A new method that limits the number of blood transfusions needed during heart surgery showed no additional risk to patients when it came to kidney injury, a common outcome of the surgery, according to a recent study. The findings could be a game-changer for a health-care system constantly seeking ways to balance demands on its blood supply.
“More than 20 million cardiac surgeries are performed worldwide each year,” explained Epidemiology and Biostatistics professor Amit Garg. “With this being one of the more common reasons for using blood in the hospital, if each patient received one less transfusion, this suggests approximately 20 million units of blood could be saved each year, without influencing the chance a patient will develop post-operative kidney injury.”
A large amount of the blood supply in hospitals is used during cardiac surgery, with the average patient receiving three units of blood. Reducing the number of transfusions needed could not only prevent adverse events related to transfusions, but conserve the blood supply and reduce health-care costs.
The study looked at 4,531 high-risk patients undergoing cardiopulmonary bypass surgery across 73 centres in 19 countries.
Hemoglobin – the oxygen-carrying substance in red blood cells – is usually expressed in grams per deciliter (g/dL) of blood. A low level of hemoglobin in the blood relates directly to a low level of oxygen.
For the trial, one group was given transfusions only if their hemoglobin dipped below 7.5 grams per decilitre. A second group was treated with a liberal use of transfusions if their hemoglobin was less than 9.5 grams per decilitre.
On average, patients in the restrictive group received 38 per cent fewer transfusions than those in the liberal group. Both approaches were found to be equally safe for patients, as the restrictive group did not have a higher rate of acute kidney injury.
One in five patients who undergo cardiopulmonary bypass surgery experience some degree of kidney injury.
With this evidence, Garg, a Lawson Health Research Institute scientist, hopes to see clinical practice guidelines changed and distributed widely.
“A lot of people are generous in giving blood,” he said. “At the end of the day, we want to use this precious resource wisely and this study is showing us when we should and shouldn’t use it (blood transfusions), with the main concern it still being safe for the patient.”
The international study, Safety of a Restrictive versus Liberal Approach to Red Blood Cell Transfusion on the Outcome of AKI in Patients Undergoing Cardiac Surgery: A Randomized Clinical Trial, is published in the Journal of the American Society of Nephrology.