Low Dose Ketamine Infusion Versus Thoracic Epidural Infusion for Post Thoracotomy Analgesia

Ketamine, a phencyclidine derivative has got a unique set of actions among anaesthetic drugs causing dissociative anaesthesia. It has been mainly used for induction of anaesthesia and intraoperative analgesia. Recently, there has been a resurge in ketamine owing to its efficacy as an infusion for perioperative and postoperative analgesia. The aim of this study was to compare intravenous infusion of ketamine with thoracic epidural bupivacaine-fentanyl infusion in managing postoperative analgesia in patients undergoing thoracotomy.

Methods: 62 patients posted for elective thoracotomy for decortication were randomised into two groups. Patients in group K (n=32) received 0.5 mg/kg bolus followed by an infusion of 2 mcg/kg/min infusion of ketamine and patients in group E (n=30) received thoracic epidural bupivacaine fentanyl infusion for 48 hrs post-surgery. Numerical rating scale (NRS) pain scores were noted at rest and on cough every 4 hrs till 48 hrs post-surgery. Ramsay sedation scores, incidence of side effects, and dose of rescue analgesics were also noted.

Result: NRS scores were significantly lower in Group K compared to group E, both at rest and on cough (p=0.002 and p=0.001). There was no difference in the levels of sedations or the need for rescue analgesic of paracetamol (p=0.356) though there was a difference between need for second rescue analgesic of tramadol (p=0.034) in group E.

Conclusion: Low dose ketamine infusion provides better postoperative analgesia post thoracotomy compared to thoracic epidural infusion.