EFFECTS OF THORACIC VS LUMBAR EPIDURAL-ANESTHESIA ON SYSTEMIC HEMODYNAMICS AND CORONARY CIRCULATION IN SEVOFLURANE ANESTHETIZED DOGS

Background: Although many investigators reported changes in coronary c irculation during thoracic epidural anaesthesia (TEA), no previous stu dies have attempted to compare it with lumbar epidural anaesthesia (TE A) concerning coronary circulation. Our aim was to compare effects of TEA on systemic haemodynamics and coronary circulation with those of L EA in anaesthetized dogs. Methods: In dogs receiving 1.5% sevoflurane, 2% lidocaine (0.1 mi kg(-1))was injected into the epidural space via an epidural catheter inserted at either the T7-T8 (TEA group, n=8) or L5-L6 (LEA group, n=8) interspace, and the same dose was repeated agai n 30 min later. Results: Heart rate and maximum left ventricular dP/dt decreased in the TEA group but were unchanged in the LEA group. Decre ases in mean arterial pressure were found for both groups, and they we re more substantial in the TEA than in the LEA group. Decreases in lef t ventricular minute work index were found for both groups, and they t ended to be more substantial in the TEA than in the LEA group. Coronar y perfusion pressure and blood flow decreased in both groups. Calculat ed coronary vascular resistance increased in the TEA group but was unc hanged in the LEA group. Conclusion: The most significant difference b etween TEA and LEA concerning coronary circulation was characterized b y an increase in coronary vascular resistance in the TEA group, which was not present in the LEA group. The increase in coronary vascular re sistance caused by TEA may be explained by a coronary vasoconstriction caused by a lower myocardial oxygen demand.