At the preoperative clinics, nurses document histories using a structured electronic questionnaire (Clinical Anesthesia Information System PreOp Clinic, Adjuvant Informatics, Flamborough, Ontario, Canada) that captures age, sex, comorbidities, and medications in a linkable data set.24 (link) Each record includes an ASA-PS score assigned by the anaesthesiologist in the clinic (Table 1 ). Case records from the clinic database were linked to the Enterprise Electronic Data Warehouse (EDW), which captures all information recorded by the hospital electronic charting system (MISYS EPR; Quadramed Corporation, Reston, VA, USA). The EDW includes information on surgeries, laboratory tests, in-hospital medications, hospital length-of-stay, in-hospital mortality, and International Classification of Diseases 10th Revision (ICD-10) diagnostic codes. Documented surgical information includes an ASA-PS score assigned by the anaesthesiologist in the operating theatre.
Description of ASA-PS classes
| ASA-PS class | Description |
|---|---|
| Class I | A normal healthy patient |
| Class II | A patient with mild systemic disease |
| Class III | A patient with severe systemic disease |
| Class IV | A patient with severe systemic disease that is a constant threat to life |
| Class V | A moribund patient who is not expected to survive without operation |
| Class VI | A declared brain-dead patient whose organs are being removed for donation |