EFFECT OF OXYGEN ON PULMONARY HEMODYNAMICS AND INCIDENCE OF ATRIAL-FIBRILLATION AFTER NONCARDIAC THORACOTOMY

Objective: The mechanism of postthoracotomy atrial fibrillation (AF) c ould he 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 hospit al. Participants:Twenty-four noncardiac thoracotomy patients. Interven tions: At the end of the postoperative anesthesia care unit period, th e 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 hemodyna mic Variables using a thermodilution pulmonary artery catheter, oxygen ation, concentration of plasma atrial natriuretic peptide (ANP) and Ho lter monitoring were started preoperatively and continued for the 3 po stoperative days (PODs). Systolic RV pressure (systolic RVP) and pulmo nary 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 oc curred in three patients (25%) in group P and in one patient (8%) in g roup S (not significant [NS]) without deviations in plasma ANP concent ration. On each of the 3 PODs, all patients were exposed to 60% oxygen for 15 minutes. Systolic RVP decreased significantly during the expos ure 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 imme diately after thoracotomy. Conclusion: Short episodes of AF occurred i rrespective of the length of oxygen therapy. Occurrence of AF could no t be explained by changes in RV function. Copyright (C) 1998 by W.B. S aunders Company.