Discrepancy of central-peripheral arterial pressure after cardiopulmonary bypass may affect the reliability of arterial pressure waveform derived cardiac index (APCI) monitoring.

In 15 elective cardiac surgeries employing moderate hypothermic cardiopulmonary bypass (CPB), APCI from radial arterial cannula and pulmonary artery catheter derived cardiac index from thermodilution method (PACI) were measured 1) after anesthesia induction (T1), 2) before CPB (T2), 3) immediately after CPB (T3) and 4) 1 hour after CPB (T4). APCI and PACI were analyzed by using the Bland-Altman analysis.

Biases of APCI and PACI at T1, T2, T3 and T4 were 0.093 L/min/m², -0.053 L/min/m², 0.485 L/min/m² and -0.09 L/min/m², respectively. The limits of agreement (2 SD) at T1, T2, T3 and T4 were from -2.285 to 2.471 L/min/m², -2.475 to 2.369 L/min/m², -2.255 to 3.225 L/min/m² and -2.609 to 2.423 L/min/m², respectively. Bias of APCI and PACI during entire period (T1-T4) was 0.095 L/min/m² and 2 SD was from -2.387 to 2.557 L/min/m². However, mean error % (2 SD/mean) of APCI at T1, T2, T3, and T4 were greater than 30%.

Our results were not able to show that APCI measured from radial artery is comparable to PACI for hemodynamic monitoring during cardiac surgery employing moderate hypothermic CPB. Considering the limitations of PACI as a gold standard of hemodynamic monitoring in a certain clinical circumstance, further investigation employing other monitoring method than PACI may be followed to get more definitive conclusion.