[Continuous monitoring of critical patients with a newly developed pulmonary arterial catheter. A cost analysis].
The introduction of flow-directed pulmonary artery (PA) catheters has helped to improve our knowledge of cardiovascular physiology. There have been several developments of this equipment in recent years, including continuous monitoring of mixed-venous O2 saturation (SvO2) and cardiac output (CO). The high purchase price, however, is an obstacle to its use in the critically ill. The aim of the present study was to analyse the actual costs of these devices in comparison to standardly used intermittent monitoring of SvO2 and CO. METHODS. Thirty critically ill patients in a surgical intensive care unit (ICU) were prospectively studied. PA catheter monitoring was indicated by physicians who were not involved in the study. The patients were randomly allocated to one of the following groups: 1. a standard PA catheter was used, and SvO2 and CO were intermittently measured 6 times a day on a routine basis and additionally when necessary from the clinical point of view; 2. SvO2 was continuously measured using a fiberoptic PA catheter; and 3. CO was continuously monitored using a newly developed PA catheter. Costs for the catheter equipment and laboratory analyses (SvO2) were calculated and the durations of intermittent monitoring techniques were measured. Costs for the 'hardware' (monitor, blood gas analyser) were not taken into account. SvO2 was measured by the ICU staff using an ICU-owned blood gas analyser (4.78 DM/analysis) and by a central laboratory unit, which had to be paid for its analyses (30.50 DM/analysis), respectively. RESULTS. The groups were comparable with regard to their demographic data. A total of 378 intermittent measurements of SvO2 and 449 mean CO measurements (1611 single bolus CO measurements) were carried out in the patients in whom a standard PA catheter was inserted. For daily calibration, a total of 50 single SvO2 measurements were done in the group in which SvO2 was continuously monitored. A total of 27.7 h were spent for intermittent SvO2 measurements (time range of one analysis using the ICU-based blood gas analyser: 4.0 to 7.9 min); intermittent CO monitoring took a total of 14.2 h (time range of one mean CO measurement: 1.6 to 3.0 min). When blood gases were analysed by a central laboratory unit, costs for intermittent SvO2 were tremendously higher than when monitored continuously. CONCLUSION. Monitoring devices that provide us with continuous information on the patient's state may have advantages in the management of the critically ill. Whether the patient's 'outcome' can be improved by monitoring SvO2 and CO continuously was not addressed by the present study. Instead, this study focused on the question of whether these devices are more cost-intensive than standard PA catheter monitoring systems. Costs for laboratory analyses can blunt the advantage of lower costs for the standard PA catheter. Intermittent (standard) monitoring of SvO2 and CO was significantly more time-consuming than the continuous methods. It can be summarised that although purchase costs for the more advanced PA catheters are higher than for standard PA catheters, the use of these continuous monitoring devices in the critically ill can be justified from a financial point of view.