This prospective observational cohort study aims to evaluate the predictive value of interleukin-6 (IL-6) levels and hemogram-derived inflammatory scores for morbidity and in-hospital mortality in postoperative patients admitted to the intensive care unit (ICU). IL-6 levels and inflammatory indices will be assessed at ICU admission and at 24 hours using data obtained from routine clinical care. Associations between these biomarkers and clinical outcomes, including mortality, morbidity, antibiotic use, and duration of mechanical ventilation, will be evaluated after adjustment for illness severity.

This prospective observational cohort study will include adult postoperative patients admitted to the intensive care unit (ICU). The study is purely observational, and no additional interventions or procedures will be performed beyond routine clinical care.

Interleukin-6 (IL-6) levels will be recorded at ICU admission (0 hour) and at 24 hours. Routine laboratory parameters obtained during standard clinical follow-up, including complete blood count, C-reactive protein (CRP), and albumin levels, will be used to calculate hemogram-derived inflammatory indices such as the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), neutrophil-to-monocyte ratio (NMR), CRP-to-albumin ratio (CAR), CRP-to-lymphocyte ratio (CLR), and the modified systemic inflammation score (mSIS).

Illness severity and comorbidity burden will be assessed using established scoring systems, including the Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), and the Charlson Comorbidity Index. Demographic characteristics, surgical variables (type and duration of surgery), and clinical outcomes will be prospectively recorded.

The primary objective is to evaluate the predictive value of IL-6 levels and inflammatory indices for in-hospital mortality. Secondary objectives include associations with postoperative morbidity, infectious complications, antibiotic use, duration of mechanical ventilation, organ dysfunction, and ICU length of stay. Changes in IL-6 levels and inflammatory indices between ICU admission and 24 hours will also be explored.

Inclusion Criteria:

• Age ≥ 18 years
• Postoperative patients admitted to the ICU
• Availability of complete clinical and laboratory data at ICU admission and at 24 hours
• Provision of informed consent by the patient or legally authorized representative

Exclusion Criteria:

• Age < 18 years
• Thoracic surgery patients
• Cardiac surgery patients

The study population consists of adult postoperative patients (aged 18 years and older) admitted to the intensive care unit. Patients are enrolled prospectively and followed using routinely collected clinical and laboratory data obtained at ICU admission and at 24 hours. Cardiac and thoracic surgery patients are excluded.