Mortality associated with anaesthesia: a qualitative analysis to identify risk factors

From a prospectively defined cohort of patients who underwent either general, regional or combined anaesthesia from 1 January 1995 to 1 January 1997 (n = 869 483), all consecutive patients (n = 811) who died within 24 h or remained unintentionally comatose 24 h after anaesthesia were classified to determine a relationship with anaesthesia. These deaths (n = 119; 15%) were further analysed to identify contributing aspects of the anaesthetic management, other factors and the appropriateness of care. The incidence of 24-h peri-operative death per 10 000 anaesthetics was 8.8 (95% CI 8.2-9.5), of peri-operative coma was 0.5 (0.3-0.6) and of anaesthesia-related death 1.4 (1.1-1.6). Of the 119 anaesthesia-related deaths, 62 (52%) were associated with cardiovascular management, 57 (48%) with other anaesthetic management, 12 (10%) with ventilatory management and 12 (10%) with patient monitoring. Inadequate preparation of the patient contributed to 30 (25%) of the anaesthesia-related deaths. During induction of anaesthesia, choice of anaesthetic technique (n = 18 (15%)) and performance of the anaesthesiologist (n = 8 (7%)) were most commonly associated with death. During maintenance, the most common factors were cardiovascular management (n = 43 (36%)), ventilatory management (n = 12 (10%)) and patient monitoring (n = 12 (10%)). In both the recovery and the postoperative phases, patient monitoring was the most common factor (n = 12 (10%) for both). For cardiovascular, ventilatory and other anaesthetic management, human failure contributed to 89 (75%) deaths and organisational factors to 12 (10%). For inadequate patient monitoring, human factors contributed to 71 (60%) deaths and organisational factors to 48 (40%). Other contributing factors were inadequate communication (30 deaths (25%) for all four aspects of the anaesthetic management) and lack of supervision (particularly for ventilatory management). Inadequate care was delivered in 19 (16%) of the anaesthesia-related deaths with respect to cardiovascular management, in 20 (17%) with respect to ventilatory management, in 18 (15%) with respect to patient monitoring and in 23 (19%) with respect to other anaesthetic management.