Low-dose ketamine as an adjuvant for postoperative pain control in postpartum women with low pain threshold: a randomized controlled trial

INTRODUCTION: One in five women experiences high-intensity pain after a cesarean section. OBJECTIVE: Evaluation of the effectiveness of low-dose ketamine in the prevention of high-intensity pain in women with a low pain threshold after cesarean section. MATERIALS AND METHODS: A randomized controlled trial (RCT) was conducted on 90 women who underwent elective cesarean section (CS) under spinal anesthesia. Women were stratified into two categories: normal and low pain threshold. Within each subgroup, the patients were randomized into three groups: intraoperative intravenous administration of ketamine at a dose of 0.25 mg/kg; 0.5 mg/kg, and control group. The time to first request for analgesia and total tramadol dose during the first postoperative day were recorded. The frequency of adverse reactions was analyzed. RESULTS: The median and interquartile range (IQR) for mean pain intensity in the first day, pain on movement, and pain at rest 24 hours after CS were significantly higher in the control group compared to the ketamine groups (p 0.005). Adverse effects (distorted reality and visual impairment) at the minimum dosage of 0.25 mg/kg were observed exclusively in patients with a normal pain threshold. CONCLUSIONS: For patients with an initially low pain threshold, the use of ketamine at a dose of 0.25 mg/kg has the best efficacy and safety profile.