Evaluation of right ventricular function by assessment of cardiac efficiency: influence of induction of anaesthesia in coronary artery bypass grafting patients.

Considering the heart as a physical pump cardiac efficiency is calculated from the ratio of cardiac work performed to the maximum level of energy of the heart. The aim of the study was to compare cardiac efficiency with cardiac output and right ventricular ejection fraction. Nine patients scheduled for coronary artery bypass grafting were investigated. A femoral arterial and a right ventricular ejection fraction pulmonary artery catheter were placed in the awake state. Anaesthesia was induced with eltanolone and fentanyl. Cardiac output, pulmonary artery and central venous pressures, and right ventricular ejection fraction were measured in the awake state (baseline), 2 min after induction of anaesthesia and 1 and 5 min after intubation. Cardiac efficiency was calculated by dividing the stroke work by the maximum energy of the heart as calculated from the pressure volume diagram. An analysis of variance was carried out for cardiac efficiency, cardiac output and right ventricular ejection fraction. Cardiac efficiency was significantly (p < 0.05) reduced 1 min after intubation from 28 +/- 11 to 14 +/- 5%. In contrast the right ventricular ejection fraction (from 48 +/- 10 to 35 +/- 13%) and cardiac output (from 6.5 +/- 1.5 to 5.3 +/- 1.2 L/min) did not change significantly during the induction of anaesthesia. Cardiac efficiency was found to be a more sensitive parameter to describe changes in the right ventricular function than the ejection fraction and cardiac output during induction of anaesthesia with eltanolone and fentanyl which was used as a model to vary cardiac performance and afterload.