Anaemia and transfusion triggers in critically ill patients - What we have learnt thus far

Anaemia is a common finding in critically ill patients, the cause of which is multi-factorial including: sepsis, haemolysis (and disseminated intravascular coagulation), iatrogenic blood loss secondary to laboratory sampling, post-operative anaemia, bone marrow suppression/failure, decreased production of erythropoietin, anaemia secondary to drugs/toxins, overt or occult blood loss, functional iron deficiency, poor nutrition and haemodilution. Anaemia is associated with deleterious outcomes including increased risk of cardiac-related morbidity and mortality and decrease in oxygen-carrying capacity in the face of increased metabolic demands. There is a growing body of evidence, which demonstrates that packed red blood cell transfusions are associated with poorer outcomes. Clinicians therefore need to weigh the potential benefit of treating anaemia against the desire to avoid unnecessary transfusions. We explored current literature regarding transfusion triggers and morbidity and mortality associated with packed red blood cell transfusions transfusion, concentrating on studies that have been conducted in critical care patients. In addition, we reflected on trials which considered the viability of iron transfusion and erythropoietin in critically unwell patients.

What factors influence arterial blood gas sampling patterns?

STUDY OBJECTIVE

To investigate if patterns of arterial blood gas (ABG) sampling were influenced by values of fractional inspiratory oxygen (FiO2), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2) and oxygen saturation (%SaO2).

SETTING

An intensive care unit (ICU) in a university teaching hospital located in the North of England, UK.

DESIGN

A retrospective, descriptive, correlation study based on patient records.

PARTICIPANTS

All patients admitted to the ICU for 24 hours or greater and who had an arterial line in situ.

MEASUREMENTS AND RESULTS

The study included the records of 65 patients consecutively admitted to the ICU. Patients in this study had more blood gases taken than reported elsewhere in the literature. While consistent correlation was found between values of FiO2, PCO2, PO2 and %SaO(2), values of PO2 were the most consistent.

CONCLUSIONS

Values of PO2 are associated with frequency of ABG sampling and to a lesser extent on FiO2. Nurses in this study opted to track changes in oxygenation using ABGs despite continuous monitoring of %SaO2.

Blood tranfusion in critically ill patients: state of the art

Anemia is one of the most common abnormal findings in critically ill patients, and many of these patients will receive a blood transfusion during their intensive care unit stay. However, the determinants of exactly which patients do receive transfusions remains to be defined and have been the subject of considerable debate in recent years. Concerns and doubts have emerged regarding the benefits and safety of blood transfusion, in part due to the lack of evidence of better outcomes resulting from randomized studies and in part related to the observations that transfusion may increase the risk of infection. As a result of these concerns and of several studies suggesting better or similar outcomes with a lower transfusion trigger, there has been a general tendency to decrease the transfusion threshold from the classic 10 g/dL to lower values. In this review, we focus on some of the key studies providing insight into current transfusion practices and fueling the current debate on the ideal transfusion trigger.

Anemia in the long-term ventilator-dependent patient with respiratory failure

Anemia occurs in virtually all critically ill patients receiving long-term mechanical ventilation and has been associated with increased mortality and poor outcomes. Allogeneic RBC transfusions are routinely administered to critically ill anemic patients, especially during lengthy stays in ICUs or in long-term acute care facilities. Although RBC transfusions are a physiologically rational approach to raising hemoglobin levels, they may increase the risk of complications and have been associated with higher mortality in critically ill patients. Treatment with epoetin alfa, an erythropoiesis-stimulating agent, as a means of reducing transfusion requirements has been studied in the critically ill and in patients receiving long-term mechanical ventilation. Promising results have been reported, including a potential survival benefit, although larger and more definitive studies are needed in order to establish whether raising hemoglobin levels affects clinical outcomes in patients receiving mechanical ventilation.

Blood conservation in the critically ill patient

This review focuses on transfusion practice in the critically ill.

Anemia in critically ill patients

Anemia is common in acute critically ill patients. Although blood loss, either by trauma, surgery, phlebotomies or gastrointestinal bleeding, may play a role, the anemia in these patients bears many similarities to the anemia characteristic of chronic disease. Serum iron is low with a high concentration of ferritin and low-to-normal transferrin and serum transferrin receptor levels. Several mechanisms may be involved, with inflammation playing a crucial role. Although the exact nature of the inflammatory response and the role of various cytokines need further elucidation, it is known that inflammation blunts the responsiveness of the hormone erythropoietin and induces functional iron deficiency. Iron is trapped in cells of the mononuclear phagocytic system and its release is temporarily blocked. The bone marrow is still capable of incorporating iron and of responding to treatment with recombinant human erythropoietin (rh-EPO). The duration of the anemia is related to the persistence of the inflammation. Although the effects of anemia on morbidity and mortality in the critically ill are poorly defined, a restrictive transfusion policy, in which hemoglobin concentration is maintained between 7.0 and 9.0 g/dl, proves to be at least as effective as, if not superior to, a more liberal regimen. In individual situations, such as in cardiovascular and cancer patients, higher thresholds may be appropriate. The administration of rh-EPO is an alternative to reduce the need for red blood cell transfusions and to avoid transfusion-related complications. Although its efficacy has been shown, questions regarding cost-benefit, dose regimen and clinical outcomes need to be answered before its large-scale use can be recommended.

