March 20, 2015
2 min read

Frequency of blood tests, phlebotomy volumes high in patients undergoing cardiac surgery

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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.

“After an investigation into the prevalence and outcomes associated with development of hospital-acquired anemia in our health system, we began to critically examine factors contributing to its occurrence,” Colleen G. Koch, MD, MS, MBA, from the department of cardiothoracic anesthesia, Heart and Vascular Institute, Cleveland Clinic, and colleagues wrote. “We were not cognizant of the overall frequency of testing and cumulative phlebotomy volumes associated with hospitalization for cardiac surgical procedures.”

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).

According to the results, phlebotomy volume varies between ICU and hospital floors. The median volume was 332 mL in the ICU and 118 mL outside the ICU. The cumulative median volume for the entire hospitalization was 454 mL.

“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,” Koch said in a press release.

More complex procedures were associated with higher overall phlebotomy volume. Patients undergoing combined CABG and valve procedures had the highest median cumulative phlebotomy volume (653 mL) compared with patients undergoing isolated CABG (median, 448 mL) or isolated valve procedures (median, 338 mL).

Along with increases in cumulative phlebotomy volume, the need for blood products also rose. Forty-nine percent of patients received red blood cell transfusions, 25% fresh frozen plasma, 33% platelets and 15% cryoprecipitate. In addition, longer length of stay was associated with increasing phlebotomy volume and need for red blood cell transfusion.

In an invited commentary, Milo Engoren, MD, from the University of Michigan in Ann Arbor, emphasized the importance of reducing blood loss to decrease risk for complications during cardiac surgery, minimizing use through strategies such as using smaller tubes, better blood-conservation devices and noninvasive monitoring.

“But we also need to step back and ask, ‘Does this patient need this test?’ Are we getting this test because the answer will change therapy? Or are we getting the test from habit or other inappropriate reason?” Engoren wrote. “Avoiding unnecessary blood tests will not only help anemia, but will also save money.” – by Jennifer Byrne

Disclosures: Koch and Engoren report no relevant financial disclosures.