Normobaric hyperoxia reduces cardiac index in patients after coronary artery bypass surgery

Objective: The purpose of this study was to assess the hemodynamic changes in response to normobaric hyperoxia in patients immediately after coronary artery bypass surgery. Design: Observational study. Setting: Single-center university hospital. Participants: Patients immediately after coronary artery bypass surgery. Intervention: Change of fractional inspired oxygen concentration from baseline (<= 0.60) to 1.0 and return to baseline. Measurements and Main Results: Cardiovascular changes were assessed with a lithium dilution technique. Cardiac index decreased from 2.82 to 2.52 L/min/m(2) (10.6%). Heart rate decreased from 85.9 to 82.5 beats/min (4.0%), and the systemic vascular resistance index increased from 1,858 to 2,304 dyne/s/cm(5)/m(2) (24.1%). Stroke index or mean arterial pressure did not change significantly. On reducing the F1O2 from 1.0 to the baseline F1O2, there was significant reversal of the previous changes in heart rate and systemic vascular resistance. Heart rate increased from 82.5 to 84.0 beats/min (1.8%), and the systemic vascular index decreased from 2304 to 1932 dyne/s/cm(5)/m(2) (16.1%). The cardiac output did not return to baseline, and the mean arterial pressure decreased from 69.6 to 64.4 mmHg (7.6%). Conclusions: Exposing patients after coronary artery surgery to hyperoxia induces significant hemodynamic changes. (c) 2005 Elsevier Inc. All rights reserved.