A COMPARISON OF METHODS OF MEASURING CARDIAC-OUTPUT DURING CARDIAC-CATHETERIZATION IN AN ELDERLY POPULATION

Objectives Most methods of measuring oxygen consumption for the purpos e of calculating cardiac output were not developed in elderly patients , so we sought to examine the differences between the various methods in an elderly population. Methods We prospectively studied 54 patients (29 women, 25 men) aged 60 years and over(mean 72.6 +/- 6.9; range 60 -86) who underwent right and left heart catheterization. We compared t hermodilution with Fick-derived cardiac output based on measurement of oxygen consumption with a metabolic rate meter and estimated oxygen c onsumption derived from five different formulas. Results The cardiac o utput as measured by the metabolic rate meter was significantly higher than the thermodilution cardiac output and all of the estimated-oxyge n Fick cardiac outputs. The degree of disparity between thermodilution and Fick cardiac output was significantly greater for the metabolic r ate meter than for any of the estimated oxygen-consumption formulas. C onclusion The different methods of measuring cardiac output may result in significantly different estimates of the cardiac output in an elde rly population. The metabolic rate meter, a method that ostensibly dir ectly measures oxygen consumption, may have no advantage over estimate d oxygen consumption, These observations have important implications i n cases where accurate measurement of a cardiac output is of paramount importance, such as in the assessment of stenotic valves.