Clinical relevance of morphine-induced emesis and esophageal pH value in dogs during anesthesia

Objective To investigate the relevance of morphine-induced emesis and esophageal pH in dogs undergoing non-abdominal surgery.

Animals A total of 47 dogs, 6.1 ± 4.4 years old, and weighing 9.9 ± 8.9 kg. There were 31 dogs in the study group, and 16 dogs in the control group.

Methods The study included dogs presenting to the National Taiwan University Veterinary Hospital for non-abdominal surgery. The premedication of the study group should included morphine (0.5mg/kg, I.M.). The control group had no morphine and other opioid analgesics in their anesthetic plan. The use of morphine was determined by the anesthetist based on patients’ clinical condition. All dogs were induced with propofol and maintained with isoflurane. Dogs with chronic gastrointestinal diseases or being persistently treated with drugs known to affect gastric motility, acid secretion and the tone of gastroesophageal sphincter were excluded. The pH of the vomitus and esophageal pH were measured with the esophageal pH meter and recorded by anesthetists during the anesthesia.

Result In the study group, 19 of 31 dogs experienced vomiting after morphine premedication, and 16 of 31 dogs had gastroesophageal reflux during the anesthesia. 10 of 19 dogs with vomiting and 7 of 12 dogs without vomiting had subsequent gastroesophageal reflux. The administration of morphine and incidence of vomiting have no significant relevance with starting esophageal pH. The incidence of gastroesophageal reflux is significantly increased with the premedication of morphine comparing to the control group.

Conclusion Morphine-induced emesis has no effect on starting esophageal pH suggests the good efficacy of acid clearance of esophagus. Administration of morphine is related to the increased incidence of gastoesophageal reflux. The adverse effect of morphine premedication could be ignored in short term observation.