A Randomized Observer-Blinded Controlled Trial to Compare Pre-Emptive with Postoperative Ultrasound-Guided Mandibular Nerve Block for Postoperative Analgesia in Mandibular Fracture Surgeries.

Background and aims: Ultrasound-guided (UG) mandibular nerve block is effective for providing postoperative analgesia in mandibular fracture surgeries. The pre-emptive nerve blockade prolongs the duration of postoperative analgesia and reduces the consumption of intraoperative opioids. The aim of this prospective, randomized, single-blinded study was to compare the efficacy of pre-emptive and postoperative UG mandibular nerve block for postoperative analgesia in mandibular fracture surgeries.

Methods: Sixty patients scheduled for unilateral mandibular fracture surgeries were randomly divided into two groups by computer-generated random numbers and sealed envelope method: Group A received UG mandibular nerve block before surgical incision and group B received after surgery with ropivacaine 0.5% 10mL. The second anesthesiologist, who was blinded to the group involved, monitored the patient. The patients as well as the statistician were also blinded. The patients were started on patient-controlled analgesia (PCA) morphine with bolus 1mg and a lockout interval of 10min. The morphine consumption for 24h was recorded. The pain was assessed by the VAS score. The additional intraoperative fentanyl consumption and time for a request for rescue analgesic were recorded.

Results: The total morphine consumption was reduced in group A (4.566±0.717mg) than group B (5.93±0.876mg) with a p-value of <0.0001. The time for a request for rescue analgesic was also prolonged in group A (794.08±89.561min) than group B (505.333±3.159min). In group A, only four patients required an additional dose of fentanyl as against 11 patients in group B. The heart rate was also lower in group A 30min after the administration of the block and persisted for two hours intraoperatively.

Conclusion: Pre-emptive ultrasound-guided mandibular nerve block reduces morphine consumption, prolongs the time for a request for rescue analgesic, reduces intraoperative fentanyl consumption, provides better control of intraoperative heart rate, and better pain scores postoperatively when compared to the postoperative mandibular nerve block.