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.