Small-Volume Tubes to Reduce Transufusion (STRATUS): A Pilot Study

Background: Blood sampling for diagnostic testing can result in significant blood loss, particularly in critically ill patients who undergo frequent testing and in whom anemia and red blood cell (RBC) transfusion are frequent. Only 10% of blood collected is used for testing procedures suggesting that small-volume tubes may reduce the incidence/severity of anemia and RBC transfusion without compromising care.

Small-volume Vacutainer® tubes for blood collection (2-3 mL) have the same cost, physical dimensions, and blood draw techniques as standard-draw tubes (4-10 mL), and are compatible with laboratory equipment. Our objective was to evaluate the feasibility of a pragmatic randomized trial to determine whether a policy of small-volume tubes reduces RBC transfusion compared to standard tubes in adult intensive care unit (ICU) patients.

Methods: We performed a mixed-methods prospective pilot study (before-after design) in the cardiovascular ICU in Hamilton, Canada. The study consisted of a 6-week control period (current practice of standard-volume tubes) and a 6-week intervention period (small-volume tubes) separated by a 2-week washout period. All patients admitted to the ICU were included and followed for 30 days, or until discharge or death. The primary outcome was feasibility as follows: (i) successful switch to small-volume tubes; (ii) adherence to correct tube size; (iii) sufficient volume for testing (less than 3% inadequate); (iv) user acceptance (nurses, lab techs, etc.); (v) assessment of barriers and facilitators to implementation; and (vi) 95% complete primary data collection. Secondary outcomes were reduction in blood loss with small-volume tubes, change in hemoglobin (Hb) level from ICU admission to discharge (adjusted for RBC transfusion), RBC transfusion, ICU/hospital mortality and ICU/hospital length of stay. End-user acceptability and barriers/facilitators to implementation were explored using focus group discussions (FGD). Thematic analysis from FGDs was conducted using NVivo software (QSR International).

Results: From December 1 to February 6, 2018, 369 patients were included in the study, 165 in the control and 204 in the intervention periods. The median (IQR) age was 70 yrs (61 - 76) in the control group and 67 yrs (59 - 74) in the intervention group. The median (IQR) ICU stay was 1 day (1-35) for both groups. Random audits demonstrated 100% compliance with allocated tube size. Median (IQR) estimated blood loss due to laboratory testing per patient per day in ICU was 11 mL (8-17) in the control period and 6 mL (4-8) mL intervention period, corresponding to a 45% reduction in blood loss. Total median (IQR) estimated blood loss was 24 mL (16-58) and 15 mL (11-26), in the control and intervention periods, respectively. The median (IQR) adjusted Hb at discharge was 62 g/L (43 - 70) in the control period and 63 g/L (56 - 70) in the intervention period. The proportion of samples with inadequate volume for testing was similar for both groups (0.2% vs. 0.2%, p= 0.72). RBC transfusions were administered to 46 patients (28%) in the control group and 41 (20%) patients in the intervention group (p=0.084). The median (IQR) number of transfusions in the control and intervention periods was 2 units (1-4) and 2 units (1-2) units, respectively. There were 9 deaths (5.5%) in the control group and 3 deaths (1.5%) in the intervention group (0.04).

Based on 10 FGDs with 24 ICU nurses and 9 laboratory staff, small-volume tubes were acceptable with no significant barriers to implementation identified.

Conclusion: In this pilot study, small-volume tubes were successfully implemented for routine laboratory testing with acceptability to end-users and without significant barriers. Use of small-volume tubes resulted in a reduction in blood loss for laboratory testing by 45% with no increased frequency of inadequate samples. Our results suggest that small-volume tubes are a feasible intervention to reduce the volume of blood taken for laboratory testing in adult ICU patients. These results will inform a full-scale stepped wedge cluster randomized trial to determine whether a policy of small-volume tubes reduces RBC transfusion in adult ICU patients.