Demographic and comorbidity characteristics
Basic demographic data including age, gender, date of birth, height, weight, body mass index (BMI) and American Society of Anaesthesiologists (ASA) grade was documented. Specific pre-operative conditions were grouped into comorbid groups and documented for each patient: cardiovascular (ischemic heart disease, previous coronary artery bypass grafting, previous percutaneous coronary intervention, pacemaker insertion, defibrillator insertion, previous valve repair, heart failure, cardiomyopathy, hypertension, pulmonary hypertension and atrial fibrillation), respiratory (asthma, COPD, bronchiectasis, cystic fibrosis and obstructive sleep apnoea), metabolic (type I diabetes, type II diabetes and hyperlipidaemia), autoimmune (rheumatoid arthritis, psoriasis, polymyalgia rheumatica, and systemic lupus erythematosus) and renal disease.