The measurement of right ventricular ejection fraction by thermodilution

Abstract

SummaryThermodilution measurements of cardiac output and right ventricular ejection ,fraction were obtained using a rapid rcqwnsi~ pulmonnrji artery catheter. Vulues were compared when injectate M'US administered via either a cannula within the right internul .jugular vein or the dedicated right atrial port of' the pulmonary artery catheter. Meun ( S D ) bias ,for curdiac output and right ventricular qjc~ction ,fraction measurements were 0.08 (0.32) 1.min-I and 2.6 (6.6) % respectively. We therefore conclude that both injectate techniques will provide similar vulues.for cardiac output but dissimilar values j i w right ventricular ejection jiruction nieasurement . Key wordsCurdiuc output. Ejection fruction. Pulmonarj> urtrry catheter. Thermistor. Therniodilution.The measurement of cardiac output (QT) by thennodilution has been extensively used for monitoring the critically ill [ 1-31, Such thermistor-tipped catheters have a multilumen construction and a dedicated lumen for injectate administration. This injectate channel outlet is designed to lie either within the thoracic caval system or right atrium [I] yet valid estimates of QT can also be obtained using any cannula sited within a central vein [4-71. A rapid response thermistor (time constant 95 ms) within a pulmonary artery catheter enables direct measurement of right ventricular ejection fraction (RVEF) [8, 91. The calculation of RVEF assumes conservation of heat energy during consecutive ventricular systoles provided there is adequate mixing of the cold injectate bolus in the right atrium.The purpose of this study was to compare the thermodilution measurement of both QT and RVEF using either the dedicated injectate lumen or a cannula placed within the right internal jugular vein. ventricular ejection fraction < 30%), were studied after elective cardiac surgery. Before surgery, an 8.5 F r percutaneous introducer sheath (American Edwards Laboratories, CA) was placed in the right internal jugular vein through which a REF-ITM balloon-tipped flow-directed pulmonary artery catheter (Model 93A-43 I H-7.5F, American Edwards Laboratories, CA) was advanced. Pressure waveform monitoring of both right atrial and pulmonary arterial channels confirmed correct placement and the catheter position was subsequently confirmed by chest X ray. After surgery we made a series of measurements of QT and RVEF. Bolus (10 ml) injections of iced 5% dextrose solution were delivered through either the right atrial injection lumen of the pulmonary artery catheter or the introducer sheath. Six measurements were taken (three right atrial port, three introducer sheath) over a 5 min period using a closed injectate system (American Edwards Laboratories, CA). Mean values for right atrial port and introducer sheath were then calculated. Five paired measurements of QT and RVEF were obtained over a 5 h period for each patient.The mean bias (right atrial port-introducer sheath) was calculated for both QT and RVEF data and the differences between the two injectate techniques plotted against the me...

Behaviour and stability of thermodilution signals in a closed extracorporeal circuit: a bench study

“…This might indicate there still is a redistribution of injectate at this position, although rise time and peak temperature do not seem to be affected. This is in line with previous findings, where distance to the injectate port and catheter positioning impacted right ventricular indices [ 21 , 22 ]. Our study confirms that changes in the exponential decay, depending on flow and catheter position, will inherently impact estimates of ventricular function.…”