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Blood Loss From Tests May Cause Anemia in Patients, Study Finds

Patients who enter hospitals due to heart attacks may be leaving with anemia caused by laboratory tests that draw too much blood, raising their risk of declining health and death, a study found.

In an analysis of almost 18,000 patients in 57 U.S. hospitals from 2000 to 2008, researchers found that 20 percent of patients who didn’t have anemia when admitted for heart attacks developed moderate to severe cases of the red blood-cell deficiency by the time they left. The study is published today in the journal Archives of Internal Medicine.

Anemia is associated with greater death rates and worse health in patients who have already suffered heart attacks, the study said. Patients who developed anemia left the hospital suffering from fatigue, shortness of breath and physical weakness. Doctors may need to change some of their practices, said Mikhail Kosiborod, an associate professor of medicine at the University of Missouri-Kansas City and the study’s senior author.

“The amount of blood we take from patients is a major risk factor” for anemia, Kosiborod said. “If they have other medical problems their body can’t regenerate blood cells fast enough.”

Preventable adverse events in hospitals such as infections and sickness cost $4.4 billion a year, and happen to 1 in 7 beneficiaries of Medicare, the U.S. health program for the elderly and disabled, according to the Department of Health and Human Services. Kosiborod said the findings weren’t related to medical mistakes, though steps may be taken to reduce the amount of blood drawn.

Blood Volumes

The study found that the average volume of blood drawn from patients who developed anemia was 173.8 milliliters. That’s more than double the 83.5 milliliters from patients who didn’t get anemia, according to the study. For every 50 milliliters of blood drawn, the risk of moderate to severe hospital-acquired anemia increased by 18 percent.

Many doctors have become accustomed to drawing blood without an immediate need for the sample, said Stephanie Rennke, an assistant clinical professor at the University of California, San Francisco and lead author of a commentary article on the anemia study.

“Some doctors indiscriminately take blood tests without consciously asking why they need it and what they’re looking for,” she said in an interview. “It’s hard to change when they get into the routine of doing things.”

She said facilities can prevent hospital-acquired anemia by providing proper nutrition to patients, testing from a single blood sample each day and only testing on the day of discharge if absolutely necessary.

The average blood loss across hospitals ranged from 119 to 246 milliliters, indicating that some blood loss could be prevented by eliminating routine testing, the study’s authors said.

By using smaller tubes and sampling from blood that has already been drawn, hospitals may be able to reduce the amount of blood loss, Kosiborod said.

“Doctors have to take blood to help patients,” he said.

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