Pharmacokinetics and effect of postoperative lidocaine infusions on pain and nausea scores in canine patients undergoing gastrointestinal foreign body surgery

OBJECTIVE: To evaluate the effects of postoperative lidocaine infusions on pain, nausea, hospitalization duration, incidence of vomiting and diarrhea, and opioid requirement in dogs undergoing exploratory laparotomies for foreign body obstructions. METHODS: 24 client-owned dogs with confirmed obstructive gastrointestinal foreign bodies underwent surgery with identical anesthetic protocols, including a 2 mg/kg lidocaine IV bolus followed by a continuous rate infusion of 3 mg/kg/h. After recovery, dogs were randomly assigned to receive either lidocaine (1.8 mg/kg/h) or saline placebo for 24 hours. Pain was assessed using the Glasgow Composite Measure Pain Scale short form (CMPS-SF) and visual analog scale (VAS). Rescue analgesia with hydromorphone was administered when CMPS-SF scores reached 6. Nausea was scored using a nausea VAS. Blood samples were collected for pharmacokinetic analysis. RESULTS: No differences were found in pain scores between the lidocaine and placebo groups (CMPS-SF, P > .160; VAS, P > .292). Both groups maintained pain scores below the rescue analgesia threshold. Nausea scores showed no significant differences (P > .119) but were higher in dogs requiring rescue analgesia (P = .017). No differences were observed in hospitalization time (P = .861), time to defecation (P = 1.0), or vomiting/regurgitation (P = .087). Significantly more dogs in the lidocaine group required rescue analgesia (P = .033). CONCLUSIONS: Postoperative lidocaine infusions did not significantly reduce pain, nausea, hospitalization time, defecation, or vomiting/regurgitation. Pain and nausea scores in both groups were overall low. CLINICAL RELEVANCE: Hydromorphone rescue analgesia increased nausea, suggesting careful monitoring of pain and nausea to prevent hydromorphone overuse.