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Greater blood loss during surgery is associated with postoperative delirium

Delirium, one of the most common complications after surgery in older patients, often leads to other complications, poor recovery, longer hospital stays, and higher costs. Greater blood loss during surgery, more postoperative blood transfusions, and postoperative anemia are associated with postoperative delirium in older adults. The route of anesthesia and intraoperative hemodynamic complications—including hypotension and irregular heart rhythms (tachycardia and bradycardia)—are not associated with subsequent development of delirium, according to a study supported in part by the Agency for Health Care Policy and Research (HS06573).

Lee Goldman, M.D., M.P.H., of the University of California, San Francisco, Thomas Lee, M.D., M.Sc., of Partners Community Healthcare in Boston, and their colleagues studied 1,341 patients 50 years of age and older who were admitted for major elective noncardiac surgery at an academic medical center. The researchers used patients' medical charts to determine route of anesthesia; intraoperative hypotension, bradycardia, and tachycardia; blood loss; number of blood transfusions; and lowest postoperative hematocrit (proportion of red blood cells to total blood volume). They diagnosed delirium using daily patient interviews with the Confusion Assessment Method, medical records, and index of nursing intensity.

Delirium developed on or after postoperative day 2 in 9 percent of patients. The route of anesthesia was not relevant, with 7 percent of patients who received either general or spinal anesthesia developing postoperative delirium. Intraoperative hemodynamic complications did not differ in patients who did and did not develop delirium. However, despite blood transfusions, patients with a postoperative hematocrit of less than 30 percent had nearly twice the risk (odds ratio of 1.7) of delirium as those with higher hematocrits. The researchers conclude that a low postoperative hematocrit is likely to cause a central nervous system insult that predisposes the patient to delirium. They suggest that a transfusion strategy to keep hematocrit greater than 30 percent could be one component of a multifactorial intervention to reduce delirium in high-risk patients.

More details are in "The association of intraoperative factors with the development of postoperative delirium," by Edward R. Marcantonio, M.D., S.M., Dr. Goldman, E. John Orav, Ph.D., and others in the November 1998 American Journal of Medicine 105, pp. 380-384.

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