There were 25 survivors with a hemoglobin of 5 g/dl or less. Except for three patients who died after cardiac surgery, all patients whose deaths were attributed to anemia died with hemoglobin concentrations of 5 g/dl or less. Of the 50 deaths, 23 were thought to be primarily due to anemia. In a review of 61 medical and surgical reports published from 1970 to 1993, Viele and Weiskopf identified 50 deaths attributed to anemia in untransfused Jehovah's Witnesses with hemoglobin concentrations of 8 g/dl or less, or hematocrit of 24% or less. Experience in Jehovah's Witness patients has allowed an assessment of human tolerance of severe acute anemia and demonstrated the feasibility of survival in the case of very low hematocrit. In patients who are not critically ill, most studies have demonstrated that a substantially lower hemoglobin level (7 g/dl) can be tolerated if normovolemia is maintained. The optimal hemoglobin level is more closely approximated by physiologic measurements. However, current practice and available evidence is gradually shifting from transfusing to an arbitrary hemoglobin (10/30) to achieving a level of hemoglobin necessary to meet the patient's tissue oxygen demands. Despite these data, many clinicians continue to provide transfusion using a hematocrit of 30% as a 'transfusion trigger'. Recent studies have provided compelling evidence against the 10/30 rule in critically ill patients as well as in the perioperative period. Most authorities attribute this bias to a 1942 report by Adams and Lundy in which they recommended a hemoglobin of 10 g/dl and a hematocrit of 30% in the perioperative setting based on their clinical experience. Despite the paucity of objective data to support this contention, the so-called '10/30 rule' persisted until recently. The hemoglobin level at which serious morbidity or mortality occurs in critically ill patients with active ischemic heart disease is a subject of continued debate but it is likely that a set transfusion trigger will not provide an optimal risk–benefit profile in this population.įor years many physicians firmly believed that a hemoglobin of 10 g/dl and a hematocrit of 30% represented desirable goals in anemic patients, especially those undergoing surgical procedures and those with cardiac disease. Transfusions should be administered as clinically indicated for patients with acute, ongoing blood loss and those who have objective signs and symptoms of anemia despite maintenance of euvolemia. Based on the available evidence, transfusion in the critically ill patient without active ischemic heart disease should generally be withheld until the hemoglobin level falls to 7 g/dl. The impact of this accumulating evidence on clinical practice is evident in large reports, which show that the average transfusion trigger in critically ill patients was a hemoglobin level in the range 8–8.5 g/dl.
#CRITICAL LOW HEMATOCRIT AND HEMOGLOBIN LEVELS TRIAL#
A recent randomized controlled trial provided compelling evidence that similar, and in some cases better, outcomes result if a restrictive transfusion strategy is maintained. An expanding body of literature suggests that an arbitrary trigger for transfusion (the '10/30 rule') is ill advised.
Past retrospective and observational studies suggested that liberal transfusion strategies were more beneficial in patients whose hematocrit levels fell below 30%. Despite the increasing availability of data supporting more restrictive transfusion practices, the risks and benefits of transfusing critically ill patients continue to evoke controversy.
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