Acid aspiration syndrome at the induction of anesthesia is a serious complication and both pH and volume of the gastric juice which is aspirated affect its severity.

Nishina and colleagues sought to compare the effects of a proton pump inhibitor – rabeprazole, lansoprazole, and ranitidine on gastric fluid properties. They designed a prospective, randomized, double-blinded study and included 180 adult patients undergoing elective surgery.

Patients were segregated into six groups of 30 patients each based on premedication. Patients in each group were given placebo-rabeprazole (PLA-RAB), rabeprazole-placebo (RAB-PLA), rabeprazole-rabeprazole (RAB-RAB), lansoprazole-lansoprazole (LAN-LAN), placebo-ranitidine (PLA-RAN), or placebo-placebo (PLA-PLA) for the first-second medication. The first medication was administered orally at 9:00 PM on the day prior to the surgery and the second dose was given at 5:30 AM on the day of surgery. Each patient underwent overnight fasting.

Gastric fluid was aspirated following tracheal intubation and the volume and pH of the aspirate was assessed.

• The study drugs improved preoperative gastric fluid acidity and volume in the following sequence: PLA-RAN (pH 5.3, volume 0.10 mL/kg), RAB-RAB, LAN-LAN, PLA-RAB, and RAB-PLA (pH 3.8, volume 0.22 mL/kg).
• The proportion of patients who were at risk of acid aspiration syndrome was minimized in PLA-RAN and RAB-RAB groups.

A single morning dose of ranitidine instead of two doses of rabeprazole was found to be the most effective approach for controlling gastric fluid properties and restricting the risk of aspiration pneumonitis to a minimum.

Source: Nishina K, Mikawa K, Takao Y, et al. A comparison of rabeprazole, lansoprazole, and ranitidine for improving preoperative gastric fluid property in adults undergoing elective surgery. Anesth Analg. 2000 Mar;90(3):717-21.