Muscle relaxation was facilitated with 0.15 mg/kg pancuronium, and the trachea was intubated.
Anesthesia was then induced (Narkomed NAD 6000 Draeger Medical Inc., Telford, PA) with either an inhaled agent using calibrated vaporizers, with 10 l/min oxygen, or a fentanyl–midazolam infusion over 1 min. After application of standard monitors and recording of heart rate, oscillometric blood pressure, and arterial oxygen saturation by pulse oximetry (Spo 2), a baseline transthoracic echocardiogram was performed with the patient breathing room air. All patients received premedication with 0.05–0.3 mg/kg intravenous midazolam to achieve a sedated but responsive state.
The two groups were fentanyl–midazolam and sevoflurane. Patients were randomized to one of two groups by selecting the first of a lot of prelabeled cards representing each group. 10MPI is 0.43 ± 0.15 in patients who are clinically thriving after the Norwood operation for a single functional right ventricle. 9MPI has been validated in the functional single ventricle population to the extent that, in children aged younger than 2 yr, MPI correlates with ventricular end-diastolic pressure, and with weight gain after palliative surgery. Normal MPI values in infants and children with two-ventricle hearts and no cardiac disease are 0.32 ± 0.03 for the right ventricle and 0.35 ± 0.03 for the left ventricle. 7Because MPI is an index involving systolic and diastolic time intervals, a higher MPI signifies worsening ventricular function, e.g ., longer systolic and diastolic time intervals. 8MPI is independent of heart rate and ventricular geometry 3and relatively independent of preload and afterload. 7MPI values also correlate well with clinical status and outcome of heart failure patients. MPI can be measured in the right or left ventricle 5and has been validated in the adult population, both invasively with cardiac catheterization measurements of systolic and diastolic function 6and noninvasively with conventional echocardiographic measurements such as ejection fraction. Independent time intervals for the isovolumic contraction time and the isovolumic relaxation time can be calculated from a simultaneous electrocardiogram. The MPI is a global measurement of combined systolic and diastolic ventricular function and can be calculated from pulsed-wave Doppler spectra of atrioventricular valve inflow and ventricular outflow.