Gastro-oesophageal reflux during anaesthesia in the dog: the effect of preoperative fasting and premedication.

Lower oesophageal pH was monitored in 240 anaesthetised dogs. The incidence of gastro-oesophageal reflux was 16.3 per cent and most of the reflux episodes occurred shortly after the induction of anaesthesia. The refluxate was nearly always acid (pH < 4.0), but in 10.3 per cent of the cases it was alkaline (pH > 7.5); gastric contents of pH below 2.5 were refluxed on 19 occasions (7.9 per cent). Regurgitation occurred in only one dog. Prolonging preoperative fasting was associated with an increased incidence of reflux and increased gastric acidity. Premedication with diazepam was associated with fewer reflux episodes than premedication with atropine and propionylpromazine.