How should an acute asthma exacerbation in an adult be managed, including severity assessment, oxygen targets (SpO₂ ≥ 92 % or ≥ 94 % in pregnancy), short‑acting β2‑agonist (SABA) therapy, inhaled anticholinergic, systemic corticosteroids, intravenous magnesium sulfate for severe cases, and discharge planning?

Management of Acute Asthma Exacerbation in Adults

Begin immediate treatment with high-dose inhaled albuterol (2.5–5 mg via nebulizer or 4–8 puffs via MDI with spacer every 20 minutes for three doses), systemic corticosteroids (prednisone 40–60 mg orally), and supplemental oxygen to maintain SpO₂ ≥ 92% (≥ 95% in pregnancy or cardiac disease), while simultaneously assessing severity using peak expiratory flow and clinical features. 1, 2

Severity Assessment & Oxygen Targets

Measure peak expiratory flow (PEF) or FEV₁ immediately to objectively classify severity—failure to obtain objective measurements is the most common preventable cause of asthma death. 1, 2

Severity Categories

• Severe exacerbation: Inability to complete sentences in one breath, respiratory rate > 25 breaths/min, heart rate > 110 beats/min, PEF < 50% predicted or personal best 1, 2
• Life-threatening features: PEF < 33% predicted, silent chest, cyanosis, feeble respiratory effort, altered mental status (confusion, drowsiness), bradycardia or hypotension, normal or elevated PaCO₂ ≥ 42 mmHg 1, 2

Oxygen Therapy

• Target SpO₂ ≥ 92% in non-pregnant adults via nasal cannula or face mask 3, 2
• Target SpO₂ ≥ 95% in pregnant patients or those with cardiac disease 1, 2, 4
• Continue continuous pulse oximetry until clear response to bronchodilator therapy 1, 2

Immediate First-Line Treatment (First 15–30 Minutes)

Short-Acting β₂-Agonist (SABA) Therapy

Administer albuterol immediately—do not delay while obtaining additional assessments. 1, 2

• Nebulizer: 2.5–5 mg every 20 minutes for three doses 1, 2, 5
• MDI with spacer: 4–8 puffs every 20 minutes for three doses (equally effective when properly administered) 1, 2
• For severe exacerbations (PEF < 40%): Consider continuous nebulization rather than intermittent dosing 2, 5

Systemic Corticosteroids

Give systemic corticosteroids immediately—do not delay while "trying bronchodilators first." 1, 2

• Prednisone 40–60 mg orally in single or divided doses 1, 2, 5
• Oral route is as effective as IV and strongly preferred unless patient is vomiting or critically ill 1, 2
• IV hydrocortisone 200 mg if unable to tolerate oral (repeat every 6 hours; a single 100 mg dose is insufficient) 1
• Clinical benefits require 6–12 hours minimum to manifest 1

Reassessment Protocol (15–30 Minutes After Initial Treatment)

Measure PEF or FEV₁ before and after each bronchodilator dose—response to treatment is a better predictor of hospitalization need than initial severity. 1, 2, 5

Response-Based Management Algorithm

Good Response (PEF > 75% Predicted)

• Continue usual maintenance therapy with modest increase if needed 1
• Monitor symptoms and PEF on a chart 1
• Arrange follow-up within 48 hours 1

Incomplete Response (PEF 50–75% Predicted)

• Continue nebulized albuterol every 4–6 hours 1
• Continue systemic corticosteroids 1
• Consider hospital admission if severe features persist 1

Poor Response (PEF < 50% Predicted or Persistent Severe Features)

• Increase albuterol frequency to every 15–30 minutes 3, 1
• Add ipratropium bromide (see below) 1, 2
• Arrange immediate hospital admission 1, 2

Adjunctive Therapies for Moderate-to-Severe Exacerbations

Inhaled Anticholinergic

Add ipratropium bromide to albuterol for all moderate-to-severe exacerbations—this combination reduces hospitalizations, particularly in patients with severe airflow obstruction. 1, 2, 5

