Cardiac Index Assessment by the Pressure Recording Analytic Method in Critically Ill Unstable Patients After Cardiac Surgery

ObjectiveThe authors measured cardiac index in unstable patients after cardiac surgery with the Pressure Recording Analytic Method (PRAM) and compared it with the reference method of thermodilution (ThD) with the pulmonary artery catheter; using the hypothesis that there were no significant differences between the 2 methods.DesignA prospective study.SettingCardiac surgery intensive care unit in a teaching hospital.ParticipantsNinety-four measurements from 59 patients with ongoing high doses of inotropic drugs and/or an intra-aortic balloon pump for low-cardiac-output syndrome after cardiac surgery were studied.InterventionsThe pulmonary artery catheter and the radial or femoral arterial catheter for measuring blood pressure were already in place for standard hemodynamic monitoring.Measurements and Main ResultsThe mean of the total CI measurements was 2.94±0.67 L/min/m2 with PRAM and 2.95±0.63 L/min/m2 with ThD, with no significant difference according to the linear mixed models analysis. The PRAM and ThD techniques were similar in unstable patients without atrial fibrillation (mean bias 0.047±0.395 L/min/m2 and a percentage error of 29%), while no agreement between PRAM and ThD was found in unstable patients with atrial fibrillation (mean bias 0.195±0.885 L/min/m2 and a percentage error of 69%).ConclusionCardiac index measurements after cardiac surgery performed with PRAM and with ThD showed a good agreement in hemodynamically unstable patients given high doses of inotropes and/or an IABP in patients in sinus rhythm, but not in those with atrial fibrillation.