. Sensitivity and specificity analysis are used along with the mean absolute difference between blood units predicted and units transfused to demonstrate that ANNs can accurately predict most ER patient transfusion requirements, while only using information available at the time of entry into the ER.

Clinical Outcomes in Cardiac Surgery: Conventional Surgery versus Bloodless Surgery

Bleeding during and after cardiac operations and the effects of cardiopulmonary bypass hemodilution commonly result in blood transfusions. Excessive microvascular bleeding can result in re-exploration and prolonged hospitalization. Nearly 20% of all blood transfusions in the United States are associated with cardiac surgery. The risks associated with the use of allogeneic blood product transfusion include mistransfusion, immunologic complications, and transmission of infectious diseases. The large demand for blood products places significant pressure on the national blood supply, resulting in frequent shortages. The variability in transfusion practice of cardiac surgery patients suggests that sound blood management and a conservative approach to this population can result in reduced transfusions without increasing morbidity or mortality and avoiding complications associated with allogeneic blood transfusion.

Beneficial effect of acute normovolemic hemodilution in cardiovascular surgery

OBJECTIVE

The efficacy of acute normovolemic hemodilution (ANH) in avoiding homologous blood transfusion (HBT) during cardiovascular surgery remains controversial. Our objective was to evaluate the impact of ANH on blood transfusion requirements during open cardiovascular surgery using cardiopulmonary bypass (CPB).

METHODS

We retrospectively reviewed 243 patients who had undergone open cardiac or thoracic aortic surgery using CPB between September 2001 and July 2003 in our department. ANH was performed when the hematocrit was over 35% and the patient was hemodynamically stable. Risk factors were selected in accordance with the Japanese Adult Cardiovascular Surgery Database and analyzed to determine their effect on perioperative HBT requirement.

RESULTS

Of the 243 patients, 64 (26%) underwent preoperative autologous blood donation and 62 (26%) ANH. HBT was required in 62% of patients (150/243) overall, in 32% (20/62) of ANH patients, and in 76% (130/171) of non-ANH patients. Multivariate stepwise logistic regression analysis revealed that preoperative or pre-donation hemoglobin value (p < 0.001), duration of surgery (p = 0.001), intraoperative minimum rectal temperature (p = 0.001), age (p = 0.002), need for emergency surgery (p = 0.003), amount of ANH (p = 0.018), blood loss (p = 0.033) and amount of preoperative autologous blood donation (p = 0.042) were independent predictors of the need for perioperative HBT.

CONCLUSIONS

Our data showed that open cardiovascular surgery using CPB continues to pose a high risk of HBT, but that ANH is an effective means of reducing this risk in those patients undergoing these operations.

Predictors of transfusion requirements for cardiac surgical procedures at a blood conservation center

BACKGROUND

Previous studies defining perioperative risk factors for allogeneic transfusion requirements in cardiac surgery were limited to highly selected cardiac surgery populations or were associated with high transfusion rates. The purpose of this study was to determine perioperative risk factors and create a formula to predict transfusion requirements for major cardiac surgical procedures in a center that practices a multimodality approach to blood conservation.

METHODS

We performed an observational study on 307 consecutive patients undergoing coronary artery bypass grafting, valve, and combined (coronary artery bypass grafting and valve) procedures. An equation was derived to estimate the risk of transfusion based on preoperative risk factors using multivariate analysis. In patients with a calculated probability of transfusion of at least 5%, intraoperative predictors of transfusion were identified by multivariate analysis.

RESULTS

Thirty-five patients (11%) required intraoperative or postoperative allogeneic transfusions. Preoperative factors as independent predictors for transfusions included red blood cell mass, type of operation, urgency of operation, number of diseased vessels, serum creatinine of at least 1.3 mg/dL, and preoperative prothrombin time. Intraoperative factors included cardiopulmonary bypass time, three or fewer bypass grafts, lesser volume of acute normovolemic hemodilution removed, and total crystalloid infusion of at least 2,500 mL. The derived formula was applied to a validation cohort of 246 patients, and the observed transfusion rates conformed well to the predicted risks.

