American Society of Anesthesiologists Score: still useful after 60 years? Results of the EuSOS Study.
OBJECTIVE
The European Surgical Outcomes Study described mortality following in-patient surgery. Several factors were identified that were able to predict poor outcomes in a multivariate analysis. These included age, procedure urgency, severity and type and the American Association of Anaesthesia score. This study describes in greater detail the relationship between the American Association of Anaesthesia score and postoperative mortality.


METHODS
Patients in this 7-day cohort study were enrolled in April 2011. Consecutive patients aged 16 years and older undergoing inpatient non-cardiac surgery with a recorded American Association of Anaesthesia score in 498 hospitals across 28 European nations were included and followed up for a maximum of 60 days. The primary endpoint was in-hospital mortality. Decision tree analysis with the CHAID (SPSS) system was used to delineate nodes associated with mortality.


RESULTS
The study enrolled 46,539 patients. Due to missing values, 873 patients were excluded, resulting in the analysis of 45,666 patients. Increasing American Association of Anaesthesia scores were associated with increased admission rates to intensive care and higher mortality rates. Despite a progressive relationship with mortality, discrimination was poor, with an area under the ROC curve of 0.658 (95% CI 0.642 - 0.6775). Using regression trees (CHAID), we identified four discrete American Association of Anaesthesia nodes associated with mortality, with American Association of Anaesthesia 1 and American Association of Anaesthesia 2 compressed into the same node.


CONCLUSIONS
The American Association of Anaesthesia score can be used to determine higher risk groups of surgical patients, but clinicians cannot use the score to discriminate between grades 1 and 2. Overall, the discriminatory power of the model was less than acceptable for widespread use.
Unidade de Cuidados Intensivos Neurocríticos, Hospital de São José, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
Rui Paulo
RP
Moreno
Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Londres, Reino Unido.
Rupert
R
Pearse
Terapia Intensiva, St. George's Healthcare NHS Trust and St. George's, University of London, Londres, Reino Unido.
Andrew
A
Rhodes
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000776:Anesthesiology; D015331:Cohort Studies; D003663:Decision Trees; D005060:Europe; D005260:Female; D005500:Follow-Up Studies; D006304:Health Status; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000401:mortality*; D012955:Societies, Medical; D014481:United States