Effect of norepinephrine dosage and calibration frequency on accuracy of pulse contour-derived cardiac output

Matthias Gruenewald,Norbert Weiler,Markus Steinfath,Ole Broch,Amke Caliebe,Jochen Renner,Patrick Meybohm,Jens Scholz,Berthold Bein

doi:10.1186/cc9967

Abstract

IntroductionContinuous cardiac output monitoring is used for early detection of hemodynamic instability and guidance of therapy in critically ill patients. Recently, the accuracy of pulse contour-derived cardiac output (PCCO) has been questioned in different clinical situations. In this study, we examined agreement between PCCO and transcardiopulmonary thermodilution cardiac output (COTCP) in critically ill patients, with special emphasis on norepinephrine (NE) administration and the time interval between calibrations.MethodsThis prospective, observational study was performed with a sample of 73 patients (mean age, 63 ± 13 years) requiring invasive hemodynamic monitoring on a non-cardiac surgery intensive care unit. PCCO was recorded immediately before calibration by COTCP. Bland-Altman analysis was performed on data subsets comparing agreement between PCCO and COTCP according to NE dosage and the time interval between calibrations up to 24 hours. Further, central artery stiffness was calculated on the basis of the pulse pressure to stroke volume relationship.ResultsA total of 330 data pairs were analyzed. For all data pairs, the mean COTCP (±SD) was 8.2 ± 2.0 L/min. PCCO had a mean bias of 0.16 L/min with limits of agreement of -2.81 to 3.15 L/min (percentage error, 38%) when compared to COTCP. Whereas the bias between PCCO and COTCP was not significantly different between NE dosage categories or categories of time elapsed between calibrations, interchangeability (percentage error <30%) between methods was present only in the high NE dosage subgroup (≥0.1 μg/kg/min), as the percentage errors were 40%, 47% and 28% in the no NE, NE < 0.1 and NE ≥ 0.1 μg/kg/min subgroups, respectively. PCCO was not interchangeable with COTCP in subgroups of different calibration intervals. The high NE dosage group showed significantly increased central artery stiffness.ConclusionsThis study shows that NE dosage, but not the time interval between calibrations, has an impact on the agreement between PCCO and COTCP. Only in the measurements with high NE dosage (representing the minority of measurements) was PCCO interchangeable with COTCP.

Highlights

Continuous cardiac output monitoring is used for early detection of hemodynamic instability and guidance of therapy in critically ill patients
The present prospective observational study investigated a large group of critically ill patients with regard to whether agreement between pulse contour-derived cardiac output (PCCO) and COTCP is affected by different NE dosages or by the time interval between calibrations
Calibrations were regularly performed by an intensive care unit (ICU) physician at defined time points (0:00 AM, 8:00 AM or 4:00 PM) with the patient in a supine position during a time period without acute hemodynamic instability using three subsequent boluses of 15 mL of ice-cold saline injected into the central venous line as proposed by the manufacturer [9]

Summary

Introduction

Continuous cardiac output monitoring is used for early detection of hemodynamic instability and guidance of therapy in critically ill patients. We examined agreement between PCCO and transcardiopulmonary thermodilution cardiac output (COTCP) in critically ill patients, with special emphasis on norepinephrine (NE) administration and the time interval between calibrations. Investigators in several studies evaluating goal-directed protocols have reported improved scenarios such as acute hemorrhage and subsequent norepinephrine (NE) administration [11], changes in vascular tone [12], increased intra-abdominal pressure [13] or time interval between calibrations [14]. The present prospective observational study investigated a large group of critically ill patients with regard to whether agreement between PCCO and COTCP is affected by different NE dosages or by the time interval between calibrations. We retrospectively evaluated whether NE dosage or severity of disease as measured by the Acute Physiology and Chronic Health Evaluation II score (APACHE II score) had an influence on calibration frequency on our intensive care unit (ICU)

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