CONCLUSIONS

A multimodality approach to blood conservation in cardiac surgery resulted in a low transfusion rate. Identifying patients' risks for transfusion should alter patient management perioperatively to decrease their transfusion rate and make more efficient use of blood resources.

Avoidance of Bleeding During Surgery in Patients Receiving Anticoagulant and/or Antiplatelet Therapy

Perioperative management of chronically anticoagulated patients and/or patients treated with antiplatelet therapy is a complex medical problem. This review considers the pharmacokinetic and pharmacodynamic properties of commonly used antiplatelet and anticoagulant drugs with special emphasis on loss of effects after discontinuation and possible counteracting (or antidote) strategies. These drugs are aspirin (acetylsalicylic acid), ticlopidine/clopidogrel, abciximab, tirofiban and eptifibatide, heparin (unfractionated and low-molecular-weight), warfarin and direct thrombin inhibitors. Since the pharmacological mechanisms of some of these drugs are based on irreversible or slowly reversible effects, their pharmacokinetic profiles are not necessarily predictive for their pharmacodynamic profiles. A close and direct relationship between plasma concentrations and effects is seen only for the glycoprotein (GP) IIb/IIIa inhibitors tirofiban and eptifibatide with a fast off-rate for dissociation from the GPIIb/IIIa receptor, and for direct thrombin inhibitors (hirudin and argatroban). For other compounds, drug concentrations in plasma and pharmacodynamic effects are not closely correlated because of, for example, irreversible binding to their target (aspirin, clopidogrel and abciximab), inhibition of the generation of a subset of clotting factors with differing regeneration and degradation rates (coumarins) or sustained binding to the vascular wall (heparins). Surgery in patients on anticoagulant and/or antiplatelet therapy may be categorised as: (i) elective versus urgent; and (ii) cardiopulmonary bypass (CPB) versus non-CPB. Monotherapy with clopidogrel or aspirin need not be discontinued in elective non-CPB surgery, and temporary discontinuation of warfarin should be accompanied by preoperative intravenous heparin only in selected high-risk patients. Vitamin K as an antidote for warfarin should only be used subcutaneously and solely in urgent/emergency surgery. In elective surgery requiring CPB (coronary artery bypass grafting), it is recommended to discontinue aspirin 7 days preoperatively in patients with a low risk profile. Patients requiring urgent CPB surgery (e.g. after failure of a percutaneous coronary angioplasty with or without coronary stent deployment) are usually pretreated with several antiplatelet agents (e.g. aspirin and clopidogrel, together with a GPIIb/IIIa inhibitor) together with unfractionated or low-molecular-weight heparin. With judicious planning, urgent/emergency cardiac surgery can be safely performed on these patients. Delaying surgery (e.g. for 12 hours in patients treated with abciximab) should be considered if possible. Standard heparin doses should be given to achieve optimal anticoagulation for CPB. Prophylactic use of aprotinin (intra- and/or postoperatively), aminocaproic acid or tranexamic acid should be considered. Early (in the operating theatre prior to chest closure) and judicious use of replacement blood products (platelets) should be commenced when clinically indicated.

Review of the clinical practice literature on patient characteristics associated with perioperative allogeneic red blood cell transfusion

There is evidence to suggest that there exists considerable variation in red blood cell (RBC) transfusion practices, especially in the surgical specialties. This is in large part related to difficulties in defining specific transfusion threshold criteria, given that there is no minimum acceptable hemoglobin threshold concentration and there is variability in assigning importance to patient factors. The purpose of this study is to identify patient-related factors that might be associated with the need for allogeneic RBC transfusion in surgical patients. We systematically identified, selected, and reviewed all observational or interventional studies describing patient-specific or related variables associated with the need for allogeneic RBC transfusion in the surgical patient population. We also evaluated the methodological characteristics of the individual studies. Sixty-two studies met our inclusion criteria and were analyzed for this review. Most of these studies were conducted in patients undergoing cardiac surgery (n = 30) and orthopedic surgery (n = 16). Decreased preoperative red cell reserve was most frequently associated with RBC transfusions, being identified as a significant variable in 46 studies. The other factors commonly associated with transfusion were advancing age (n = 28), female gender (n = 21), and small body size (n = 14). Only 2 studies attempted to prospectively validate a predictive model for RBC transfusion based on the variables identified. This systematic review shows that preoperative anemia, advancing age, female gender, and small body size are often associated with perioperative allogeneic RBC transfusion. However, the retrospective nature of most of the studies and the small sample sizes make it difficult to formulate a clinically useful prediction rules regarding allogeneic RBC transfusion. Ongoing research in designing large prospective cohort studies evaluating transfusion patterns are needed to further elucidate how patient characteristics impact the transfusion threshold.

