The purpose of this study is to assess the effectiveness from early infusion of norepinephrine in pediatric patients submitted to mechanical ventilation for the use of sedative and analgesics drugs.

Inclusion Criteria:

• Children, who, in the arrival or during the admission in pediatric intensive care unit, develop the need for mechanical ventilation and continuous infusion of sedatives and/or analgesics

Exclusion Criteria:

• Patients after cardiac arrest
• Patients with tracheostomy
• Patients with renal and/or hepatic failure
• Patients with previous episode of cardiac arrythmia
• Patients with mechanical ventilation forecast lesser that four days