Anemia and blood transfusion in a surgical intensive care unit

Abstract

Introduction: Studies in intensive care unit (ICU) patients have suggested that anemia and blood transfusions can influence outcomes, but these effects have not been widely investigated specifically in surgical ICU patients.

Methods: We retrospectively analyzed the prospectively collected data from all adult patients (>18 years old) admitted to a 50-bed surgical ICU between 1st March 2004 and 30th July 2006.

Results: Of the 5925 patients admitted during the study period, 1833 (30.9%) received a blood transfusion in the ICU. Hemoglobin concentrations were < 9 g/dl on at least one occasion in 57.6% of patients. Lower hemoglobin concentrations were associated with a higher Simplified Acute Physiology Score II and Sequential Organ Failure Assessment score, greater mortality rates, and longer ICU and hospital lengths of stay. Transfused patients had higher ICU (12.5 vs. 3.2%) and hospital (18.3 vs. 6.5%) mortality rates (both p < 0.001) than non-transfused patients. However, ICU and in-hospital mortality rates were similar among transfused and non-transfused matched pairs according to a propensity score (n = 1184 pairs), and after adjustment for possible confounders in a multivariable analysis, higher hemoglobin concentrations (RR 0.97[0.95-0.98], per 1 g/dl, p < 0.001) and blood transfusions (RR 0.96[0.92-0.99], p = 0.031) were independently associated with a lower risk of in-hospital death, especially in patients aged from 66 to 80 years, in patients admitted to the ICU after non-cardiovascular surgery, in patients with higher severity scores, and in patients with severe sepsis.

Conclusions: In this group of surgical ICU patients, anemia was common and was associated with higher morbidity and mortality. Higher hemoglobin concentrations and receipt of a blood transfusion were independently associated with a lower risk of in-hospital death. Randomized control studies are warranted to confirm the potential benefit of blood transfusions in these subpopulations.

Figure 1

Time course of hemoglobin concentration during the first two weeks in the ICU. This was classified according to hemoglobin concentrations on admission (categories with increments of 1 g/dl). Mean values are displayed.

Figure 2

Relative risk of in-hospital death due to blood transfusion in selected subgroups of ICU patients. Left panel demonstrates non-adjusted relative risks (RR). Right panel demonstrates relative risks adjusted to age, gender, comorbidities, severity scores on admission to the ICU, referring facility, type of surgery, the presence of sepsis syndromes, hemoglobin concentration on admission to the ICU, and the number of transfused units of blood. Blood transfusion was introduced in the model as a time-dependent variable in relation to the day on which blood transfusion was carried out. CI: confidence interval; SAPS: simplified acute physiology score; SOFA: sequential organ failure assessment.