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Too Much Blood Taken for Hospital Tests Can Cause Anemia, Increasing Risk of Complications and Death

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August 9, 2011

A new study has found that if hospitals draw too much blood for diagnostic testing from patients admitted for heart attacks, they place those patients at risk for hospital-acquired anemia (HAA) and increased chance of complications and death.

People with anemia have a shortage of healthy red blood cells that carry oxygen. Anemia can be a chronic condition caused by problems with bone marrow, a nutritional deficiency or other medical condition. Some hospital patients can develop a sudden hospital-acquired anemia or HAA. Blood loss is a known cause of HAA and hospitals already take precautions to limit blood loss from bleeding. However, HAA commonly occurs in hospital patients who have not suffered any bleeding.

Researchers in this study set out to determine if phlebotomy, or the taking of blood for testing, could be linked to hospital-acquired anemia. If so, hospitals could develop protocols to reduce the amount of blood taken for testing and therefore prevent HAA.

They studied medical records for nearly 18,000 patients admitted for acute myocardial infarction (AMI) at 57 hospitals across the United States who were not anemic when admitted. They found that 1 in 5 of those patients developed moderate to severe hospital-acquired anemia during their hospital stay.

Heart attack patients who develop hospital-acquired anemia actually feel worse and have a higher rate of mortality than those without HAA.

The researchers then calculated the amount of blood taken for diagnostic testing, called diagnostic blood loss (DBL), finding that patients who developed hospital-acquired anemia had a higher DBL than those without HAA. The average amount of DBL was equivalent to half of a unit of whole blood. The study also showed that average amounts of DBL varied widely between hospitals, suggesting that some hospitals took blood to run “routine” tests that may have been unnecessary.

“Our findings are likely generalizable to other populations of seriously ill medical patients,” researchers said. “In this regard, further studies that establish whether minimizing DBL can prevent HAA and improve patient outcomes could have broad implications for hospitalized patients.”

To prevent unnecessary diagnostic blood loss, study researchers recommended the use of smaller pediatric tubes for blood collection or filling standard adult tubes with less blood in addition to determining if certain blood tests are necessary.

The study entitled “Diagnostic Blood Loss from Phlebotomy and Hospital-Acquired Anemia during Acute Myocardial Infarction” appears in the current issue of Archives of Internal Medicine.

“With the increasing evidence that health care system interventions can reduce or prevent many hospital-acquired complications, efforts to implement effective strategies to make medical care safer and more effective are crucial,” said Stephanie Rennke, MD and Margaret C. Fang, MD, MPH in a commentary. “As [researchers] highlight in their study, HAA could potentially be considered a hazard of hospitalization. Investigations on how to modify this risk (eg, through reducing unnecessary phlebotomy or reducing the volume of blood obtained during a hospitalization) could provide important insights into how to reduce anemia in the hospital and improve the value and appropriateness of care.”