Agreement between PiCCO pulse-contour analysis, pulmonal artery thermodilution and transthoracic thermodilution during off-pump coronary artery by-pass surgery

Background: Haemodynamic instability during off-pump coronary artery bypass surgery (OPCAB) may appear rapidly, and continuous monitoring of the cardiac index (CI) during the procedure is advisable. With the PiCCO monitor, CI can be measured continuously and almost real time with pulse-contour analysis and intermittently with transthoracic thermodilution. The agreement between pulmonal artery thermodilution CI (Tpa), transthoracic thermodilution CI (Tpc) and pulse-contour CI (PCCI) during OPCAB surgery has not been evaluated sufficiently. Methods: In 30 patients scheduled for OPCAB surgery, a pulmonary artery catheter and a PiCCO catheter were inserted. At different time points during surgery, Tpa, Tpc and PCCI were compared. Measurements were performed after induction of anesthesia (T1), after pericardiothomy (T2), after grafting on the anterior (T3), posterior (T4) and lateral (T5) walls and after chest closure (T6). The PCCI was recalibrated at time point T2-T6. Results: Mean difference and the limits of agreements (percentage error) between Tpa and Tpc were: -0.14 +/- 0.60 (22.0%) l/min/m(2), between Tpa and PCCI: -0.07 +/- 0.92 (33.5%) l/min/m(2) and between Tpc and PCCI: 0.10 +/- 1.00 (35.5%) l/min/m(2). For changes in CI from one time point to the next (Delta CI), the limits of agreements between Delta CI Tpa and Delta CI Tpc were 0.04 +/- 0.90 l/min/m(2), between Delta CI Tpa and Delta CI PCCI: -0.02 +/- 1.22 l/min/m(2) and between Delta CI Tpc and Delta CI PCCI: -0.08 +/- 1.32 l/min/m(2). Conclusion: In OPCAB surgery, limits of agreement comparing thermodilution methods were smaller than comparing PCCI with thermodilution. Recalibration of PCCI is therefore advisable.