Hemodyamic Effects of Verapamil on Canine Cardiovascular System Under Variable Concentrations of Isoflurane Anesthesia

Moon, Hyun Soo; Kim, Yong Lak

Abstract

Isoflurane has been known to reveal relatively stable hemodynamic effects on cardiovas-cular system,so many anesthesiologists recommend it as the anesthetic of choice for cardiovascular surgery in spite of its higher cost. Verapamil has been indicated in many cardiovascular diseases and its pharmacological effects are known to be infiuenced by the patients hemodynamic condition, disease state, and concurrent drug therapy. The author performed this experimental study to evaluate the hemodynamic effects of verapamil on cardiovascular system under variable concentrations of isoflurane anesthesia with 7 mongrel dogs. Heart rate (HR), mean arterial pressure(MAP), central venous pressure (CVP), pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) were measured, and stroke volume (SV), cardiac index (CI), left ventricular stroke work index (LVSWI),systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were calcurated after 0.3 minimum alveolar concentrations of anesthetic (MAC) N2O anesthesia with pancuronium relaxation as controls, after 20 minutes of 1 MAC and 2 MAC of isoflurane anesthesia, after verapamil 0.15 mg/ kg bolus with 0.005mg/kg/min infusion, and after 20 minutes of 1 MAC and 2 MAC of isoflurane anesthesia with verapamil infusion respectively. Following results were obtained by comparing each data, and data between isolfurane alone and isoflurane with verapamil infusion. 1) Most of hemodynamic indices of cardiovascular system were decreased significantly with increase of isoflurane concentration except CVP and PVR. 2) Verapamil infusion decreased HR, MAP and SVR significantly but increased CO, CI and SV significantly. 3) PCWP was increased only under 2 MAC isoflurane, PAP and PCWP were increased slightly after verapamil infusion without significance. 4) Isoflurane with verapamil infusion decreased HR and MAP more significantly that islurane alone in a dose dependent manner but it decreased CO, CI and LVSWI less than isoflurane alone because of verapamil interaction. 5) Comparing with isoflurane alone, isoflurane with verapamil infusion increased CVP significantly by the interaction of verapamil effect. 6) General hemodynamic changes were enhanced according to increasing concentration of isoflurane. With the above results the author concluded that comparing with isoflurane alone, isoflurane with verapamil infusion not only increased CO, CI and HR, so that it is important to control isoflurane concentration prudently in accordance with the changes of MAP and HR for safe anesthetic management.