The Effect of Phenylephrine on Cardiac Performance and Myocardial Oxygen Balance in Resuscitation from Hemorrhagic Shock / 대한마취과학회지

BACKGROUND: The issue of using phenylephrine in hemorrhagic shock treatment has been controversial because it is known that phenylephrine improves the tissue perfusion by increasing arterial blood pressure but deteriorates the myocardium by increasing afterload and decreasing myocardial oxygen delivery via coronary vasoconstriction. This study was aimed to assess the effects of phenylephrine on hemodynamic variables, cardiac performance, and myocardial oxygen balance in resuscitation from hemorrhagic shock. METHODS: Twenty anesthetized dogs were randomly divided into phenylephrine group and control group. After inducing hemorrhagic shock, resuscitation was done with phenylephrine and 0.9% normal saline respectively. We measured hemodynamic indices, blood gas parameter and cardiac enzymes which indicate myocardial demage. RESULTS: In both groups, cardiac output and hemodynamic indices improved. In phenylephrine group, the systemic oxygen delivery and consumption was much higher and the myocardial oxygen extraction ratio was maintained at the lower level than the control group. In addition, the CK-MB was higher at the early phase of resuscitation and the troponin T was also higher than the control group during the whole period of resuscitation. Creatine kinase-MB increased during early resuscitation in phenylephrine group but kept decreasing after that and there's no difference between two groups. Troponin T was higher in the phenylephrine group after resuscitation. CONCLUSIONS: We concluded that phenylephrine improves myocardial oxygen balance and contractility without serious myocardial demage during resuscitation from hemorrhagic shock.

Effects of Amrinone and Dobutamine on Regional Myocardial Function and Oxygen Balance in Normal and Stunned Myocardium in Dogs / 대한구급학회지

BACKGROUND: We examined the effects of amrinone and dobutamine on regional mechanical function, coronary blood flow (CBF), and myocardial oxygen consumption (MVO2) in normal and stunned myocardium in an open-chest canine model. METHODS: Dogs were instrumented to measure aortic and left ventricular pressures, pulmonary and left anterior descending (LAD) coronary blood flows, and subendocardial segment length in the region supplied by LAD. Incremental doses of either amrinone (2~10microgram/ml of LAD flow, n=13) or dobutamine (0.05~0.375microgram/ml of LAD flow, n=14) were directly infused into a coronary artery before (normal) and after a 15 min of LAD occlusion and subsequent 30 min-reperfusion (stunned). Percent segment shortening (%SS) and percent post-systolic shortening (%PSS) were evaluated. Myocardial extraction of oxygen (EO2) and lactate (Elac) was calculated. RESULTS: Amrinone or dobutamine in the normal myocardium caused dose-dependent increases in %SS that were comparable (range, 20~40%) but had no effect on %PSS. MVO2 increased in parallel with %SS for both amrinone and dobutamine. With amrinone, CBF increased more than MVO2, resulting in a modest decrease in EO2, whereas with dobutamine, CBF increased in proportion to MVO2, resulting in no change in EO2. After the ischemia and reperfusion, %SS and Elac were reduced, but similar %SS and CBF responses to both agents were observed, except that both agents caused progressive reductions of %PSS. CONCLUSIONS: These results indicate that both amrinone and dobutamine exert positive inotropic effects in normal and stunned canine myocardium. It is also indicated that amrinone causes direct coronary vasodilation, which is not affected by ischemia and reperfusion, while dobutamine has no direct effect on coronary vascular tone in either normal or stunned myocardium.

Effects of Amrinone on Regional Myocardial Function and Oxygen Balance in Stunned Myocardium in Dogs / 대한마취과학회지

BACKGROUND: Brief myocardial ischaemia has been demonstrated to result in mechanical and coronary endothelial dysfunction. We examined whether the mechanical and vascular responses to amrinone are altered in the postischaemic, reperfused myocardium. The effects of amrinone were compared with those of dobutamine. METHODS: In an open-chest canine model, coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and regional mechanical function in response to either amrinone (2, 5, 7.5, and 10 ng/mL of CBF) or dobutamine (0.05, 0.125, 0.25, 0.375, and 10ng/mL of CBF) directly infused into the left anterior descending (LAD) artery were determined before (normal) and 30 min after 15-min- period of LAD occlusion (stunned). Percent segment shortening (%SS), peak segment lengthening rate (dL/dt(max)), and percent post-systolic shortening (%PSS) in the LAD territory was determined using ultrasonic crystals and CBF using Doppler transducer. Myocardial extractions of oxygen (EO2) and lactate (Elac) were calculated. RESULTS: Both amrinone and dobutamine in the normal myocardium caused a dose-dependent increase in mechanical functions (%SS and dL/dt(max)) and MVO2 that were comparable (range, 20 40%), but they had no effects on %PSS. Amrinone caused an increase of CBF in excess of MVO2, resulting in a modest decrease in EO2, whereas dobutamine increased CBF in proportion to MVO2, resulting in no changes in EO2. The ischemia and reperfusion insult reduced %SS, dL/dt(max), and Elac, while it did not affect mechanical (%SS and dL/dt(max)) and CBF responses to either agent, except for progressive reductions of %PSS. CONCLUSIONS: These results indicate that amrinone, similar to dobutamine, exert positive inotropic and lusitropic effects in normal and stunned canine myocardium. It is also indicated that amrinone causes direct coronary vasodilation, which is not affected by an ischemia and reperfusion insult.

Effects of Enflurane on the Left Ventricular Function in Isolated Diltiazem-Pretreated Rat Heart / 대한마취과학회지

BACKGROUND: Calcium channel blockers and volatile anesthetics have depressant effects on cardiac function. Both of them appear to exert, qualitatively and quantitatively, different effects on myocardial contractility, coronary flow, and myocardial oxygen balance. The aim of this study was to examine the direct cardiac effects of the enflurane in the presence of diltiazem. METHODS: Isolated Sprague-Dawley rat hearts (N=45) were perfused at constant pressure with oxygenated Modified-Krebs solution (pH 7.4, 37oC). Isovolumetric left ventricular pressure (LVP) and dP/dt were measured via a latex balloon and transducer. Also, coronary flow and oxygen tensions at the coronary inflow and outflow were measured. After stabilization period, all hearts were subjected to the application with diltiazem (100 ng/ml). Thereafter, they were subdivided into three groups; group 1, 2, 3. Groups subjected to the combination of diltiazem (100 ng/ml) with enflurane 1.1, 2.2, or 3.3 vol%, respectively. RESULTS: After the application of diltiazem, myocardial contractility and heart rate were significantly decreased, and coronary flow were significantly increased. The combination of diltiazem with enflurane depressed myocardial contractility, heart rate, myocardial O2 consumption, and percentage of O2 extraction more than diltiazem alone, and their effects were dependent on the concentration of enflurane. However, there was no difference in the change of coronary flow and oxygen delivery between diltiazem and the combination of diltiazem with enflurane. CONCLUSIONS: These in vitro findings demonstrate that the combination of diltiazem with enflurane shows greater direct negative inotropic and negative chronotropic effect, and is associated with less attenuation of coronary autoregulation, but with a larger reduction in O2 utilization. The present results suggest that high enflurane anesthesia in the diltiazem-pretreated patients could result in profound cardiac depression.