• Nebulizer: 0.5 mg every 20 minutes for three doses, then every 4–6 hours as needed 3, 1, 2
• MDI: 8 puffs every 20 minutes for three doses, then as needed 1, 2

Intravenous Magnesium Sulfate

Consider IV magnesium sulfate for severe refractory asthma (PEF < 40% after initial treatment) or life-threatening features. 1, 2, 6

• Dose: 2 g IV over 20 minutes 1, 2, 6
• Most effective when administered early in the treatment course 5, 6
• A Cochrane meta-analysis demonstrated improved pulmonary function and reduced hospital admissions 1

Therapies to Avoid

• Never administer sedatives of any kind—this is absolutely contraindicated and may be fatal 3, 1, 2
• Avoid IV aminophylline due to erratic pharmacokinetics, significant side effects, and lack of evidence of benefit over standard therapy 1
• Do not give aminophylline bolus to patients already taking oral theophylline 3, 1
• Avoid IV isoproterenol due to danger of myocardial toxicity 1, 2

Hospital Admission Criteria

Admit immediately for any of the following: 1, 2

• Any life-threatening feature present (PEF < 33%, silent chest, altered mental status, PaCO₂ ≥ 42 mmHg) 1, 2
• Features of severe attack persisting after initial treatment 1, 2
• PEF < 50% predicted after 1–2 hours of intensive treatment 1, 2

Lower Threshold for Admission

• Presentation in afternoon or evening (rather than morning) 1
• Recent nocturnal symptoms or worsening pattern 1
• Previous severe attacks requiring intubation or ICU admission 1, 2
• ≥ 2 hospitalizations or ≥ 3 ED visits in past year 1
• Poor social circumstances or inadequate support systems 1

ICU Transfer Criteria

Transfer to ICU accompanied by a physician prepared to intubate if: 3, 1

• Deteriorating PEF despite therapy 3, 1
• Worsening or persistent hypoxia/hypercapnia 3, 1
• Exhaustion, confusion, drowsiness, or altered consciousness 3, 1
• Impending respiratory arrest 3, 1

Discharge Planning

Discharge Criteria

Patients may be discharged when all of the following are met: 1, 2

• PEF ≥ 70–75% of predicted or personal best 1, 2
• Symptoms minimal or absent 1, 2
• Oxygen saturation stable on room air 1, 2
• Clinical stability for 30–60 minutes after last bronchodilator dose 1, 2

Discharge Medications & Education

• Continue oral prednisone 40–60 mg daily for 5–10 days—no taper needed for courses < 10 days 1, 2, 7
• Initiate or continue inhaled corticosteroids at discharge 1, 2, 7
• Verify correct inhaler technique and document competency 3, 1
• Provide written self-management plan with peak-flow zones 3, 1
• Supply peak-flow meter if patient does not already have one 3, 1
• Ensure immediate access to rescue bronchodilator—waiting until the next day is unacceptable 1

Follow-Up

• Primary care follow-up within 1 week 3, 1
• Respiratory specialist clinic within 4 weeks 3, 1

Critical Pitfalls to Avoid

• Do not underestimate severity—always measure PEF or FEV₁ objectively; subjective clinical impression alone is insufficient 1, 2
• Do not delay corticosteroid administration while "trying bronchodilators first"—both should be given concurrently 1, 2
• Never discharge without immediate access to rescue bronchodilator 1
• Do not delay intubation once deemed necessary—it should be performed semi-electively before respiratory arrest 1
• Avoid aggressive hydration in older children and adults (may be appropriate for infants and young children) 1
• Do not routinely prescribe antibiotics unless strong evidence of bacterial infection (e.g., pneumonia or sinusitis) 1

Special Considerations in Pregnancy

• Target SpO₂ ≥ 95% (higher than non-pregnant adults) 1, 2, 4
• Maternal well-being and pulmonary function are essential to ensure optimal outcomes for both mother and fetus 4, 8
• Treatment approach is identical to non-pregnant patients—benefits of treatment far outweigh theoretical risks 4, 8, 9
• Continuous inhaled corticosteroids reduce readmission rate by 55% in pregnant women 7