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

CONTEXT

The ability to predict the use of blood components during surgery will improve the blood bank's ability to provide efficient service.

OBJECTIVE

Develop prediction models using preoperative risk factors to assess blood component usage during elective coronary artery bypass graft surgery (CABG).

DESIGN

Eighty-three preoperative, multidimensional risk variables were evaluated for patients undergoing elective CABG-only surgery.

MAIN OUTCOMES MEASURES

The study endpoints included transfusion of fresh frozen plasma (FFP), platelets, and red blood cells (RBC). Multivariate logistic regression models were built to assess the predictors related to each of these endpoints.

SETTING

Department of Veterans Affairs (VA) health care system.

PATIENTS

Records for 3034 patients undergoing elective CABG-only procedures; 1033 patients received a blood component transfusion during CABG.

RESULTS

Previous heart surgery and decreased ejection fraction were significant predictors of transfusion for all blood components. Platelet count was predictive of platelet transfusion and FFP utilization. Baseline hemoglobin was a predictive factor for more than 2 units of RBC. Some significant hospital variation was noted beyond that predicted by patient risk factors alone.

CONCLUSIONS

Prediction models based on preoperative variables may facilitate blood component management for patients undergoing elective CABG. Algorithms are available to predict transfusion resources to assist blood banks in improving responsiveness to clinical needs. Predictors for use of each blood component may be identified prior to elective CABG for VA patients.

Preoperative blood volume deficit influences blood transfusion requirements in females and males undergoing coronary bypass graft surgery

STUDY OBJECTIVE

To evaluate whether preoperative blood volume and postoperative blood loss influence blood transfusion in females and males undergoing coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective study.

SETTING

Anesthesiology department of a teaching hospital.

PATIENTS

57 CABG patients (21 females and 36 males).

MEASUREMENTS

Blood volume was determined using the radioactivity dilution method. Preoperatively, each patient received intravenous (IV) injection of 1 mL Albumin I(131) tracer having 25 microcuries of radioactivity. Five-milliliter blood samples were collected at different intervals. From these samples, hematocrit (Hct) value, preoperative total blood volume, red blood cell (RBC) volume, and plasma volume were determined. Postoperatively, some consenting patients received another 1 mL dose of the tracer, and the postoperative blood volumes were determined. If a patient received a blood transfusion, the units of packed red blood cells (PRBCs), platelets, or fresh frozen plasma (FFP) transfused were recorded. For each patient we recorded the gender, age, weight, height, body surface area (BSA), preoperative Hct, duration of surgery, and discharge Hct.

RESULTS

Preoperatively, the mean total blood volume, RBC volume, and plasma volume, respectively, were 2095 mL/m(2), 631 mL/m(2), and 1,465 mL/m(2) in females; and 2,580 mL/m(2), 878 mL/m(2), and 1,702 mL/m(2) in males. The preoperative blood volumes were significantly lower (p < 0.01) in females than in males. There was no significant difference between males and females in the extent of blood loss during CABG. Intraoperatively, females received PRBC transfusion of 1.38 units, significantly more (p < 0.01) than the 0.39 units received by males. During the entire hospital stay, females received 4.33 units of PRBC, significantly more than (p < 0.02) the 1.33 units received by males. Significantly more (p < 0.01) females (12 of 21) received intraoperative PRBC transfusion than did males (6 of 36). Multiple logistic regression analysis of the data showed that PRBC transfusion was significantly correlated with the preoperative total blood volume and RBC volume.

