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Mendoza, Rizielle Anne S.

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Critical Care Nursing

Nurse-determined assessment of cardiac output comparing a non-invasive cardiac

output device and pulmonary artery catheter: A prospective observational study

By Corley, A., Barnett, A.G., Fraser, J.F.

International Journal of Nursing Studies

Background:

I chose this topic because as what I have read, there is no study conducted yet thatinvestigated the utilization of ICU nurses of the USCOM to determine CO. Also, I was intrigued

by the title since what is taught in school is that pulmonary artery catheter is standard way of

measuring CO. USCOM is never taught or heard and relatively new to student nurses like us.

Summary:

Monitoring the hemodynamic status of the critically ill patient is an integral part of critical

care nursing. It ensures optimal diagnosis, organ support and definitive management.

Measurement of cardiac output (CO) in particular has been shown to improve outcomes in

patients with low CO states and those in sepsis. What is known today is that CO can bemeasured by the pulmonary artery catheter (PAC) using a thermodilution technique or the Fick

equation with supplemental blood gas analyses. But these methods bring different

complications like pulmonary artery rupture and infections and these problems led to the

increasing use of less invasive methods to measure CO. One example of this less invasive

method is the Ultrasonic Cardiac Output Monitor or USCOM which is currently in use across

Australia, Asia, Europe and the United States. It is a noninvasive continuous wave (CW)

Doppler device designed to measure trans-aortic and trans-pulmonary CO. USCOM also allows

the bedside ICU RN to independently measure CO and act on the measures if provided with a

structured algorithm to follow.

The aim of the study is to compare CO measurement using USCOM operated by a non-echocardiograhically trained ICU Registered Nurse with the conventional pulmonary artery

catheter (PAC) using both thermodilution and Fick methods. This is a prospective observational

study conducted at a tertiary level cardiothoracic hospital in Australia. All data were collected

between the period of April 2006 and March 2007 and 30 participants consented to be included

in the study.

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The results showed that in 6 of 30 patients,an adequate USCOM signal was not achieved. The

mean difference between USCOM and PAC, USCOM and Fick, and Fick and PAC CO were

small across a range of outputs from 2.6 L/min to 7.2 L/min. Signal acquisition time reduced on

average by 0.6 min per measure to less than 10 min at the end of the study.

The study also found out that the mean time to acquire USCOM CO is approximately 10 min.

Given that the method is non-invasive and is being performed by an ICU RN, this suggests cost-

effectiveness ramifications for clinical practice when compared to PAC and Fick. The learning

curve for operation of the USCOM is also found to be satisfactorily short in a user without formal

ultrasound experience.

Conclusion:

The USCOM measures of CO in spontaneously breathing heart failure and pulmonary

hypertension patients operated by a non-echocardiographically trained RN were comparable to

measures by PAC thermodilution and Fick. This technology can be safely and effectivelyoperated by a critical care nurse with no formal ultrasound training and that the learning curve

associated with its use is short. This finding has the potential to extend the clinical role of the

ICU RN in addition to providing more rapid assessment of cardiac output and safer treatment to

the patients.

Implications:

At present, the role of the bedside ICU RN is limited to assisting with the insertion of the PAC,

documenting the data generated by the PAC and carrying out the orders of the doctors based

on the PAC data. The ICU RN does not perform any thermodilution measures therefore the

skills and knowledge of these staff nurses are not being fully utilized. With this study, theautonomy of the ICU RN can be extended and because of its non-invasive nature, ease and

portability, USCOMcould be extended well beyond the ICU into other clinical and non-clinical

areas where the evaluation of CO may be useful to guide treatment, particularly to rural and

remotepractice settings where the lack of safe and reliablemethods of CO estimation can mean

a delay in optimaltreatment.