What are the steps of management and investigations for severe bronchial asthma in the emergency department?

Severe Bronchial Asthma in the Emergency Department

Definition of Severe Bronchial Asthma

Severe bronchial asthma is defined by specific clinical and objective criteria: inability to complete sentences in one breath, respiratory rate >25 breaths/minute, heart rate >110 beats/minute, and peak expiratory flow (PEF) or FEV₁ <50% of predicted or personal best. 1

Life-threatening features include:

• PEF <33% of predicted 1
• Silent chest, cyanosis, or feeble respiratory effort 1
• Bradycardia, hypotension, or arrhythmia 1
• Exhaustion, confusion, altered consciousness, or coma 1
• Oxygen saturation <90% despite supplemental oxygen 2

Immediate Assessment and Triage

All patients presenting with asthma exacerbation must be evaluated and triaged immediately, with treatment instituted promptly upon determination of severity. 1

Critical History Elements

• Time of onset and potential triggers 1
• Severity compared to previous exacerbations 1
• Current medications and time of last dose 1
• Previous intubations or ICU admissions (strongest predictor of asthma-related death) 3
• Number of hospitalizations, ED visits in past year 1, 3
• Use of >2 short-acting beta-agonist canisters per month 1, 3

Physical Examination Priorities

• Level of alertness and ability to speak in sentences 1
• Respiratory rate, heart rate, and use of accessory muscles 1
• Presence or absence of wheezing (silent chest indicates critical obstruction) 1
• Oxygen saturation before oxygen administration 1

Common pitfall: Physicians' subjective assessments of airway obstruction are often inaccurate; objective measurements are essential. 2, 4

Investigations in the Emergency Department

Essential Objective Measurements

• Peak expiratory flow (PEF) or FEV₁ measurement immediately 1
• Pulse oximetry before oxygen administration 1, 4
• Arterial blood gas if PEF <50% predicted or patient appears severely ill 1

Additional Investigations for Severe Cases

• Chest radiography to exclude pneumothorax, pneumomediastinum, or pneumonia 1, 5
• Serial PEF or FEV₁ measurements every 15-30 minutes after treatment 1

Critical consideration: Response to treatment is a better predictor of hospitalization need than initial severity. 2, 6

Immediate Management Protocol

First-Line Treatment (Administer Simultaneously)

All patients with severe asthma require oxygen, inhaled β₂-agonists, and systemic corticosteroids immediately. 1

1. Oxygen 40-60% via face mask to maintain SaO₂ >90% 1, 6

2. Nebulized salbutamol 5 mg or terbutaline 10 mg via oxygen-driven nebulizer 1, 6

   • Repeat every 20 minutes for 3 doses 6
   • Alternative: MDI with spacer (4-8 puffs every 20 minutes) 6
   • Continue until adequate clinical response occurs 5

3. Systemic corticosteroids immediately 1, 6

   • Prednisolone 30-60 mg orally OR 1, 6
   • Hydrocortisone 200 mg IV 1, 5
   • Clinical benefits may not occur for 6-12 hours, so early administration is critical 4

Reassessment at 15-30 Minutes

• Measure PEF or FEV₁ 1
• Assess symptoms, vital signs, oxygen saturation 6
• Evaluate response to determine next steps 1

Management Based on Response to Initial Treatment

If PEF Remains <50% or Severe Features Persist

Add ipratropium bromide 0.5 mg via nebulizer every 20 minutes for 3 doses, then as needed 1, 6, 7

• Reduces hospitalizations, particularly in severe airflow obstruction 6

Consider IV magnesium sulfate 2 g over 20 minutes for severe or refractory cases 6, 5

Consider IV aminophylline 2 mg/kg loading dose, then 4 mg/kg over 30 minutes 1, 5

• Use caution if patient already taking theophyllines 1

Life-Threatening Features Requiring ICU Admission

If patient shows exhaustion, confusion, silent chest, or deteriorating blood gases despite aggressive treatment, immediate ICU admission is required. 1, 2

• IV adrenaline 20-200 mcg bolus followed by infusion of 1-10 mcg/min may be needed 5
• Prepare for possible intubation with ketamine sedation (1-2 mg/kg) 5, 8
• Mechanical ventilation requires controlled hypoventilation to avoid dynamic hyperinflation 8

Hospitalization Criteria

Admit to hospital if any of the following persist after 1-2 hours of intensive treatment: 2

• FEV₁ or PEF <40% of predicted 2
• FEV₁ or PEF 40-69% with persistent symptoms 2
• Any life-threatening features present 1, 2
• Previous severe exacerbation requiring intubation or ICU admission 2, 3

Discharge Criteria and Planning

Patients may be discharged when PEF ≥70% of predicted or personal best, symptoms are minimal or absent, and oxygen saturation is stable on room air for 30-60 minutes after last bronchodilator. 1, 6

Mandatory Discharge Interventions

• Prescribe oral corticosteroids for 3-10 days 1, 6
• Initiate or continue inhaled corticosteroids 1
• Provide written asthma action plan (reduces mortality risk by 70% in severe asthma) 3
• Schedule follow-up appointment before discharge 1
• Verify correct inhaler technique 1

Critical pitfall: Discharged patients from ED have high mortality risk and require extra care with close follow-up. 1