Comparison of three kinds of less invasive cardiac output measuring systems in aged patients

BACKGROUND: Recently, the number of operations for aged patients have been increasing. They usually have various preoperative complications especially cardiovascular systems, and cardiac output measuring under general anesthesia is useful for their operative managements. The aim of this study was to compare the accuracy of three kinds of less invasive equipments for cardiac output measurements, i.e. the impedance cardiography (ICG), the partial CO2 rebreathing (NICO), and the arterial pressure-based cardiac output (APCO). METHODS: Subjects are 40 patients over 65 years of age scheduled for elective lower abdominal or surface surgery. During anesthesia, three kinds of cardiac output measuring systems obtained cardiac output simultaneously every five minutes. RESULTS: Both bias and percentage error between APCO and NICO were the smallest. There were statistically significant correlations between ICG and NICO, NICO and APCO, and APCO and ICG. Accuracy of the three kinds of cardiac output measuring systems was confirmed in this study. Although when arterial pressure was above 100 mmHg cardiac output values were reliable, values were not reliable below 100 mmHg. The four factors i. e. age, blood pressure level, history of hypertension and body structure effected cardiac output measurements. There was no statistic relationship between arterial pressure and cardiac output in all measurements. CONCLUSIONS: Three kinds of less invasive cardiac output measurement systems have enough functions to use during surgery for aged patients.