Granisetron Reduces Norepinephrine Requirement for Preventing Post‑Induction Hypotension in Elderly Patients Undergoing Laparoscopic Gastrointestinal Surgery.

BACKGROUND

Prophylactic antiemetics are routinely used in gastrointestinal surgery. This study investigated whether granisetron pretreatment alters norepinephrine requirements for preventing post-induction hypotension in elderly patients.

METHODS

In this randomized double-blind trial, 64 patients (60-74 years) undergoing laparoscopic gastrointestinal resection received intravenous granisetron (3 mg) or saline placebo before induction. The 50% effective dose (ED50) of norepinephrine to prevent hypotension (>20% decrease in mean arterial pressure) within 30 min post-induction was determined using the up-down sequential method, with probit regression as confirmatory analysis.

RESULTS

Baseline characteristics were comparable between the two groups. The up-down sequential analysis revealed that the ED50 of norepinephrine was significantly lower in the granisetron group (0.037 μg/kg/min [95% CI 0.031-0.040 μg/kg/min]) than in the control group (0.049 μg/kg/min [95% CI 0.043-0.052 μg/kg/min]) (P < 0.001) representing an approximate 24% reduction. This finding was supported by probit regression analysis, which estimated ED50 values of 0.040 μg/kg/min [95% CI 0.033-0.051 μg/kg/min] and 0.052 μg/kg/min [95% CI 0.045-0.064 μg/kg/min] for the granisetron and control groups, respectively. No significant difference was observed in the incidence of postoperative nausea and vomiting between the two groups.

CONCLUSION

Granisetron pretreatment significantly reduces the ED50 of norepinephrine required to prevent post-induction hypotension in elderly patients by approximately 24% indicating a pharmacodynamic interaction consistent with enhanced vasopressor efficacy. These findings indicate that pre-induction antiemetic administration may represent a potentially favorable timing strategy.