Mon25October0757PM 15

Measuring cardiac output by the thermodilution method:

True / False

Injecting less than the required volume of injectate leads to an over-estimation of the cardiac output Incorrect answer selected

Cardiac output measurements will be unchanged by wedging of the pulmonary artery catheter Correct

Looping of the catheter in the right ventricle may cause inaccuracies in the measurement Correct

Injection should be performed over about ten seconds Correct

The cardiac output is assessed by measuring the area under the temperature change curve Correct

Explanation

The thermodilution technique using a pulmonary artery catheter gives an accurate, repeatable measurement of cardiac output. The cardiac output is assessed by measuring the area under the curve of measured temperature change recorded at the distal end of the catheter by a thermistor. Injection should be performed smoothly over less than 4 seconds.

Inaccuracies secondary to:

Patient factors:

right heart valvular abnormalities

intracardiac shunts

arrhythmias

phase of respiration

Injectate factors:

too little injectate will lead to an over-estimation

errors in injectate temperature measurement

prolonged injection duration

Thermistor factors:

wedging or partial wedging of the catheter produces unreliable results as the cooled mixture does not make adequate contact with the thermistor

looping of the catheter reduces the distance between the injection port and the thermistor so mixing of the injectate with blood may be incomplete

thrombi on the catheter will produce an under-estimation of cardiac output)

Answer Statistics

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Average score: 73.35%

Times answered: 325