MONITORING OF RIGHT-VENTRICULAR FUNCTION USING A CONVENTIONAL SLOW RESPONSE THERMISTOR CATHETER

Objective: To investigate whether determination of right ventricular end-diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF) can be performed with reasonable accuracy and reproducibility using a conventional slow response thermistor pulmonary artery catheter (CPAC) applying an adaptive algorithm. Design: To study RVEDV and RVEF simultaneously with pulmonary artery catheters equipped with slow and fast response thermistors (FRPAC) under a broad range of cardiac output. Setting: Laboratory of Institute of Experimental Surgery, Technical University. Animals: 11 anaesthetised piglets. Interventions: Hypovolemia (V-) was induced by withdrawal of blood up to 50 ml/kg, hypervolemia (V+) was produced by retransfusing blood and adding up to 30 ml/kg hydroxyethyl starch. In 5 animals in phases V-and V+ beta-adrenergic stimulation was achieved with dobutamine. Finally pulmonary artery hypertension was induced by infusion of small air bubbles. Measurements and results: Cardiac output (CO), RVEDV and RVEF were determined simultaneously with FRPAC and CPAC placed in the same pulmonary artery branch. Measurements were repeated 8 times sequentially in steady state normovolemia. A total of 130 measurements could be analysed. The coefficient of variation was 6.7+/-4.2% for CO(FRPAC) and 4.6+/-1.7% for CO(CPAC); for RVEF it was 9.7+/-6.2% (FRPAC) and 9.9+/-3.9% (CPAC); for RVEDV it was 11.6+/-4.8% (FRPAC) and 8.54+/-3.2 (CPAC). Mean difference (bias) was 0.06+/-0.391/min for CO measured with both methods, 19+/-35ml for RVEDV and -3.3+/-6.5% for RVEF. CO(CPAC) displayed a strong correlation to CO(FRPAC) (R = 0.97, p = 0.001) as well as RVEF (R for RVEF(cpAC) versus RVEF(FRPAC) = 0.90, p = 0.001). R for RVEDV(cpAC) versus RVEDV(FRPAC) was 0.67, p = 0.001. We conclude that this animal study demonstrates good agreement between RVEF and RVEDV obtained with catheters equipped with a fast response thermistor or with a conventional slow response thermistor allowing accurate monitoring of right ventricular function with a conventional pulmonary artery catheter.