CONCLUSION

The greater need for blood transfusion in females than in males during CABG is primarily attributable to significantly lower preoperative total blood volume and RBC volume in females.

Prophylactic positive end-expiratory pressure and reduction of postoperative blood loss in open-heart surgery

BACKGROUND

Various strategies have been introduced to minimize transfusion requirements in cardiac surgery. One strategy is the use of positive end-expiratory pressure (PEEP) postoperatively. Currently, PEEP is used in many centers to control increased mediastinal chest-tube drainage. The purpose of this study was to determine whether the prophylactic application of a PEEP of 10 cm H2O compared with a PEEP of 5 cm H2O in the immediate postoperative period reduces mediastinal chest-tube output without causing clinically significant hemodynamic compromise.

METHODS

We prospectively studied 84 elective coronary artery bypass grafted patients and randomized treatment groups to a PEEP of 5 or 10 cm H2O. Forty-four patients were assigned a PEEP of 5 cm H2O and 40 patients received a PEEP of 10 cm H2O.

RESULTS

Preoperative, intraoperative, and postoperative demographics were similar between groups. There was no statistically significant difference between the 5 cm H2O PEEP group and the 10 cm H2O PEEP group with regard to chest-tube output at 6 hours, at 24 hours, or in total output. There was no statistical difference in hemoglobin levels immediately postoperatively, at 8 hours, or at 36 hours.

CONCLUSIONS

This study demonstrates that the use of postoperative PEEP levels of 10 cm H2O, although safe, does not reduce chest-tube output or transfusion requirements.

Aspirin and postoperative bleeding after coronary artery bypass grafting

OBJECTIVE

To evaluate the relationship between aspirin ingestion and postoperative bleeding complications, and to test the hypothesis that there is a subset of patients who are aspirin hyperresponders with a proclivity toward platelet dysfunction.

SUMMARY BACKGROUND DATA

Despite numerous retrospective and prospective analyses, it is still controversial as to whether aspirin ingestion before coronary artery bypass grafting (CABG) is associated with significant postoperative bleeding.

METHODS

Between January 1995 and December 1999, the records of 2,606 consecutive patients undergoing CABG were reviewed to identify patients with a history of aspirin ingestion up until the time of surgery. Aspirin ingestion was correlated with postoperative blood transfusion using multivariate analysis. In a subset of preoperative aspirin users (n = 40), bleeding times were measured before and after aspirin use. Flow cytometry was performed in another cohort of patients with known heart disease (n = 30) to determine the effect of aspirin on platelet surface receptors.

RESULTS

During the 5-year study period, 63% of the CABG patients were identified as aspirin users. Among these, 23.1% required blood transfusions compared with 19% for the nonusers. Non-red blood cell transfusions were more common in aspirin users, as was reexploration for bleeding. Stratification of these results according to the frequency of aspirin use showed that aspirin is an independent multivariate predictor of postoperative blood transfusion only in high-risk patients. In the prospective studies, aspirin treatment resulted in a significant increase in the template bleeding time, an increase in platelet PAR-1 thrombin receptor activity, and a decrease in the binding of platelets to monocytes.

CONCLUSIONS

The findings support the hypothesis that aspirin is associated with a greater likelihood of postoperative bleeding. A platelet function testing algorithm that combines preoperative risk factor assessment, template bleeding times, and flow cytometry may allow the identification of aspirin hyperresponders who are at increased risk for bleeding.

