Effect of Low-dose Ketamine on Inflammatory Markers, Perioperative Analgesia, and Chronic Pain in Patients Undergoing Laparoscopic Inguinal Hernia Surgery: A Prospective, Randomized, Double-blind, Comparative Study.

Objective: The neutrophil lymphocyte ratio (NLR) and platelet lymphocyte ratio (PLR) are indicators of postoperative inflammatory response. Low-dose ketamine has analgesic and anti-inflammatory properties. Inguinal hernia surgery is associated with a higher incidence of chronic pain.

Methods: Sixty patients aged 18-60 years; American Society of Anesthesiologists status I and II who were scheduled for laparoscopic inguinal hernia surgery were included. After the induction of general anaesthesia, a ketamine 0.5 mg kg^-1 bolus, followed by a 0.2 mg kg^-1 h^-1 infusion (group K) or saline bolus and infusion (group S) was administered until the end of the surgery. Blood samples were collected at various time intervals. Fentanyl requirement, hemodynamics, verbal analog scale (VAS), emergence delirium, recovery, postoperative nausea and vomiting, and chronic pain were recorded.

Results: Median (interquartile range) NLR was 4.63 times increased at 2 hours postoperatively from the baseline in group S [2.07 (1.72-2.79) to 7.91 (5.74-14.7)] as compared to 2.53 times increase in group K [1.85 (1.4-2.61) to 5.45 (2.89-7.61)] (P=0.02). The increase in median PLR from baseline to 2 hours postoperatively was greater in group S (2.98 times) than in group K (1.94 times) (P=0.02). The NLR and PLR were comparable on POD1 between the groups. Fentanyl requirement was significantly higher in group S compared to Group K both intraoperatively, (P=0.01) and two hours postoperatively (P=0.047). More patients had chronic pain and VAS scores in group S than in group K (13 vs 5, P=0.05).

Conclusion: Low-dose ketamine reduces postoperative inflammatory response, decreases perioperative opioid requirement, and reduces incidence of chronic pain after laparoscopic inguinal hernia surgery with no significant side effects.