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Asthma, Adult, Emergency Medicine

Basics

Description

- 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

- 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

- WBC: - Leukocytosis is nonspecific - Pneumonia - Chronic steroid use - Stress of an asthma exacerbation - Demargination occurs after administration of epinephrine and steroids.

- 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

- Transient changes in severe asthma: - Right axis deviation - Right bundle branch block - Abnormal P-waves - Nonspecific ST-T-wave changes

- 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.

- 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

- 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

- Anticholinergics - Ipratropium bromide: 0.5 mg in 3 mL NS q1h — 3 doses

- 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

  • Increased expiratory resistance:Airway inflammationBronchospasmMucosal edemaMucous pluggingSmooth muscle hypertrophy
  • Consequences:Air trappingAirway remodelingIncreased dead spaceHyperinflation
  • Status asthmaticus refers to disease that does not respond to therapy within 30-60 min
  • Risk factors for life-threatening disease:Prior intubationsIntensive care unit admissionsChronic steroid useHospital admission for asthma during the past yearInadequate medical managementIncreasing ageEthnicity (African Americans)Lack of access to medical careMultiple 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:NeutrophilsMast cellsEosinophilsMacrophagesT lymphocytesEpithelial cellsCytokines
  • Triggers:PollenDust mitesMoldsAnimal danderOther environmental allergensViral upper respiratory infectionsOccupational chemicalsTobacco smokeEnvironmental changeCold airExercise inducedEmotional factorsMenstrual associatedDrugs:

Diagnosis

Signs and Symptoms

  • Wheezing
  • Dyspnea
  • Chest tightness
  • Cough
  • Tachypnea
  • Tachycardia
  • Respiratory distress:Posture sitting upright or leaning forwardUse of accessory musclesInability to speak in full sentencesDiaphoresisPoor air movement
  • Impending failure:Altered mental statusWorsening 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 evaluationThe decision to intubate should be based on clinical criteria.Mild-moderate asthma: Respiratory alkalosisSevere 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 nonspecificPneumoniaChronic steroid useStress of an asthma exacerbationDemargination 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 PEFRDifficult to use as a screening toolOften unavailable in the EDSevere airway obstruction: FEV1 <30-50%
  • CXR:Indications:FeverSuspicion of pneumoniaSuspicion of pneumothorax or pneumomediastinumForeign body aspiration1st episode of asthmaComorbid illness: For example: Diabetes, renal failure, CHF, AIDS, cancerNot responding to treatmentTypical findings:HyperinflationScattered atelectasis
  • ECG:Indicated in patients at risk for cardiac disease:DysrhythmiasMyocardial ischemiaTransient changes in severe asthma:Right axis deviationRight bundle branch blockAbnormal P-wavesNonspecific 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 minSevere asthmatic: Continuous nebulized treatmentSC β-agonist (terbutaline and epinephrine):Severe exacerbationsLimited inhalation of aerosolized medicineMore side effects because of systemic absorptionTerbutaline-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 inflammationAdministered earlyOnset of action may take 4-6 hrAdminister IV or POIV Solu-Medrol in the treatment of severe asthma exacerbationMild-moderate exacerbations may be treated with oral prednisone burst or Depo-Medrol IMInhaled corticosteroids are currently not recommended as initial therapy.
  • Anticholinergic agents:If minimal response to initial β-agonist treatmentSevere airflow obstructionInhaled anticholinergic agents should be used in conjunction with β-agonists.
  • Magnesium sulfate:No benefit in mild-moderate asthmaMay 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 airDecrease airway resistance.Decrease in respiratory exhaustionNot currently recommended for routine useConsider in severe asthma
  • Noninvasive positive pressure ventilation:CPAP and BiPAPMay improve oxygenation and decrease respiratory fatigueCan only be used in an alert patientShould not replace intubationNot currently recommended for routine useConsider in severe asthma
  • Ketamine:Bronchodilator and an anesthetic agentUseful as an induction agent during intubationContraindications:HTNCoronary diseasePreeclampsiaIncreased intracranial pressure
  • Halothane:Inhalation anesthetics are potent bronchodilators.Refractory asthma in intubated patients
  • Intubation of the asthmatic patient:Rapid sequence intubationLidocaine to attenuate airway reflexesEtomidate or ketamine as an induction agentSuccinylcholine 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 patientPermissive hypercapnia

Medication

  • β-agonistsAlbuterol: 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
  • AnticholinergicsIpratropium 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 IVLidocaine: 1-1.5 mg/kg IVSuccinylcholine: 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 intubationRecent ED visitMultiple ED visits or hospitalizationsSymptoms for more than 1 wkFailure of outpatient therapyUse of steroidsInadequate follow-up mechanismsPsychiatric 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)