Observational group (160 patients )

Data collection: (upon admission to ICU)~All the study subjects will be submitted to:~I) Careful clinical evaluation including:~* Demographics.~* Comorbid conditions.~* Medication usage (including intravenous fluids and vasoactive medications).~* Vital signs .~* Mental status (Glasgow Coma Score)~* SOFA (Sequential Organ Failure Assessment) score.~* Duration of antibiotics treatment.~II) Laboratory Investigations including:~* Complete blood picture (CBC): including Neutrophils and Lymphocytes count.~* Serum albumin and serum lactate.~* Prothrombin time and concentrations.~* Liver function tests (LFTs), serum creatinine and urea.~* Electrolytes, arterial blood gases.~* Highly sensitive C -reactive protein (Hs CRP).~III) Microbiological investigations:~Various body fluid cultures, including sputum, blood, and urine will be obtained to identify source of sepsis.~All investigations will be done at Ain Shams University, central lab unit.