The aim of this prospective randomized study is to evaluate blood loss caused by laboratory blood draws in patients in the paediatric ICU (Intensive Care Unit) of a tertiary hospital among two groups of patients with established long-term or mid-term intravenous access. In the first group, patients will undergo blood draws using the standard method. In the second group of patients, blood draws will be performed using a closed system.

Anaemia is one of the most common comorbidities among patients hospitalized in intensive care units. Hospital-acquired anaemia (HAA) is a newly developed anaemia that occurs during hospitalization in patients who were not anaemic prior to admission. Patients with HAA have a higher risk of developing complications such as infections, muscle weakness, and neurocognitive developmental disorders; an increased incidence of blood and blood product transfusions (and related complications); longer hospital stays, and higher morbidity and mortality. According to available data, the incidence of anaemia in adults hospitalized in the ICU ranges from 40 to 74%. There a feq data describing anemia in critically ill pediatric patients, with the estimated incidence being up to 50%.

The etiology of HAA is multifactorial and is related to the severity of the underlying disease (sepsis, coagulation disorders, bleeding, renal failure, malnutrition, bone marrow suppression, decreased erythropoietin production, etc.). Another factor contributing to the development of anaemia in critically ill patients is iatrogenic blood loss caused by blood draws for laboratory testing.

In addition to the standard blood collection method, closed-loop sampling (in-line sampling) can also be used, with studies in adult patients showing a reduction in the amount of blood drawn, ranging from 20 to 80% after its implementation.

Inclusion Criteria:

• Signed informed consent for the study.
• Patients with established intravenous access: CVC (Central Venous Catheter), CICC (Centrally Inserted Central Catheter), PICC (Peripherally Inserted Central Catheter), MVC (Midline Venous Catheter), venous port, from which blood can be drawn.
• Anticipated length of stay in the ICU more than 24 hours

Exclusion Criteria:

• Age outside the specified range.
• Peripheral venous access only.
• Anticipated length of stay in the ICU less than 24 hours.
• Organ donors.
• Lack of consent from the legal representative/patient.

Patients will be randomized into two groups: a group with standard blood sampling technique and a group with closed technique blood sampling by using randomizing software.