Efficacy of red blood cell transfusion in the critically ill

This article has evaluated the published data regarding the efficacy of RBC transfusions in the critically ill. Taken together, these studies generally support conservative RBC transfusion strategies in critical care to reduce the risk of transfusion-related adverse effects. The TRICC trial has established the safety ofa restrictive transfusion strategy, suggesting that physicians could minimize exposure to allogeneic RBCs by lowering their transfusion threshold. Further research will add to the generalizability of this study and explore the possible mechanism to explain why RBC transfusions do not improve outcomes in the critically ill. Additional studies will be necessary to determine the effects of RBC storage time and the presence of allogeneic leukocytes in allogeneic RBC. The following conclusions are evident: 1. RBC transfusion does not improve tissue oxygen consumption consistently in critically ill patients, either globally or at the level of the micro-circulation. 2. RBC transfusion is not associated with improvements in clinical outcome in the critically ill and may result in worse outcomes in some patients. 3. Specific factors that identify patients who will improve from RBC transfusion are difficult to identify. 4. Lack of efficacy of RBC transfusion likely is related to storage time, increased endothelial adherence of stored RBCs, nitric oxide binding by free hemoglobin in stored blood, donor leukocytes, host inflammatory response, and reduced red cell deformability.

Is there a place for epoetin alfa in managing anemia during critical illness?

BACKGROUND

Anemia is a common problem in critically ill patients. As a result, blood transfusions are often used in the intensive care unit (ICU) setting. However, mounting evidence shows that blood transfusions may contribute to negative outcomes, such as transfusion-related infections, organ dysfunction, and immunosuppression. Supplementation with epoetin alfa is currently used in some medical centers to manage anemia in critically ill patients.

OBJECTIVE

This review discusses the risks with blood transfusions and the clinical evidence supporting the use of epoetin alfa in managing edema during critical illness.

METHODS

A search was conducted in MEDLINE and Current Contents (1966-2003) using the terms epoetin alfa, recombinant human erythropoietin, and anemia. Articles addressing anemia and the use of epoetin alfa in critically ill patients were selected and assessed. From this selection, the cited references addressing the etiology of anemia in the ICU and the risks associated with blood transfusions were manually extracted and reviewed.

RESULTS

Several reports have shown that critically ill patients display evidence of anemia due to a blunted erythropoietin response. One large, randomized, placebo-controlled study assessed the effect of SC epoetin alfa on blood transfusions in the ICU. In this study, 40, 000 IU administered weekly for up to 4 weeks resulted in an overall transfusion reduction (9.9% absolute risk reduction; P<0.001 ). Other, smaller studies using different dosing regimens in critically ill patients have also demonstrated that epoetin alfa can decrease the need for transfusion.

CONCLUSION

The use of epoetin alfa in critically ill patients can decrease the number of blood transfusions required during hospitalization, and potentially result in transfusion avoidance. Because of the scarce amount of evidence and the diversity of dosing regimens used used, no strict recommendations can be drawn from this review.

The CRIT Study: Anemia and blood transfusion in the critically ill—Current clinical practice in the United States*

OBJECTIVE

To quantify the incidence of anemia and red blood cell (RBC) transfusion practice in critically ill patients and to examine the relationship of anemia and RBC transfusion to clinical outcomes.

DESIGN

Prospective, multiple center, observational cohort study of intensive care unit (ICU) patients in the United States. Enrollment period was from August 2000 to April 2001. Patients were enrolled within 48 hrs of ICU admission. Patient follow-up was for 30 days, hospital discharge, or death, whichever occurred first.

SETTING

A total of 284 ICUs (medical, surgical, or medical-surgical) in 213 hospitals participated in the study.

PATIENTS

A total of 4,892 patients were enrolled in the study.

MEASUREMENTS AND MAIN RESULTS

The mean hemoglobin level at baseline was 11.0 +/- 2.4 g/dL. Hemoglobin level decreased throughout the duration of the study. Overall, 44% of patients received one or more RBC units while in the ICU (mean, 4.6 +/- 4.9 units). The mean pretransfusion hemoglobin was 8.6 +/- 1.7 g/dL. The mean time to first ICU transfusion was 2.3 +/- 3.7 days. More RBC transfusions were given in study week 1; however, in subsequent weeks, subjects received one to two RBC units per week while in the ICU. The number of RBC transfusions a patient received during the study was independently associated with longer ICU and hospital lengths of stay and an increase in mortality. Patients who received transfusions also had more total complications and were more likely to experience a complication. Baseline hemoglobin was related to the number of RBC transfusions, but it was not an independent predictor of length of stay or mortality. However, a nadir hemoglobin level of <9 g/dL was a predictor of increased mortality and length of stay.

