The primary purpose of this study is to assess the status of vitamin A in critically ill children with sepsis and its association with the ill severity. The second purpose is to evaluate the performance of three tools in predicting mortality in our population which are used for measuring the illness severity in pediatric intensive care units.

Sepsis is a worldwide health problem, resulting in million of deaths each year. Sepsis caused by infectious diseases is also a common cause of death in children, and infectious diseases account for more than 50% of the deaths. The prevalence of sepsis and severe sepsis in children steadily rose in past decade. Although tremendous resources and efforts were consumed for the disease, the mechanism of sepsis is still unknown. However, sepsis 3.0 recommended that sepsis should be defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Study found that sepsis is characterized by a hyperinflammatory immune response in early phase and suppression of immune system in the later phase of sepsis. There are 10% of the deaths in the early phase due to overwhelming inflammation presenting with fever, shock, and multiorgan failure, while 30% of deaths caused by superinfection occur in the later phase.

Vitamin A, one of lipid soluble vitamins, plays an important role in immune system. Vitamin A deficiency increases the risk of infection, and vitamin A deficiency is highly prevalent among children, especially in developing country. Vitamin A is essential for T cells differentiation, induced regulatory T cells (iTregs) and Th17 cells balance, and orchestrating immune responses, etc, which contribute to the immune response in patients with sepsis.Our previous studies revealed that vitamin A deficiency presented in children with enterovirus 71 (EV71) infection was associated with reduced immunity and more severe illness.So we hypothesize that vitamin A or vitamin A deficiency may play an essential role in sepsis. However, data on status of vitamin A or prevalence of vitamin A deficiency in children with sepsis is limited.We conduct a study to to assess the status of vitamin A in critically ill children with sepsis and its association with the illness severity.

There are three widely used score systems for measuring the illness severity in pediatric intensive care units: the pediatric risk of mortality (PRISM), the pediatric index of mortality (PIM) and the pediatric logistic organ dysfunction (PELOD) score. Though the three systems are validated in other populations, they are not commonly used in our population because lack of validation. We will evaluate the performance of the three tools in our population simultaneously in this study.

Inclusion Criteria:

• Age ≤16 years old
• Diagnose of sepsis
• Consent of both parents (or the person having parental authority in families)

Exclusion Criteria:

• Discharging against medical advise
• Age>16 years
• Condition of underlying chronic disease (hepatic, renal, cardiac,neurological, pulmonary and gastrointestinal)
• Patients with haematological malignancies and immunodeficiency

(As for evaluating the performance of the three score systems, all patients admitted to the PICU are included except adolescents >16 years of age and those patients who stayed in the PICU for < 2h.)

Patients admitted to the pediatric intensive care unit of West China Hospital of Sichuan University are screened and recruited.