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 (Delta CO) was estimated using the Bland-Altman method. Results. Significant changes in mean arterial pressure (Delta MAP), central venous saturation, PCCO and STAT-CO were seen only during Period 1. Delta MAP 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 Delta CO measurements, the limits of agreements were wider in Period I than in the more haemodynamically stable Period 2. Conclusions. PCCO 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.