Using hemoglobin-based blood substitutes has been linked to hiking risk of heart attacks by three times and the risk of death by 30 percent by a new analysis.
Clinical trials completed as early as 1996 have underlined questions about the safety of hemoglobin-based blood substitutes and have yet to prove clinical benefits, according to Charles Natanson of the National Institutes of Health, the lead author of the study.
The Food and Drug Administration, the US agency that regulates medicine, probably could have prevented deaths linked to the products by halting further clinical trials eight years ago when data raised safety questions, the authors wrote in the online edition of the Journal of the American Medical Association.
Prompt analyses of clinical trials of blood substitutes by the FDA "most likely would have demonstrated significant risks by 2000," it said.
The FDA did not make public the results of clinical trials because the blood substitutes had not received approval to be sold on the market.
But the authors argue that results of all trials of experimental drugs in humans should be released promptly and in full for the sake of scientific progress and patient safety.
Despite concerns about risk, at least one hemoglobin-based blood substitute has been approved for use outside the United States and new clinical trials are underway or planned worldwide, according to a statement announcing the analysis.
Five trials with blood substitutes are being carried out in eight countries and at least one trial is scheduled for the United States.
The authors analyzed sixteen previous clinical trials, involving five different blood substitutes and 3,771 patients.
The analysis showed a total of 164 deaths among patients treated with blood substitutes compared to 123 deaths among patients treated with normal blood.
The hemoglobin-based substitutes were linked to a 30 percent increase in the risk of death with 59 heart attacks among patients treated with substitutes compared to 16 heart attacks in the control groups.
The combined studies of trials showed the risk of heart attack increased 2.7 times for patients receiving blood substitutes compared to patients receiving normal blood.
The increased risk was not limited to a particular hemoglobin-based product or clinical condition.
A successful blood substitute -- a long-lasting liquid that does not require refrigeration and does not cause infection -- offers the potential of saving the lives of patients suffering from shock and loss of blood, particularly in rural areas or in military combat.
So far a large portion of the blood substitutes developed have been hemoglobin-based products. Hemoglobin carries 98 percent of oxygen in red blood cells.