Patient Harm from Repetitive Blood Draws and Blood Waste in the ICU: A Retrospective Cohort Study

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.57-57
• Main Authors: Bodley, Thomas, Chan, Maverick, Clarfield, Lauren, Levi, Olga, Longmore, Avery, Lin, Wendy, Yip, Drake, Orla, Smith, Friedrich, Jan O, Hicks, Lisa K.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-127394

Introduction: Frequent blood testing in the intensive care unit (ICU) is instrumental to patient diagnosis, monitoring, and titration of invasive therapies. However, there is a growing appreciation that a significant proportion of ICU blood tests are reflexive and unnecessary.1,2 Serial phlebotomy is associated with extended hospital length of stay and acquired anemia in the general hospital population.3 Since patients in the ICU are prone to developing anemia,4,5 they are likely at increased risk of harm from serial phlebotomy. In response, multiple recent campaigns advocate for physician restraint in laboratory test ordering.6,7 However, relatively little is known about the effect of excessive phlebotomy on outcomes in critically ill patients. Better understanding of ICU phlebotomy practices, and harms associated with serial testing, is important in planning, implementing, and evaluating phlebotomy reduction interventions. Objectives: 1) Quantify average daily phlebotomy volume for ICU patients including blood discarded as waste when accessing vascular devices. 2) Identify if average daily phlebotomy volume is an independent risk factor for ICU acquired anemia (hemoglobin < 80 g/L) or the need for red blood cell transfusion. 3) Explore the relationship between daily phlebotomy volume and hospital mortality. Methods: This was a retrospective cohort study at an academic tertiary care center in Toronto, Ontario, utilizing hospital administrative data, laboratory data, and select chart review. Index Medical Surgical ICU admissions between September 2014 and August 2015 with an ICU stay of three days or greater were included. Major bleeding events were defined as a hemoglobin drop of 30 g/L within a 24 hour period. Average daily phlebotomy volumes were calculated using the number of samples received by the lab multiplied by standard blood volumes required for each sample type. A bedside prospective audit was conducted in March 2018 to quantify average blood volume discarded as waste during phlebotomy. Blood discard/waste data were summarized with descriptive statistics, but not included in further analysis. Multivariable logistic regression was used to study the association between average daily phlebotomy volume and each of: nadir hemoglobin (< 80 g/L), the need for red blood cell transfusion, and hospital mortality. Patients with a major bleeding event were excluded from the regression. Control variables included sex, age, ICU length of stay, admission hemo