Intravenous low-dose ketamine in addition to systemic analgesia versus systemic analgesia alone for post-operative pain management in laparotomies:Adouble-blind randomised controlled study

Abstract

The use of Ketamine, an NMDA receptor antagonist, in sub-anesthetic doses for analgesia is increasingly being administered in inpatient settings with acute pain service guidance and in outpatient settings under a variety of models. At sub-anesthetic doses, ketamine possesses centrally mediated analgesic properties with minimal effects on consciousness and cognition.In this study we have compared the efficacy of IV low-dose Ketamine as an adjunct to conventional systemic analgesia to examine preventive effect on post-operative pain and opioid consumption in patients undergoing laparotomies.The study was carried out on 50 patients, 25 patients received a pre-incisional IV bolus of 0.15 mg/kg of Ketamine,10 mins before the incision followed by IV infusion of 2mcg/kg/min continued for 24 hours postoperatively in addition to systemic analgesia (Group K)and 25 Patients received IV bolus of Normal Saline 10 min before the incision, followed by an IV infusion of normal saline (Group C) till 24 hours post-op and systemic analgesia alone. Saline bolus and infusion were given at equivalent volume/rate of the study group. The analgesic efficacy was judged by NRS (Numeric Pain Rating Scale), Time to first rescue analgesia (TFA) and Total opioid consumption (Tramadol in mg) in 24 hours. Ketamine related side effects were also recorded.Patients in the Ketamine group had significantly lower Mean total opioid consumption (88.04 ± 29.07 mg vs. 210 ± 23.93 mg)and Numerical pain Rating Scale (NRS) (3.13 +0.34 vs. 4.44+ 0.77). Time to first rescue analgesia was significantly delayed in Ketamine group as compared to Control group (20.65 ± 9.2 mins vs. 5.4 ± 5.38 mins). Ramsay Sedation scores (RSS) were significantly higher in the Ketamine group (2.4 +0.76vs. 1.52 +0.51)in the immediate post-operative period. There were no demonstrable side-effects related to Ketamine in Group K.Pre-emptive IV low-dose Ketamine is an effective adjunct to systemic analgesia in abdominal surgeries as it significantly prolongs the time to first rescue analgesia (TFA), reduces mean total analgesic requirement and lowers pain scores (NRS) in the post-operative period with negligible side effects.