Risk factor	P
Pre-operative anaemia	<0.001
Malnutrition	<0.001
High score of ASA (American Society of Anesthesiologists)	0.029
Prolonged pre-operative hospitalization	0.001
Prolonged operation time	0.001
Blood transfusion	<0.001
ICU hospitalization	<0.001
High National Nosocomial Infections Surveillance (NNIS) risk index	<0.001