title: Effects of inspired oxygen tension on hemodynamics and pulmonary gas exchange in patients undergoing coronary artery surgery.
abstract: This study was designed to compare the effect of intraoperative administration of 100% oxygen (F1O2 = 1.0) with 50% O2 (air-O2 mixture, F1O2 = 0.5) on cardiovascular and respiratory parameters in adults undergoing coronary artery surgery. Nineteen patients were assigned to receive either F,O2 = 1.0 (group A) or F1O2 = 0.5 (group B) in a randomized fashion. Anesthesia was induced with fentanyl (15 microg/kg) and diazepam (0.1 to 0.2 mg/kg) and maintained with fentanyl (total dose 50 microg/kg) and isoflurane. A bubble oxygenator (F1O2 = 1.0) was used during cardiopulmonary bypass (CPB) in both groups. Hemodynamic and respiratory profiles were determined at specific intervals prior to incision, following CPB, and postoperatively. Patients ventilated with F1O2 = 0.5 were well oxygenated at measured intraoperative intervals (PaO2 range 90 to 268 mmHg, saturation 95% to 99%), with adequate mixed venous O2 levels (PvO2 range 35 to 65 mmHg, saturation 63% to 89%). Compared with patients receiving F1O2 = 1.0, those receiving F1O2 = 0.5 had significantly greater increases in cardiac index (CI) (mean +/- SEM B: 87% +/- 18% v A: 26% +/- 12%) and stroke index (B: 10% +/- 5% increase vA: 14% +/- 7% decrease), and a larger decrease in peripheral resistance (B: 38% +/- 7% v A: 4% +/- 12%) at postoperative day 1 relative to preincision values (P < 0.05). At postoperative day 1, both groups had an elevated alveolar-to-arterial O2 gradient (A: 55% +/- 19% v B: 48% +/- 17% increase) and shunt fraction (A: 58% +/- 28% v B: 99% +/- 35% increase). Although O2 consumption increased similarly in both groups at postoperative day 1 relative to preincision values (A: 91% +/- 23% v B: 113% +/- 16%), O2 delivery was enhanced more in group B than in group A (67% +/- 17% v 20% +/- 13% increase, respectively, P < 0.05). The data suggest that significant hemodynamic derangements may occur with hyperoxia and that intraoperative administration of 50% O2 may be more appropriate during coronary artery surgery.
authors.affiliation: Departments of Anaesthesia, Montreal Heart Institute, and McGill University.
authors.forename: C E
authors.initials: CE
authors.lastname: Smith
authors.forename: J G
authors.initials: JG
authors.lastname: Maille
authors.forename: G
authors.initials: G
authors.lastname: Tousignant
mesh_terms: D001026:Coronary Artery Bypass; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D014655:Vascular Resistance
chemical_list: D010100:Oxygen