II: Should we demand fresh red blood cells for perioperative and critically ill patients?

Strategies to avoid empiric blood product administration in liver transplant surgery

Massive blood loss has been a dreaded complication of liver transplantation, and the accompanying transfusion is associated with adverse outcomes in the form of decreased patient and graft survival. With advances in both surgical techniques and anesthetic management during transplantation, blood and blood products requirements reduced significantly. However, transfusion practices vary among different centers. The altered coagulation parameters in patients with liver cirrhosis results in a state of “rebalanced hemostasis” and patients are just as likely to clot as they are to bleed. Commonly used coagulation tests do not always reflect this new state and can, therefore, be misleading. Transfusion of blood products solely to correct abnormal parameters may worsen the coagulation status, thus adversely affecting patient outcome. Point-of-care tests such as thromboelastometry more reliably predict the risk of bleeding in these patients and in addition may provide quicker turnaround times compared to routine tests. Perioperative management should also include the possibility of thrombosis in these patients, and the use of low-molecular-weight heparin correlates with better patient survival. This review article aims to highlight the concept of rebalanced hemostasis, limitation of routine coagulation tests, and harmful effect of empiric transfusion of blood products.

Minimum haemoglobin in intensive care

Multiple and complex aetiological factors contributes to anaemia in critically ill patients. This article sets out to examine the clinical evidence and physiological rationale for transfusion, traditionally based on an arbitrary haemoglobin trigger of 10 g=dL. Maintenance of haemoglobin concentration level of 10 g=dL or above may benefit only a small group of patients with an acute myocardial infarction, unstable angina or those who have severe coronary artery disease. However, most critically ill patients tolerate anaemia very well due to physiological compen satory mechanisms and clinical studies suggest that there is an increase in adverse outcome if transfusion is carried out using this traditional trigger threshold.

Transfusion of Blood Products Affects Outcome in Cardiac Surgery

There remains controversy as to when patients undergoing cardiac surgery should receive a transfusion and whether a low hematocrit and its treatment with a transfusion of red cells influences outcome. The data related to this controversy are reviewed. Although the risk of known viral transmission is currently low, stored red cells do not function normally, and each unit contains activated inflammatory cells and mediators. These changes cause limited oxygen release, impaired microcirculatory flow, and immune suppression. A number of studies have observed decreased survival associated with transfusions in trauma, coronary artery bypass grafting, and intensive care unit patients. Studies that show an adverse outcome associated with low hematocrit are not definitive, because they fail to distinguish between the impact of low hematocrit per se and the possible adverse effects of transfusion, for what the low hematocrit may simply be a surrogate. The observation that a low hematocrit is associated with an adverse outcome does not necessarily prove that “treatment” of the anemia with a red cell transfusion will improve the outcome. Stored platelets contain a highly activated mixture of platelets with storage lesions and inflammatory mediators. Two retrospective post hoc multifactorial analyses suggest that platelet transfusions are associated with substantial increased morbidity and mortality. Clearly, large prospective studies are required to define the proper trigger for blood product transfusion to balance the adverse effects of anemia and platelet deficiency or dysfunction with the adverse effects of transfusion of blood products on morbidity and mortality associated with cardiac surgery and anesthesia.

Red blood cell storage time and the outcome after coronary surgery

BACKGROUND

The impact of transfusion of aged red blood cells (RBCs) on the outcome after coronary artery bypass grafting (CABG) is controversial. This issue has been investigated in the present study.

MATERIALS AND METHODS

Data on perioperative blood transfusion, storage time of RBCs, and adverse events were available for 819 consecutive patients who underwent isolated CABG and received two to four units of RBCs. The maximum RBC storage time was 35 d.

RESULTS

Repeated-measure test showed that transfusion of all RBC units >14 d and at least one RBC unit >14 d was associated with similar postoperative C-reactive protein (P = 0.245 and P = 0.103, respectively) or creatinine levels (P = 0.414 and P = 0.259, respectively) compared with newer RBC units. Propensity score-adjusted analysis showed similar immediate and late outcome in patients receiving only newer RBCs compared with those who received only older RBCs. Similar findings were observed in patients receiving only newer RBCs compared with patients who received at least one unit of older RBCs. Logistic and proportional hazards analyses adjusted for the number of RBC units showed that the median storage duration of RBCs was not associated with either any of the immediate outcome end points or late mortality.

CONCLUSIONS

These findings suggest that, when the maximum RBC storage time is 35 d, the duration of storage of transfused RBCs does not affect the immediate and late outcome of patients with moderate bleeding after CABG.

