Acute asthma exacerbation
This page is for adult patients. For pediatric patients, see: asthma (peds)
- Quickly establish severity of current presentation and history of severe exacerbations (e.g. need for ICU, intubation, etc)
- Identify any treatable precipitant (e.g. pneumonia, URI, GERD, exposure to irritants, aspirin/NSAIDs)
- Status asthmaticus is a life-threatening form of asthma in which progressively worsening reactive airways are unresponsive to usual appropriate therapy leading to pulmonary insufficiency.
- Dyspnea, wheezing, and cough (+/- sputum production)
- Prolonged expiration
- Accessory muscle use
- Sign of impending ventilatory failure:
- Paradoxical respiration (chest deflation and abdominal protrusion during inspiration)
- Altered mental status
- "Silent chest"
- Low peak flows
- Cyanosis is uncommon (respiratory alkalosis -> left shift of the oxyhemoglobin dissociation curve)
- Airway obstruction
- Cor pulmonale
- Inhalation exposure
- Noncardiogenic pulmonary edema
- Pneumocystis Pneumonia (PCP)
- Pulmonary embolism
- Pulmonary hypertension
- Tension pneumothorax
- Idiopathic pulmonary fibrosis acute exacerbation
- Cystic fibrosis exacerbation
- Other Associated with Normal/↑ Respiratory Effort
- Other Associated with ↓ Respiratory Effort
- Uncorrected ASD
- Congenital heart disease
- COPD exacerbation
- Interstitial lung disease
- Panic attack
- Pleural effusion
- Rib fracture
- Spontaneous pneumothorax
- Thyroid Disease
Consider CXR if:
- Normally a clinical diagnosis
- ABG unlikely to add to clinical decision making unless pulse oximetry unavailable
- However, a blood gas with a normal or elevated CO2 suggest impending respiratory failure (asthmatics typically hypocapneic during exacerbation)
|Severity||Symptom frequency||Night-time symptoms||%FEV1 of predicted||FEV1 variability||SABA use|
|Mild persistent||>2/week||3–4/month||≥80%||20–30%||>2 days/week|
|Severe persistent||Continuously||Frequent (7/week)||<60%||>30%||≥twice/day|
- Titrate to an arterial oxygen saturation >90% (>95% in pregnant women and with coexistent heart disease)
Favor continuous nebulization to decrease the chance of admission when compared to intermittent dosing
- Intermittent: 2.5-5mg q20min x3, then 2.5-10mg q1-4hr as needed OR
- Continuous: 0.5mg/kg/hr (max 15mg/hr)
- If using intermitent nebs at home PTA, start on continuous
- 6-12 puffs q20min up to 4h, then q1-4hr as needed
- Levalbuterol is pure R-enantiomer, whereas racemic albuterol as above is 50:50 mix of R and S albuterol
- Levalbuterol at 5x the cost, may not warrant the small benefits seen in some studies
- In severe asthma exacerbation, be aware of lactic acidosis that develops due to pathology and the added lactic acidosis from albuterol,
- Manifests as worsening respiratory distress, tachypnea, compensatory increase in ventilation
- Ensure adequate intravascular volume, but carefully volume expand as acute asthma may increase ADH secretion
- Rarely, clinically important hypokalemia, alongside hyperglycemia and leukocytosis, may result from repeated beta agonists and sympathomimetics
- 0.25-0.5mg q20min x2-3 doses
- Only shown to be effective in the acute setting to reduce hospitalization rates and improve lung function
- No benefit of adding to inpatient, hospitalized regimens
Should be given in the first hour with effects to reduce admission and rate of relapses Options include:
- 40-60mg /day x5d
- Inhaled corticosteroids may be considered as a rescue effort for severe asthma, given over a 90 min period
- 25-75 mg/kg over 30 min (2-3 g IV in most adults)
- Duration of action approximately 20 min, beware of hypotension in rapid administration due to smooth muscle relaxation mechanism
- In patients with moderate to severe asthma there is a decreased rate of admission with an NNT of 2
- High-dose, prolonged magnesium may expedite discharge from the ED in non-infectious asthma in pediatric study
- 50 mg/kg/hr for 4 hours
- MAX 8,000 mg for 4 hours, monitor for cardiopulmonary complications
- No interventions or discontinuations of magnesium sulfate due to adverse events in the study
- NNT of 2-3, for hospital discharge before 24 hours
- Inhalation is preferred route of administration, but adequate drug delivery to small airways may be hampered in severe attacks
- Terbutaline and epinephrine can be administered IM/IV/SubQ
- Need to monitor for arrhythmias, tachycardia, hypertension, cardiac ischemia
- 1:1000 0.01 mg/kg (max 0.5mg) subQ or IM Q20min x3
- Nebulized racemic epinephrine 0.03 mL/kg (2.25% solution) diluted in 3-5 mL NS via jet nebulizer q3-4hr PRN shown to be as safe as nebulized albuterol
- In severe, life-threatening asthma, IV epinephrine may be safe to consider, substantiated only by a case series of adults in 2003, however
- Longer-acting beta2-agonist promoting bronchodilation
- Caution in elderly/CHF with greater potential for cardiotoxicity
- 0.25mg subQ/IM q20min x 3
- Then followed by infusion at 1 µg/kg/min, titrated up by increments of 1 to max of 10 1 µg/kg/min
- Elevated troponins q4hrs during infusion, more common in cTnI vs. cTnT, with EKG changes of ischemia should prompt re-evaluation for stopping infusion
- Some experts have nebulized IV form
- 5 mg of IV form terbutaline
- However, significantly higher cost than albuterol
- Consider as alternative to intubation
- Alleviates muscle fatigue which leads to larger tidal volumes
- May drive nebulized treatments deeper into airways
- Maximize inspiratory support
- Inspiratory pressure 8
- PEEP 0-3, only enough to match patient's auto-PEEP
Intubation and Invasive Ventilation
- Relative indications include worsening hypercapnea, exhaustion, altered mental status, CO2 narcosis without any specific number endpoint on blood gases, refractory hypoxemia, status asthmaticus
- Consider induction with Ketamine
- Provides bronchodilation and sedation however it does promote secretions
- Ketamine is the preferred induction agent for intubation in an asthmatic.
