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 (< or =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/m2 (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/cm5/m2 (24.1%). Stroke index or mean arterial pressure did not change significantly. On reducing the FIO2 from 1.0 to the baseline FIO2 , 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/cm5/m2 (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.