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 mg/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 +/- 0.39 l/min for CO measured with both methods, 19 +/- 35 ml 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.