Effect of the reverse Trendelenburg position on the incidence of gastroesophageal reflux in dogs anesthetized for elective stifle surgery

Objective: To determine if a 15° reverse Trendelenburg position decreases the incidence of gastroesophageal reflux (GER) compared with a horizontal position in dogs anesthetized for stifle surgery. Study design: Prospective, randomized parallel-arm study. Animals: A total of 44 healthy client-owned dogs were enrolled and data from 36 dogs were analyzed. Methods: Dogs requiring preoperative radiographs under anesthesia, or with a history of gastrointestinal signs or administered gastroprotectant therapy within 1 month of surgery were excluded. Anesthesia protocol was standardized to include hydromorphone, dexmedetomidine, ketamine, propofol and isoflurane. Dogs were randomly assigned at enrollment to be positioned in a 15° reverse Trendelenburg or a horizontal position for surgery. Continuous pH monitoring was documented throughout the procedure with a 6.4 Fr (2.13 mm) esophageal pH probe positioned in the distal esophagus via the oral cavity. GER was defined as pH < 4.0 (acidic) or > 7.5 (alkaline) for more than 30 seconds. The proportions of dogs developing GER were compared between groups using Fisher's exact test. Time to reflux was compared using survival curves and the Gehan–Breslow–Wilcoxon test. Statistical significance was set as p < 0.05. Results: An episode of GER occurred in 11/36 (30%) dogs. Reflux was alkaline in two dogs and acidic in nine dogs. The proportion of dogs with GER was 5/18 (28%) and 6/18 (33%) for dogs in the reverse Trendelenburg position and horizontal position, respectively, and was not statistically significant (p > 0.99). Median (range) time until reflux was 44 (23–135) and 44.5 (9–56) minutes when dogs were positioned in reverse Trendelenburg position and horizontal position, respectively (p = 0.66; two-tailed Mann–Whitney U test). Conclusions and clinical relevance: Positioning the surgery table in a 15° rostral elevation for dogs anesthetized for elective stifle surgical procedures did not decrease the incidence of GER.