Although IV salbutamol is frequently used in children in a wide range, pharmacodynamic data are scarce. To date, there is an insufficient evidence base to guide initial and subsequent dosing recommendation for its IV use in children. Especially the need for a loading dose needs to be addressed. Therefore, pharmacodynamic and kinetic data are needed to guide initial dosing strategies of IV salbutamol in children. To assess the efficacy of a loading dose of intravenous salbutamol in children admitted to a PICU for severe acute wheeze or severe acute asthma. Efficacy is measured by the reduction in asthma score (Qureshi) at 1 hour after administration of the loading dose, compared to placebo.

Inclusion Criteria:

• Between 2-18 years of age at moment of inclusion
• Admitted to PICU for Severe Acute Asthma or Severe acute (viral) wheeze
• Requiring administration of IV salbutamol

Exclusion Criteria:

• Patient is outside of specified age range
• Patient has already received a -loading dose- of IV salbutamol in the general hospital
• Lower airway infection with consolidation on a chest X ray -Patient has Down's Syndrome
• Patient has a congenital/acquired heart defect that interferes with normal asthma treatment
• Patient has a primary/secondary immunodeficiency
• Patient has a pre-existing chronic pulmonary condition, known to mimic asthma: Cystic fibrosis, Bronchopulmonary dysplasia, Bronchiolitis obliterans