The study seeks to determine potential correlations between ventilation and hematological alterations, contributing to a better understanding of its physiological effects and optimizing patient management in critical care settings.

• Sepsis is a clinical disorder caused by a dysregulated host response to severe infection. Pediatric sepsis remains a major public health issue and a significant cause of morbidity and mortality despite the development of standardized treatment guidelines, universal immunization programs, and advanced intensive-care organ support techniques. Severe sepsis is responsible for > 8% of all pediatric intensive care unit (PICU) admissions and causes > 4.5 million childhood deaths worldwide per year.
• However, the clinical manifestations of these infections vary from minimal symptoms to multiple organ failure and death. The currently accepted definitions of sepsis, severe sepsis, and septic shock were developed and refined using different criteria to help identify, treat, and study patients with infections who are at higher risk of significant morbidity and mortality as it is responsible of 25% of deaths in children worldwide.
• The onset, progression and outcome of sepsis are frequently associated with coagulation abnormalities, and the excessive crosstalk between inflammation and coagulation plays a vital role in these pathogenesis, which includes dysfunction of clotting cascade process, anticoagulant and fibrinolytic systems, together with related endothelial damage. Sepsis-related coagulopathy can range in severity from mildly decreased platelet counts and prolonged clotting time, which are indicative of subclinical issues, to more severe coagulopathies such as disseminated intravascular coagulation (DIC). Classic coagulation laboratory tests, such as activated partial thromboplastin time (APTT), prothrombin time (PT), and platelet count, mainly indicate signs of consumption and impaired synthesis instead of ongoing coagulopathy and change slowly in the disease course .
• Mechanical ventilation (MV) is a common practice in pediatric intensive care units (PICUs). Its utilization rate, as reported in multicenter and prospective studies in heterogeneous cohorts, varies from 20% to 50% of the patients admitted to these units. Mechanical ventilation is a crucial intervention in pediatric intensive care units (PICUs), particularly for children with sepsis. Sepsis, a life-threatening condition resulting from an uncontrolled immune response to infection, often necessitates invasive mechanical ventilation (IMV) to manage respiratory failure and maintain adequate blood gas levels. The duration of mechanical ventilation can significantly impact patient outcomes, with prolonged use associated with increased risks of complications such as ventilator-associated pneumonia (VAP) and longer hospital stays.
• Accurate and early diagnosis is important to initiate effective treatment and improve the prognosis of sepsis. Therefore, a large number of biomarkers have been developed to diagnose sepsis. Unfortunately, none of these biomarkers exhibit a high degree of sensitivity and specificity. The most common of these markers is C-reactive protein (CRP), which is a major acute-phase reactant in infection and inflammation.
• CBC is an inexpensive, simple, routine, and repeatable test used to indicate the presence of infection. Leucocyte numbers and neutrophil ratios were the most commonly used indices for detecting infections. Recently, other CBC parameters, such as NLR and PLR, have been used in children and adult patients to identify inflammatory processes. These parameters are routinely measured in all patients admitted to the PICU.
• The collaboration between mechanical ventilation and hematological parameters in pediatric sepsis patients is an area that warrants thorough investigation. Hematological abnormalities, including anemia, thrombocytopenia, and coagulopathies, are prevalent in sepsis and can adversely affect patient outcomes. Understanding how MV influences these parameters is essential for optimizing treatment protocols and improving prognoses. Despite the high incidence of MV in Egyptian PICUs, there is a gap in research focusing on its impact on hematological profiles in this demographic. Addressing this gap could lead to enhanced clinical practices and better patient outcomes in pediatric sepsis care.

Inclusion Criteria:

• 1- Pediatric patients aged 1 month to 18 years 2- Diagnosis of sepsis based on (Specify Criteria, e.g., Sepsis-3 criteria) 3- Requirement for invasive mechanical ventilation for at least 24 hours. 4- Patients admitted to the PICU during the study period. 5- Availability of complete hematological data before and during mechanical ventilation

Exclusion Criteria:

• 1- Patients with pre-existing hematological disorders (e.g., leukemia, aplastic anemia, congenital coagulopathies).

  2- Patients who received a blood product transfusion within the 7 days before MV initiation or during it.

  3- Patients with incomplete medical records or missing hematological data.

  4- Patients discharged or deceased within 24 hours of mechanical ventilation initiation.

  5- Patients who received Hematopoietic drugs during MV.

the study will take place in Pediatric Intensive Care Unit (PICU) of (Assiut University Children's Hospital) with Pediatric patients aged 1 month to 18 years and Diagnosis of sepsis