Summary

Abstract

The influence of various anesthetics-ether, halothane, ketamine, methoxyflurane, nitrous oxide, piritramide and neuroleptanesthesia (nla = droperidol plus fentanyl) &x2014; on the oxygen consumption of the left ventricle was investigated in 7&x2013;9 closed chest dogs. The experiments were carried out under controlled ventilation with nitrous oxide and oxygen (80%:20%). The O₂-consumption of the left ventricle was measured simultaneously by two independent technics: first by the conventional way (M$\dot V$O₂ = $\dot V$_cor · avD-O₂) measuring myocardial blood flow with a pitotcatheter after BRETSCHNEIDER and secondly by means of a new complex hemodynamic parameter for estimation of myocardial O₂-consumption which consists of five additive determinants (E_T = E₀ + E₁ E₂ + E₃ + E₄ (BRETSCHNEIDER et al., 1970). Except for ketamine both methods of determination of myocardial O₂-consumption showed a good correlation. Ketamineanesthesia produced a 15% greater mean value for „$\dot V$cor · avD02“ compared with the calculated ET. After the degree of oxygen consumption the anesthetics devided in two groups: ether, N_2O, and ketamine as well as the sole application of droperidol caused a myocardial oxygen consumption in the range from 10.2–11.3 ml O₂/min · 100 g close to the upper limit of the O₂-consumption of the “normal beating” heart. In the contrary halothane, methoxyflurane, piritramide and the complete nla (after additional injection of fentanyl following droperidol) led to a significant lower myocardial O₂-consumption between 7.0 and 7.9 ml O₂(min · 100 gat the lower limit of the physiological range. The use of the complex hemodynamic parameter allowed to clifferentiate the total myocardial O₂-consumption (ET) into the five O₂-consuming working processes (E₀, E₁, E₂, E₃, E₄) of the heart. Quantitatively the determinants E₂-oxygen cost of maintenance of tension-and E₃-oxygen cost of development of tension-represented under all anesthetic conditions about 80% of ET.