By Trushil Shah, MD, MS
Assistant Professor of Medicine, University of Texas Southwestern, Dallas
SYNOPSIS: The STRATUS randomized clinical trial was a stepped-wedge cluster randomized trial in 25 adult medical-surgical intensive care units (ICUs) in Canada that studied standard-volume to small-volume vacuum tubes for blood collection in the ICU. In the primary analysis, there was no significant difference in red blood cell transfusion between groups. However, in a pre-specified secondary analysis, red blood cell transfusion decreased after the transition from standard-volume tubes to small-volume tubes.
SOURCE: Siegal DM, Belley-Cote EP, Lee SF, et al. Small-volume blood collection tubes to reduce transfusions in intensive care: The STRATUS randomized clinical trial. JAMA 2023;330:1872-1881.
Among critically ill patients in intensive care units (ICUs), approximately 40% receive blood transfusions and more than half of these are given in the absence of active bleeding.1,2 ICU patients have multiple daily blood draws for laboratory testing, which result in significant iatrogenic blood loss that is estimated to be equivalent to one unit of whole blood every eight days.1,2 Modern laboratory equipment requires only a small fraction of the blood collected for testing; hence, more than 90% of the blood collected is discarded.3 Small-volume vacuum blood collection tubes are designed to draw about 50% less blood than standard-volume tubes by using less vacuum strength.4
The STRATUS randomized clinical trial was a stepped-wedge cluster randomized trial that studied the effect of small-volume blood collection tubes compared to standard-volume blood collection tubes on the need for red blood cell (RBC) transfusions, measured in units per patient per ICU stay. The study began Feb. 5, 2019, and ended Jan. 21, 2021. From March 2, 2020, to Aug. 17, 2020, the transition to small-volume tubes was delayed for 5.5 months. Patients admitted during this period were excluded from the primary analysis because of uncertainty during the COVID-19 pandemic (n = 6,210). However, these patients were included in the secondary analysis.
A total of 28,549 RBC units were given to 6,362 patients (30%) in the primary analysis population, and 35,687 RBC units were given to 8,136 patients (30%) in the secondary analysis population. In the primary analysis population (excluding 6,210 patients admitted during the COVID-19 pandemic), mean RBC units transfused per patient was 0.79 (95% confidence interval [CI], 0.58 to 1.07) before the transition and 0.72 (95% CI, 0.52 to 0.98) after the transition to small-volume tubes (relative risk [RR], 0.91; 95% CI, 0.79 to 1.05; P = 0.19). The absolute difference in RBC units given per 100 patients per ICU stay was 7.24 RBC units (95% CI, −3.28 to 19.44). In the secondary analysis population (whole cohort with ICU stay ≥ 48 hours), the number of RBC units transfused per patient during the ICU stay was 0.80 (95% CI, 0.61 to 1.06) before the transition to small-volume tubes and 0.71 (95% CI, 0.53 to 0.93) after the transition (RR, 0.88; 95% CI, 0.77 to 1.00; P = 0.04), which corresponds to an absolute difference of 9.84 (95% CI, 0.24 to 20.76) RBC units transfused per 100 patients during their ICU stay. Moreover, the number of specimens reported as having insufficient quantity for analysis was similar between small-volume and standard-volume tubes (0.03% vs. 0.02%, respectively). There was no significant interaction between the treatment variable and study periods (P = 0.71) or COVID-19 pandemic phases (P = 0.92).
COMMENTARY
Iatrogenic anemia due to frequent blood draws unfortunately is a common problem for patients admitted to the ICU.5 Currently, standard blood draw tubes contain approximately 4 mL to 6 mL, of which 90% is discarded.4 Small-volume blood collection tubes decrease the amount drawn by half, thereby decreasing waste/discarded blood. This potentially would decrease the need for blood transfusions in the ICU population and avoid health risks associated with frequent transfusions.
This trial by Siegal et al is the first randomized clinical trial that studied small-volume vs. standard-volume blood collection. While the need for RBC transfusion was not statistically significant in the primary analysis (excluding 6,210 patients admitted during the COVID-19 pandemic), it was significantly lower in the small-volume tube group in a pre-specified secondary analysis (including all patients). Moreover, there was no effect on laboratory analysis with the small-volume tubes when compared to standard-volume tubes. This study highlights the effectiveness of small-volume tube collection and indicates a possible decrease in the need for RBC transfusions when small-volume tubes are used for blood collection.
Based on prior retrospective and observational studies and this current randomized clinical trial, small-volume blood collection may decrease RBC transfusions without affecting laboratory analysis. The use of small-volume blood collection tubes can be one of many steps taken to decrease the downstream effects of iatrogenic anemia and the demand for blood transfusions in the ICU.
REFERENCES
- Jackson Chornenki NL, James TE, Barty R, et al. Blood loss from laboratory testing, anemia, and red blood cell transfusion in the intensive care unit: A retrospective study. Transfusion 2020;60:256-261.
- Vincent JL, Baron JF, Reinhart K, et al; ABC (Anemia and Blood Transfusion in Critical Care) Investigators. Anemia and blood transfusion in critically ill patients. JAMA 2002;288:1499-1507.
- Levi M. Twenty-five million liters of blood into the sewer. J Thromb Haemost 2014;12:1592.
- Siegal DM, Manning N, Jackson Chornenki NL, et al. Devices to reduce the volume of blood taken for laboratory testing in ICU patients: A systematic review. J Intensive Care Med 2020;35:1074-1079.
- Ranasinghe T, Freeman WD. ‘ICU vampirism’— time for judicious blood draws in critically ill patients. Br J Haematol 2014;164:302-303.
