Randomized controlled trial of vagal modulation by sham feeding in elective non-gastrointestinal (orthopaedic) surgery.

BACKGROUND Enhanced recovery, in part, aims to reduce postoperative gastrointestinal dysfunction (PGID). Acquired - or established- vagal dysfunction may contribute to PGID, even for surgery not involving the gastrointestinal tract. However, direct evidence for this is lacking. We hypothesized that chewing gum reduces morbidity (including PGID) by preserving efferent vagal neural activity postoperatively after elective orthopaedic surgery. METHODS In a two-centre randomized controlled trial (n=106), we explored whether patients randomized to prescribed chewing gum for five days postoperatively sustained less morbidity (primary outcome, defined by the Postoperative Morbidity Survey), PGID and faster time to become morbidity free (secondary outcomes). In a subset of patients (n=38), cardiac parasympathetic activity was measured by serial Holter monitoring and assessed using time and frequency domain analyses. RESULTS Between September 2011 and April 2014, 106 patients were randomized to chewing gum or control. The primary clinical outcome did not differ between groups, with similar morbidity occurring between patients randomized to control (26/30) and chewing gum (21/28; absolute risk reduction (ARR):13% (95%C I:- 6-32); P=0.26). However, chewing gum reduced PGID (ARR:20% (95% CI: 1-38); P=0.049). Chewing gum reduced time to become morbidity-free (relative risk (RR): 1.62 (95% CI: 1.02-2.58); P=0.04) and was associated with a higher proportion of parasympathetic activity contributing to heart rate variability (11% (95% CI: 1-20); P=0.03). CONCLUSIONS Chewing gum did not alter overall morbidity, but reduced PGID. These data show for the first time that prescription of sham feeding preserves vagal activity in surgery not directly involving the gastrointestinal tract. CLINICAL TRIAL REGISTRATION ISRCTN20301599.