熱希釈法による心拍出量測定時の循環変動に関する実験的研究
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Effects of cold injectate (5% dextrose solution) on the hemodynamics were studied in anesthetized dogs. Hemodynamic parameters (heart rate, systemic and pulmonary arterial pressure, and right atrial pressure) and electrocardiogram were recorded continuously before and after injectates (10, 5, and 3ml iced, 10ml room temperature, and 10ml 37℃) were rapidly administered into the right atrium. To clarify the mechanism of heart rate slowing induced by cold injectate, the continuous measurement of temperature of the sinoatrial node region was performed, and the hemodynamic responses to cold tracer after autonomic blockade (cervical vagotomy or intravenous atropine and stellate ganglionectomy or intravenous propranolol) were also evaluated. Further study was undertaken in order to investigate whether alterations in pulmonary or aortic blood flow are responsible for changes in pulmonary or systemic arterial pressure in both normally innervated and denervated dogs. Blood flows were measured continuously by an electromagnetic flowmeter. The results obtained were as follows: 1) Heart rate decreased after the administration of injectate in a temperature-dependent manner. 2) A close correlation was obtained between heart rate slowing and falls in myocardial temperature of the sinoatrial node region. 3) Parasympathectomy or sympathectomy had little effect upon heart rate slowing. 4) Systemic and pulmonary arterial pressure showed a triphasic change, i.e., a slight increase during injection, a pronounced decrease at slowing of heart rate, and a re-increase during recovery of heart rate. In contrast, right atrial pressure increased slightly during injection and slowing of heart rate. 5) Both pulmonary and aortic blood flows increased slightly during injection, then decreased markedly at slowing of heart rate, followed by increases during recovery of heart rate. 6) Sympathectomy augmented the depressor responses at slowing of heart rate, though parasympathectomy had the opposite influence. ?These results suggest that slowing of heart rate after cold injectate is primarily due to the direct cooling of the sinoatrial node, but not vagal mediated reflex. Autonomic nervous activities may modulate the responses elicited by cold injectate. Finally, changes in pulmonary blood flow elicited by cold injectate, even if transiently or to a certain extent, can lead to an erroneous estimation of cardiac output by the thermodilution method.
- 札幌医科大学の論文
- 1987-02-02
札幌医科大学 | 論文
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