Preoperative cimetidine--effects on gastric fluid

Area of Science:

• Anesthesiology
• Gastroenterology
• Pharmacology

Background:

• Maintaining optimal gastric pH during anesthesia is crucial for preventing aspiration pneumonitis.
• Cimetidine is a histamine H2-receptor antagonist with known effects on gastric acid secretion.

Purpose of the Study:

• To evaluate the effect of cimetidine on gastric fluid pH and volume during anesthesia.
• To assess the potential of cimetidine in reducing gastric acidity in patients undergoing anesthesia.

Main Methods:

• A double-blind, placebo-controlled study involving 44 patients.
• Patients received either cimetidine or a placebo during anesthesia.
• Gastric fluid pH and volume were measured at timed intervals post-intubation.

Main Results:

• Cimetidine significantly increased gastric fluid pH compared to placebo at all measured time points (0, 15, 30, 45 minutes).
• Mean gastric pH at induction was 4.5 with cimetidine versus 2.0 with placebo.
• Approximately 70% of patients on cimetidine achieved a gastric pH above 2.5, compared to 20% on placebo.
• No significant difference in gastric aspirate volume was observed between the groups.

Conclusions:

• Cimetidine effectively elevates gastric fluid pH during anesthesia, suggesting a potential prophylactic role against acid aspiration.
• While gastric volume was not significantly reduced, the marked increase in pH is a key finding for anesthetic safety.
• Further investigation may be warranted to understand the reasons for pH < 2.5 in a subset of cimetidine-treated patients.