Hogue Charles W, Talke Pekka, Stein Phyllis K, Richardson Charles, Domitrovich Peter P, Sessler Daniel I
Department of Anesthesiology and Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Anesthesiology. 2002 Sep;97(3):592-8. doi: 10.1097/00000542-200209000-00012.
The purpose of this study was to determine the effects of dexmedetomidine on systemic and cardiac autonomic reflex responses during rest and during thermal stress.
Volunteers received either placebo or low- or high-dose dexmedetomidine (target plasma concentrations 0.3 or 0.6 ng/ml, respectively) infusions in a prospectively randomized, double-blinded crossover study design. After 1 h, baroreflex sensitivity was assessed, and then core body temperature was raised to the sweating threshold and then lowered to the shivering threshold. Plasma catecholamines and blood pressure were measured, and cardiac autonomic responses were assessed by analysis of heart rate variability.
Compared with placebo, plasma norepinephrine concentrations, blood pressure, heart rate, and some heart rate variability measures were lower after 1-h infusion of dexmedetomidine, but baroreflex responses did not differ significantly. Dexmedetomidine blunted the systemic and cardiac sympathetic effects of sweating observed during placebo infusion but had no effect on parasympathetic measures. Increases in blood pressure, and systemic catecholamines due to shivering were observed during placebo and dexmedetomidine, but these responses were less with dexmedetomidine. During shivering, dexmedetomidine infusion was associated with higher low-frequency and high-frequency heart rate variability power but lower heart rate compared with the sweating threshold and with the control period, suggesting nonreciprocal cardiac autonomic responses.
Infusion of dexmedetomidine results in compensated reductions in systemic sympathetic tone without changes in baroreflex sensitivity. Dexmedetomidine blunts heart rate and the systemic sympathetic activation due to sweating, but it is less effective in blunting cardiac sympathetic responses to shivering. During dexmedetomidine infusion, cardiac sympathetic and parasympathetic tone may have nonreciprocal changes during shivering.
本研究旨在确定右美托咪定对静息状态及热应激期间全身和心脏自主反射反应的影响。
在一项前瞻性随机、双盲交叉研究设计中，志愿者接受安慰剂或低剂量或高剂量右美托咪定（目标血浆浓度分别为0.3或0.6 ng/ml）输注。1小时后，评估压力反射敏感性，然后将核心体温升至出汗阈值，再降至寒战阈值。测量血浆儿茶酚胺和血压，并通过心率变异性分析评估心脏自主反应。
与安慰剂相比，输注右美托咪定1小时后，血浆去甲肾上腺素浓度、血压、心率及一些心率变异性指标较低，但压力反射反应无显著差异。右美托咪定减弱了安慰剂输注期间观察到的出汗的全身和心脏交感神经效应，但对副交感神经指标无影响。在安慰剂和右美托咪定输注期间均观察到因寒战导致的血压和全身儿茶酚胺增加，但右美托咪定组这些反应较小。在寒战期间，与出汗阈值及对照期相比，输注右美托咪定与更高的低频和高频心率变异性功率相关，但心率较低，提示心脏自主反应非相互性。
输注右美托咪定导致全身交感神经张力代偿性降低，而压力反射敏感性无变化。右美托咪定减弱因出汗引起的心率和全身交感神经激活，但对减弱心脏对寒战的交感神经反应效果较差。在输注右美托咪定期间，寒战期间心脏交感神经和副交感神经张力可能有非相互性变化。
