Nebulized Ketamine Plus Standard Care vs. Standard Care Alone in Moderate to Severe Asthma Exacerbations

Inclusion Criteria: 1. Adults aged 18 years or older presenting to the Emergency Department with a clinical diagnosis of moderate to severe asthma exacerbation based on SIGN (Scottish Intercollegiate Guidelines Network) criteria. 2. PEFR between 33% and 75% of predicted value or personal best, as measured using a peak flow meter. 3. Stable vital signs as deemed by the treating physician 4. Alert and oriented, able to understand the study purpose and provide informed consent. 5. Not requiring immediate advanced airway intervention, including intubation or emergency non-invasive ventilation. Exclusion Criteria: 1. Known hypersensitivity or allergy to ketamine or any component of the nebulized solution. 2. History of psychosis, schizophrenia, or other severe uncontrolled psychiatric disorders. 3. Uncontrolled hypertension, defined as systolic BP \> 180 mmHg or diastolic BP \> 110 mmHg on two consecutive readings at least 5 minutes apart, despite initial ED management. 4. Hemodynamic instability, including persistent hypotension (SBP \< 90 mmHg) or tachyarrhythmias requiring urgent treatment. 5. Significant chronic lung disease, including: * COPD with frequent exacerbations or baseline FEV₁ \< 50% predicted * Interstitial lung disease (ILD) * Clinically significant bronchiectasis with baseline productive cough or infection 6. Pregnancy or currently breastfeeding. 7. Home BiPAP use or requirement for non-invasive ventilation (e.g., BiPAP/CPAP) during the ED visit (Note: isolated home CPAP for sleep apnea without daytime symptoms is acceptable). 8. Current intubation or imminent need for mechanical ventilation based on clinical judgment. 9. Severe cardiac disease, including decompensated heart failure, recent myocardial infarction (\<6 weeks), or known severe valvular disease. 10. Any other medical, surgical, or psychiatric condition that in the opinion of the investigator would place the patient at undue risk from study participation or interfere with the interpretation of study results.