[Continuous measurement of cardiac output based on the Fick principle in cardiac anesthesia]

With the development of fiberoptic and pulse oximetry, as well as the development of the more modern methods of oxygen consumption measurements, the online monitoring of Fick cardiac (FCO) output has become possible in the clinical treatment routine. The aim of this study was to compare fiberoptically measured mixed venous oxygen saturation with values from blood samples and continuously determined Fick cardiac output with intermittent thermodilution cardiac output (TCO). Ten patients undergoing coronary artery bypass grafting were measured during the perioperative period. Total body oxygen consumption was determined with a metabolic monitor (Deltatrac Datex) from respiratory gases. Arterial oxygen saturation was assessed by pulse oximetry (Nellcor). Mixed venous oxygen saturation was measured by a balloon tipped pulmonary artery fiberoptic catheter (Opticath) attached to an electronic device based on three wavelengths (Oximetrix cardiac output monitor). Hemoglobin, Methemoglobin and CO-hemoglobin were determined from intermittent blood samples by in vitro analysis. FCO was calculated from corresponding differences in arterial mixed venous oxygen and total body oxygen consumption. TDCO values were calculated from microcomputer recordings of the thermodilution data by monoexponential curve-fitting with respect to baseline drift. A significant systematic difference between FCO and TCO was observed. FCO exceeded TCO on average by 0.42 +/- 0.12 l/min. The limits of confidence (95%) were 0.18 to 0.66 l/min. There was no systematic difference between mixed venous saturation measurements with the fiberoptic system and from blood samples. The cardiac output values derived from fiberoptic and pulse oximetry can be considered sufficiently reliable for clinical purposes.(ABSTRACT TRUNCATED AT 250 WORDS)