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Spinal plus anxiolytics may cause oversedation.

CHICAGO -- Spinal anesthesia for elective cesarean section may produce sedation, according to a study that provides the first evidence of spinal anesthesia's sedative effects in obstetrics.

The research suggests that "the usual sedative doses of anxiolytic drugs during spinal anesthesia may lead to an unanticipated oversedation with its undesirable clinical consequences," Dr. John Cowen said at the annual meeting of the Society for Obstetric Anesthesia and Perinatology. The study of 61 patients scheduled for elective C-section with spinal anesthesia (SA) measured sedation at 5-minute intervals using a Bispec-tral Index (BIS) monitor, and the Observer's Assessment of Alertness/Sedation Scale (OAA/S), an instrument that rates aspects of a patient's responsiveness, speech, facial expression, and eye appearance on a 1-5 scale, with 5 being most alert. Measurements were taken until discharge from the postanesthesia care unit.

Women with a history of psychotropic medications, neurologic diseases, or coagulopathy were excluded from the study, as were women who received fewer than 5 hours of sleep the night before surgery or who received intravenous sedation.

Data for both BIS, which scores alertness on a 1-100 scale, with 100 being most alert, and OAA/S were analyzed between the baseline and each interval as well as between each adjacent 5-minute interval.

BIS scores dropped significantly from a baseline average of 97.9 to a low of 85.5 at 25 minutes following SA and declined between each 5-minute interval. The first significant drop in OAA/S scores occurred 15 minutes after baseline, and scores continued to decline through the 40-minute interval.

Significant changes in sedation occurred at four of the 5-minute intervals.

Patients who had lower BIS scores also tended to be rated as more sedated by OAA/S.

The findings may shed some light on why some patients under SA for C-section report feeling sleepy, Dr. Cowen of Henry Ford Hospital, Detroit, said in an interview.

"I've always attributed it to other things," such as the increased relaxation that often accompanies the decrease in pain with SA, he said.

"I was a little surprised at just how frequently sedation occurred," he added, noting that the underlying mechanism for the sedation could be deafferentation of the reticular activating system.

"This is further evidence that even small doses of anxiolytics could have a detrimental effect for the mother," he said. "A normal dose might be too much for these patients."


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Author:Birk, Susan
Publication:OB GYN News
Date:Jun 1, 2008
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