Effects of dexmedetomidine during combined intravenous-inhalational anesthesia on motor evoked potentials monitoring and postoperative agitation in elderly patients undergoing cervical spine sur-gery / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of different doses of dexmedetomidine during com-bined intravenous-inhalational anesthesia on motor evoked potentials ( MEPs) monitoring and postoperative agitation in elderly patients undergoing cervical spine surgery. Methods Sixty patients of both sexes, aged 65-81 yr, weighing 51-78 kg, of American Society of Anesthesiologists physical statusⅠorⅡ, undergo-ing elective cervical spine surgery under general anesthesia, were divided into 3 groups ( n=20 each) using a random number table method: control group ( group C) , low-dose dexmedetomidine group ( group D1 ) and high-dose dexmedetomidine group ( group D2 ) . Anesthesia was induced by intravenous injection of mid-azolam 0. 04 mg∕kg, cisatracurium 0. 15 mg∕kg, propofol 2 mg∕kg and sufentanil 0. 3-0. 4 μg∕kg. MEPs was assessed with nerve electrophysiology monitor after induction of anesthesia. Anesthesia was maintained by inhalation of sevoflurane ( end-tidal concentration 1％) and target-controlled infusion of propofol ( target plasma concentration 2-3 μg∕ml). Narcotrend index was maintained at D2-E1. When T4∕T1>75％ (at T0 ) , dexmedetomidine was intravenously infused over 10 min in a loading dose of 0. 6μg∕kg, followed by an infusion of 0. 3μg·kg-1 ·h-1 until the end of surgery in group D1 . Dexmedetomidine was intravenously infused over 10 min in a loading dose of 1 μg∕kg, followed by an infusion of 0. 3 μg·kg-1 ·h-1 until the end of surgery in group D2 . The equal volume of normal saline was given intravenously in group C. At T0 , immediately after the end of administration of dexmedetomidine loading dose ( T1 ) and at 60 min of dexme-detomidine infusion ( T2 ) , the effective elicitation of MEPs and amplitude and latency of MEPs were recor-ded. The intraoperative cardiovascular events and occurrence of postoperative agitation in postanesthesia care unit were recorded. Results Compared with group C, no significant change was found in the latency, amplitude and effective elicitation rate of MEPs at each time point in group D1 ( P>0. 05) , the amplitude of MEPs was significanty decreased, the latency of MEPs was prolonged, and the elicitation rate of MEPs was decreased at T2 in group D2 , and the incidence of bradycardia during operation was significanty in-creased, and the incidence of postoperative agitation was decreased in D1 and D2 groups ( P<0. 05) . Com-pared with group D1 , the amplitude of MEPs was significantly decreased, the latency of MEPs was pro-longed, and the effective elicitation rate of MEPs was decreased at T2 ( P<0. 05), and no significant change was found in the incidence of intraoperative bradycardia and postoperative agitation in group D2 ( P>0. 05) . Conclusion Dexmedetomidine infused over 10 min in a loading dose of 0. 6 μg∕kg, followed by an intravenous infusion of 0. 3 μg·kg-1 ·h-1 until the end of surgery during combined intravenous-inhala-tional anesthesia exerts no effect on MEPs monitoring, and can decrease the incidence of postoperative agita-tion at the same time in elderly patients undergoing cervical spine surgery.