Table 2.

Top five important variables of the logistic regression model and random forest model

Rank	Permutation variable importance (PVI) of logistic regression model			Gini importance of random forest model
	Standard scaler	Min-max scaler	Robust scaler	Standard scaler	Min-max scaler	Robust scaler
1	Morbidity POSSUM	Postoperative infection	Morbidity POSSUM	Charlson comorbidity index	Charlson comorbidity index	Charlson comorbidity index
2	PRBC transfusion	PRBC transfusion	Postoperative infection	Age	Age	Age
3	Mortality POSSUM	Age	PRBC transfusion	Creatinine	Creatinine	Creatinine
4	Age	Morbidity POSSUM	Mortality POSSUM	Systolic blood pressure	Systolic blood pressure	Systolic blood pressure
5	ASA class	Number of operations	Age	Morbidity POSSUM	Morbidity POSSUM	Morbidity POSSUM

ASA, American Society of Anaesthesiology; PRBC, packed red blood cell