Hemostatic Abnormalities in Cardiopulmonary Bypass: Pathophysiologic and Transfusion Considerations

Cardiac surgical procedures typically use cardiopulmo nary bypass (CPB), a technique that diverts blood from the heart and lungs, where it is oxygenated and pumped back into the circulation. CPB is associated with significant pathophysiologic changes leading to an increased bleeding risk. Bleeding during CPB occurs for multiple reasons; the primary reason is the expo sure of blood to the material components of the CPB system, with intense systemic coagulation and platelet, fibrinolytic, and endothelial activation. To counteract the coagulation activation, extremely high levels of heparin anticoagulation are required to prevent sys temic thrombosis. Thrombin generation through tissue factor pathway activation is now thought to be the predominant mechanism of coagulation activation in CPB. The stimulus for tissue factor exposure to blood is thought to be a systemic activation of tissue factor on monocytes and endothelial cells caused by comple ment activation by the CPB materials and circulating inflammatory mediators. Despite improvements in the CPB system, surgical techniques, and blood conserva tion methods, the demand for blood in such procedures remains sustantial. Optimal blood use can be achieved by combining blood conservation measures with the transfusion of blood components according to strict guidelines. Blood is a limited resource and must be used wisely and cautiously. The risks and costs associ ated with transfusion are compelling reasons to mini mize unnecessary exposure to blood. However, the bene fits of transfusion are well established, and the risks are reasonably low. New developments in the surfaces of the CPB system, use of established and new protease inhibitors, and new blood conservation measures offer promise in decreasing the bleeding risk associated with CPB.

Warfarin therapy does not increase bleeding in patients undergoing heart transplantation

BACKGROUND

Historically, warfarin has been discontinued or rapidly reversed with fresh frozen plasma in patients awaiting heart transplantation because of concerns regarding excessive bleeding. Because preoperative warfarin may have effects on bleeding after cardiac operations, we reviewed our experience to determine the risks in patients undergoing heart transplantation while maintained on warfarin.

METHODS

The records of consecutive adult patients undergoing heart transplantation from January 1996 to December 1998 were reviewed. Preoperative and 24-hour postoperative data were obtained, including patient demographics; hematologic laboratory values; medication use; repeat or primary sternotomy data; allogeneic blood product administration; and chest tube drainage. Multivariate linear and logistic regression analyses were performed using these variables to determine risk factors for bleeding after heart transplantation.

RESULTS

Ninety adult patients, mean age 50 years, underwent orthotopic heart transplantation during the 36-month period. No relationships existed between preoperative international normalized ratio (INR, mean = 1.83 +/- 0.1, p = 0.84) or postoperative INR (mean = 2.2 +/- 0.9, p = 0.63) and chest tube drainage (mean = 721 +/- 63 mL). Relationships were observed between total blood product administration and preoperative INR (partial r = 0.30, p = 0.01) and postoperative INR (partial r = -0.37, p = 0.002); however, preoperative INR did not correlate (p = 0.29) when perioperative use of fresh frozen plasma was factored as a covariate. Inverse relationships were evident between postoperative INR and total blood product exposures, as well as transfusions of platelets (partial r = -0.26, p = 0.03), fresh frozen plasma (partial r = -0.28, p = 0.02), and red cells (partial r = -0.25, p = 0.04).

CONCLUSIONS

Although we noted no correlations between INR and chest tube output, inverse relationships were observed with transfusion requirements in the first 24 hours after transplantation. Preoperative warfarin may be safely continued in patients awaiting heart transplantation.

Discontinuation of the Bleeding Time Test without Detectable Adverse Clinical Impact

Background: The bleeding time (BT) test predicts a higher bleeding complication rate in populations at risk for inherited or acquired platelet dysfunction, but it is of limited assistance in evaluating individual patients. There are no reports of clinical outcomes after discontinuation of the BT test.

Methods: Interviews with a subset of the physicians who had ordered the BT test before discontinuation of the test were conducted. The total number of platelet-aggregation tests, the mean number of monthly, unmodified platelet units transfused, the incidence of kidney biopsy complications, and the number of doses of 1-deamino-8-d-arginine vasopressin (DDAVP) administered 5 months before and after discontinuation of the BT test were compared. We recorded the rates of bleeding complications in the Major Surgery Risk Pool during the 12 months before and the 5 months after the discontinuation of the BT test.

