Effect of oxygen on pulmonary hemodynamics and incidence of atrial fibrillation after noncardiac thoracotomy

Abstract

Objective: The mechanism of postthoracotomy atrial fibrillation (AF) could be related to right ventricular (RV) strain. The effect of oxygen on the occurrence of postoperative AF and on RV function was studied. Design: A prospective, randomized study. Setting: A university hospital. Participants: Twenty-four noncardiac thoracotomy patients. Interventions: At the end of the postoperative anesthesia care unit period, the patients were randomly allocated to receive 35% oxygen until either the third (P = prolonged group) or the first postoperative morning (S = short group). Measurements and Main Results: Measurement of hemodynamic variables using a thermodilution pulmonary artery catheter, oxygenation, concentration of plasma atrial natriuretic peptide (ANP) and Holter monitoring were started preoperatively and continued for the 3 postoperative days (PODs). Systolic RV pressure (systolic RVP) and pulmonary vascular resistance (PVR) increased postoperatively only in group S. Major changes in RV performance were not seen with echocardiography or the thermodilution method in any patient. Silent episodes of AF occurred in three patients (25%) in group P and in one patient (8%) in group S (not significant [NS]) without deviations in plasma ANP concentration. On each of the 3 PODs, all patients were exposed to 60% oxygen for 15 minutes. Systolic RVP decreased significantly during the exposure to 60% oxygen only in group S, but not in patients developing AF. Predictive factors for AF were a high preoperative PVR, intraoperative bleeding necessitating volume loading, and elevated systolic RVP immediately after thoracotomy. Conclusion: Short episodes of AF occurred irrespective of the length of oxygen therapy. Occurrence of AF could not be explained by changes in RV function.