Effectiveness of Low Dose Dexmedetomidine for an Oligaemic Field in Middle Ear Surgery: A Randomised Control Trial

Introduction: Microscopic middle ear surgeries are best done under hypotensive anaesthesia to provide an oligaemic field. Dexmedetomidine is an a2 agonist which produces hypotension by sympathetic response blockade. Aim: To study the effectiveness of low dose dexmedetomidine in providing an oligaemic field. The additional requirement of inhalational agent required to maintain the oligaemic field in the control group, intubation response and postoperative analgesia were also assessed. Materials and Methods: The randomised, placebo-controlled double-blind study was conducted by recruiting 48 patients in the study, who were divided into two groups i.e, study group (n=24) and placebo group (n=24). The study group received low dose dexmedetomidine infusion (0.5 pg/kg loading dose followed by 0.2 pg/kg/hr) and placebo group received weight -adjusted saline. The quality of the surgical field was assessed on a score of 0-5. The Minimum Alveolar Concentration (MAC) of inhalational agent needed, postoperative sedation score and pain score were noted. All the data were recorded in Statistical Package for Social Sciences (SPSS) software, version 22.0. Results: The mean score of quality of the surgical field in the study group was 2.00 +/- 0.59, compared to 3.50 +/- 0.88 in the placebo group. The mean MAC of isoflurane was 1.32 +/- 0.31 in the placebo group and 0.85 +/- 0.23 in the study group (p-value=0.03). The study group had a Ramsay sedation score of 3.08 +/- 0.65 compared to 2.29 +/- 0.75 in the placebo group at 5 minutes after extubation (p-value < 0.001). The mean pain score in the dexmedetomidine group in 10 minutes postoperative period was 1.83 +/- 2.25, while in placebo group it was 3.25 +/- 1.96 (p-value=0.025). However, over the next 20-60 minutes postoperative period the pain score between the two groups were comparable, with no significant difference in analgesia, postoperative shivering and other side-effects. Conclusion: A low dose dexmedetomidine can effectively provide a bloodless field for middle ear microsurgical procedures.