Indexation of cardiac output to biometric parameters in critically ill patients: A systematic analysis of a transpulmonary thermodilution-derived database.

PURPOSE: Cardiac output (CO) (liters per minute) is usually normalized (ie, indexed) to the patient's body surface area (BSA) resulting in the hemodynamic variable cardiac index (CI) (liters per minute per square meter). We aimed (1) to evaluate the impact of different body weight-based CO indexations on the resulting CI values and (2) to identify biometric parameters independently associated with CO in critically ill patients.
MATERIALS AND METHODS: The study is an analysis of a database containing transpulmonary thermodilution-derived hemodynamic variables of 234 medical intensive care unit patients.
RESULTS: Cardiac index indexed to actual BSA was statistically significantly lower compared with CI indexed to predicted BSA in the totality of patients and in the subgroups of patients with body mass index greater than or equal to 25 kg/m(2) but less than 30 kg/m(2) and body mass index greater than or equal to 30 kg/m(2) (with a statistically significant difference in the proportion of low and high CI measurements). Multivariate analysis of the first CO measurement of each patient demonstrated that CO was independently associated with age (P < .001), height (P = .001), and actual body weight (BWact) (P = .030). Multivariate analysis of the mean of the patients' CO measurements confirmed age (P < .001), height (P = .001), and BWact (P < .001) as biometric factors independently associated with CO. Age was identified as the most important factor with each year of age decreasing CO by 66 mL/min (95% confidence interval, 47-86 mL/min).
CONCLUSIONS: The indexation of CO to BSA is highly dependent on the body weight estimation formula used to calculate BSA. Cardiac output is independently associated with the biometric factors age, height, and BWact. These factors might be considered for indexation of CO.