Abstract
Serotonin 3 receptor antagonists, a commonly used drug for preventing postoperative nausea and vomiting, have recently been reported to decrease the incidence of hypotension and the need for vasoactive drugs after spinal anaesthesia in obstetric surgery. However, it remains unknown whether they could also prevent hypotension after induction of general anaesthesia. In the current study, we aimed to investigate the effect of intravenous granisetron on prophylactic ephedrine for preventing hypotension after general anaesthesia induction in elderly patients. Sixty elderly patients were randomly assigned to receive granisetron or saline control 30 min before induction of general anaesthesia. The first patient in each group received a prophylactic dose of ephedrine (0.15 mg kg(-1)) to prevent hypotension. The prophylactic dose for each patient was increased or decreased by 0.05 mg/kg based on the efficacy results of the previous patient. The up-down sequential allocation analysis and probit regression was used to calculate the effective dose for 50% of patients (ED50) with prophylactic ephedrine. In the up-down sequential allocation analysis, the ED50 of ephedrine was significantly lower in group granisetron (0.08 mg kg(-1) [95% CI, 0.06-0.11 mg kg(-1)]) when compared with group control (0.14 mg kg(-1) [95% CI, 0.13-0.16 mg kg(-1)]) (P < 0.001). The conclusion was further supported by probit regression analysis (0.09 mg kg(-1) [95% CI, 0.05-0.12 mg kg(-1)] in group granisetron and 0.14 mg kg(-1) [95% CI, 0.12-0.16 mg kg(-1)] in group control). Intravenous granisetron reduced the requirement of prophylactic ephedrine in preventing hypotension after general anaesthesia induction in elderly patients.