Efficacy of pre-incisional subcutaneous infiltration of low-dose ketamine on postoperative pain after cesarean section

Objective: To evaluate the efficacy of pre-incisional subcutaneous infiltration of low-dose ketamine at the site of incision on the postoperative pain management after cesarean section (C.S).
Methodology: In a randomized, double-blind, and placebo-controlled clinical trial, 70 healthy parturients were scheduled for cesarean section under spinal anesthesia. Three minutes before surgical incision, patients received either 30 mg ketamine (study group; n=35) or 0.9% saline (placebo group, n=35) as subcutaneous at the site of incision. The volume of solution was 6 ml. In the placebo group 30 mg ketamine was intramuscularly injected to the control for any related systemic ketamine side effects. Hemodynamic parameters were recorded at regular intervals during operation. The patients were followed up for 24 hours to determine postoperative analgesia and side effects.
Results: Incidence of pain-free status (pain score=0) was significantly lower in the study parturients at the post-anesthesia care unit (91.44% vs 0%; p < 0.0001) and at three hours after surgery (42.85% vs 25.71%; p < 0.001). The time to first request to analgesic were significantly longer in the study patients (4.16�2.86 hr v.s 0.17�0.51 hr; p < 0.0001). Cumulative analgesic (tramadol) consumption during 24h after surgery was significantly lower in the study group (62.00�12.50 mg vs. 31.14�9.82 mg; p < 0.0001). Nausea-vomiting was recorded in the six (17.14%) patients of placebo group (p = 0.002).
Conclusion: Low-dose ketamine decreased locally postoperative pain scores with a significant decrease of analgesics consumption when it was infiltrated local subcutaneously before surgical incision in patients undergoing cesarean section. This method was associated with no systemic or local side effects.