Objectives:Surgical stress and pain affect the respiratory condition of patients and can cause complications that affect morbidity and mortalityin cardiac surgeries. The authors studied the effect of thoracic epidural analgesia (TEA) versus traditional intravenous analgesia on postoperativerespiratory mechanics in cardiac surgery.Design:Retrospective, observational study.Setting:Single, university hospital.Participants:Patients undergoing cardiac surgery.Interventions:Comparing the postoperative respiratory effects of TEA with bupivacaine or intravenous analgesia with tramadol or paracetamolor dexmedetomidine.Measurements and Main Results:A total of 1,369 patients were screened, and 1,280 patients were enrolled in the study. Postoperative sedationand analgesia level, extubation times, respiratory complications, lengths of intensive care and hospital stay, morbidity, and mortality werecompared.Additional sedative and analgesic drug requirement in the TEA group (25.3% and 60.1% respectively) were significantly lower than the intra-venous group (41.4% and 71.8%, respectively; p<0.001 and p<0.05, respectively). Extubation time in the TEA group also was significantlylower than the intravenous group (p<0.01). Respiratory complication and hospital stay in the TEA group were lower than intravenous group (p<0.05).