The effects of intravenous cimetidine and metoclopramide on gastric pH and volume in outpatients.

STUDY OBJECTIVE

To evaluate and compare the preinduction effects of intravenously (IV) administered cimetidine alone and combined with metoclopramide on gastric contents and postoperative nausea and vomiting in outpatients undergoing elective surgery.

DESIGN

Patients were allocated randomly to 4 groups with 20 patients in each group.

SETTING

Ambulatory surgery at a university-affiliated city hospital.

PATIENTS

Eighty patients undergoing elective gynecologic or orthopedic procedures were studied.

INTERVENTIONS

Outpatients in Group 1 and inpatients in Group 2 served as controls. Outpatients in Group 3 received 300 mg of cimetidine, and outpatients in Group 4 received 300 mg of cimetidine and 10 mg of metoclopramide. All drugs were administered IV as an infusion over a 15-minute period, 30 to 45 minutes prior to induction of anesthesia.

MEASUREMENTS AND MAIN RESULTS

After induction of general anesthesia and endotracheal intubation, stomach contents were retrieved and volume and pH measured. Group 1 outpatients had a large residual gastric volume of 29.2 +/- 15.9 ml, with a very low pH of 2.32 +/- 1.23 and 15% frequency of postoperative vomiting. These patients are at high risk of developing significant pneumonitis in the event of the aspiration of gastric contents. The combination of cimetidine and metoclopramide in Group 4 provided the optimal, or safest, condition--i.e., high gastric pH [6.15 +/- 0.71 (p less than 0.005)] and low gastric volume [11.6 +/- 7.37 ml (p less than 0.001)], with no postoperative vomiting.

CONCLUSIONS

The combination of cimetidine and metoclopramide given to ambulatory patients during the preinductive phase may prevent severe pulmonary consequences should aspiration occur and is more effective in this regard than cimetidine alone.