Variation in red cell transfusion practice in the intensive care unit: a multicentre cohort study

Abstract

OBJECTIVES: To determine the degree of interinstitutional transfusion practice variation and reasons why red cells are administered in critically ill patients. STUDY DESIGN: Multicentre cohort study combined with a cross-sectional survey of physicians requesting red cell transfusions for patients in the cohort. STUDY POPULATION: The cohort included 5298 consecutive patients admitted to six tertiary level intensive care units in addition to administering a survey to 223 physicians requesting red cell transfusions in these units. MEASUREMENTS: Haemoglobin concentrations were collected, along with the number and reasons for red cell transfusions plus demographic, diagnostic, disease severity (APACHE II score), intensive care unit (ICU) mortality and lengths of stay in the ICU. RESULTS: Twenty five per cent of the critically ill patients in the cohort study received red cell transfusions. The overall number of transfusions per patient-day in the ICU averaged 0.95 +/- 1.39 and ranged from 0.82 +/- 1.69 to 1.08 +/- 1.27 between institutions (P < 0.001). Independent predictors of transfusion thresholds (pre-transfusion haemoglobin concentrations) included patient age, admission APACHE II score and the institution (P < 0.0001). A very significant institution effect (P < 0.0001) persisted even after multivariate adjustments for age, APACHE II score and within four diagnostic categories (cardiovascular disease, respiratory failure, major surgery and trauma) (P < 0.0001). The evaluation of transfusion practice using the bedside survey documented that 35% (202 of 576) of pre-transfusion haemoglobin concentrations were in the range of 95-105 g/l and 80% of the orders were for two packed cell units. The most frequent reasons for administering red cells were acute bleeding (35%) and the augmentation of O2 delivery (25%). CONCLUSIONS: There is significant institutional variation in critical care transfusion practice, many intensivists adhering to a 100g/l threshold, and opting to administer multiple units despite published guidelines to the contrary. There is a need for prospective studies to define optimal practice in the critically ill.

Figure 1

Average pre-transfusion haemoglobin values over time in participating institutions. This figure illustrates all haemoglobin concentrations during the first 10 days of intensive care unit (ICU) stay. There was an average decrease of 16 g/l in haemoglobin concentrations in all patients admitted to the ICU over the 10-day monitoring interval. Institution 1 had the highest values over time while institution 3 recorded the lowest concentrations during the 10 days. The solid thick line illustrates overall concentrations.

Figure 2

Average pre-transfusion haemoglobin concentrations stratified by institution, APACHE II categories and transfusion status. Average pre-transfusion hemoglobin concentrations stratified by transfusion status, institution and high (> 15) versus low (≤ 15) APACHE II score. Institution 3 and 6 had the lowest concentrations overall and patients who received red cells. The influence of APACHE II scores appeared least important in centres (3 and 6) with a conservative approach to the administration of red cells. This graph also illustrates significant variations in haemoglobin concentrations in both APACHE II groups and in transfused and non-transfused patients.