The impact of intraoperative transfusion of platelets and red blood cells on survival after liver transplantation

BACKGROUND

Intraoperative transfusion of red blood cells (RBC) is associated with adverse outcome after orthotopic liver transplantation (OLT). Although experimental studies have shown that platelets contribute to reperfusion injury of the liver, the influence of allogeneic platelet transfusion on outcome has not been studied in detail. In this study, we evaluate the impact of various blood products on outcome after OLT.

METHODS

Twenty-nine variables, including blood product transfusions, were studied in relation to outcome in 433 adult patients undergoing a first OLT between 1989 and 2004. Data were analyzed using uni- and multivariate stepwise Cox's proportional hazards analyses, as well as propensity score-adjusted analyses for platelet transfusion to control for selection bias in the use of blood products.

RESULTS

The proportion of patients receiving transfusion of any blood component decreased from 100% in the period 1989-1996 to 74% in the period 1997-2004. In uni- and multivariate analyses, the indication for transplantation, transfusion of platelets and RBC were highly dominant in predicting 1-yr patient survival. These risk factors were independent from well-accepted indices of disease, such as the Model for End-Stage Liver Disease score and Karnofsky score. The effect on 1-yr survival was dose-related with a hazard ratio of 1.377 per unit of platelets (P = 0.01) and 1.057 per unit of RBC (P = 0.001). The negative impact of platelet transfusion on survival was confirmed by propensity-adjusted analysis.

CONCLUSION

This retrospective study indicates that, in addition to RBC, platelet transfusions are an independent risk factor for survival after OLT. These findings have important implications for transfusion practice in liver transplant recipients.

Age of transfused red cells and early outcomes after cardiac surgery

BACKGROUND

Red blood cells (RBC) undergo many changes during storage. Such changes are associated with reduced oxygen-carrying capacity and transfusion-related inflammatory reactions. The clinical significance of these changes in the cardiac surgical setting is unclear. This observational cohort study investigates the association between age of transfused RBC and early outcomes after cardiac surgery.

METHODS

The cardiac surgery database at St. Vincent's Hospital Melbourne was cross-referenced with the Blood Transfusion Services database. In all, 670 consecutive patients who had nonemergency coronary artery bypass grafting or aortic valve replacement, or both, between June 2001 and June 2007 and had at least 2 RBC units transfused were studied. The storage variables studied were mean age of RBC, age of oldest RBC unit transfused, and transfusion of RBC stored longer than 30 days. Age of transfused blood was analyzed using logistic and linear regression analysis to determine an independent association with clinical outcomes: postoperative early mortality, renal failure, pneumonia, intensive care unit stay, and ventilation hours. Patient preoperative risk profile (EuroSCORE) and total number of RBC units transfused were adjusted for.

RESULTS

The storage age of RBC was not independently associated with any of the endpoints studied. The total quantity of RBC transfused was significantly associated with all studied endpoints.

CONCLUSIONS

Under current transfusion practice, the age of transfused RBC is not associated with early mortality and morbidity after cardiac surgery.

Survival of red blood cells after transfusion: a comparison between red cells concentrates of different storage periods

BACKGROUND

The use of fresh red blood cells (RBCs) is recommended for critically ill patients and patients undergoing surgery, although there is no conclusive evidence that this is beneficial. In this follow-up study, the short-term and the long-term recovery of irradiated, leukoreduced RBCs transfused after either a short storage (SS) or a long storage (LS) period were compared. By consecutive transfusion of RBCs with a SS and LS period, a direct comparison of their survival within the same patient was possible.

STUDY DESIGN AND METHODS

Ten transfusion-requiring patients each received a SS RCCs (stored 0-10 days) and a LS RCCs (stored 25-35 days) consecutively. Short-term and long-term survival of the transfused RBCs was followed by flow cytometry using natural differences in RBC antigens between donors and patients. Posttransfusion recovery (PTR) was measured at several time points after transfusion.

RESULTS

The mean 24-hour PTR of SS RBCs is 86.4 +/- 17.8 percent and that of LS RBCs 73.5 +/- 13.7 percent. After the first 24 hours, the mean times to reach a PTR of 50 percent of the 24-hour PTR (T50) and mean potential life spans (mPLs) of the surviving SS and LS RBCs (41 and 116 days and 41 and 114 days, respectively) do not differ.

CONCLUSIONS

The mean 24-hour PTR of both SS and LS RBCs complies with the guidelines, even in a compromised patient population. The 24-hour PTR of SS RBCs, however, is significantly higher than that of LS RBCs. The remaining population of SS and LS RBCs has a nearly identical long-term survival. Therefore, depletion of the removal-prone RBCs before transfusion may be an efficient approach for product improvement.

