Semi-invasive monitoring of cardiac output by a new device using arterial pressure waveform analysis: a comparison with intermittent pulmonary artery thermodilution in patients undergoing cardiac surgery.

BACKGROUND: Thermodilution technique using a pulmonary artery catheter (PAC) is a widely used method to determine cardiac output (CO). It is increasingly criticized because of its invasiveness and its unclear risk-benefit ratio. Thus, less invasive techniques for measuring CO are highly desirable. We compared a new, semi-invasive device (FloTrac/Vigileo) using arterial pressure waveform analysis for CO measurement in patients undergoing cardiac surgery with bolus thermodilution measurements.

METHODS: Forty patients undergoing coronary artery bypass grafting or valve repair were enrolled. A PAC was inserted and routine radial arterial access was used for semi-invasive determination of CO with the Vigileo. CO was measured simultaneously by bolus thermodilution and the Vigileo technique after induction of anaesthesia (T1), before cardiopulmonary bypass (CPB) (T2), after CPB (T3), after sternal closure (T4), on arrival in the intensive care unit (ICU) (T5), and 4 h (T6), 8 h (T7), and 24 h after surgery (T8). CO was indexed to the body surface area (cardiac index, CI).

RESULTS: A total of 244 pairs of CI measurements were analysed. Bias and precision (1.96 sd of the bias) were 0.46 litre min(-1) m(-2) and +/- 1.15 litre min(-1) m(-2) (r = 0.53) resulting in an overall percentage error of 46%. Subgroup analysis revealed a percentage error of 51% for data pairs obtained intraoperatively (T1-T4), 42% in ICU (T5-T8), and 56% for values obtained during low CI (T1-T8).

CONCLUSIONS: In cardiac surgery patients, CO measured by a new semi-invasive arterial pressure waveform analysis device showed only moderate agreement with intermittent pulmonary artery thermodilution measurement.