Background: Off-pump coronary artery bypass grafting (OPCAB) can be associated with severe cardiovascular changes, thus requiring advanced haemodynamic monitoring. Our aim was to investigate the feasibility of transpulmonary single thermodilution (STD) combined with pulse-contour analysis, a newly introduced method for cardiovascular monitoring, for assessment of changes in haemodynamics during different anaesthetic techniques in OPCAB.
Methods: Thirty-six patients scheduled for elective OPCAB were randomized to receive anaesthesia either with midazolam, propofol or isoflurane, in addition to fentanyl and pipecuronium. After catheterization of the femoral artery, haemodynamic parameters were assessed using STD and pulse-contour analysis. The measurements were performed after induction of anaesthesia, during surgery and at 2, 4 and 6 h post-operatively.
Results: At the end of surgery, the global ejection fraction decreased by 29% and 19% in the midazolam and the propofol groups, respectively, (P < 0.05) but remained unchanged in the isoflurane group. Moreover, in the isoflurane group, the left ventricular contractility index was higher and the mean arterial pressure (MAP) and the systemic vascular resistance index (SVRI) decreased in comparison with pre-operative values. Post-operatively, the cardiac index (CI) and the cardiac function index (CFI) increased in all groups (P < 0.05). The peri-operative requirement for ephedrine and nitroglycerin increased in the propofol and the midazolam groups, respectively (P < 0.05).
Conclusion: During OPCAB, STD and pulse-contour analysis displayed changes in preload, myocardial function and afterload that gave valuable guidance for the conduct of anaesthesia, fluid management, and the administration of vasoactive agents. As assessed using STD, isoflurane within the present dose range appears to maintain myocardial performance and vascular tone better than midazolam or propofol.