Duration of red-cell storage and complications after cardiac surgery

BACKGROUND

Stored red cells undergo progressive structural and functional changes over time. We tested the hypothesis that serious complications and mortality after cardiac surgery are increased when transfused red cells are stored for more than 2 weeks.

METHODS

We examined data from patients given red-cell transfusions during coronary-artery bypass grafting, heart-valve surgery, or both between June 30, 1998, and January 30, 2006. A total of 2872 patients received 8802 units of blood that had been stored for 14 days or less ("newer blood"), and 3130 patients received 10,782 units of blood that had been stored for more than 14 days ("older blood"). Multivariable logistic regression with propensity-score methods was used to examine the effect of the duration of storage on outcomes. Survival was estimated by the Kaplan-Meier method and Blackstone's decomposition method.

RESULTS

The median duration of storage was 11 days for newer blood and 20 days for older blood. Patients who were given older units had higher rates of in-hospital mortality (2.8% vs. 1.7%, P=0.004), intubation beyond 72 hours (9.7% vs. 5.6%, P<0.001), renal failure (2.7% vs. 1.6%, P=0.003), and sepsis or septicemia (4.0% vs. 2.8%, P=0.01). A composite of complications was more common in patients given older blood (25.9% vs. 22.4%, P=0.001). Similarly, older blood was associated with an increase in the risk-adjusted rate of the composite outcome (P=0.03). At 1 year, mortality was significantly less in patients given newer blood (7.4% vs. 11.0%, P<0.001).

CONCLUSIONS

In patients undergoing cardiac surgery, transfusion of red cells that had been stored for more than 2 weeks was associated with a significantly increased risk of postoperative complications as well as reduced short-term and long-term survival.

Effects of storage time of red blood cell transfusions on the prognosis of coronary artery bypass graft patients

BACKGROUND

In different centers for cardiothoracic surgery throughout the world, different policies are followed concerning the maximum storage time of to-be-transfused red blood cells (RBCs). The aim in this study was to investigate the possible role of the storage time of RBC transfusions on the outcome of coronary artery bypass graft (CABG) surgery patients.

STUDY DESIGN AND METHODS

In a single-center study, all patients who had undergone CABG surgery in the period 1993 until 1999 were identified. Only those patients who had received standard, allogeneic, buffy coat-depleted, unfiltered RBCs in saline-adenine-glucose-mannitol were entered in the analyses (n = 2732). Endpoints were 30-day survival, hospital stay, and intensive care unit (ICU) stay. Storage time of the perioperative RBC transfusions was analyzed in the following four ways: 1) mean storage time of all perioperative RBC transfusions; 2) storage time of the youngest RBC transfusion; 3) storage time of the oldest RBC transfusion; and 4) comparing outcome in patients receiving only RBCs with a storage time below the median storage of 18 days with patients receiving only RBCs with a storage time above the median.

RESULTS

The univariate analyses showed a strong correlation between storage time and the endpoints survival and ICU stay, but also a correlation with an established risk factor such as the number of transfusions. The multivariate analyses showed no independent effect of storage time on survival or ICU stay.

CONCLUSION

In these analyses, pertaining to 2732 CABG patients, no justification could be found for use of a particular maximum storage time for RBC transfusions in patients undergoing CABG surgery.

Transfusion in the intensive care unit

OBJECTIVE

To summarize the incidences of anemia and blood transfusions in critically ill patients, assess their comparative risks and benefits, and briefly speculate on the possible effects of leukoreduction and blood storage on the need to reevaluate transfusion triggers.

DESIGN

A review of the current literature was performed.

RESULTS

Anemia is common in intensive care unit patients and is associated with increased mortality. Some 20-53% of intensive care unit patients will receive a blood transfusion during their stay, and these have also been associated with worse outcomes. Leukoreduction may limit some of the infectious and immunomodulatory risks associated with blood transfusion.

CONCLUSIONS

Data on the risks and benefits of blood transfusion are conflicting, and with recent changes in blood transfusion practice, including the widespread introduction of leukoreduction, it is time to reevaluate our transfusion triggers.

