PREDICTIVE FACTORS FOR USEFULNESS OF FIBEROPTIC PULMONARY-ARTERY CATHETER FOR CONTINUOUS OXYGEN-SATURATION IN MIXED VENOUS-BLOOD MONITORINGIN CARDIAC-SURGERY

The main goal of this prospective study was to identify among cardiac surgery patients, usually monitored through a standard pulmonary arter y catheter (PAC), those in whom a fiberoptic catheter oximeter to meas ure oxygen saturation in mixed venous blood (SVO(2)PAC) would be most useful. Data from 286 patients who underwent coronary artery bypass gr aft (50%) or valvular surgery were recorded, including ASA physical st atus, New York Heart Association (NYHA) classification, and Parsonnet score (PS). Hemodynamic events and SVO2, changes were collected intra- and postoperatively until weaning from mechanical ventilation. The an esthesiologist in charge graded the usefulness of SVO(2)PAC, and anoth er anesthesiologist carried out a blindly controlled overall evaluatio n. Usefulness was defined as the presence of a change in therapeutic m aneuver triggered solely by continuous SVO2 data that would not have o ccurred based on other routine parameters. SVO2 was also considered us eful if earlier recognition of significant adverse events occurred. SV O(2)PAC was useful in 57% of the patients. Independent predictive fact ors (multivariate analysis) for the perioperative usefulness of SVO2 i n the whole population consisted of ASA class greater than or equal to 4 (P < 10(-5); relative risk [RR] 1.78, 1.51-2.07), mitral surgery (P < 10(-4); RR 1.72, 1.4-2.02), and NYHA score greater than or equal to 3 (P < 0.01; RR 1.66, 1.35-2.05). Independent predictive factors for the perioperative usefulness of SVO2 in the coronary artery bypass gra ft population were NYHA score greater than or equal to 3 (P < 10(-5); RR 1.90, 1.42-2.55) and ASA class greater than or equal to 4 (P < 0.01 ; RR 1.99, 1.51-2.63). The presence of three stenosed coronary arterie s showed borderline significance (P < 0.06). Independent predictive fa ctors for perioperative usefulness of SVO2, in the valvular population were mitral pathology (P < 10(-5)) and ASA class greater than or equa l to 4 (P < 0.01). The receiver operator characteristic curve assessed the predictivity of the PS. SVO(2)PAC was more useful in the group of patients with the greatest severity of illness (PS in useful group 17 .0 +/- 10.3; in nonuseful group 8.7 +/- 6.6; P < 10(-4)). Intensive ca re unit duration and hospital stay in the useful group was prolonged c ompared with the nonuseful group. Similarly, morbidity was frequent in the useful group, although it was not always significantly different from the nonuseful group according to the type of complications. Morta lity was comparable in the groups despite their different degree of il lness and was reduced when taking into account the predictive and obse rved mortality provided by the PS. This study defined independent preo perative factors associated with SVO(2)PAC monitoring and proposed a c utoff point above which SVO2 may be useful.