Predictive factors for usefulness of fiberoptic pulmonary artery catheter for continuous oxygen saturation in mixed venous blood monitoring in cardiac surgery

The main goal of this prospective study was to identify among cardiac surgery patients, usually monitored through a standard pulmonary artery catheter (PAC), those in whom a fiberoptic catheter oximeter to measure oxygen saturation in mixed venous blood (SVO(2)PAC) would be most useful. Data from 286 patients who underwent coronary artery bypass graft (50%) or valvular surgery were recorded, including ASA physical status, 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 anesthesiologist in charge graded the usefulness of SVO(2)PAC, and another anesthesiologist carried out a blindly controlled overall evaluation. Usefulness was defined as the presence of a change in therapeutic maneuver triggered solely by continuous SVO2 data that would not have occurred based on other routine parameters. SVO2 was also considered useful if earlier recognition of significant adverse events occurred. SVO(2)PAC was useful in 57% of the patients. Independent predictive factors (multivariate analysis) for the perioperative usefulness of SVO2 in 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 graft 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 arteries showed borderline significance (P < 0.06). Independent predictive factors for perioperative usefulness of SVO2, in the valvular population were mitral pathology (P < 10(-5)) and ASA class greater than or equal 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 care unit duration and hospital stay in the useful group was prolonged compared 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. Mortality was comparable in the groups despite their different degree of illness and was reduced when taking into account the predictive and observed mortality provided by the PS. This study defined independent preoperative factors associated with SVO(2)PAC monitoring and proposed a cutoff point above which SVO2 may be useful.