Results: Clinicians reported they did not significantly change their preprocedural work-ups, postpone an invasive procedure, experience an increase in bleeding complications, or increase their use of blood products after discontinuation of the BT test. Platelet-aggregation tests (n = 9, before and after), platelet transfusions (P = 0.958), and DDAVP administration (before = 24; after = 10) did not increase after discontinuation of the BT test. The rate of postprocedural bleeding complications did not increase significantly in either Major Surgery Risk Pool cases (&lt;3ς deviation from the mean rate) or in patients undergoing renal biopsies (P = 0.225 for decrease in hematocrit; P = 1.000 for the percentage of patients transfused) after discontinuation of the BT test.

Conclusions: Our study failed to identify a clinically significant, negative impact of discontinuing the BT test.

Predicting blood transfusion factors in coronary artery bypass surgery

OBJECTIVE

Blood conservation has become one of the most important issues in cardiac surgery. We clarified preoperative predictors of the need for blood transfusions during coronary artery bypass graft surgery.

METHODS

Subjects were 89 patients--66 men (74%) and 23 women (26%) 40 to 84 years old (mean: 66.2 +/- 8.3 years)--undergoing isolated coronary artery bypass surgery from September 1997 to December 1999. Of these, 66 patients (74%) received transfusion during hospitalization and 23 (26%) did not. Nine risk factors detected by univariate study were entered in a multivariate logistic regression model of the relationship between preoperative variables and blood transfusion.

RESULTS

Independent predictors were emergency surgery (P = .0023), lower hematocrit (P = .0027), older age (P = .0043), and the presence of peripheral vascular disease (P = .0070). Optimal cutoff of hematocrit for blood transfusion was 39% and age 64 years via receiver-operating characteristics curves based on the relation between sensitivity and specificity.

CONCLUSION

Patients older than 64 years with hematocrit less than 39% and/or peripheral vascular disease should be treated routinely using preoperative storage of autologous blood whenever the patient's condition permits. For patients undergoing emergency surgery, further studies are required, including lowering transfusion threshold and using determinants other than hematocrit.

Heparin reacts with and inactivates nitric oxide

Although heparin is a well-known anticoagulant, in some cases it promotes a prothrombotic state and does so through both antibody-dependent and antibody-independent platelet activation. In this study, heparin was found to reverse the antiplatelet effect of an NO donor. S-nitroso-glutathione (SNO-Glu), with an EC(50) of 1.8 U/mL. Ultraviolet/visible spectral analysis and the Griess assay showed that increasing heparin concentrations on a dose-dependent basis eliminated acidified NO(x) species. Since heparin is a heterogeneous mixture of glycosaminoglycans, the effects of six different heparin disaccharides were compared with various substitutions on the hexose rings to determine which functional group(s) of the polysaccharide interact with acidified NO(x). Among the six disaccharides tested, only types I-S and II-S had the effect, suggesting that the sulfamino-group at the C2 position of the glucosamine moiety was critical for the elimination of acidified NO(x) species. Mass spectrometry experiments gave results consistent with these observations, indicating that only the I-S and II-S heparin disaccharides were modified upon treatment with NaNO(2)/HCl. Negative-ion electro-spray ionization MS and tandem MS analyses of the native compounds and their deuterium-labeled analogs confirmed that the reaction products from nitrosation of these N-sulfated disaccharides had eliminated the C2-sulfamino-moiety and replaced it with methoxide derived from the solvent. Participation of the 6-sulfato-substituent appears to facilitate the elimination reaction. These data show that heparin can impair the antiplatelet properties of nitric oxide by interacting with the nitrosating species, and suggest that heparin-like glycosamino-glycans may interact with endothelium-derived nitric oxide in vivo to regulate the bioactivity of this important antiplatelet and vasorelaxant substance.

