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Blood conservation strategy helpful in aortic valve replacement

NEW YORK (Reuters Health) – A blood conservation strategy can reduce red blood cell (RBC) use during aortic valve replacement surgery without increasing mortality or morbidity, a retrospective study suggests.

In general, the strategy involved limits on intraoperative hemodilution, tolerance of perioperative anemia, and blood management education of the cardiac surgery team.

After the strategy was implemented, patients were 2.7 times less likely to receive RBCs and 1.7 times less likely to have major complications, including sepsis, respiratory failure, renal failure, or death, the authors wrote.

They say clinical practice guidelines from the Society of Thoracic Surgeons and the Society of Cardiovascular Anesthesiologists for blood conservation in routine cardiac surgery should be extended to aortic valve replacement.

“We can safely extend blood conservation protocols developed for patients undergoing CABG to heart patients requiring aortic valve surgery,” said senior investigator Dr. Eugene Grossi, a cardiothoracic surgeon at the New York University Langone Medical Center in New York City.

“We can be a lot stingier with blood transfusions,” he told Reuters Health. “By exposing the patients to less blood, we lower their risk of having reactions from the blood or of getting infectious diseases from the blood. We also save money for the hospital, and because blood is always in chronic shortage, we can keep it in reserve for patients who need it most.”

Dr. Grossi’s team conducted a four-year before-and-after study of RBC use during aortic valve replacment surgery at their hospital and published their findings online November 21 in The Annals of Thoracic Surgery.

The researchers gradually introduced their blood conservation strategy during the middle of the study period. Dividing the study into two equal time periods yielded a pre-BCS group with 391 patients and a post-BCS group with 387.

Among the changes: everyone on the team – surgeons, residents, perfusionists, anesthesiologists, and recovery room and ICU nurses – was taught to tolerate a perioperative hemoglobin of 8 g/dL or higher rather than using 10 mg/dL as a trigger for transfusion. Also, the researchers report, “transfusions were performed according to physiologic need and not reflexively in response to laboratory values or for empiric or prophylactic reasons.”

The average patient was 72 years (range, 18 to 96); a third of the cohort was 80 or older.

The groups weren’t equivalent. The “after” group had lower rates of peripheral vascular disease, chronic obstructive pulmonary disease, aortic calcification, congestive heart failure, and previous cardiac surgeries, the authors acknowledge.

Overall, there were 23 deaths (3.0%), including nine deaths (1.7%; n=522) in patients undergoing isolated primary aortic valve replacement. Deaths occurred only in patients who received two or more units of RBCs, with no difference in mortality or major complications between the pre-BCS and post-BCS groups.

RBC transfusion incidence decreased from 82.9% (324 of 391) to 68.0% (263 of 387; p<0.01).

A decreased risk of RBC transfusion was associated with isolated aortic valve replacement (p<0.01), a minimally invasive approach (p<0.01), and the blood conservation strategy (p<0.01).

In contrast, an increased risk of RBC transfusion was associated with older age (p<0.01), previous cardiac operation (p=0.01), female sex (p<0.01), and smaller body surface area (p<0.01).

Mortality was associated with RBC transfusion of two or more units on the day of surgery (p=0.01), prolonged intubation (p<0.01), post-op renal failure (p=0.01), and increase of any complication (p<0.01).

On multivariate analysis, the blood conservation strategy had no effect on mortality rates and was associated with a lower risk of major complications (odds ratio 1.7; p=0.046).

The researchers acknowledged that limitations to their study include the study’s design, the baseline differences between the two groups, the gradual change in practice during the study period, and their use of hematocrit data as a surrogate for unavailable hemoglobin data.

“Blood conservation strategy requires a shift in the institutional culture of managing patients before, during and after surgery by a team that includes perfusionists, anesthesiologists, ICU nurses, critical care doctors and others,” Dr. Grossi emphasized in an email.

His colleague and co-author Dr. Abe DeAnda observed in an email that “the direct comparison between groups demonstrated that not only did a blood conservation approach do as well as a more liberal approach, but patients may have actually done better.”

Regarding the cultural shift involved in extending blood conservation guidelines to aortic valve replacement surgery, he observed, “In truth, guidelines apply to ALL types of surgeries, but tradition and habits are hard to break.”

SOURCE: http://bit.ly/1kPKVZz

Ann Thorac Surg 2013.