Effects of different isoflurane concentratios on tissue perfusion in dogs

Abstract

Isoflurane is an inhalatory anesthetic that is commonly used in Veterinary Medicine, for it provides safety in critical patients, by maintenance of cardiac output and low hepatic metabolization rate. However, its effects on cardiovascular system still requires elucidation when it comes to tissue perfusion. The present study aims to evaluate the effects of isoflurane on tissue perfusion in dogs undergoing anesthesia with concentrations that correspond to two different MAC multiples. Eight dogs will be used in the study, being them the same contents of two experimental groups (G1,5 and G2,0). In the first phase of the experiment, the individual MAC value will be determined by electrical stimulation to assess the response considered positive or negative. During the second phase, anesthesia will be held with the concentrations equivalent to 1,5 MAC for G1,5 and 2,0 MAC for G2,0, being the minimun interval between procedures that of one week. The monitorization will occur every 20 minutes during 2 hours, consisting of HR, arterial pressure (SAP, DAP and MAP), f, cardiac output, central venous pressure, pulmonary arterial pressure and occluded pulmonary arterial pressure, hemogasometric analysis of arterial and mixed venous blood, EKG, esophageal, rectal and interdigital temperatures and capnometry. Blood lactate, glucose and pyruvate will be measured and, using values obtained with previous parameter, the following will be calculated mathematically: arterial and venous content of O2, PaO2/FiO2 ratio, O2 delivery and uptake, O2 extraction rate, cardiac and systolic index, pulmonary vascular resistance index, left ventricle work index and total peripheral resistance index will be obtained mathematically. Every dog will be monitored until it fully recovers from anesthesia, and will also be observed during the first 24 hours subsequently. (AU)