 2. Data were collected on all patients admitted into different hospitals during the study period. The following information was recorded:demographic characteristics and admission category whether medical, scheduled surgery, nonoperative trauma, or unscheduled surgery, presence of preexisting organ insufficiency,using definitions included in the Acute Physiology and Chronic Health Evaluation APACHE II score11; co- morbidities and the estimated prognosis of any preexisting underlying disease, following the classification of McCabe and Jackson. 