Prophylactic ondansetron does not reduce the incidence of itching induced by intrathecal sufentanil

Postoperative itching after intrathecal (IT) narcotics may be a difficult and important problem for both the anesthesiologist and the patient in the postanesthetic care unit. Since some studies have reported success in preventing itching with ondansetron, we designed a prospective, randomized, double-blinded, and controlled study to test whether prophylactic iv ondansetron effectively reduces the incidence of IT sufentanil-induced pruritus.

Thirty-four patients (ASA I-III, age 18-74 yr) underwent ambulatory surgery after spinal anesthesia with IT lidocaine (15-100 mg) and IT sufentanil (10 microg). The patients were randomized into two groups to receive iv either 4 mL saline (n = 13) or 8 mg ondansetron (n = 21) before the IT injection. The incidence of pruritus and other variables was recorded. Pruritus scores were obtained with a verbal analogue score with 0 meaning none and 10 the worst itching that the patient could imagine. Statistical difference was assumed if P < 0.05.

Ondansetron did not reduce the incidence of pruritus (77 vs 81%) compared to placebo (P = 1.000). The pruritus scores (4.4 vs 3.6) of the two groups were not significantly different (P = 0.670).

There are contradictory findings in the literature regarding the effectiveness of ondansetron in preventing narcotic-induced itching. Although some studies have indicated that ondansetron could prevent this side effect of IT narcotics, a recent report suggested that ondansetron is not effective in preventing narcotic-induced itching (sufentanil-morphine) after a Cesarean section. In the present study we obtained similar, negative results.