Influence of Extracellular Acidosis on the Direct Cardiac Effects of Ketamine

細胞外酸中毒對 Ketamine 之直接心臟作用的影響

葉富欽(Fuh-Cheng Yen) ； 曾稼志(Chia-Chih Tzeng) ； 張傳林(Chuan-Lin Chang) ； 陳幸一(Hsing I. Chen)

《慈濟醫學雜誌》 7卷4期 (1995/12) Pp. 261-267

https://doi.org/10.6440/TZUCMJ.199512.0261

摘要

Ketamine在休克病患血循環作用表現不一，可以是興奮，也可以是抑制作用。續發於循環休克及動脈低血氧之代謝性酸中毒，加強Ketamine之心臟直接抑制作用可能是引發血循環抑制的一大因素。本實驗以Langendorff模式研究細胞外液酸中毒對Ketamine之心臟直接作用的影響。在正常(7.4)組，Ketamine低劑量有直接增加心收縮力的作用，但高劑量則有明顯抑制心收縮力與心率的結果。輕度細胞外液酸中毒(7.2)並無明顯改變Ketamine之心臟作用效果，但重度酸中毒(PH7.0與6.8)是有明顯加強Ketamine之直接心臟抑制作用。

關鍵字

Ketamine ； 細胞外酸中毒 ； 心收縮力 ； 心率

並列摘要

The selection of ketamine as an anesthetic agent in patients with shock is still controversial. Hemodynamic effects of both stimulatory and depressive in nature have been reported. It is possible that metabolic acidosis secondary to the circulatory shock and/or arterial hypoxemia may potentiate the direct negative inotropic effect of ketamine and thereby producing circulatory depression in some of the poor risk patients. In the present investigation, we used a modified Langendorff preparation to study the influence of extracellular acidosis on the direct cardiac effects of ketamine. The changes of maximum left ventricular dP/dt ( LV dP/dtmax ) and heart rate ( HR) from baseline levels after exposure to ketamine 5, 25, 125 µg/ml in the normal pH ( 7.4 ) group averaged +7.1%, +0.8%, -42.6%, and -2.4%, -9.4%, -36.8%, respectively, and in the most severe acidosis ( pH 6.8 ), they were -10.9%, -19.3%, -49.8%, and -12.1%, -21.9%, -43.1%,respectively. At ketamine 5 and 25 µg/ml, a decrease in pH from 7.4 to 7.2 did not affect the ketamine effects significantly. When the pH was furher decreased to 7.0 and 6.8, the cardiac depression of ketamine became prominent. However, the degree of depression was not different between pH 7.0 and 6.8. At ketamine 125 µg/ml, the marked decreases in cardiac contractility and rate by this large dose did not appear to be significantly altered by the pH. The results indicate that low dose of ketamine directly increase cardiac contractility whereas high dose depresses the cardiac contractility and rate. Mild extracellular acidosis ( pH 7.2 ) does not significantly affect the ketamine effects. However, severe extracellular acidosis ( pH 7.0 and 6.8 ) does potentiate the direct negative inotropic and chronotropic effects of ketamine.

並列關鍵字

ketamine ； extracellular acidosis ； myocardial contractility ； heart rate