Incidence, predictors and outcomes of postoperative coma: an observational study of 858,606 patients

Coma is a state of profound unresponsiveness that can occur as a serious perioperative complication. The study of risk factors for, and sequelae of, postoperative coma has been limited due to the rarity of the event.

To determine the incidence, risk factors and impact of postoperative coma in a large patient population.

Observational study using a prospectively gathered national dataset.

Data from 858 606 patients were analysed.

The incidence of postoperative coma of more than 24-h duration was identified. Logistic regression was used to identify independent predictors and develop a risk model of postoperative coma in derivation and validation cohorts; 30-day mortality was also analysed.

The incidence of postoperative coma was 0.06%. Multivariate analysis revealed the following independent predictors: liver disease, systemic sepsis, age at least 63 years, renal disease, emergency operation, cardiac disease, hypertension, prior neurological disease, diabetes mellitus and BMI 25 to 29.99 kg m (protective). These predictors were incorporated into a risk index classification; odds ratios for postoperative coma increased from 2.5 with one risk factor to 18.4 with three. Coma was associated with 74.2% all-cause mortality; coma associated with cardiac arrest had a 1.9-fold higher mortality.

This is the largest study of postoperative coma ever reported and will be useful for determining risk of coma of more than 24 h duration when evaluating an unresponsive patient following surgery. Data on prognosis will aid medical and ethical decision-making for the comatose surgical patient.