A randomized controlled trial to evaluate the efficacy of inferior alveolar nerve block as an adjunct to general anaesthesia in mandibulectomy: a pilot study

Background: Mandibulectomy is considered as the initial definitive treatment for oral cancer. Inferior alveolar nerve block (IANB) is the commonly used nerve block procedure for mandibular anaesthesia. Hence, we evaluate the efficacy of IANB for intraoperative analgesia to block consumption of opioids and propofol in intraoperative period and to note hemodynamic stability by monitoring pulse rate, systolic, diastolic, and mean arterial pressure (MAP) during the intraoperative period. Methods: This randomized pilot study comprised of 25 patients with American Society of Anaesthesiologists (ASA) grade 1 or 2 were scheduled for mandibulectomy. The study was conducted at a tertiary care centre in south India between November 2017 and December 2018. The patients were then randomly assigned using computer-generated random number tables into two groups: A and B. Group A received only general anaesthesia and group B received general anaesthesia with IANB. The group allocation was done using concealed envelopes by the principal investigator and hemodynamic variables were noted by an independent observer who was not part of group allocation or administration of block. The group allocation was revealed to the surgical team only on the day of surgery. The primary outcome measured was consumption of fentanyl and propofol boluses in intraoperative period. The hemodynamic variability was also measured. Secondary outcomes were vascular and neurological complications if any. Statistical significance was accepted as P<0.05. Results: A total of 13 patients were randomized to Group A and 12 to Group B. Mean fentanyl consumption [Group A: n=8 (66.67%), µ=67.5±24.35 mcg/kg vs. Group B: n=6 (60%), µ=41.67±14.72 mcg/kg, P>0.99] and bolus propofol required (Group A n=5, 24±20.74 mg/kg vs. Group B n=3, 23.33±5.77 mg/kg, P=0.69) were not significantly different in both the groups. The mean time of onset of action was observed at 8.35±4.5 minutes after nerve block, where all twelve patients in Group B reported numbness of teeth and nine of them reported numbness in the tongue and two of them also were positive for aspiration test. The mean pulse rate, systolic and diastolic blood pressures were also comparable between both the groups, however, the mean MAP was significantly less in Group B than Group A during dental extraction and at 30 minutes during intraoperative period (P=0.009). Conclusions: Based on primary outcome, the efficacy of IANB with general anaesthesia was comparable to that of general anaesthesia alone. Consumption of opioids and propofol in intraoperative period and hemodynamic stability during the intraoperative period was not significantly altered after administration of IANB. Trial Registration: The study was prospectively registered with the clinical trial registry of India CTRI/2017/09/009837 (19/09/2017). The status of the trial is now closed.