Assessment of intrathoracic blood volume as an indicator of cardiac preload: Single transpulmonary thermodilution technique versus assessment of pressure preload parameters derived from a pulmonary artery catheter

Objective: To analyze the clinical value of a new device (PiCCO) for cardia c output measurement and volume preload parameter assessment, based on tran spulmonary thermodilution technique, as an alternative to the pulmonary art ery thermodilution technique and assessment of pressure preload parameters derived from the pulmonary artery catheter. Design: Prospective, controlled, clinical study. Setting: University hospital. Participants: Eighteen patients with ejection fraction >50% undergoing coro nary artery bypass graft surgery. Interventions: A baseline measurement was performed after induction of anes thesia under clinical steady-state conditions (T1). Hypovolemia, defined as central venous pressure (CVP) <10 mmHg and pulmonary capillary wedge press ure (PCWP) <12 mmHg, was treated by infusion of 6% hydroxyethyl starch 200/ 0.5 (7 mL/kg). After 10 minutes, a second measurement (T2) was performed. Measurements and Main Results: The mean difference (bias) between transpulm onary thermodilution cardiac output and pulmonary artery thermodilution car diac output did not differ at the 2 sample points. Changes in pressure prel oad parameters of the pulmonary artery catheter (CVP, PCWP) did not correla te with changes in cardiac output or stroke volume, whereas changes in volu me preload parameter intrathoracic blood volume (ITBV) of the PiCCO correla ted significantly with changes in cardiac output and stroke volume (r = 0.5 5, p < 0.05; r = 0.62, p < 0.01). Conclusion: These results suggest that increased cardiac preload is more re liably reflected by ITBV than by CVP or PCWP. The assessment of ITBV by the transpulmonary single indicator dilution technique is an interesting alter native to the pressure preload parameters. Copyright (C) 2001 by W.B. Saund ers Company.