Assessment of the clinical utility of an ultrasonic monitor of cardiac output (the USCOM) and agreement with thermodilution measurement.
OBJECTIVE
To assess the clinical utility of an ultrasonic monitor of cardiac output (USCOM), its reliability in tracking cardiac output (CO) changes and agreement with thermodilution (TD) measurements of CO.


METHODS
Prospective comparison study.


METHODS
55 adults undergoing thermodilution (TD) CO monitoring in a cardiothoracic or general intensive care unit between December 2006 and December 2007.


METHODS
USCOM and TD measurements of CO on two occasions in each patient were compared by Bland-Altman analysis for bias and limit of agreement. A mean percentage error <30% was considered acceptable. Per cent change in cardiac index (CI) was determined by each method. Doppler profiles obtained by the USCOM were assessed against an ideal standard ("acceptable").


RESULTS
55 patients had measurements on 110 occasions, but Doppler waveforms were not obtained on 18 of these (16%), leaving 39 patients with paired comparisons for analysis (including 27 men; mean age, 64.7 [SD, 14.5] years). Mean TD CI was 3.4 +/-1.0L/min/m(2) (range, 2.0-6.0L/min/m(2)). The bias was 0.6L/min/m(2) (95% confidence limits [CLs], 0.4-0.8 L/min/m(2)), and the mean percentage error was 56% (95% CLs, 45%-65%). Twenty-two Doppler profiles (28%) were classed as acceptable; the mean percentage error for these was 62% (95% CLs, 38%-65%). On 15/19 occasions (74%) where TD CI changed > 15%, USCOM CI also changed >15%, but three of these changes (16%) were in the opposite direction. USCOM CI changed >15% on 9/20 occasions (45%) when TD CI did not.


CONCLUSIONS
Poor agreement with TD and a substantial rate of failure to obtain an USCOM measurement suggest that this device is unsuitable as a monitoring tool in intensive care.
Boyle
Martin
M
Department of Intensive Care, Prince of Wales Hospital, Sydney, NSW. martin.boyle@sesiahs.health.nsw.gov.au
Steel
Liz
L
Flynn
Gordon M
GM
Murgo
Margherita
M
Nicholson
Lisa
L
O'Brien
Maureen
M
Bihari
David
D
D000368:Aged; D006348:Cardiac Surgical Procedures; D015150:Echocardiography, Doppler / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006331:Heart Diseases / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume / Q000502:physiology*; D013815:Thermodilution / Q000706:statistics & numerical data*