Should we inhibit gastric acid secretion before cardiac surgery?

Area of Science:

• Anesthesiology
• Gastroenterology
• Pharmacology

Background:

• Major stress from cardiac surgery and cardiopulmonary bypass can decrease intragastric pH, potentially leading to gastric mucosal erosion.
• Understanding the impact of anesthetic agents and adjunct medications on gastric physiology is crucial for patient safety.

Purpose of the Study:

• To evaluate the effects of ranitidine (H2-receptor antagonist) and pirenzepine (M1-muscarinic antagonist) on intragastric pH during elective cardiac surgery.
• To assess the impact of these medications on gastric bacterial counts and postoperative complications.

Main Methods:

• A randomized study involving 60 patients undergoing elective cardiac surgery under fentanyl-diazepam-nitrous oxide anesthesia.
• Intragastric pH was continuously monitored using a digital pH-meter.
• Patients received either diazepam alone, diazepam plus ranitidine, or diazepam plus pirenzepine preoperatively.

Main Results:

• Intragastric pH at induction was significantly higher with ranitidine compared to diazepam alone (P < 0.01). Pirenzepine showed no significant difference compared to diazepam alone.
• Intragastric pH remained stable throughout the surgery in all groups.
• Gastric juice was sterile in 92% of the diazepam-only group, versus 25% with ranitidine and 71% with pirenzepine (P < 0.01).
• A trend towards increased nosocomial pneumonias was observed in the ranitidine and pirenzepine groups (15%) compared to the diazepam-only group (0%) (P = 0.06).

Conclusions:

• Preoperative diazepam alone results in a relatively high intraoperative intragastric pH.
• Adding ranitidine or pirenzepine preoperatively is not necessary and may be associated with potential hazards, including increased risk of nosocomial pneumonia.
• Further research is needed to fully elucidate the risks and benefits of these medications in the context of cardiac surgery.