Impact of closed versus open venous reservoirs on patient outcomes in isolated coronary artery bypass graft surgery

Data were collected retrospectively on 1,681 consecutive isolated coronary artery bypass graft patients at Millard Fillmore Hospital (Buffalo, New York, USA) undergoing coronary artery bypass. No patients were excluded. There were 616 patients in the open circuit group and 1,065 in the closed circuit group. Patients in the closed circuit group exhibited a trend towards a higher incidence of most pre-existing comorbidities, with acute myocardial infarction, pre-existing cerebrovascular disease and the incidence of extensively calcified aortas all being significantly higher. Significantly different postbypass outcomes favored the closed circuit group, with levels of sepsis of 1% for open and 0% for closed and respiratory failure of 4% for open and 1% for closed. The length of stay approached significance with a p-value of 0.057 (open 9.85 days and closed 7.53). Use of an open circuit was a significant, independent predictor for increased use of units of packed red blood cells and total units of blood products. This study provides evidence that closed venous reservoirs can favorably impact surgical outcomes and reduce resulting healthcare costs.

Assessment of perioperative blood transfusion in cardiac surgery using administrative data

We have analysed the blood transfusion requirements in 288 consecutive adult patients undergoing cardiac surgery using data from the discharge reports, coded in accordance with the international disease classification. 114 patients were transfused (39.6%). The transfusion rate was higher in patients with a principal diagnosis of two valve disorders, acute/subacute ischemic heart disease, congenital anomalies, tumour and injuries. All of these had a transfusion rate greater than 50%. Controlling the confounding effects by multivariate logistic regression analysis, there was an adjusted association of the transfusion rate only with the principal diagnosis and with sex, not with type of admission, preoperative anemia, surgical procedure or age.

Prediction of the mediastinal drainage after coronary artery bypass surgery

Using multiple correlation and linear regression approaches, we investigated the association between the amount of mediastinal drainage for the first 24 postoperative hours and clinical variables as well as multiple haematological tests performed at three time points: before anaesthesia induction, 10 minutes after protamine administration and just after skin closure, on 46 patients undergoing primary coronary artery bypass grafting. Three models from the three times were then developed to predict mediastinal drainage. The number of internal mammary grafts, the total number of grafts and plasma fibrinogen concentration were useful predictors of mediastinal drainage at all three times. The platelet count taken only after skin closure was found to provide additional predictive information. Each regression model explained approximately 60% of the variation in postoperative mediastinal drainage. The information obtained from these predictive models is useful in defining high-risk populations.

Blood loss from coronary angiography increases transfusion requirements for coronary artery bypass graft surgery

OBJECTIVE

To determine the blood loss associated with coronary angiography and its impact on hemoglobin and transfusion requirements for subsequent coronary artery bypass graft (CABG) surgery.

DESIGN

Retrospective chart review.

SETTING

Tertiary-care, academic medical center.

PARTICIPANTS

A total of 506 adult patients undergoing coronary angiography and CABG surgery.

INTERVENTIONS

None (observational study).

MEASUREMENTS AND MAIN RESULTS

Coronary angiography was associated with a reduction in hemoglobin of 1.8 g/dL. This reduction in hemoglobin was a significant predictor of allogeneic red blood cell transfusion.

CONCLUSION

Coronary angiography contributes to a 1.8 g/dL reduction in hemoglobin concentration before CABG surgery and was associated with increased transfusion of allogeneic blood products. Measures aimed at maintaining red cell volume during coronary angiography, increasing erythropoiesis, or delaying surgery beyond 2 weeks may result in a decrease in transfusion requirements for patients undergoing CABG surgery.

Gender is an essential determinant of blood transfusion in patients undergoing coronary artery bypass graft procedure

STUDY OBJECTIVE

To determine factors that account for gender difference in the need for blood transfusion in coronary artery bypass graft (CABG) patients.

DESIGN

Retrospective study of consecutive patients.

SETTING

Anesthesiology department of a teaching hospital.

PATIENTS

253 CABG patients (163 males and 90 females).

INTERVENTIONS

Packed red blood cells (PRBCs), platelets, and fresh frozen plasma (FFP) were transfused depending on the need of each patient.

