Comparision between Femoral Nerve Block, Intravenous Fentanyl and Ketamine as Preemptive Analgesics

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Comparision between Femoral Nerve Block, Intravenous Fentanyl and Ketamine as Preemptive Analgesics

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Photo by Rook of Arts on Unsplash

Photo by Rook of Arts on Unsplash

Why is it important?

Background: Spinal & combined spinal epidural anaesthesia are the preferred techniques for facilitation of surgical fixation of the fractures of the lower limb. Extreme pain does not allow ideal positioning for these procedures. Intravenous fentanyl and femoral nerve block are commonly used techniques to reduce the pain during positioning for central neuraxial blockade. Aim: Tocompare the analgesic effect provided by femoral nerve block, IV fentanyl and low dose IV ketamine given prior to positioning for central neuraxial block in patients undergoing surgery for lower limb fractures. Material and methods: This is a prospective, randomized, comparative study conducted at Nizam’s Institute of Medical Sciences from June 2017 to August 2017. 60 patients with lower limb fractures were divided into 3 groups of 20 each - Group A (Femoral Nerve Block with 1% Lignocaine), Group B (IV Fentanyl - 1µg/kg) and Group C (low dose IV Ketamine – 0.1mg/kg). Baseline/pre-intervention VAS score was noted. Pain assessment was done using visual analog scale (0 = no pain, 10 = maximal pain). Depending on the group to which they were included, a particular intervention amongst the three was done for evaluating the analgesic efficacy for positioning for central neuraxial blockade.VAS pain scores were noted again 10 mts after the intervention. The difference in VAS pain score 10 mts after the intervention and baseline was derived at. Significant pain control was identified as the difference of at least 2 points on the VAS score before and after the procedure in an alert and conscious patient. Percentage of patients in each VAS strata (0= no pain, 1-3= mild pain, 4-6= moderate pain, 7-9= severe pain & 10= very severe pain) in comparision to total number of patients in each group (FNB, IV Fent, Low dose IV Ketamine) at different time points (before and 10 minutes after the specified intervention in each group ) was also noted and the percentage change in the specific vas strata of a group at different points of time was also calculated. Total number of patients in each group with VAS  3, 10 minutes after the intervention was noted. Results: Baseline VAS scores in the 3 groups – Group A (FNB group): 7.55±1.47 vs Group B (IV Fentanyl group): 7.25±1.29 vs Group C (Low dose IV Ketamine group): 7.55±1.43, p = 0.737, statistically not significant . The baseline VAS scores were comparable amongst the 3 groups. The VAS score after 10 min in the 3 groups - Femoral nerve block group: 2.5±1.43 vs IV fentanyl group: 3.45±2.06 vs Low dose IV Ketamine group: 2.70±1.98, p= 0.238, statistically not significant. The difference of VAS scores before and after 10 min after the specific intervention amongst the 3 groups - Femoral nerve block group: 5.00±1.75 vs IV Fentanyl group: 3.7±1.66 vs IV Low dose IV Ketamine group: 4.65±1.35 with p = 0.035 which was significant (p 0.05 was considered significant). VAS score difference of before/after was significantly less in Group B, or higher outcome (pre-post difference of VAS score) was observed in Group A, followed by Group C. The number of patients whose VAS score after 10 min came down to 3, corresponding to mild pain in the VAS strata: 11(55%) in FNB group vs 10(50%) in IV Fentanyl group vs 15 (75%) in IV Low dose Ketamine group. The number of patients with VAS score 3, 10 minutes after the intervention were higher in Group C, followed by Group A and Group B. Though the pre/post VAS score difference and the separate mean VAS score at 10 mts was significantly low in the FNB group compared to the other groups, the total no of patients with a VAS score of 3, 10 minutes after the intervention were more in the IV low dose ketamine group. Conclusion: Femoral nerve block with 1% lignocaine appeared to provide better analgesia than IV fentanyl and IV low dose ketamine for positioning for central neuraxial block in patients with lower limb fractures. However, IV low dose ketamine appears to alter the pain scores to clinically comfortable levels for the patient in a quick and non-invasive way.

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