CONCLUSIONS

Anemia is common in the critically ill and results in a large number of RBC transfusions. Transfusion practice has changed little during the past decade. The number of RBC units transfused is an independent predictor of worse clinical outcome.

Pharmacoeconomic considerations in the health system management of anaemia in patients with chronic kidney disease and end stage renal disease

Anaemia is prevalent in patients with chronic kidney disease and end stage renal disease. If left untreated, it greatly affects patient survival, quality of life and functional status. Epoetin and darbepoetin are two biotechnology drugs that effectively stimulate the production of red blood cells. These drugs have been shown to significantly increase haemoglobin concentrations and improve quality of life. So far, there have been no head-to-head pharmacoeconomic studies that have compared epoetin to darbepoetin. Health system decision makers need to evaluate important considerations when comparing these agents. These considerations include drug acquisition costs, the patient population being treated, the location of drug administration (in-patient versus ambulatory) and federal government reimbursement. This review details these important pharmacoeconomic considerations.

Impact of allogenic packed red blood cell transfusion on nosocomial infection rates in the critically ill patient

OBJECTIVE

To determine whether critically ill patients who receive allogenic packed red blood cell transfusions are at increased risk of developing nosocomial infections during hospitalization.

DESIGN

Retrospective database study utilizing Project IMPACT.

SETTING

A 40-bed medical-surgical-trauma intensive care unit in an 825-bed tertiary referral teaching hospital.

PATIENTS

One thousand seven hundred and seventeen patients admitted to the medical-surgical-trauma intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Data were collected by using the Project IMPACT database. Nosocomial infection rates were compared among three groups: the entire cohort, the transfusion group, and the nontransfusion group. We determined the nosocomial infection rates in these groups while adjusting for probability of survival by using Mortality Prediction Model (MPM-0) scores, age, gender, and number of units of packed red blood cells transfused. The average number of units transfused per patient was 4.0. The nosocomial infection rate for the entire cohort was 5.94%. The nosocomial infection rates for the transfusion group (n = 416) and the nontransfusion group (n = 1301) were 15.38% and 2.92%, respectively (p <.005 chi-square). Transfusion of packed red blood cells was related to the occurrence of nosocomial infection, and there was a dose-response pattern (the more units of packed red blood cells transfused, the greater the chance of nosocomial infection; p< 0.0001 chi-square). The transfusion group was six times more likely to develop nosocomial infection compared with the nontransfusion group. In addition, for each unit of packed red blood cells transfused, the odds of developing nosocomial infection were increased by a factor of 1.5. A subgroup analysis of nosocomial infection rates adjusted for probability of survival by using MPM-0 scores showed nosocomial infection to occur at consistently higher rates in transfused patients vs. nontransfused patients. A second subgroup analysis adjusted for patient age showed a statistically significant increase in rates of nosocomial infection for transfused patients regardless of age.

CONCLUSIONS

Transfusion of packed red blood cells is associated with nosocomial infection. This association continues to exist when adjusted for probability of survival and age. In addition, mortality rates and length of intensive care unit and hospital stay are significantly increased in transfused patients.

Blood Transfusion Issues in the Critically Ill

Anemia is a common clinical problem seen in the critically ill and results in a large RBC transfusion requirement for these patients. The view that RBC transfusion is risk-free is no longer tenable today. There is the accumulating evidence that allogeneic blood transfusion is immunosuppressive. More reently, attention has focused on the age of RBCs transfused. Transfused RBCs, especially during the time period immeditely following transfusion, are not normal. The duration of RBC storage may be an important determinant of the efficacy of RBCs as oxygen carriers as well as a determinant of transusion related morbidity. Adding to the controversy about risk/benefit ratio for RBC transfusion are recent data showing that an aggressive RBC transfusion strategy may decrease the likelihood of survival in selected subpopulations of critically ill adults. The optimal hematocrit for the ICU patient remains to be determined. It seems clear that hemoglobin levels falling significantly below the “10/30” threshold can be tolerated. However, it is not clear that this is applicable to the critically ill ICU patient population. Therefore, while hemoglobin levels in the 7-10 mg/dL range are well tolerated in the “stable” “nontressed” patient, this range might not be optimal for the critcally ill patient. Conservative transfusion thresholds as well as strategies to minimize loss of blood and increase the producion of RBCs are important in the management of critically ill patients.

Anesthesia considerations for pediatric cancer

The multidisciplinary approach to the care of children with cancer demands an understanding of all aspects of its treatment. Recognition of potential anatomic and physiologic derangements which may result from specific types of malignancy allows optimal preoperative preparation. Understanding the anesthetic implications of cancer chemotherapy, irradiation and surgery, and the medical complications which result, is essential. The anesthesiologist is involved in critical perioperative issues during surgical resection in the operating room, but just as importantly plays a crucial role in a variety of procedures performed in remote locations. An awareness of special problems related to cancer and its treatment allows optimal anesthesia care while dealing with such issues as radical surgery, organ system failure, acute and chronic pain, and terminal illness.