Use of Intraperitoneal Lidocaine in Horses Undergoing Laparotomy for Colic

Perioperative lidocaine is widely used in horses with acute abdomen for its analgesic, prokinetic, anti-inflammatory, and anti-endotoxic effects, although evidence of its visceral analgesic efficacy remains inconclusive. Given the potential of alternative routes of administration for local anaesthetics, this prospective, randomised, unblinded clinical trial evaluated whether intraperitoneal (IP) lidocaine improves early postoperative recovery, including recovery from anaesthesia and the first 24 h after laparotomy for colic. A Multifactorial Numerical Rating Composite Pain Scale for equines was used for pain assessment. Covariates including aetiology, times of surgery, anaesthesia and recovery, and eventual postoperative constant rate infusion (CRI) of lidocaine were further analysed. Fifty-four horses were enrolled and equally distributed between two groups differing from the IP administration of 2 mg/kg lidocaine (group L) or not (group C) at the end of laparotomy. Postoperative lidocaine CRI (p = 0.007), higher ASA status (p = 0.005), longer recovery time (p = 0.0012), and large intestinal disease compared with small intestinal disease (p = 0.006) were significantly associated with higher pain scores, particularly within the first 24 h. No horse showed signs of toxicity. Although group L demonstrated a trend toward faster pain reduction, IP lidocaine did not significantly improve early postoperative pain outcomes. Postoperative 'lidocaine CRI' was associated with more severe cases, questioning its analgesic efficacy. Further research is warranted to optimise safe and effective protocols.