Too Many Blood Tests Can Cause Anemia In Heart Patients: Study

The findings of new research suggest that heart surgery patients may face a risk of serious complications if too many blood tests are done immediately after the procedure.  

Blood tests both before cardiac surgery and after are common, yet researchers from the Cleveland Clinic, which specializes in heart surgery, found that a higher frequency of blood draws may lead to complications, including excessive blood loss, hospital-acquired anemia and may require patients to have blood transfusions.

The findings were published in the March issue of the Annals of Thoracic Surgery.

The study focused on nearly 2,000 patients who underwent cardiac surgery at the Cleveland Clinic between January 1, 2012, and June 30, 2012. More than 220,000 cumulative lab tests were performed, with  an average of 115 tests per patient. The average amount of blood taken during a patient’s hospital stay was about 15 ounces, or 454 milliliters.

The most frequently performed tests were blood gas analysis, performed nearly 90,000 times. Also conducted frequently, included nearly 40,000 coagulation tests, 30,000 complete blood counts, and nearly 30,000 metabolic panels.

The highest blood loss occurred among patients undergoing the most complex heart surgeries, placing them at even more risk of suffering other complications. Researchers found that the higher number of lab tests and the longer the patient stayed in the hospital, the more likely the patient was to need a blood transfusion.

“Prior research shows that patients who receive blood transfusions during heart surgery have more infections after surgery, spend more time on the ventilator, and die more frequently — even after adjusting for how sick they were prior to surgery,” said Dr. Colleen G. Koch, lead author of the study.

Those tests included the combined coronary artery bypass grafting (CABG) and valve procedures which averaged a loss of 653 milliliters and 338 milliliters of blood.

Researchers also tabulated the average amounts of blood taken between the intensive care unit (ICU) and hospital floors, averaging 332 milliliters and 118 milliliters respectively.

Koch likened the overuse of blood tests to a modern day blood letting.

“We were astonished by the extent of bloodletting, with total phlebotomy volumes approaching amounts equivalent to 1 to 2 red blood cell units, which is roughly equivalent to one to two cans of soda,” said Koch.

Researchers calculated the cumulative phlebotomy volume from the time of the initial surgical consultation to the patient’s discharge from the hospital.

Koch recommends if patients are worried about the volume of blood being taken, ask doctors if a specific test is necessary. Researchers also advise patients to find out what the specific indication is for the test, will the results change the patient’s care and if it the tests need to be done every day.