Augmenting Subarachnoid Block Analgesia in Caesarean Section Delivery with Sub-Psychotomimetic Dose of Ketamine

This study investigated the effect of low sub-psychotomimetic dose (0.3 mg/kg) of ketamine on subarachnoid block-induced analgesia with a view to assessing the analgesic effectiveness of combination of low dose ketamine with subarachnoid block in management of post caesarean section pain. Spinal anaesthesia was performed in 120 healthy pregnant women scheduled for elective caesarean delivery using 10 mg hyperbaric bupivacaine. Parturient mothers were randomly selected into four groups (n=30) consisting of K1, K2, NK1 and NK2. K1 received 0.3 mg/kg intravenous ketamine diluted with sterile water for injection to 5 mL, as a bolus dose 2 min before surgical incision; K2 was treated as K1 but at 2 minutes after delivery of baby, while NK1 and NK2 received equivalent volumes of normal saline 2 min before surgical incision and 2 min after baby extraction respectively. Age, weight, duration of surgery (DOS) and the time of first request for analgesia (TFA) for all participants were recorded. Post-operative pain intensity was assessed using a visual analogue scale (VASPI) at 2, 4, 8, 12, 24 and 36 h after spinal anaesthesia induction. Results were analyzed using ANOVA and Kruskal-Wallis tests. Student Newman-Keuls and Man-Whitney rank sum tests were used for post hoc analysis as appropriate. P value<0.05 was considered statistically significant. There was no significant difference in age and weight across groups, but duration of surgery was statistically prolonged in K1 group relative to NK1 group. Low dose ketamine significantly augmented the analgesic effect of spinal block anaesthesia, especially when given at two minutes before surgical incision.