MEASUREMENTS AND MAIN RESULTS

For each patient, we recorded the gender, age, weight, height, body surface area (BSA), and duration of surgery. Hematocrit (Hct) levels prior to surgery, end of surgery, and at discharge from the hospital were recorded. PRBC administration and use of FFP and platelets were noted. Differences between the data for female and male patients were evaluated using Student's t-test, Chi-square test, and regression analysis. Approximately 60% female and only 20% male patients received PRBCs intraoperatively, whereas 78% females and only 43% males received PRBCs during their entire hospital stay. On average, females received 1.20 units of PRBCs intraoperatively and 2.38 units during the entire hospital stay, while the males received 0.31 units and 1.36 units for similar periods. Gender differences in PRBC transfusion persisted even when females and males were compared within the same subgroups for age, weight, duration of surgery, and preoperative Hct. PRBC units given intraoperatively had a significant correlation with age and preoperative Hct in females, but they had a significant correlation with age, preoperative Hct, and duration of surgery in males. PRBCs given during the entire hospital stay, however, had significant correlation with age, preoperative Hct, and duration of surgery in both females and males. Multiple logistic regression analysis showed that the probability of a patient receiving or not receiving PRBC transfusion is significantly influenced by age, preoperative PRBC mass, duration of surgery, and gender.

CONCLUSION

Gender is an independent essential determinant of blood transfusion in CABG patients, and it may interact with age, weight, preoperative Hct, duration of surgery, and other factors in determining the probability of transfusion.

Etiology of preoperative anemia in patients undergoing scheduled cardiac surgery

PURPOSE

Ten percent of our cardiac surgical patients have preoperative anemia. Anemia diagnosed before scheduled cardiac surgery is a strong predictor of the need for homologous blood transfusion (RBC) perioperatively but the cause of this preoperative anemia is not known. The purpose of this study was to evaluate the etiology of preoperative anemia.

METHODS

Seventy-five consecutive anemic cardiosurgical patients (Hb = < 120 g x L(-1) the day before surgery) were studied prospectively. All had multiple diagnostic blood tests done in the preoperative period to diagnose the cause of the anemia and subsequently underwent non-emergency cardiac surgery. Anesthesia and RBC transfusion were standardized according to the protocol. Data in respect to operation, RBC and other blood product transfusion during operation and hospital stay were recorded.

RESULTS

Hospital-acquired anemia was present in 37.3% of anemic patients (hemoglobin decrease during hospitalization before surgery > or =9 g x l(-1)). The second most common diagnosis was iron deficiency anemia (29.3% patients) followed by anemia of chronic renal disease (10.7% patients). When coronary angiography was performed close to operation time, patients had a higher decrease in hemoglobin concentration during hospitalization --suggesting that blood loss during angiography was, in part, responsible for anemia. Seventy-five percent of anemic patients were transfused with RBC perioperatively compared with our overall transfusion rate of 30% of cardiac surgery patients.

CONCLUSIONS

In the majority of patients, preoperative anemia is potentially preventable. Investigation and treatment of anemia before cardiac surgery should be a priority in preparing the patient for surgery.

A prospective, randomized study of cardiopulmonary bypass temperature and blood transfusion

BACKGROUND

We hypothesized that normothermic cardiopulmonary bypass (CPB) would be associated with decreased blood loss and allogeneic transfusion requirements relative to hypothermic CPB.

METHODS

After obtaining institutional review board approval and informed patient consent, we conducted a prospective, randomized study of 79 patients undergoing CPB for a primary cardiac operation at normothermic (37 degrees C) (n = 44) or hypothermic temperature (25 degrees C) (n = 35). Blood loss and transfusion requirements in the operating room and for the first 24 hours in the intensive care unit were determined. A paired t test and rank sum tests were used. A p value of less than 0.05 was considered significant.

RESULTS

The normothermic and hypothermic CPB groups did not differ in demographic variables, CPB or cross-clamp duration, heparin sodium or protamine sulfate dose, prothrombin time, or thromboelastogram results. There were no differences between the two CPB groups in blood loss or transfusion requirements.

CONCLUSIONS

We found that when there was no difference in duration of CPB, normothermic and hypothermic CPB groups demonstrated similar blood loss and transfusion requirements even though other studies have shown hypothermia induces platelet dysfunction and alters the activity of the coagulation cascade.