Effects of Intracoronary Epinephrine on Coronary Blood Flow, Oxidative Metabolism and Mechanical Function in Normal and Stunned Myocardium in Dogs / 대한마취과학회지

BACKGROUND: Epinephrine is frequently administered during cardiac surgery. The vascular response to epinephrine might be altered by ischemia and reperfusion, since altered vascular control has been demonstrated even after a short period of ischemia. To test the hypothesis, the effects of epinephrine on regional myocardial contractility, coronary blood flow (CBF) and myocardial oxygen consumption (MVO2) were investigated before and after ischemia in an open-chest canine myocardium. METHODS: Fifteen dogs were acutely instrumented under enflurane anesthesia to measure aortic and left ventricular pressures, pulmonary and left anterior descending (LAD) blood flows via Doppler flowmeter, and subendocardial segment length in the region supplied by LAD. Incremental doses of epinephrine (4, 10, 20, 30 ng/mL of LAD flow) were infused directly into LAD before (normal) and after a 15 min of LAD occlusion and subsequent 30 min-reperfusion (stunned). Segment shortening (%SS), as an index of regional myocardial contractility was evaluated. Simultaneous arterial and coronary venous contents of oxygen and lactate were measured during epinephrine (0.0, 4, 10, and 30 ng/mL) infusion. Effectiveness of metabolic vasodilation was determined from oxygen extraction ratio (EO2). RESULTS: Epinephrine infusions before ischemia resulted in dose-dependent increases in %SS and MVO2. These changes were accompanied by excessive increases in CBF, resulting in decreased EO2. After the ischemia and reperfusion, %SS was depressed and lactate extraction (Elac) was reduced, but similar mechanical responses to epinephrine were observed. However, in the stunned myocardium, CBF increased in parallel with increases in MVO2, resulting in unaltered EO2. Epinephrine infusion further decreased Elac dose-dependently in stunned myocardium. Heart rate and left ventricular systolic and diastolic pressures were little but similarly affected during epinephrine infusions before and after myocardial ischemia. CONCLUSIONS: The results suggest that epinephrine exerts positive inotropic effects in both normal and stunned myocardium, and that epinephrine causes direct coronary vasodilation in normal myocardium, but this effect is abolished in stunned myocardium in dogs. It is also suggested that epinephrine infusion depresses Elac dose-dependently in stunned myocardium.

Efficacy of a Simulated Epidural Test Dose in Isoflurane-Anesthetized Adults / 대한마취과학회지

BACKGROUND: An epidural test dose containing epinephrine may be incomplete marker of incidental intravenous injection or migration of the epidural catheter in adult patients under general anesthesia. This study tests the hypothesis that the efficacy of simulated epidural test doses in anesthetized adult can be used to predict the adequacy of correct catheter placement. METHODS: Seventy-five healthy adult patients were randomly assigned to inject intravenously one of 5 solutions, either 2% lidocaine 3ml and epinephrine 15 microgram(Group E15, n=15) or epinephrine 20 microgram (Group E20. n=15) or isoproterenol 3microgram (Group I3, n=15) or isoproterenol 5microgram (Group I5, n=15) and 0.9% saline(Group NS, n=15), which was anesthetized with isoflurane and nitrous oxide. After the injection, a blinded observer recorded systolic blood pressure(SBP) and heart rate(HR) every 30seconds for 4minutes and the changes were analyzed. RESULTS: Although none in the saline group developed a HR increase> or20bpm, 6, 10, 12 and 15 patients elicited positive reponses in group E15, I3, E20, and I5(40%, 67%, 80% and 100% sensitivities), respectively. Meanwhile, none in the saline group developed a SBP increase> or15mmHg and 11, 1, 14 and 4 patients elicited positive reponses in E15, I3, E20, and I5(73%, 7%, 93% and 27% sensitivities), respectively. CONCLUSIONS: We conclude that under isoflurane anesthesia, (a) epinephrine 15 microgram or isoproterenol 3microgram is not reliable marker for incidental intravenous injection or migration of the epidural catheter, (b) epinephrine 20 microgram is applicable on SBP criterion and, (c) isoproterenol 5 microgram is applicable on HR criterion.

A Comparative Study of Arrhythmogenic Doses of Epinephrine during Sevoflurane or Halothane Anesthesia in the Dogs / 대한마취과학회지

BACKGROUND: Epinephrine used in surgery to provide hemostasis may elicit ventricular arrhythmias. A desirable anesthetic would not sensitize the myocardium to exogenously administered epinephrine. So the effect of sevoflurane, which was introduced to clinical anesthesia recently, on cardiac arrhythmias induced by the infusion of epinephrine was compared with those of halothane which was already known to epinephrine-induced arrhythmia in the 14 mongrel dogs. METHODS: The authors compared the arrhythmogenicity (three or more premature ventricular contractions, PVCs)of intravenously administered epinephrine in 14 mongrel dogs who were randomly assigned to receive sevoflurane (1.7 vol%) or halothane (0.75 vol%) anesthesia equipotently. The arrhythmogenic doses of epinephrine determined in this comparative study were expressed by both infusion rates of epinephrine during sevoflurane and halothane anesthesia. RESULTS: The mean values of the arrythmogenic infusion rates of epinephrine were 27.1 7.6 g/kg for sevoflurane and 2.7 0.8 g/kg for halothane. CONCLUSIONS: We concluded that the arrythmogenic doses of epinephrine during sevoflurane were significantly higher than those during halothane anesthesia.