Severe Asthma Exacerbation With Rising CO2
A 9-year-old boy with a history of asthma presents to the emergency department with 2 days of worsening cough and wheeze after a viral upper respiratory infection. He has received three albuterol/ipratropium nebulizers and IV methylprednisolone 2 mg/kg. He is anxious, speaking in short phrases, RR 42/min, HR 150/min, SpO2 89% on room air, and peak expiratory flow 40% of predicted. Breath sounds are diffusely diminished with a prolonged expiratory phase and audible wheeze. He has subcostal and suprasternal retractions. A venous blood gas shows pH 7.32, PaCO2 42 mmHg, PaO2 68 mmHg, HCO3 21 mmol/L. He has not received magnesium sulfate yet.
1. Assess the severity of this exacerbation and identify warning signs. What immediate therapies should be added?
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This is a severe asthma exacerbation with impending respiratory failure. Warning signs include tachypnea (RR 42), tachycardia (HR 150), hypoxemia (SpO2 89%), PEF 40% of predicted, diminished breath sounds, and a PaCO2 of 42 mmHg. In a tachypneic asthmatic, PaCO2 should be low; a normal value signals fatigue and rising CO2. Add IV magnesium sulfate 50 mg/kg (max 2 g) over 20 minutes, continue continuous albuterol, and consider heliox (70:30) if available. Prepare for possible noninvasive ventilation or intubation; do not delay calling for senior help.
2. What are the indications for intubation in this patient, and how would you prepare?
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Indications include exhaustion, altered mental status, silent chest, worsening hypoxemia despite maximal therapy, rising PaCO2 with acidosis, apnea, or cardiac arrest. Prepare for rapid-sequence intubation with preoxygenation, ketamine for induction (bronchodilation and hemodynamic stability), and rocuronium. Use a cuffed tube, lung-protective ventilation with permissive hypercapnia, and be prepared for hypotension. Avoid histamine-releasing agents. Have a plan for difficult ventilation and consult pediatric critical care early.
3. What complications should you monitor for during treatment?
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Monitor for hypokalemia, hyperglycemia, and lactic acidosis from high-dose albuterol; arrhythmias; tremors; and rhabdomyolysis. Magnesium can cause hypotension and bradycardia, so infuse slowly with cardiac monitoring. Watch for pneumothorax or pneumomediastinum from air trapping and barotrauma. Aspiration and ventilator-associated pneumonia are risks if intubated. Track response with breath sounds, work of breathing, SpO2, and blood gases, and avoid over-sedation that can mask deterioration.