Table 2 Variables used in P‐POSSUM and O‐POSSUM equations.

Physiological score	Operative severity score
Age (years)*	Operative severity
Cardiac signs/chest radiograph	Multiple procedures†
Respiratory history/chest radiograph	Total blood loss (ml)†
Systolic blood pressure (mm Hg)	Peritoneal soiling†
Pulse (beats/min)	Presence of malignancy
Glasgow Coma Scale	Mode of surgery
Haemoglobin
White cell count (×1012/l)
Urea (mmol/l)
Sodium (mmol/l)
Potassium (mmol/l)
Electrocardiogram

*Age was regressed independently from the Physiological and Operative severity score for the enumeration of Mortality and morbidity (POSSUM).

†Risk factors not used in scoring specific for upper gastrointestinal surgery (O‐POSSUM) (used from reference 8).