January 2024

Leah Lawrence

New data indicate that the use of tubes that automatically collect less blood in the intensive care unit (ICU) may decrease red blood cell (RBC) transfusions without affecting laboratory analysis. Deborah M. Siegal, MD, of Ottawa Hospital in Canada, and colleagues published their findings in JAMA.

“Small change … big savings,” Dr. Siegal said. “The tubes look the same. They cost the same. They go into the same equipment.”

The investigators performed a pragmatic stepped-wedge cluster randomized trial to test the hypothesis that switching to so-called “small-volume” tubes (those that have less vacuum and fill to a lower predetermined volume) reduces RBC transfusion in ICU patients. The investigators implemented small-volume tubes within routine clinical practice using hospital processes and in-service training of clinical and laboratory staff. Standard-volume and small-volume tubes were obtained by local hospital purchasing departments from usual commercial suppliers at what the authors described as “essentially the same cost.”

The researchers noted that one limitation of their study is that it took place during the COVID-19 pandemic, a time when both care and clinical research were disrupted in Canada. The primary analysis of the study included 21,201 patients (mean age = 63.5 years; 39.9% female) and excluded 6,210 patients admitted during the early COVID-19 pandemic. The investigators documented that over the course of their study (February 5, 2019, to January 21, 2021) more than 36,000 units of blood were given to more than 27,000 ICU patients who stayed in the ICU for 48 hours or longer.

In the primary analysis, the researchers found that RBC transfusions did not differ significantly before and after transition from standard- to small-volume blood collection tubes (relative risk [RR] = 0.91 [95% CI 0.79-1.05]; p=0.19; absolute reduction of 7.24 RBC units/100 patients per ICU stay [95% CI -3.28-19.44]). Secondary outcomes were patients receiving at least one RBC transfusion, hemoglobin decrease during ICU stay, specimens with insufficient volume for testing, length of stay in the ICU and hospital, and mortality in the ICU and hospital. In the prespecified secondary analysis (n=27,411 patients), however, RBC units per patient per ICU stay decreased after transition from standard-volume to small-volume tubes (RR=0.88 [95% CI 0.77-1.00]; p=0.04; absolute reduction of 9.84 RBC units/100 patients per ICU stay [95% CI 0.24-20.76]). The researchers calculated that implementation of these small-volume tubes could reduce blood transfusion during ICU admission by 10 units per 100 patients in the ICU.

Dr. Siegal explained that there is a high prevalence of anemia among patients in the ICU, and about 30% to 50% of patients receive at least one transfusion. Reducing RBC transfusion is thus widely viewed as a clinical priority for patients in the ICU. Not only does sparing transfusions save money, but it presents an “opportunity to use those units for other people who need it amongst blood product shortages,” said Dr. Siegal. She explained that while anemia is multifactorial, blood sampling for laboratory testing is substantial and a potentially modifiable contributor to anemia and RBC transfusion, especially because only 10% of the blood collected is required for testing; the remainder is discarded as waste. “Taking more blood from people than is needed does not add value to their care and could cause harm,” Dr. Siegal said.

Dr. Siegal said she and her colleagues found it “surprisingly straightforward and uncomplicated” to make the tube switch. The research team engaged with multiple stakeholders, including individuals in the clinical laboratory, the critical care community, and hematologists, when planning the study. The main concern about the change was that it would somehow compromise test procedures. The investigators were pleased to learn that the change was associated with very low rates of specimen insufficiency that were similar before and after the transition.

Dr. Siegal began the work in 2014 when she participated as a resident in the American Society of Hematology’s (ASH) Clinical Research Training Institute. The project started with the question, “If smaller tubes can be used for children, why can’t they be used for adults?” She explained that it wasn’t a new idea, but with ASH’s support, she led the multidisciplinary team that had the expertise and motivation to conduct the first and only randomized trial to address this question and change practice.