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Saturday, March 7, 2009

Asthma, Adult

Asthma, Adult

Description

  • Increased expiratory resistance:
    • Bronchospasm
    • Airway inflammation
    • Mucosal edema
    • Mucous plugging
  • Consequences:
    • Air trapping
    • Increased dead space
    • Hyperinflation
  • 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

Etiology

Mechanism

  • Pollen
  • Dust mites
  • Molds
  • Animal dander
  • Other environmental allergens
  • Viral upper respiratory infections
  • Occupational chemicals
  • Tobacco smoke
  • Environmental change
  • Cold air
  • Exercise
  • Emotional factors
  • Drugs:
    • Aspirin
    • NSAIDs
    • Beta-blockers

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
  • Altered mental status

Essential Workup

  • Primarily a clinical diagnosis
  • Measure and follow severity with peak expiratory flow rate (PEFR)
  • Assess for underlying disease
  • Pneumonia:
    • Pneumothorax

Tests

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
  • Pulse oximetry:
    • Less than 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.

Imaging

  • Peak expiratory flow rate:
    • Estimates the degree of airflow obstruction:
      • Normal peak flow in an adult is 400–600
      • Between 100 and 300 indicates moderate airway obstruction.
      • <100>
      • Use serially as an objective measure of the response to therapy
  • Forced expiratory volume (FEV):
    • More reliable measure of lung function than PEFR
    • More operator dependent
    • Difficult to use as a screening tool
    • Often unavailable in the ED
    • Severe airway obstruction: FEV1 less than 30–50%
  • Chest radiograph:
    • Indications:
      • Fever
      • Suspicion of pneumonia
      • Suspicion of pneumothorax or pneumomediastinum
      • Foreign body aspiration
      • First episode of asthma
      • Comorbid illness
      • Diabetes
      • Renal failure
      • AIDS
      • Cancer
    • 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

  • Congestive heart failure
  • Myocardial ischemia
  • Pulmonary embolus
  • Pneumonia
  • Bronchitis
  • Bronchiolitis
  • Croup
  • Foreign body aspiration
  • Upper airway obstruction
  • Angioedema
  • Allergic reaction
  • Chronic obstructive pulmonary disease
  • Chronic cor pulmonale
  • Chemical pneumonitis
  • Carcinoid tumors
  • Smoke inhalation
  • Immersion injury
  • Venous air embolus

Treatment

Pre Hospital

  • Recognize the ‘quiet chest’ as respiratory distress.
  • Supplemental oxygen
  • Continuous nebulized β2-agonist
  • Administration of subcutaneous epinephrine
  • Severe disease with decreased breath sounds

Initial Stabilization

  • Immediate initiation of inhaled β2-agonist treatment
  • Intubate for fatigue and respiratory distress.
  • Steroids

ED Treatment

β2Adrenergic Agonist

  • Mild-moderate asthmatic:
    • Administer every 20 minutes
  • Severe asthmatic:
    • Continuous nebulized treatment
  • Selective β2-agonists (albuterol)
  • Subcutaneous β-agonist:
    • Severe exacerbations
    • Limited inhalation of aerosolized medicine
    • More side effects because of systemic absorption:
      • Tachycardia
      • Tremors
    • Relative contraindications: age >40 years and coronary disease
  • Corticosteroids:
    • Reduce airway wall inflammation
    • Administered early
    • Onset of action may take 4-6 hours
    • Administer intravenously or orally
    • IV Solu-Medrol in the treatment of severe asthma exacerbation
    • Mild-moderate exacerbations may be treated with oral prednisone.
    • Inhaled corticosteroids are currently not recommended as initial therapy.
  • Oxygen:
    • Maintain an oxygen saturation above 90%
  • Aminophylline:
    • Rare utility in acute management
    • Toxicity:
      • Nausea
      • Tremor
      • Anxiety
      • Palpitations
      • Tachycardia
  • Anticholinergic agents:
    • If minimal response to initial β2-agonist treatment
    • Severe airflow obstruction
    • Inhaled anticholinergic agents should be used in conjunction with β2-agonists.
  • Magnesium sulfate:
    • No benefit in mild-moderate asthma
    • Benefit of magnesium remains unclear in severe asthma
  • 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
  • Ketamine:
    • Bronchodilator and an anesthetic agent
    • Useful as an induction agent during intubation
    • Contraindications:
      • Hypertension
      • Coronary disease
      • Pre-eclampsia
      • 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 (Drugs)

  • β2-agonists
    • Albuterol: 2.5 mg in 2.5 mL normal saline q20min inhaled (peds: 0.1-0.15 mg/kg/dose q20min [minimum dose 1.25 mg])
    • Epinephrine: adult: 0.3 mg (1:1,000) SC q0.5h-q4.0h × three doses (peds: 0.01 mg/kg up to 0.3 mg SC)
    • Terbutaline: 0.25 mg SC q0.5h × two 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 hours)
    • Prednisone: 40-60 mg PO (peds: 1-2 mg/kg/day in single or divided doses)
  • Anticholinergics
    • Ipratropium bromide: 0.5 mg in 3 mL NS q1h × three doses
  • Magnesium: 2 g IV over 20 minutes
  • Aminophylline: 0.6 mg/kg/h IV infusion
  • Rapid sequence intubation:
    • Etomidate: 0.3 mg/kg, or ketamine: 1-1.5 mg/kg
    • Lidocaine: 1-1.5 mg/kg
    • Succinylcholine: 1.5 mg/kg

Follow-Up

Disposition

Admission Criteria

  • Persistent respiratory distress
  • PEFR <100>
  • Intubated patients

Medical Wards or Observation Unit

  • PEFR <40%>
  • Patients without subjective improvement
  • Patients with continued wheeze and diminished air movement
  • Patients with moderate response to therapy and no respiratory distress:
    • Factors that should favor admission
    • Prior intubation
    • Recent ED visit
    • Multiple ED visits or hospitalizations
    • Symptoms for more than 1 week
    • Failure of outpatient therapy
    • Use of steroids
    • Inadequate follow-up mechanisms
    • Psychiatric illness
  • Complications:
    • Pneumothorax
    • Pneumomediastinum
    • Pneumonia
    • Fatigue

Discharge Criteria

  • Patient reports subjective improvement
  • Clear lungs with good air movement
  • PEFR or FEV1 greater than 70% of predicted
  • Peak flow should be greater than 300.
  • Adequate follow-up within 48–72 hours

References

1. Corbridge TC, Hall JB. The assessment and management of adults with status asthmaticus. Am J Respir Crit Care Med. 1995;151:1296-1316.

2. Guidelines for the diagnosis and management of asthma: National Asthma Education Program Expert Panel Report. Bethesda, MD: Department of Health and Human Services; 1991. NIH 91-3042.

3. Jagoda A, Shepherd SM, Spevitz A, et al. Refractory asthma, part 1: epidemiology, pathophysiology, pharmacologic interventions. Ann Emerg Med. 1997;29:262-274.

4. Jagoda A, Shepherd SM, Spevitz A, et al. Refractory asthma, part 2. Airway interventions and management. Ann Emerg Med. 1997;29:275-281.

5. Manthous CA. Management of severe exacerbations of asthma. Am J Med. 1995;99:298-308.

Codes

ICD9-CM

493

ICD10

J45.9

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