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:
    • Aspirin
    • NSAIDs
    • β-blockers

[Outline]

• DESCRIPTION
• ETIOLOGY

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

[Outline]

• SIGNS AND SYMPTOMS
• ESSENTIAL WORKUP
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

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, or ketamine: 1–1.5 mg/kg IV
  • Lidocaine: 1–1.5 mg/kg IV
  • Succinylcholine: 1.5 mg/kg IV

[Outline]

• PRE-HOSPITAL
• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• MEDICATION

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

FOLLOW-UP RECOMMENDATIONS

Encourage patients to contact their PMD or pulmonologist for asthma related problems over the next 3–5 days.

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

• 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.

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

ICD10

• J45.901 Unspecified asthma with (acute) exacerbation
• J45.902 Unspecified asthma with status asthmaticus
• J45.909 Unspecified asthma, uncomplicated

[Outline]

• ICD9
• ICD10

• 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. Rosen's 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.

Melissa H. White

Carolyn Maher Overman