Hendolin and colleagues evaluated the effects of an oral proton pump inhibitor (PPI) and oral ranitidine on gastric fluid volume and pH in 95 patients undergoing elective surgery.

The patients received either a PPI or 300 mg of ranitidine orally at 6.00 am on the morning of surgery. One third of the patients were not given any antacid treatment.

Following induction, a no. 18 nasogastric tube was passed into the stomach and all the gastric fluid was aspirated. Investigators measured the pH and volumes.

Study findings -

• In the both the PPI- and ranitidine-treated patients, the mean pH was > 5.4 after induction, at the end of surgery and 1 h after operation. However, at least one patient in both the groups had pH < 2.5.
• The volumes of gastric aspirates were equally reduced in both the groups.
• Two patients in the PPI group, zero in the ranitidine group and eight in the control group (26%) had pH < 2.5 with volume > 25 ml at induction.

Both ranitidine and the PPI were found to be effective at reducing the volume of intragastric fluid and acidity in patients undergoing elective laparotomy.

Source: Hendolin H, Suojaranta-Ylinen R, Alhava E. Effect of single-dose omeprazole and ranitidine on gastric juice acidity and volume in patients undergoing laparotomy. Acta Anaesthesiol Scand. 1993 Jul;37(5):484-7.