EVALUATION OF A CONTINUOUS CARDIAC-OUTPUT AND MIXED VENOUS OXYGEN-SATURATION CATHETER IN CRITICALLY ILL SURGICAL PATIENTS

Objective: To evaluate the agreement of continuous cardiac output and mixed venous oxygen saturation measurements, obtained with a modified pulmonary artery catheter, with those values obtained by standard inte rmittent bolus thermodilution and co-oximetry. Design: Prospective, cl inical investigation. Setting: A surgical intensive care unit in a ter tiary referral center. Patients: Twenty-one adult critically iii surgi cal patients, requiring pulmonary artery catheter monitoring. Interven tions: None. Measurements and Main Results: A modified pulmonary arter y catheter capable of continuous monitoring of cardiac output and mixe d Venous oxygen saturation was used with either an 8.5-Fr or a 9-Fr in troducer, At random intervals, the continuous cardiac output measureme nt was compared with the cardiac output obtained using standard interm ittent bolus thermodilution. The system was calibrated every 24 hrs fo r mixed venous oxygen saturation monitoring. Each saturation obtained by the laboratory cooximeter was compared with that value recorded usi ng the catheter. Data points for 202 pairs of cardiac output (21 patie nts, 31 catheters) and 65 pairs of mixed venous oxygen saturation (20 patients, 28 catheters) were obtained, The bias and precision of the c ardiac output data were 0.49 and 1.01 L/min, respectively, The agreeme nt between the continuous and bolus values decreased as the cardiac ou tput increased, Heart rate did not affect the agreement between the co ntinuous and bolus techniques, The bias and precision of the mixed ven ous oxygen saturation data were -0.57% and 3.76%, respectively. The he matocrit did not affect the bias or precision of the venous saturation data over the hematocrit range observed (23.2% to 44.6%), Fewer cathe ter malfunctions were observed when the catheter was used with a 9-Fr introducer than with an 8.5-Fr introducer. Conclusions: The test cathe ter adequately measures continuous cardiac output and mixed venous oxy gen saturation in the clinical setting. Because intermittent bolus the rmodilution is not a true ''gold standard'' for cardiac output determi nation, new techniques compared with bolus thermodilution may fail to achieve accuracy expectations. A 9-Fr introducer is recommended, as fi beroptic damage may have occurred when the 8.5-Fr introducer was used.