Han Young-Soo, Tveita Torkjel, Kondratiev Timofei V, Prakash Y S, Sieck Gary C
Department of Physiology & Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Cryobiology. 2008 Dec;57(3):246-50. doi: 10.1016/j.cryobiol.2008.09.006. Epub 2008 Sep 19.
The purpose of this study was to determine cardiovascular beta-adrenergic responses during hypothermia. In the present study, we used isoproterenol (Iso), a nonselective, potent beta-adrenoceptor agonist, well known for its positive chronotropic and inotropic pharmacologic actions at normothermia. Rats were instrumented to measure mean arterial pressure (MAP) and left ventricular (LV) pressure-volume changes using a Millar pressure-volume conductance catheter. Core temperature was manipulated from 37 (normothermia) to 24 degrees C (hypothermia) and back to 37 degrees C (rewarming) using both internal and external heat exchangers. During cooling at each temperature (33, 30, 27, and 24 degrees C), central hemodynamic variables and MAP were measured while intravenously infusing Iso (doses of 1.7, 5, 10, and 20 ng/min). Seven animals underwent all phases of the protocol. At normothermia Iso infusion resulted in a significant, dose-dependent increase in heart rate (HR), stroke volume (SV), cardiac output (CO), LV dP/dt(max) (left ventricular maximum derivative of systolic pressure over time) but no change in MAP. During cooling Iso infusion caused no dose-dependent change in any of the hemodynamic variables. After rewarming, baseline HR and LV dP/dt(max) were increased, whereas SV was significantly reduced when compared with their pre-hypothermic baseline values. This study shows that physiological cardiovascular responses mediated by the beta-adrenoceptor are significantly diminished during core hypothermia.
本研究的目的是确定低温期间心血管β-肾上腺素能反应。在本研究中，我们使用了异丙肾上腺素（Iso），一种非选择性、强效β-肾上腺素能受体激动剂，在常温下因其正性变时和变力药理作用而闻名。使用Millar压力-容积传导导管对大鼠进行仪器安装，以测量平均动脉压（MAP）和左心室（LV）压力-容积变化。使用内部和外部热交换器将核心温度从37℃（常温）调节至24℃（低温），然后再回到37℃（复温）。在每个温度（33℃、30℃、27℃和24℃）冷却期间，静脉输注Iso（剂量为1.7、5、10和20 ng/min）时测量中心血流动力学变量和MAP。七只动物接受了该方案的所有阶段。在常温下输注Iso导致心率（HR）、每搏输出量（SV）、心输出量（CO）、LV dP/dt（max）（左心室收缩压随时间的最大变化率）显著且剂量依赖性增加，但MAP无变化。在冷却期间，输注Iso未引起任何血流动力学变量的剂量依赖性变化。复温后，与低温前基线值相比，基线HR和LV dP/dt（max）升高，而SV显著降低。本研究表明，在核心体温过低期间，由β-肾上腺素能受体介导的生理性心血管反应显著减弱。
