Continuous cardiac output during off-pump coronary artery bypass surgery: pulse-contour analyses vs pulmonary artery thermodilution.

BACKGROUND: No gold standard method exists for monitoring continuous cardiac output (CO). In this study, the agreement between the two most frequently used methods, PiCCO pulse-contour analysis (PCCO) and STAT pulmonary artery thermodilution (STAT-CO), was assessed during multiple-vessel off-pump coronary artery bypass (OPCAB) surgery.

METHODS: Thirty patients were enrolled in the study. Two time periods were defined during surgery; Period 1 included positioning of the heart and stabilizer device and Period 2 included the coronary occlusion. Measurements were obtained every minute during both periods. The agreement for the continuous CO and the change in CO (DeltaCO) was estimated using the Bland-Altman method.

RESULTS: Significant changes in mean arterial pressure (DeltaMAP), central venous saturation, PCCO and STAT-CO were seen only during Period 1. DeltaMAP correlated only with changes in PCCO, (P < 0.001, r = 0.60). The mean difference (2sd) between PCCO and STAT-CO ranged from - 0.29 (1.82) to - 0.71 (2.57) litre min(-1), and the percentage error varied from 32 to 50%. For the CO measurements, the limits of agreements did not differ between Period 1 and Period 2. In contrast, for the DeltaCO measurements, the limits of agreements were wider in Period 1 than in the more haemodynamically stable Period 2.

CONCLUSIONS: CCO and STAT-CO show large discrepancies in CO during OPCAB surgery. Clinically acceptable agreement was seen only for trends in CO during haemodynamically stable periods.