This is a double-blinded, randomised, placebo-controlled trial enrolling 60 children aged 1 to 13 years with severe asthma exacerbation. All participants will receive standard therapy. Children not responding to standard therapy will be randomised to intervention arms. Randomization will occur in a 1:1 ratio using a computer-generated Excel sequence with permuted blocks of four, stratified by age (1-5 and 6-13 years). Patients will receive either nebulized ketamine (1 mg/kg every 6 hours for 24 hours) or 0.9% normal saline placebo. Randomization codes will be maintained by the hospital pharmacy, which will prepare identical numbered packs. During working hours, the pharmacist will dispense the allocated medication; at nights and weekends, pre-prepared packs will be stored securely in the PHDU/PICU under the supervision of the nursing in-charge. Blinding will be maintained for patients, clinicians, and outcome assessors. PRAM scores will be recorded at baseline and at 20, 60, 90, and 120 minutes post-dose. The primary outcome is pediatric respiratory assessment measure (PRAM) score change. Secondary outcomes include need for NIV or intubation and HDU/PICU length of stay.