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