Acute asthma exacerbation
For pediatrics patients see Asthma (peds)
- 1 Background
- 2 Clinical Features
- 3 Differential Diagnosis
- 4 Evaluation
- 5 Management
- 6 Outpatient Treatment
- 7 Disposition
- 8 See Also
- 9 External Links
- 10 References
- 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)
- 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
- 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
- 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
- Normally a clinical diagnosis
Consider CXR if
Favor continuous nebulization to decrease the chance of admission when compared to intermittent dosing
- Intermitent: 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
- 4-8 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 the 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
- 40-60mg/day in one or two divided doses x5d
- 1mg/kg IV q 4–6hr
- Only use IV if cannot tolerate PO since equal effectiveness between dosing routes
- Inhaled corticosteroids may be considered as a rescue effort for severe asthma, given over a 90 min period
- Nebulized fluticasone 500 µg q15 min
- Nebulized budesonide 800 µg q30 min
- 25-75 mg/kg over 30 min (1-2 gm 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
- 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
- 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
- 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
- Relative indications include worsening hypercapnea, exhaustion, altered mental status, CO2 narcosis without any specific number endpoint on blood gases
- 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
- Ventilation settings
- Assist-control ventilation
- Resp rate
- Start slow to avoid air-trapping
- RR ~ 8-10 in adults
- Make sure plateau pressure <30, with inspiratory hold
- If >30 must lower respiratory rate
- 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 6-8cc/kg ideal wt
- PEEP 0
- 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 bilateral chest tubes
- Fluid bolus
|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)
- Discharge - if symptoms resolve
- Admit - 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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- National Asthma Education and Prevention Program (NAEPP), “Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma,” Clinical Practice Guidelines, National Institutes of Health, National Heart, Lung, and Blood Institute, NIH Publication No. 08-4051, prepublication 2007; available at http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm.
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