Nishikawa T, Dohi S
Department of Anesthesiology, University of Tsukuba, Ibaraki, Japan.
Anesthesiology. 1991 Aug;75(2):217-22. doi: 10.1097/00000542-199108000-00008.
Clonidine, recently introduced into anesthesia practice, may cause bradycardia. Whether this bradycardia is reversible with atropine is not known. Accordingly, we studied heart rate (HR) responses to intravenous atropine in 80 patients assigned randomly to either a control group, who received no medication (n = 20), or a clonidine group, who received oral clonidine of approximately 1.2 micrograms.kg-1 (n = 20), 2.5 micrograms.kg-1 (n = 20), or 5 micrograms.kg-1 (n = 20). All patients received incremental doses of atropine, 2.5, 2.5, and 5 micrograms.kg-1, at 2-min intervals (total dose 10 micrograms.kg-1). Positive chronotropic response to the cumulative atropine dose of 10 micrograms.kg-1 was attenuated significantly only in patients given clonidine 5 micrograms.kg-1 (7 +/- 1 beats per min, mean +/- standard error) when compared with those given smaller doses of clonidine (15 +/- 2, 16 +/- 2 beats per min) or no clonidine (19 +/- 2 beats per min) (P less than 0.05). To determine whether HR hyporesponsiveness to atropine induced by clonidine can be overcome by a larger dose of atropine, the authors studied 30 additional patients given clonidine 5 micrograms.kg-1 or no medication. In all patients not receiving clonidine (n = 15), HR increased by more than 20 beats per min when atropine of 15 micrograms.kg-1 was administered, whereas in only 5 patients (33%) receiving clonidine did the HR increase by 20 beats per min after atropine 15 micrograms.kg-1 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
可乐定最近被引入麻醉实践中，可能会导致心动过缓。目前尚不清楚这种心动过缓能否被阿托品逆转。因此，我们对80例患者进行了研究，这些患者被随机分为对照组（未接受任何药物治疗，n = 20）和可乐定组（接受约1.2微克·千克⁻¹口服可乐定，n = 20；2.5微克·千克⁻¹，n = 20；或5微克·千克⁻¹，n = 20），观察他们静脉注射阿托品后的心率（HR）反应。所有患者每隔2分钟接受递增剂量的阿托品，分别为2.5、2.5和5微克·千克⁻¹（总剂量10微克·千克⁻¹）。与接受较小剂量可乐定（每分钟15±2次、16±2次心跳）或未接受可乐定（每分钟19±2次心跳）的患者相比，仅接受5微克·千克⁻¹可乐定的患者对累积剂量为10微克·千克⁻¹阿托品的正性变时反应明显减弱（每分钟7±1次心跳）（P<0.05）。为了确定可乐定引起的对阿托品的HR低反应性是否能被更大剂量的阿托品克服，作者又对另外30例接受5微克·千克⁻¹可乐定或未接受任何药物治疗的患者进行了研究。在所有未接受可乐定的患者（n = 15）中，给予15微克·千克⁻¹阿托品后HR增加超过每分钟20次心跳，而在接受可乐定的患者中，只有5例（33%）在给予阿托品15微克·千克⁻¹后HR增加每分钟20次心跳（P<0.001）。（摘要截选至250字）
