Continuous cardiac output monitoring after cardiopulmonary bypass: acomparison with bolus thermodilution measurement

Bendjelid, Karim ; Schütz, Nicolas ; Suter, Peter ; Romand, Jacques-Andre

In: Intensive Care Medicine, 2006, vol. 32, no. 6, p. 919-922

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    Summary
    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: A20-bed surgical ICU at auniversity hospital. Patients: Fourteen deeply sedated, ventilated, post-cardiac surgery patients, all equipped with apulmonary artery catheter. Interventions: Six hours after the end of the CPB, 56 simultaneous bolus and continuous measurements were compared by alinear regression analysis and Bland-Altman analysis. Bolus CO was estimated by averaging triplicate injections of 10 ml room-temperature NaCl 0.9%, delivered randomly during the respiratory cycle. Astringent maximum difference of 0.55 l min—1 (about 10% of the mean bolus measured) was considered as aclinically acceptable agreement between the two types of measurements. To be interchangeable the limits of agreement (± 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 acorrelation coefficient of r2 = 0.68. (p< 0.01). The Bland-Altman analysis demonstrated an objective mean bias of 0.33 ± 0.6 l min-1 (confidence interval of -0.87 - 1.58) with 34% of measured values falling outside of the clinically acceptable limits. Conclusion: Our results suggest that, in the first 6 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