Background For patients undergoing off-pump coronary artery bypass grafting (OPCABG),it is important to establish a hemodynamic monitoring system to obtain powerful parameters for better intraoperative treatment.This study aimed to observe the clinical feasibility of artedal pressure-based cardiac output (APCO) for cardiac output (CO) monitoring and to evaluate the correlation between APCO and pulmonary artery catheter (PAC) for CO measurement for patients undergoing OPCABG intraoperatively.Methods Fifty patients of Amedcan Society of Anaesthesiologists (ASA) classification Ⅱ-Ⅲ,undergoing elective OPCABG at Beijing Anzhen Hospital were randomly enrolled into this study.All patients were assigned to CO monitoring by PAC and APCO simultaneously.Patients with pacemaker,severe valvular heart disease,left ventdcular ejection fraction (EF) ＜40％,cardiac arrhythmias,peripheral vascular disease,application of intra-aortic balloon pump (IABP) and emergent diversion to cardiac pulmonary bypass were excluded.The radial artery wavaform was analyzed to estimate the stroke volume (SV) and heart rate (HR) continuously.CO was calculated as SV x HR; other derived parameters were cardiac index (CI),stroke volume index (SVI),systemic vascular resistance (SVR),and systemic vascular resistance index (SVRI).PAC was placed via right internal jugular vein and the correct position was confirmed by PAC waveforms.Continuous cardiac output (CCO),CI and other hemodynamic parameters were monitored at following 5 time points:immediate after anesthesia induction (baseline value),anastomosis of left intemal mammary artery to left anterior descending artery (LAD),anastomosis of left circumflex (LCX),anastomosis of posterior descending artery (PDA) and immediate after sternal closure.Results In the 50 patients,preoperative echocardiography measured left ventricular EF was (52.8±11.5)％,and 35 patients (70％) showed regional wall motion abnormalities.The correlation coefficient of CO monitored by APCO and PAC were 0.70,0.59,0.78,0.74 and 0.85 at each time point.The bias range of CI monitored from both APCO and PAC were (0.39±0.06) L·min-1·m-2,(0.48±0.12) L·min-1·m-2,(0.26±0,06) L·min-1·m-2,(0.27±0.06) L·min-1·m-2,(0.30±0.05)L·min-1·m-2 at each time point.The results of SVR by two hemodynamic monitoring techniques had good correlation during OPCABG.The variation trends of SVR were opposite comparing with the results of CO.SVR collected from PAC obtained the highest value of (1220.0±254.0) dyn·s·cm-5 at PDA anastomosis,but the highest value obtained from APCO was (1206.0±226.5) dyn·s·cm-5 in LCX anastomosis.Conclusions APCO is feasible in hemodynamic monitoring for patients undergoing OPCABG.The results of hemodynamic monitoring dedved from APCO and PAC are closely correlated.Its characterizations of timely,accurate and continuous display of hemodynamic parameters are also obviously demonstrated in the present study.