Bloodletting during Cardiac Surgical Care
Researchers from Cleveland Clinic examined the number of laboratory tests and volume of blood drawn from 1894 patients undergoing cardiac surgery between January 1 and June 30, 2012. Cumulative number of tests and phlebotomy volume were tabulated for each patient from the time of initial surgical consultation to hospital discharge. A total of 221, 498 laboratory tests were performed during the study period, averaging 115 tests per patient. The most frequently ordered tests were blood gases, coagulation tests, complete blood counts and chemistry metabolic panels.
Cumulative median blood volume for the entire hospital stay was 454 mL. Cumulative volume of blood collected in the ICU was almost three times higher than on hospital nursing units. Median volume drawn was 332 mL in the ICU compared to 118 mL on hospital floors. The difference was largely attributed to the 7 to 10 mL of blood that was discarded before each blood draw in the ICU to clear intravenous lines. More complex cardiac surgery procedures and longer length of stay were associated with a larger number of laboratory tests and a higher median phlebotomy volume.
Total phlebotomy volumes were the equivalent of 1 to 2 units of red blood cell units. Higher phlebotomy volumes were associated with increased transfusion of red blood cells. Approximately 10% of patients in the lowest quartile of phlebotomy volume were transfused compared to more than 60% in the highest quartile. Since longer hospital stay was associated with greater median phlebotomy volume, it was also associated with increased likelihood of transfusion.
The greater the number of laboratory tests ordered and the longer the hospital stay, the more likely patients were transfused. Previous studies have demonstrated that patients who are transfused have a higher incidence of postoperative infections, longer ventilator time, higher risk adjusted mortality and longer length of stay.
Hospitals can improve patient outcomes by implementing strategies to reduce the number of laboratory tests ordered and the volume of blood drawn during phlebotomy. Possible solutions include eliminating unnecessary laboratory tests, batching test requests, purchasing in-line blood conservation devices, collecting blood in smaller volume, and creating a cumulative log of phlebotomy volume in medical flow sheets.
Koch CG, et al. Contemporary bloodletting in cardiac surgical care. Ann Thorac Surg 2015;99;779-85.
Koch CG, et al. Hospital acquired anemia: prevalence, outcomes, and healthcare implications. J Hosp Med 2013;8:506-12.