- Dosing 1-2mg/kg
- Ventilation of asthmatic patients requires deep sedation
- Initial ventilation settings - severe asthma
- Assist-control ventilation
- Resp rate
- Start slow to avoid air-trapping
- RR ~ 8-10 in adults
- Goal: obtaining a pH above 7.2 and plateau pressure below 30 cmH2O
- If Pplat >30 must lower respiratory rate
- If Pplat under 30 cannot be maintained, other causes of decreased respiratory system compliance must be considered (i.e. pneumothorax, misplaced endotracheal tube, pulmonary edema, etc.)
- May require "permissive hypoventilation"
- Sacrifice MV for full exhalation
- Lower I:E ratio
- Low peak pressure/avoidance of breath stacking more important than correcting CO2 
- Tidal volume 6-8mL/kg ideal wt
- PEEP 0-5 cmH2O
- Flow rate 80-100L/min
- Keep FiO2 minimum to achieve SpO2 > 90%
- Use bronchodilators even when intubated
- Monitor for breath stacking (inspiratory holds, plateau pressures)
- Most common cause of post-intubation hypotension
- Check ventilator tracing
- Disconnect ventilator
- Decompress chest
- Consider empiric bilateral chest tubes or rapid ultrasound to identify pneumothorax
- IVF bolus
- Administration of antibiotics only when physical exam or ancillary testing supportive of bacterial infection
- Antibiotics may be considered for select patients and may improve symptoms and peak expiratory flow, further understanding needed to identify which patients may be most likely to benefit 
- 60 to 80% helium is blended with 20 to 40% oxygen
- Heliox improves non laminar flow and may increases the diffusion of carbon dioxide by improving ventilation
- Not indicated for acute treatment
- Zafirlukast (20 mg bid) and montelukast (10 mg/day)
New guidelines by Global Initiative for Asthma (GINA) 2019 endorse the use of an ICS-LABA combined product as both rescue and maintenance inhaler based off of a 2018 meta analysis 
- GINA recommends budesonide or beclomethasone as the inhaled corticosteroid, and formoterol as the long acting beta agonist. The only U.S. formulation meeting this recommendation is Symbicort (budesonide-formoterol).
|Severity||Day Sx||Night Sx||Treatment (WHO 2008 Formulary)|
|Mild intermittent, > 80% peak flow||< 2/wk||< 2/mo||Albuterol MDI 100-200 mcg PRN QID|
|Mild persistent, > 80% peak flow||>2/wk||>2/mo||Albuterol MDI 100-200 mcg PRN QID AND
Beclometasone 100-250 mcg bid
|Moderate persistent, 60-80% peak flow||Daily with exacerbations weekly||> 1/wk||Albuterol MDI 100-200 mcg PRN QID AND
Beclometasone 100-500 mcg BID AND
Salmeterol inhaled 50 mcg bid
|Severe persistent, < 60% peak flow||Continuous daily||Frequent||Albuterol MDI 100-200 mcg PRN QID AND
Beclometasone 1mg BID (high dose) AND
Salmeterol inhaled 50 mcg BID AND (if needed)
- If symptoms resolve
- Often, patients will still have mild wheezing, but should have complete resolution of tachypnea, hypoxia, and work of breathing if being discharged
- A short course of glucocorticoids decreases chance of relapse - prednisone in adults (40-60 mg/day for 5-10 days without tapering) or dexamethasone (0.6mg/kg) in children
- If symptoms persist or are severe
- Classically disposition is based on peak flow measurements - however, these measurements are often not available in the ED
- Predicted = (30 x age (yrs)) + 30
- PEF >70% predicted → high likelihood of successful discharge
- PEF <40% predicted → should be admitted
- Asthma (peds)
- Modified pulmonary index score
- Ventilation settings
- Deterioration after intubation
- COPD exacerbation
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