Accuracy Of Cardiac Output Monitoring By Pulse Contour Analysis Under Different Haemodynamic Conditions

Backgrounds and Objectives: Despite bolus cardiac output measurement (BCO) with pulmonary artery catheter thermodilution is still the most common cardiac output measurement technique, Continuous and less-invasive determination of cardiac output by transpulmonary thermodilution calibrated arterial pulse contour analysis (PCCO) is gaining clinicical acceptance. However , there is doubt whether this method is reliable and accurate under different haemodynamic conditions. The aim of this study was to: (1) observe the change of PCCO before and after calibrated under different haemodynamic conditions;(2) assess the degree of agreement between PCCO after calibrated and BCO measurement;(3) evaluate whether PCCO monitoring is reliable and clinically acceptable. Materials and methods: eleven anesthetized domestic pigs were investigated. Different haemodynamic situations were induced in every pig by three analogously performed interventions: the infusion of dopatamine (5 ug kg~-1 min~-1) , norepinephrine (4ug min~-1) andocclusion of inferior vena cava sequentially. Every haemodynamic interventionwas followed by a stabilization period of 15 minutes to equilibrate the haemodynamic situation before a consecutive intervention. CO was measured by pulmonary artery catheter thermodilution and arterial pulse-contour analysis respectively. Statistical analysis was performed with Bland - Altman analysis and ttest. Results: After the infusion of dopatamine, BCO and non-calibrated PCCO increased markedly( P<0.05 )and PCCO increased more markedly after calibration (P<0.05) compared with the baseline value. There is no statistically significant difference between PCCO values before and after calibration. After the infusion of norepinephrine, BCO didn' t change (P>0.05) while non-calibrated PCCO decreased markedly (P<0.05) , but PCCO didn' t change after calibration compared with the baseline value (P>0.05) . There is no statistically significant difference between PCCO values before and after calibration. After occlusion of inferior vena cava, BCO decreased markedly (P<0.05), while PCCO were no change before calibration (P>0.05) and decreased markedly (P<0.05) after calibration compared with the baseline value. After freed from inferior caval occlusion, BCO increased markedly (P<0.05) ,however, while PCCO were no change before calibration (P>0.05) and increased markedly (P<0.05) after calibration compared with the baseline value. After occlusion and de-occlusion of inferior vena cava, there were statistically significant differencesbetween PCCO values before and after calibration. Cardiac output measurements yielded 77 data pairs with a range of 1.41 ~7.06 L min"1 (Mean 3.94 L min^for calibrated PCCO and 1.44 -6.88 L min1 (Mean 3.85 L min"1) for BCO. Bland-Altman analysis showed a mean bias and limits of agreement of 0.07 L min"1 and - 0.67 to +0.81 L min"1 .The relative error of PCCO measurements was 3.5±3.1%. Conclusions.' The pulse contour analysis thus should be re-calibrated under hemodynamic instability. PCCO after re-calibrated can reflect the changes of CO. PCCO measurements after re-calibrated have a good agreement with BCO determinations. The accuracy of PCCO measurements after re-calibrated was clinically acceptable.