NEW YORK (Reuters Health) – The adverse effects of intraoperative blood transfusions are dose-dependent, and even relatively small amounts may worsen outcomes, according to a report in the January issue of the Archives of Surgery.

“The clear implication is that limiting intraoperative blood loss and blood transfusion may improve outcomes in certain patients,” the authors advise.

Dr. Victor A. Ferraris, with the University of Kentucky, Lexington, and colleagues note that adverse surgical outcomes are often seen in high-risk patients given excessive amounts of blood products.  However, the most common intraoperative blood transfusion is a single donor unit of packed red blood cells (PRBCs), and it is not clear whether such small transfusions are associated with adverse effects.

To look into this question, the team examined outcomes in a national database covering 941,496 operations performed at 173 hospitals.  While 893,205 (94.9%) of the patients did not receive intraoperative transfusions, 15,186 (1.6%) received 1 unit of PRBCs and the remaining 33,105 patients received more than 1 unit.

The crude 30-day mortality rate was 1.1% in the non-transfused group and 6.3% in the group given 1 PRBC unit.  It increased incrementally with all higher numbers of transfused units, up to about 40% with transfusions of 16 or more units, the report indicates.

The unadjusted morbidity rate (a composite of pulmonary, renal, CNS and cardiac complications, sepsis, wound complications, and return to OR) was 11.8% among patients not given intraoperative transfusion compared with 34.6% in those receiving a single unit.

The authors used propensity matching by multiple preoperative risk factors in order to compare 11,855 patients who did not receive intraoperative transfusion to the same number of similar patients given 1 unit of PRBCs.

The propensity-adjusted mortality rate in the two groups was 5.2% versus 6.1% (p=0.005) and the composite morbidity rate was 30.1% vs 34.2% (p<0.001).  Postoperative lengths of stay were 10.3 versus 11.8 days (p<0.001), respectively, Dr. Ferraris and colleagues report.

They conclude, “It is likely that a small, possibly discretionary amount of intraoperative transfusion leads to increased mortality, morbidity, and resource use, suggesting that caution should be used with intraoperative transfusions for mildly hypovolemic or anemic patients.”

In a brief commentary, Dr. John B. Holcomb at the University of Texas Health Science Center, Houston, asks why patients are given 1 or 2 units of PRBCs, and answers: “We simply use (or allow the use of) blood products much too freely in hemodynamically stable patients.  Usually we allow treatment for an isolated laboratory value rather than the entire patient, something we routinely tell our residents and students not to do.”

He concludes, “This approach should stop.”

SOURCE: Arch Surg 2012;147:49-55.