Continuous cardiac output monitoring after cardiopulmonary bypass: a comparison with bolus thermodilution measurement.

摘要

OBJECTIVE: The interchangeability of continuous measurement of cardiac output (CO) with the traditional bolus method in patients after cardiopulmonary bypass (CPB) is uncertain. DESIGN: Prospective observational clinical study. SETTING: A 20-bed surgical ICU at a university hospital. PATIENTS: Fourteen deeply sedated, ventilated, post-cardiac surgery patients, all equipped with a pulmonary artery catheter. INTERVENTIONS: Six hours after the end of the CPB, 56 simultaneous bolus and continuous measurements were compared by a linear regression analysis and Bland-Altman analysis. Bolus CO was estimated by averaging triplicate injections of 10[Symbol: see text]ml room-temperature NaCl 0.9%, delivered randomly during the respiratory cycle. A stringent maximum difference of 0.55 l[Symbol: see text]min(-1) (about 10% of the mean bolus measured) was considered as a clinically acceptable agreement between the two types of measurements. To be interchangeable the limits of agreement (+/-[Symbol: see text]2 SD of the mean difference between the two methods) should not exceed the chosen acceptable difference. MEASUREMENTS AND RESULTS: Continuous was correlated with bolus CO, with a correlation coefficient of r(2)[Symbol: see text]=[Symbol: see text]0.68. (p<[Symbol: see text]0.01). The Bland-Altman analysis demonstrated an objective mean bias of 0.33[Symbol: see text]+/-[Symbol: see text]0.6 l[Symbol: see text]min(-1) (confidence interval of -0.87[Symbol: see text]-[Symbol: see text]1.58) with 34% of measured values falling outside of the clinically acceptable limits. CONCLUSION: Our results suggest that, in the first 6[Symbol: see text]h after CPB, continuous and bolus CO determinations are not interchangeable; one third of the values obtained by continuous CO fell outside the strict limits of clinically useful precision.