Laboratory testing among patients undergoing cardiac surgery can lead to excessive bloodletting, which can increase the risk for developing hospital-acquired anemia and the need for blood transfusion.

In a new study, researchers evaluated the frequency of laboratory testing and cumulative phlebotomy volume in 1,894 patients who underwent cardiac surgery at the Cleveland Clinic from January to June 2012. The number and type of blood tests performed were recorded from the time patients met their surgeons until hospital discharge. The researchers then calculated the total amount of blood taken from each patient.

During the study period, 221,498 laboratory tests were performed, an average of 115 tests per patient. The most prevalent laboratory tests were blood gas analyses (n = 88,068), coagulation tests (n = 39,535), complete blood counts (n = 30,421) and metabolic panels (n = 29,374).

“We were astonished by the amount of blood taken from our patients for laboratory testing. Total phlebotomy volumes approached 1 to 2 units of red blood cells, which is roughly equivalent to one to two cans of soda,” said Colleen G. Koch, MD, MS, MBA, from the department of cardiothoracic anesthesia, Heart and Vascular Institute, Cleveland Clinic.