Use of Intraperitoneal Lidocaine in Horses Undergoing Laparotomy for Colic.

Overview

• This study investigated whether directly injecting lidocaine into the abdominal cavity (intraperitoneal administration) could improve pain relief and recovery in horses undergoing surgery for colic.
• The researchers compared outcomes between horses given intraperitoneal lidocaine and those who were not, focusing on pain levels and recovery in the first 24 hours after surgery.

Background

• Lidocaine is commonly used around the time of surgery in horses with abdominal problems (acute abdomen) because it can reduce pain, promote gut movement, reduce inflammation, and counteract toxins.
• Despite these benefits, evidence that lidocaine effectively relieves visceral (internal organ) pain after surgery remains unclear.
• Alternative ways to give lidocaine, such as directly into the peritoneal cavity (the space around abdominal organs), might offer better pain relief, but this had not been thoroughly studied in horses undergoing colic surgery.

Study Design and Methods

• The study was a prospective, randomized, unblinded clinical trial involving 54 horses undergoing laparotomy (surgical opening of the abdomen) to treat colic.
• Horses were divided equally into two groups:
  • Group L received an intraperitoneal injection of lidocaine at the end of surgery at a dose of 2 mg/kg.
  • Group C did not receive this intraperitoneal lidocaine.
• Pain was assessed using a Multifactorial Numerical Rating Composite Pain Scale designed specifically for horses.
• Other factors analyzed as influencing pain or recovery included:
  • Type of colic cause (large versus small intestine problem)
  • Duration of surgery, anesthesia, and recovery
  • Whether the horse received continuous rate infusion (CRI) of lidocaine after surgery
  • American Society of Anesthesiologists (ASA) status indicating general health and severity

Results

• No horses showed toxicity from the lidocaine treatment.
• Factors associated with higher postoperative pain scores included:
  • Postoperative continuous lidocaine infusion (CRI)
  • Higher ASA status (i.e., sicker horses)
  • Longer recovery times
  • Large intestinal disease compared to small intestinal disease
• Although horses receiving intraperitoneal lidocaine (Group L) showed a tendency for quicker pain reduction, the difference was not statistically significant.
• The use of lidocaine CRI postoperatively was linked to more severe clinical cases and did not clearly improve pain management, calling into question its effectiveness in that context.

Conclusions and Implications

• Intraperitoneal administration of lidocaine at the end of colic surgery was safe but did not significantly improve pain outcomes within the first 24 hours after surgery.
• Continuous infusion of lidocaine postoperatively might reflect treatment of more severe cases rather than providing better analgesia.
• Future research is needed to optimize protocols for lidocaine use—focusing on route, dose, timing, and patient selection—to ensure both safety and effectiveness in pain control for horses undergoing abdominal surgery.