The Effect of Premedication on the Incidence of Gastroesophageal Reflux in 270 Dogs Undergoing General Anesthesia

SIMPLE SUMMARY: Gastroesophageal reflux (GOR) in anesthetized dogs has been extensively studied throughout the last 40 years. However, the factors affecting the incidence of GOR are still in debate while it is widely accepted that GOR is a multifactorial incidence. The aim of the study is to evaluate the effect of three preanesthetic agents (dexmedetomidine, acepromazine, midazolam), combined with three different opioids (morphine, pethidine, butorphanol), commonly used in small animal anesthesia, on the incidence of reflux in anesthetized dogs. Two hundred and seventy dogs were allocated into nine different groups in accordance to the premedication administered. All dogs underwent non-intrathoracic, non-intrabdominal elective surgeries or invasive diagnostic procedures, while the pH of the esophagus was measured with the use of a pH-meter electrode during the procedure. A detection of esophageal pH below 4 and above 7.5 was consider to be GOR. The study outcome suggested that the addition of opioids in premedication enhanced the incidence of GOR, within the reported values when compared to literature data. No differences were observed among the groups in which the three different opioids were used as far as the incidence of GOR was concerned. Nonetheless, castrations resulted in an increased incidence of GOR when compared to invasive diagnostic procedures. ABSTRACT: The aim of this prospective, non-randomized study was to evaluate the effect of nine different premedication medications on the incidence of gastroesophageal reflux (GOR) in anesthetized dogs. Two hundred and seventy dogs undergoing non-intrathoracic, non-intrabdominal elective surgeries or invasive diagnostic procedures were included in the study, and were allocated into nine groups (30 dogs/group) defined by the type of premedication administered. Premedication consisted of dexmedetomidine with either morphine, pethidine or butorphanol, acepromazine with either one of the three opioids or midazolam with one of the above-mentioned opioids. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. Esophageal pH was measured with the use of a pH-meter electrode and a pH-value less than 4 and over 7.5 was considered to be GOR. The study revealed that 119/270 (44.1%) dogs experienced a reflux episode during anesthesia. The incidence of reflux did not differ among groups (p = 0.117). In group AB the dogs refluxed within 10 min of the beginning of pH-measurements, in comparison with group DB in which dogs refluxed within 30 min (p = 0.029). Invasive diagnostic procedures had a lower incidence of GOR in comparison to castrations (p = 0.09). The outcome of the study suggests that none of the opioids used increased the incidence of GOR in anesthetized dogs.