Nishikawa T, Namiki A
Department of Anesthesiology, Sapporo Medical College and Hospital, Japan.
Anesthesiology. 1988 Feb;68(2):221-5. doi: 10.1097/00000542-198802000-00008.
The authors investigated the mechanism for slowing of heart rate (HR) and associated changes in the pulmonary hemodynamics caused by cold injectate during thermodilution method. To clarify whether the slowing of HR after cold injectate is due to the cooling of the sinoatrial (SA) node or a reflex mediated by the autonomic nerves, we directly measured the myocardial temperature of the SA node region by a thermistor probe, and evaluated the HR responses to iced injectate after autonomic blockade in anesthetized dogs. Additionally, pulmonary blood flow (PBF) was continuously measured by an electromagnetic flowmeter during the delivery of injectate. The direction and magnitude of changes in HR after injectate were significantly dependent upon the injectate temperature (P less than 0.01). Thereby, the changes in HR correlated well with those in myocardial temperature of the SA node region (r = 0.987, P less than 0.01). However, the HR responses to injectate were unaffected by cervical vagotomy or stellate ganglionectomy. A significant decrease in PBF was noted in most cases during the slowing of HR. It was concluded that the slowing of HR after cold injectate during thermodilution in dogs is primarily due to the direct cooling of the SA node.
作者研究了热稀释法中冷注射液导致心率（HR）减慢的机制以及肺血流动力学的相关变化。为了阐明冷注射液后心率减慢是由于窦房结冷却还是自主神经介导的反射，我们通过热敏电阻探头直接测量窦房结区域的心肌温度，并评估麻醉犬自主神经阻滞后对冰盐水注射液的心率反应。此外，在注射过程中通过电磁流量计连续测量肺血流量（PBF）。注射后心率变化的方向和幅度显著取决于注射液温度（P<0.01）。因此，心率变化与窦房结区域心肌温度变化密切相关（r = 0.987，P<0.01）。然而，对注射液的心率反应不受颈迷走神经切断术或星状神经节切除术的影响。在大多数心率减慢的情况下，肺血流量显著下降。得出的结论是，犬热稀释过程中冷注射液后心率减慢主要是由于窦房结的直接冷却。
