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A Carol A. Rauen, RN, MS, CCNS, CCRN, PCCN, replies:

This excellent question is simple and specific. It is also a very important question that critical care clinicians face daily. I wish I could offer a simple and specific answer. The first documented human-to-human blood transfusion took place in 1818¹ and today packed red blood cell (PRBC) infusions are a cornerstone therapy in modern critical care practice.² The procedure known as bloodletting has a much longer history in medical practice: 2500 years. Ironically, thought to be the major treatment for "all that ails you," bloodletting was actually proven to be detrimental to health. We can only hope that our current practice of blood administration does more good than harm.

In the absence of a simple answer to this simple question, let me share what the current body of evidence has to offer. The first trigger or threshold recommendation was proposed in 1942, which commonly became known as the "10/30" rule.³ This rule suggested that if the hemoglobin level fell below 10 g/dL or if the hematocrit level fell below 30%, the patient would probably benefit from a red cell transfusion. Despite the lack of research support for this recommendation it lasted in clinical practice for more than 40 years. In the early 1980s, when human immunodeficiency virus was identified and found to be transmitted via blood, the risk/benefit analysis of PRBC transfusions came into question. From the subsequent changes in transfusion practices and clinical outcome evaluation data, much has been learned about the benefits and risks of blood administration.

Anemia

Anemia is very common in critically ill patients, and is detrimental to recovery. As many as 95% of patients admitted to intensive care units are likely to be anemic.⁴ The causes are varied and include blood loss, decreased erythrocyte production or increased destruction, malnutrition, and hemodilution. Cellular oxygen delivery is essential for aerobic metabolism. Hemoglobin is the carrier of oxygen and its importance cannot be overstated. Simply put, anemia is bad.

Risks Associated With Blood Administration

What is worse—anemia, cellular hypoxia, or the potential side effects of blood administration? The first documented hepatitis transmission from PRBC took place 1943.¹ Since then, infection transmission, sepsis, and transfusion reactions have been the primary concerns of clinicians administering blood. During the last decade, blood transfusions have been implicated and associated with infections, transfusion-related acute lung injury or acute respiratory distress syndrome, transfusion-associated circulatory overload, transfusion-associated immunomodulation—a down regulation of immune function or immunosuppression—and the cause of nosocomial infections, ventilator-associated pneumonia, decreased outcome in acute coronary syndrome and cardiac surgery, and increased mortality after subarachnoid hemorrhage. There have been reports that using leukodepleted blood might decrease some of these risks. There is a plethora of anecdotal, observational, and research literature outlining the potential dangers of blood administration. Simply put, blood transfusions are bad.

Evidence-Based Practice Guidelines

Transfusion requirements in critical care have been studied, but more randomized control studies are needed to definitively answer this simply question. In 1999 the New England Journal of Medicine published what has become the landmark study that all subsequent studies have been based on or compared to.⁵ The investigators concluded that restrictive transfusion practices, hemoglobin 7 to 9 g/dL, are possibly superior to the traditional transfusion trigger of 10 g/dL.⁵ The Surviving Sepsis Campaign^6,7 based their recommendations for blood administration in sepsis on this study.

Further, the 2004 CRIT study⁸ was an observational study that looked at transfusion practices in the United States. The investigators found that despite the known risks, blood administration practices have not changed much in the last decade. They found that transfusion was an independent predictor of worse clinical outcome in critically ill patients. An earlier European study,⁹ the Anemia and Blood Transfusion in Critical Care Study (ABC study), reached the same conclusion. A recent analysis of blood administration using the Sepsis Occurrence in Acutely Ill Patients (SOAP) data set from European critical care units had a different finding.¹⁰ This observational study did not find that blood transfusions were associated with increased mortality in critically ill patients. Simply put, clear research-based evidence does not exist to make a definitive statement regarding transfusion safety or a specific transfusion trigger.

Summary

It is clear that more research is needed as to the transfusion trigger for critically ill patients. In the absence of ischemic heart disease, age over 65 years, pulmonary disease, or acute hemorrhage, most critically ill patients can "tolerate" a hemoglobin level of 7 to 9 g/dL. The physiologic effects of anemia and blood administration are both potentially problematic. Like many bedside questions, the answer will depend on the patient, that is, his or her unique situation and presentation. In addition to the hemoglobin and hematocrit values, clinicians need to evaluate oxygen delivery, transport/perfusion variables, hemodynamic stability, weaning ability from the ventilator, and/or vasoactive drugs on an individual level. The decision to administer a blood transfusion, like most treatment decisions in critical care, can not be made on one piece of assessment data. The goal is to give the patient what he or she needs. Our challenge is to determine what that is while doing the least harm.

References

1. Starr D. Blood: An Epic History of Medicine and Commerce. New York, NY: Alfred Knope; 1998.
2. Corwin HL, Parsonnet KC, Gettinger A. RCB transfusions in the ICU: is there a reason? Chest. 1995;108:767–771.[Medline]
3. Adam RC, Lundy JC. Anesthesia in case of poor risk: some suggestions for decreasing the risk. Surg Gynecol Obstet. 1942;74:1011–1101.
4. Rodriguez RM, Corwin HL, Gettinger A, Corwin MJ, Gubler D, Pearl RG. Nutritional deficiencies and blunted erythropoietin response as causes of the anemia of critical illness. J Crit Care. 2001;16:36–41.[Medline]
5. Hébert PC, Wells G, Blajchman MA, et al. A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. N Engl J Med. 1999;340(6):409–417.[Abstract/Free Full Text]
6. Dellinger RP, Levy MM, Carlet JM, et al. Surviving sepsis campaign: international guidelines for management of severe sepsis and septic shock: 2008. Crit Care Med. 2008; 36(1):296–327.[Medline]
7. Dellinger RP, Carlet JM, Masur H, et al. Surviving sepsis campaign guidelines for management of severe sepsis and septic shock. Crit Care Med. 2004;32(3):858–873.[Medline]
8. Corwin HL, Gettinger A, Pearl RG, et al. The CRIT Study: Anemia and blood transfusion in the critically ill—Current clinical practice in the United States. Crit Care Med. 2004;32(1):39–52.[Medline]
9. Vincent JL, Baron JF, Reinhart K, et al. Anemia and blood transfusion in critically ill patients. JAMA. 2002;288(12):1299–1507.
10. Vincent JL, Sakr Y, Sprung C, et al. Are blood transfusions associated with greater mortality rates? Results of the Sepsis Occurrence in Acutely Ill Patients study. Anesthesiology. 2008;108(1):31–39.[Medline]

This article has been cited by other articles:

				C. A. Rauen, M. B. F. Makic, and E. Bridges Evidence-Based Practice Habits: Transforming Research Into Bedside Practice Crit. Care Nurse, April 1, 2009; 29(2): 46 - 59. [Full Text] [PDF]

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