2004 OPEN FORUM Abstracts
NON-INVASIVE CARDIAC OUTPUT MONITOR (NICO) vs. BOLUS THERMODILUTION CARDIAC OUTPUT (TDCO), FICK TECHNIQUE, AND CONTINUOUS CARDIAC OUTPUT (CCO)
Steven
Desjardins, RRT; Sally Whitten, RRT, Virginia Eddy, MD, Stephen
Prato, MA, Maine Medical Center, Portland, ME
Introduction:
Cardiac Output (CO) measurements provide valuable information for the
management of patients in the critical care setting. Bolus
thermodilution cardiac output (TDCO) measurements have been available
for over twenty years. Continuous cardiac output measurements (CCO)
via the pulmonary artery catheter have seen more recent clinical
application. Currently, technological advances make such analysis
possible with both a continuous and non-invasive method. NICO
(Novametrix Medical Systems, Wallingford, CT) is a continuous,
non-invasive cardiac output monitor based on the partial CO2
rebreathing indirect technique. The ratio of the change in end-tidal
CO2 (ETCO2) and CO2 excretion (VCO2), in response to a 50-second
period of rebreathing, is used to calculate cardiac output. This
study compared the measurement of CO using the NICO rebreathing
method to the currently used intermittent bolus (TDCO) and continuous
cardiac output (CCO) techniques. Traditional oxygen-Fick technique
(FICK), utilizing bedside indirect calorimetry with an arterial blood
gas sample, was also compared.
Method:
TDCO measurements were obtained from 30 critically ill, mechanically
ventilated patients in the Intensive Care Unit (ICU) and Coronary
Care Unit (CCU). Abbott Critical Care Systems (Abbott Laboratories,
North Chicago, IL) pulmonary artery catheters were inserted according
to clinical guidelines and, when required for CCO measurement, were
attached to the Abbott CCO computer. NICO Capnostat CO2 rebreathing
sensor was placed at the wye of the ventilator circuit, connected to
the NICO computer, calibrated to manufacturer’s specifications
and left in position for a minimum of 10 minutes. TDCO from the
Abbott COM-2 Cardiac Output Computer was obtained via injection of 10
cc of 5% dextrose at room temperature (23-25oC). The
recorded value for TDCO was derived from the mean of at least three
injections that were within 5% of each other. Following TDCO, if
available, a CCO measurement was recorded. NICO results were
obtained and recorded. Comparisons between NICO and TDCO were
obtained in 30 patients, while 18 patients were compared between NICO
and FICK and 11 patients between NICO and CCO. Patients with known
valvular disease were excluded from this study.
Results:
Cardiac output measurements (for all three comparisons) ranged from
2.8 to 10.l L/min. Mean TDCO measurement was 6.0 ±
1.8 L/min. and mean NICO measurement was 5.5 ±
1.6 L/min., equal to a mean difference (bias) of minus 0.5 L/min.,
(pRegression=0.0001, R2=.42). Mean FICK measurement was
5.8 ± 1.5 L/min. compared to mean
NICO of 5.4 ± 1.5 L/min., for a
mean difference of - 0.4 L/min., (pRegression =0.0006, R2=0.53).
Mean CCO was 6.2 ± 1.9 L/min.,
mean NICO was 5.6 ± 1.8 L/min., for
a mean difference of - 0.6 L/min., (pRegression =0.02, R2=0.44).
In all three cases, NICO generated CO measurements that were lower
than the comparative technique by an average of 400 to 600 mL/min.
Conclusion:
In the intensive care population, the method of determining cardiac
output, whether by TDCO, FICK, CCO or by the new technique of NICO,
yields statistically acceptable similarities between results.