Internal Medicine · Year 3 · from Internal Medicine
Case 2: Acute Severe Asthma
Patient Presentation
A 24-year-old woman with a history of asthma since childhood presents with severe shortness of breath that started 6 hours ago after exposure to her friend's cat. She has used her albuterol inhaler approximately 15 times today with minimal relief. She has been hospitalized for asthma twice in the past year, including one ICU admission requiring intubation.
Vital Signs
- Blood Pressure: 135/82 mmHg
- Heart Rate: 124 bpm
- Respiratory Rate: 32/min
- Oxygen Saturation: 89% on room air
- Temperature: 37.0°C
- Peak flow: Unable to perform
Physical Examination
- General: Severe respiratory distress, sitting upright, unable to speak full sentences
- HEENT: Diaphoretic, using accessory muscles
- Cardiovascular: Tachycardic, pulsus paradoxus 18 mmHg
- Pulmonary: Poor air movement, minimal wheezing (ominous sign), no rhonchi
- Extremities: No cyanosis
Initial Workup
- ABG (room air): pH 7.38, PaCO2 42 mmHg, PaO2 58 mmHg
- Chest X-ray: Hyperinflation, no infiltrates or pneumothorax
- CBC: WBC 11,000/μL with 5% eosinophils
Clinical Image
Figure 2: Patient in tripod position with accessory muscle use during acute severe asthma attack, demonstrating typical posture to optimize respiratory mechanics.
Image Source: Educational illustration for teaching purposes.
Questions
- What is concerning about this patient's PCO2 level?
- A) It is too low
- B) A normal PCO2 in acute severe asthma suggests impending respiratory failure
- C) It indicates good compensation
- D) It is not concerning
- What features indicate severe/life-threatening asthma in this patient?
- A) Mild tachycardia only
- B) History of ICU admission, inability to speak sentences, poor air entry, pulsus paradoxus >12 mmHg, normal PCO2
- C) Wheezing
- D) Eosinophilia
- What is the significance of "silent chest" in asthma?
- A) Good prognostic sign - bronchospasm is resolving
- B) Life-threatening sign indicating severe air trapping with minimal air movement
- C) Normal finding during treatment
- D) Indicates pneumonia
- What is the appropriate management for this patient?
- What adjunctive therapies may be considered in severe asthma?
Answers
- B) A normal PCO2 in acute severe asthma suggests impending respiratory failure - In acute asthma, hyperventilation typically causes respiratory alkalosis with low PCO2. A normal or rising PCO2 indicates respiratory muscle fatigue and inability to maintain minute ventilation - a sign of impending respiratory failure.
- B) History of ICU admission, inability to speak sentences, poor air entry, pulsus paradoxus >12 mmHg, normal PCO2 - These are all features of severe/life-threatening asthma. Prior intubation is a strong risk factor for fatal asthma.
- B) Life-threatening sign indicating severe air trapping with minimal air movement - "Silent chest" means air flow is so severely limited that wheezes cannot be generated. This is a pre-arrest finding requiring immediate aggressive management.
- Management of acute severe asthma:
- Oxygen: High-flow to maintain SpO2 94-98%
- Bronchodilators: Continuous nebulized albuterol (or frequent SABA + SAMA)
- Corticosteroids: IV methylprednisolone 125 mg or equivalent
- Magnesium sulfate: 2 g IV over 20 minutes (bronchial smooth muscle relaxation)
- Consider: IV terbutaline, IV aminophylline, heliox
- Intubation: If respiratory failure progresses despite treatment
- ICU admission: Required for this severity
- Adjunctive therapies in severe asthma:
- IV magnesium sulfate: 2 g IV; relaxes bronchial smooth muscle
- Subcutaneous/IV epinephrine: If anaphylaxis component or no IV access
- IV ketamine: Bronchodilator properties; useful for intubation
- Heliox: Helium-oxygen mixture reduces airway resistance
- NIPPV: May help in selected patients; requires close monitoring
- ECMO: Rarely, for refractory cases with severe hypercapnia