Cimetidine in elective Caesarean section. Effect on gastric acidity

Area of Science:

• Obstetric Anesthesia
• Gastrointestinal Physiology
• Pharmacology

Background:

• Aspiration pneumonitis (Mendelson's syndrome) remains a significant risk in obstetric anesthesia, contributing to maternal morbidity and mortality.
• Routine alkali administration has limitations in preventing gastric acid aspiration.
• Histamine H2 receptor antagonists are known to reduce gastric secretions in non-obstetric settings.

Purpose of the Study:

• To evaluate the efficacy of intravenous cimetidine in increasing gastric fluid pH before elective Cesarean section.
• To assess the optimal timing for cimetidine administration to ensure adequate gastric acid suppression.

Main Methods:

• Intravenous cimetidine (200 mg) was administered to fasting patients prior to elective Cesarean section.
• Gastric content pH was measured at the time of anesthesia induction.
• Different intervals between cimetidine administration and anesthesia induction were studied (30-40 min, 60-80 min, >90 min).

Main Results:

• In 10 patients receiving cimetidine 60-80 minutes before anesthesia, gastric pH was consistently above 2.5.
• When cimetidine was given 30-40 minutes or >90 minutes prior, only two-thirds of patients achieved a pH above 2.5.
• Eight out of 10 untreated patients had a gastric pH below 2.5.
• No adverse effects were observed in mothers or infants.

Conclusions:

• Intravenous cimetidine administration 60-80 minutes before anesthesia is effective in increasing gastric pH, potentially reducing the risk of aspiration pneumonitis in obstetric patients.
• Optimal timing is critical for cimetidine's efficacy.
• Cimetidine appears to be a safe prophylactic agent for mothers and neonates undergoing Cesarean section.