Red blood cells intended for transfusion: quality criteria revisited

Great variation exists with respect to viability and function of fresh and stored red blood cells (RBCs) as well as of the contents of RBC hemoglobin (Hb) in individual units. Improved technology is available for the preparation as well as the storage of RBCs. The authors raise the question whether it may be time to revise current standards for RBC units. The establishment of a standard unit of blood based on Hb content should be a high-priority goal. It is recommended that a standard RBC unit should contain 50 g of Hb. Major organizations concerned with the collection and distribution of blood components should agree on the criteria for a standard unit of RBCs based on Hb content and for the collection of double units. Manufacturers of blood collection equipment should provide suitable technology for collecting a standard unit with defined contents of RBC Hb. Efforts should be directed at the design of storage solutions acceptable for transfusion that maximize the maintenance of both RBC viability and function during storage. The ideal storage protocol would require sterile, high-pH solutions containing both glucose and electrolytes.

Anemia during and at discharge from intensive care: the impact of restrictive blood transfusion practice

OBJECTIVE

To document the prevalence of anemia among patients admitted to intensive care (ICU) and, among survivors, at ICU discharge when restrictive transfusion practice was used.

DESIGN

This was an observational cohort study.

SETTING

Ten of the 26 general ICUs in Scotland.

PATIENTS AND PARTICIPANTS

One thousand twenty-three sequential ICU admissions over 100 days, representing 44% of all ICU admissions in Scotland during the study period, studied daily from admission to discharge or death in the ICU.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

The median transfusion trigger used, in the absence of bleeding, was 78 g/l (interquartile range 73-84); <2% of transfusion triggers were above the upper limit of the national transfusion trigger guideline (100 g/l). Overall, 25% of admissions had a hemoglobin concentration <90 g/l at ICU admission. Seven hundred sixty-six patients admitted survived to ICU discharge. Among these, the prevalence of anemia (male <130 g/l; female <115 g/l) at ICU discharge was 87.0 (95% CI: 83.6 to 89.9)% for males and 79.6 (74.8 to 83.7)% for females. Of the male survivors 24.1 (20.3 to 28.3)% and of the female 27.9 (23.4 to 33.2)% had a hemoglobin <90 g/l at ICU discharge. The prevalence was similar for patients with and without pre-existing ischemic heart disease. Logistic regression found independent associations between having a hemoglobin concentration <90 g/l at ICU discharge and the first measured hemoglobin in ICU, the presence of acute renal failure and thrombocytopenia during ICU stay.

CONCLUSIONS

Anemia is highly prevalent in ICUs that use restrictive transfusion triggers. The impact of anemia on functional recovery after intensive care requires investigation.

The application of a new quantitative assay for the monitoring of integrin-associated protein CD47 on red blood cells during storage and comparison with the expression of CD47 and phosphatidylserine with flow cytometry

BACKGROUND

After the introduction of universal leukoreduction, the role of factors other than white blood cells in red cell (RBC) storage lesion is attracting increasing attention. These include changes in the levels of CD47 and phosphatidylserine (PS) markers on RBCs during storage. The aim of this study was to monitor these changes with both flow cytometry (FACS) and a newly developed quantitative enzyme-linked immunosorbent assay (ELISA).

STUDY DESIGN AND METHODS

A new quantitative ELISA (monoclonal antibody immobilization of RBC antigens [MAIRA]) was developed. The assay yielded consistent linear curves that enabled the measurement of CD47 expression on RBCs. In addition, FACS was used to measure both CD47 expression and PS on RBCs (n = 3 units) during storage (Days 4, 10, 24, and 31).

RESULTS

A significant reduction in CD47 expression was observed both by MAIRA assay and by FACS by Days 24 and 31 (p < 0.01), and the correlation between the two assays was significant (p < 0.01). In addition, a significant increase in PS was observed by the same storage days with FACS (p < 0.01).

CONCLUSION

The MAIRA assay appears to be suitable for the quantitative measurement of RBC markers during storage. Significant changes in CD47 and PS levels were observed during storage, which may have detrimental immunomodulatory and hemostatic effects on the transfused RBCs.

Red cell storage lesion: The potential impact of storage-induced CD47 decline on immunomodulation and the survival of leucofiltered red cells

Red blood cells undergo major biochemical and biomechanical changes during storage that could effect their post transfusion performance. Biochemical effects include changes in 2,3-diphosphoglycerate (2,3-DPG), ATP, and calcium levels, as well as metabolic modulation and release of Annexin V, a cytosolic component of blood cells, as a global marker of cellular injury and fragmentation. Biomechanical changes include alterations in cellular membrane, shape changes, phospholipid content, phospholipid asymmetry, and antigenic markers. Although the extent of these changes under various storage conditions has been well documented, their clinical effects remain unclear. In the current era of universal leucodepletion, the immunomodulatory effects of some essential markers such as CD47 and phosphatidyl serine become the focus of interest as highlighted in this manuscript.