Haemodynamic changes produced by inhalation anaesthetics in the presence of phosphodiesterase inhibition

We have investigated the circulatory effects of halothane and isoflurane in the presence of the phosphodiesterase inhibitor, enoximone, in 20 patients, ASA class III, aged 40-70 yr, undergoing coronary artery bypass grafting. After induction of anaesthesia (midazolam, fentanyl, etomidate and pancuronium) all patients received enoximone 0.5 mg kg-1, followed, 10 min later, by either halothane 1 MAC (group I; n = 10) or isoflurane 1 MAC (group II; n = 10). Haemodynamic variables were measured and blood samples (arterial and mixed venous) were obtained before (control, t0), 5 (t1) and 10 (t2) min after the injection of enoximone and immediately (t3) and 5 (t4) min after steady state conditions with halothane or isoflurane, as verified by the end-expiratory concentration. Heart rate, mean arterial pressure (MAP), mean pulmonary artery pressure, pulmonary capillary wedge pressure and right atrial pressure were recorded. Cardiac (CI) and stroke volume indices, systemic (SVR) and pulmonary vascular resistance, oxygen availability (QO2), oxygen consumption and oxygen extraction rate were calculated using standard formulae. MAP decreased significantly in both groups after bolus injection of enoximone (group I: 11%; group II: 7%). Under steady state conditions with the volatile anaesthetics, a further significant decrease in MAP was observed (group I: 12%; group II: 12%). Enoximone produced a significant increase in CI (group I: 25%; group II: 27% compared with control). After administration of isoflurane, CI remained essentially unchanged, while halothane decreased CI significantly by 20%. In both groups, SVR decreased significantly after administration of enoximone (group I: 26%; group II: 24%).(ABSTRACT TRUNCATED AT 250 WORDS)