Basics
Description
- Increased expiratory resistance:
- Airway inflammation
- Bronchospasm
- Mucosal edema
- Mucous plugging
- Smooth muscle hypertrophy
- Consequences:
- Air trapping
- Airway remodeling
- Increased dead space
- Hyperinflation
- Status asthmaticus refers to disease that does not respond to therapy within 30-60 min
- Risk factors for life-threatening disease:
- Prior intubations
- Intensive care unit admissions
- Chronic steroid use
- Hospital admission for asthma during the past year
- Inadequate medical management
- Increasing age
- Ethnicity (African Americans)
- Lack of access to medical care
- Multiple comorbidities
Etiology
- Inflammatory process of the airways evidenced by episodic and reversible airflow obstruction and hyper-responsiveness with many cells and cellular elements contributing to the disease:
- Neutrophils
- Mast cells
- Eosinophils
- Macrophages
- T lymphocytes
- Epithelial cells
- Cytokines
- Triggers:
- Pollen
- Dust mites
- Molds
- Animal dander
- Other environmental allergens
- Viral upper respiratory infections
- Occupational chemicals
- Tobacco smoke
- Environmental change
- Cold air
- Exercise induced
- Emotional factors
- Menstrual associated
- Drugs:
Diagnosis
Signs and Symptoms
- Wheezing
- Dyspnea
- Chest tightness
- Cough
- Tachypnea
- Tachycardia
- Respiratory distress:
- Posture sitting upright or leaning forward
- Use of accessory muscles
- Inability to speak in full sentences
- Diaphoresis
- Poor air movement
- Impending failure:
- Altered mental status
- Worsening fatigue
- Pulsus paradoxus >18 mm Hg
Essential Workup
- Primarily a clinical diagnosis
- Measure and follow severity with peak expiratory flow rate (PEFR)
- Assess for underlying disease
Diagnosis Tests & Interpretation
Lab
- Arterial blood gas:
- Not helpful during the initial evaluation
- The decision to intubate should be based on clinical criteria.
- Mild-moderate asthma: Respiratory alkalosis
- Severe airflow obstruction and fatigue: Respiratory acidosis and PaCO2 >42
- Pulse oximetry:
- <90% is indicative of severe respiratory distress.
- Patients with impending respiratory compromise may still maintain saturation above 90% until sudden collapse.
- WBC:
- Leukocytosis is nonspecific
- Pneumonia
- Chronic steroid use
- Stress of an asthma exacerbation
- Demargination occurs after administration of epinephrine and steroids.
Diagnostic Procedures/Surgery
- PEFR:
- Estimates the degree of airflow obstruction:
- Normal peak flow (adult) is 400-600.
- 100-300 indicates moderate airway obstruction.
- <100 is indicative of severe airway obstruction.
- Use serially as an objective measure of the response to therapy
- Forced expiratory volume (FEV):
- More reliable measure of lung function than PEFR
- Difficult to use as a screening tool
- Often unavailable in the ED
- Severe airway obstruction: FEV1 <30-50%
- CXR:
- Indications:
- Fever
- Suspicion of pneumonia
- Suspicion of pneumothorax or pneumomediastinum
- Foreign body aspiration
- 1st episode of asthma
- Comorbid illness: For example: Diabetes, renal failure, CHF, AIDS, cancer
- Not responding to treatment
- Typical findings:
- Hyperinflation
- Scattered atelectasis
- ECG:
- Indicated in patients at risk for cardiac disease:
- Dysrhythmias
- Myocardial ischemia
- Transient changes in severe asthma:
- Right axis deviation
- Right bundle branch block
- Abnormal P-waves
- Nonspecific ST-T-wave changes
Differential Diagnosis
- Allergic reaction
- Angioedema
- Bronchiolitis
- Bronchitis
- Carcinoid tumors
- Chemical pneumonitis
- Chronic cor pulmonale
- Chronic obstructive pulmonary disease
- CHF
- Croup
- Foreign body aspiration
- Immersion injury
- Myocardial ischemia
- Pneumonia
- Pulmonary embolus
- Smoke inhalation
- Upper airway obstruction
- Venous air embolus
Treatment
Pre-Hospital
- Recognize the "quiet chest"¯ as respiratory distress.
- Supplemental oxygen
- Continuous nebulized β-agonist
- Administration of IM/SC epinephrine
Initial Stabilization/Therapy
- Immediate initiation of inhaled β-agonist treatment
- Intubate for fatigue and respiratory distress.
- Steroids
Ed Treatment/Procedures
- Oxygen:
- Maintain an oxygen saturation >90%
- β-adrenergic agonist:
- Selective β2-agonists (albuterol)
- Mild-moderate asthmatic: Administer every 20 min
- Severe asthmatic: Continuous nebulized treatment
- SC β-agonist (terbutaline and epinephrine):
- Severe exacerbations
- Limited inhalation of aerosolized medicine
- More side effects because of systemic absorption
- Terbutaline-longer acting β-2 agonist with bronchodilating effects equivalent to epinephrine in acute asthma.
- Relative contraindication: Age >40 yr and coronary disease
- Corticosteroids:
- Reduce airway wall inflammation
- Administered early
- Onset of action may take 4-6 hr
- Administer IV or PO
- IV Solu-Medrol in the treatment of severe asthma exacerbation
- Mild-moderate exacerbations may be treated with oral prednisone burst or Depo-Medrol IM
- Inhaled corticosteroids are currently not recommended as initial therapy.
