The effect of omeprazole on oesophageal pH in dogs during anaesthesia.

Objectives: Intra-operative, gastro-oesophageal reflux may be associated with post-anaesthestic complications such as oesophagitis and oesophageal stricture in dogs. The aim of this study was to investigate the effect of preoperative administration of omeprazole, a proton pump inhibitor, on oesophageal pH in anaesthetised dogs.

Methods: Forty-seven dogs undergoing elective pelvic limb orthopaedic surgery were enrolled into the study. These were randomly allocated to treatment group (n=22) or control group (n=25). The treatment group received one dose of omeprazole (1 mg/kg po) at least 4 h before anaesthesia. All dogs were anaesthetised by the same standardised protocol. A pH probe was inserted into the distal oesophagus after induction of anaesthesia and oesophageal pH was continuously monitored.

Results: In the treatment group, four animals (18 per cent) showed a sudden decrease in oesophageal pH (<4). In the control group the same phenomenon was detected in 13 animals (52 per cent). Gastro-oesophageal reflux occurred more frequently in the control group compared with the omeprazole group (odds ratio 4.7, 95 per cent C.I. 1.1 to 24.7, P=0.032).

Clinical Significance: This study suggests that the preoperative administration of omeprazole is effective in reducing the incidence of gastro-oesophageal reflux during anaesthesia in dogs.