SummaryWe conducted a prospective study of non-cardiac surgical patients aged 70 years or more in 23 hospitals in Australia and New Zealand. We studied 4158 consecutive patients of whom 2845 (68%) had pre-existing comorbidities. By day 30, 216 (5%) patients had died, and 835 (20%) suffered complications; 390 (9.4%) patients were admitted to the Intensive Care Unit. Pre-operative factors associated with mortality included: increasing age (80-89 years: OR 2.1 (95% CI 1.6-2.8), p < 0.001; 90+ years: OR 4.0 (95% CI 2.6-6.2), p < 0.001); worsening ASA physical status (ASA 3: OR 3.1 (95% CI 1.8-5.5), p < 0.001; ASA 4: OR 12.4 (95% CI 6.9-22.2), p < 0.001); a pre-operative plasma albumin < 30 g.l )1 (OR: 2.5 (95% CI 1.8-3.5), p < 0.001);and non-scheduled surgery (OR 1.8 (95% CI 1.3-2.5), p < 0.001). Complications associated with mortality included: acute renal impairment (OR 3.3 (95% CI 2.1-5.0), p < 0.001); unplanned Intensive Care Unit admission (OR 3.1 (95% CI 1.9-4.9), p < 0.001); and systemic inflammation (OR 2.5 (95% CI 1.7-3.7), p < 0.001). Patient factors often had a stronger association with mortality than the type of surgery. Strategies are needed to reduce complications and mortality in older surgical patients. In a study of 1100 older surgical patients in three hospitals in one Australian city (Melbourne) we previously found that 208 (19%) patients had complications and 61 (6%) died within 30 days [1]. This was one of a few prospective studies to examine the association of mortality with both patient factors and defined complications across a wide range of surgical specialties [2]. Our findings were broadly consistent with the small number of published North American and European studies [3][4][5][6]. Previous studies, including ours, have found that high rates of complications were associated with prolonged hospitalisation, increased hospital costs, and mortality [1,7,8].

Cardiopulmonary bypass-induced metabolic acidosis appears to be iatrogenic in nature and derived from the effect of pump prime fluid on acid-base balance. The extent of such acidosis and its duration varies according to the type of pump prime.

Objective: To determine the incidence of postoperative complications, including 30‐day mortality rate, and need for intensive care unit (ICU) admission in older patients after non‐cardiac surgery. Design and setting: Prospective observational study of all patients aged 70 years or older having elective and non‐elective, non‐cardiac surgery, and staying at least 1 night after surgery in one of three Melbourne teaching hospitals, June to September 2004. Main outcome measures: Postoperative complications and 30‐day mortality rate. Results: 1102 consecutive patients were audited in mid 2004; 70% had pre‐existing comorbidities. The 30‐day mortality rate was 6%; 19% had postoperative complications; and 20% of patients spent at least 1 night in ICU. On multivariate analysis, preoperative factors associated with 30‐day mortality included age (odds ratio [OR], 1.09 per year over 70 years; 95% CI, 1.04–1.13; P < 0.001); increasing severity of systemic disease (American Society of Anesthesiologists physical status classification) (OR, 2.53; 95% CI, 1.65–3.86; P < 0.001); and albumin level < 30 g/L (OR, 2.23; 95% CI, 1.09–4.57; P = 0.03). Postoperative factors associated with 30‐day mortality were unplanned ICU admission (OR, 3.95; 95% CI, 1.63–9.55; P = 0.003); sepsis (OR, 2.75; 95% CI, 1.17–6.47; P = 0.02); and acute renal impairment (OR, 2.40; 95% CI, 1.06–5.41; P = 0.04). Thoracic surgery was the only surgical specialty significantly associated with mortality (OR, 3.96; 95% CI, 1.44–9.10; P = 0.008) in the multivariate analysis. Conclusion: Older patients having surgery had high rates of comorbidities and postoperative complications, placing considerable demands on critical care services. Patient factors were often stronger predictors of mortality than the type of surgery.