- Anticholinergic agents:
- If minimal response to initial β-agonist treatment
- Severe airflow obstruction
- Inhaled anticholinergic agents should be used in conjunction with β-agonists.
- Magnesium sulfate:
- No benefit in mild-moderate asthma
- May have a benefit in severe asthma
- Aminophylline:
- Rare utility in acute management
- Leukotriene inhibitors:
- Not currently recommended for acute exacerbation
- Heliox:
- Mixture of helium and oxygen (80:20, 70:30, 60:40)
- Less dense than air
- Decrease airway resistance.
- Decrease in respiratory exhaustion
- Not currently recommended for routine use
- Consider in severe asthma
- Noninvasive positive pressure ventilation:
- CPAP and BiPAP
- May improve oxygenation and decrease respiratory fatigue
- Can only be used in an alert patient
- Should not replace intubation
- Not currently recommended for routine use
- Consider in severe asthma
- Ketamine:
- Bronchodilator and an anesthetic agent
- Useful as an induction agent during intubation
- Contraindications:
- HTN
- Coronary disease
- Preeclampsia
- Increased intracranial pressure
- Halothane:
- Inhalation anesthetics are potent bronchodilators.
- Refractory asthma in intubated patients
- Intubation of the asthmatic patient:
- Rapid sequence intubation
- Lidocaine to attenuate airway reflexes
- Etomidate or ketamine as an induction agent
- Succinylcholine should be administered to achieve paralysis.
- A large endotracheal tube >7 mm should be used to facilitate ventilation.
- May need to mechanically exhale for the patient
- Permissive hypercapnia
Medication
- β-agonists
- Albuterol: 2.5 mg in 2.5 mL NS q20min inhaled (peds: 0.1-0.15 mg/kg/dose q20min [min. dose 1.25 mg])
- Epinephrine: Adult: 0.3 mg (1:1,000) SC q0.5h-q4h — 3 doses (peds: 0.01 mg/kg up to 0.3 mg SC)
- Terbutaline: 0.25 mg SC q0.5h — 2 doses (peds: 0.01 mg/kg up to 0.3 mg SC)
- Corticosteroids:
- Methylprednisolone: 60-125 mg IV (peds: 1-2 mg/kg/dose IV or PO q6h — 24 h)
- Prednisone: 40-60 mg PO (peds: 1-2 mg/kg/d in single or divided doses)
- Depo-Medrol 160 mg IM
- Anticholinergics
- Ipratropium bromide: 0.5 mg in 3 mL NS q1h — 3 doses
- Magnesium: 2 g IV over 20 min (peds: 25-75 mg/kg)
- Aminophylline: 0.6 mg/kg/h IV infusion
- Rapid sequence intubation:
- Etomidate: 0.3 mg/kg IV, orketamine: 1-1.5 mg/kg IV
- Lidocaine: 1-1.5 mg/kg IV
- Succinylcholine: 1.5 mg/kg IV
Follow-Up
Disposition
Admission Criteria
Medical Wards
- PEFR <40% and minimal air movement
- Persistent respiratory distress:
- Factors that should favor admission:
- Prior intubation
- Recent ED visit
- Multiple ED visits or hospitalizations
- Symptoms for more than 1 wk
- Failure of outpatient therapy
- Use of steroids
- Inadequate follow-up mechanisms
- Psychiatric illness
Observation Unit
- PEFR >40% but <70% of predicted
- Patients without subjective improvement
- Patients with continued wheeze and diminished air movement
- Patients with moderate response to therapy and no respiratory distress
Discharge Criteria
- PEFR >70% should be >300
- Patient reports subjective improvement
- Clear lungs with good air movement
- Adequate follow-up within 48-72 hr
Followup Recommendations
Encourage patients to contact their PMD or pulmonologist for asthma related problems over the next 3-5 days.
Pearls and Pitfalls
- Altered mental status in asthma equals ventilatory failure.
- Patients should be able to demonstrate the correct use of their inhaler or nebulizer:
- Discharge with a peak flow meter
- If no signs or symptoms of dehydration, no evidence that IVF will clear airway secretions.
- Antibiotics should generally be reserved for patients with purulent sputum, fever, pneumonia, or evidence of bacterial sinusitis.
Additional Reading
- Camargo CA Jr, Rachelefsky G, Schatz M. Managing asthma exacerbations in the emergency department: Summary of the National Asthma Education and Prevention Program Expert Panel Report 3 guidelines for the management of asthma. J Emerg Med. 2009;37(2):S6-S17.
- Fanta CH. Asthma. N Engl J Med. 2009;360:1002-1014.
- Lazarus SC. Emergency treatment of asthma. N Engl J Med. 2010;363(8):755-764.
- Marx JA. Rosens Emergency Medicine. 7th ed. Asthma. 2009.
- National Asthma Education and Prevention Program Expert Panel Report 3. Guidelines for diagnosis and management of asthma. U.S. Dept of Health and Human Services, October 2007.
Codes
ICD9
- 493.90 Asthma, unspecified type, without mention of status asthmaticus
- 493.91 Asthma, unspecified type, with status asthmaticus
- 493.92 Asthma, unspecified type, with (acute) exacerbation
- 493.9 Asthma, unspecified
ICD10
- J45.901 Unspecified asthma with (acute) exacerbation
- J45.902 Unspecified asthma with status asthmaticus
- J45.909 Unspecified asthma, uncomplicated
- J45.90 Unspecified asthma
SNOMED
- 195967001 Asthma (disorder)
- 57546000 Asthma with status asthmaticus (disorder)
- 281239006 Exacerbation of asthma (disorder)