Acute asthma exacerbation

(Redirected from Asthma exacerbation)

This page is for adult patients. For pediatric patients, see: asthma (peds)

Background

A - Alveoli AS - Septum alveolare BR - Bronchus respiratorius BT - Bronchus terminalis D - Mucous gland DA - Ductus alveolaris M - Musculus N - Nervus PA - Branch of Arteria pulm. PV - Branch of Vena pulm.
Comparison of normal airway (B) to airway during asthma symptoms (C).
Features of remodeling in asthma.
  • Quickly establish severity of current presentation and history of severe exacerbations (e.g. need for ICU, intubation, etc)
  • Identify any treatable precipitant (e.g. pneumonia, URI, GERD, exposure to irritants, aspirin/NSAIDs)
  • Status asthmaticus is a life-threatening form of asthma in which progressively worsening reactive airways are unresponsive to usual appropriate therapy leading to pulmonary insufficiency.

Clinical Features

  • Dyspnea, wheezing, and cough (+/- sputum production)
  • Prolonged expiration
  • Accessory muscle use
  • Sign of impending ventilatory failure:
    • Paradoxical respiration (chest deflation and abdominal protrusion during inspiration)
    • Altered mental status
    • "Silent chest"
  • Low peak flows
  • Cyanosis is uncommon (respiratory alkalosis -> left shift of the oxyhemoglobin dissociation curve)

Differential Diagnosis

Bronchoconstriction

Acute dyspnea

Emergent

Non-Emergent

Evaluation

CXR with hyperinflated lungs consistent with broncoconstriction.

Workup

Consider CXR if:

  • Fever >102.2°
  • Worsening symptoms
  • Poor response to medications/treatments
  • 1st wheeze
  • Chest pain

Diagnosis

  • Normally a clinical diagnosis
  • ABG unlikely to add to clinical decision making unless pulse oximetry unavailable
    • However, a blood gas with a normal or elevated CO2 suggest impending respiratory failure (asthmatics typically hypocapneic during exacerbation)

Classification

Clinical classification (≥ 12 years old)[1]
Severity Symptom frequency Night-time symptoms %FEV1 of predicted FEV1 variability SABA use
Intermittent ≤2/week ≤2/month ≥80% <20% ≤2 days/week
Mild persistent >2/week 3–4/month ≥80% 20–30% >2 days/week
Moderate persistent Daily >1/week 60–80% >30% daily
Severe persistent Continuously Frequent (7/week) <60% >30% ≥twice/day

Management

Oxygen PRN

  • Titrate to an arterial oxygen saturation >90% (>95% in pregnant women and with coexistent heart disease)

Albuterol

Favor continuous nebulization to decrease the chance of admission when compared to intermittent dosing[2]

  • Nebulizer
    • Intermittent: 2.5-5mg q20min x3, then 2.5-10mg q1-4hr as needed OR
    • Continuous: 0.5mg/kg/hr (max 15mg/hr)[3]
    • If using intermitent nebs at home PTA, start on continuous
  • MDI
    • 6-12 puffs q20min up to 4h, then q1-4hr as needed
  • Levalbuterol is pure R-enantiomer, whereas racemic albuterol as above is 50:50 mix of R and S albuterol
    • Most clinical studies fail to show benefit over racemic albuterol[4][5]
  • Levalbuterol at 5x the cost, may not warrant the small benefits seen in some studies
  • In severe asthma exacerbation, be aware of lactic acidosis that develops due to pathology and the added lactic acidosis from albuterol,
    • Manifests as worsening respiratory distress, tachypnea, compensatory increase in ventilation
    • Ensure adequate intravascular volume, but carefully volume expand as acute asthma may increase ADH secretion[6]
  • Rarely, clinically important hypokalemia, alongside hyperglycemia and leukocytosis, may result from repeated beta agonists and sympathomimetics[7]

Ipratropium[8][9]

  • 0.25-0.5mg q20min x2-3 doses
  • Only shown to be effective in the acute setting to reduce hospitalization rates and improve lung function
  • No benefit of adding to inpatient, hospitalized regimens

Steroids

Should be given in the first hour with effects to reduce admission and rate of relapses[10] Options include:

  • Dexamethasone
    • As effective as prednisone especially in children [11]
    • Single dose dexamethasone may be equally effective to 5 days of prednisone in adults[12]
    • 0.6mg/kg IV or PO (max 16mg); 2nd dose 24hr later may be an equally good option as single dose therapy [13]
  • Prednisone
    • 40-60mg /day x5d
  • Methylprednisolone
    • 1mg/kg IV q 4–6hr
    • Only use IV if cannot tolerate PO since equal effectiveness between dosing routes[14]
    • Oral and IV steroids are safe during pregnancy (though technically Category C)
  • Inhaled corticosteroids may be considered as a rescue effort for severe asthma, given over a 90 min period[15][16]

Magnesium

  • 25-75 mg/kg over 30 min (2-3 g IV in most adults)
  • Duration of action approximately 20 min, beware of hypotension in rapid administration due to smooth muscle relaxation mechanism
  • In patients with moderate to severe asthma there is a decreased rate of admission with an NNT of 2[10]
  • High-dose, prolonged magnesium may expedite discharge from the ED in non-infectious asthma in pediatric study[17]
    • 50 mg/kg/hr for 4 hours
    • MAX 8,000 mg for 4 hours, monitor for cardiopulmonary complications
    • No interventions or discontinuations of magnesium sulfate due to adverse events in the study
    • NNT of 2-3, for hospital discharge before 24 hours

Other Beta-Agonists

  • Inhalation is preferred route of administration, but adequate drug delivery to small airways may be hampered in severe attacks
  • Terbutaline and epinephrine can be administered IM/IV/SubQ
  • Need to monitor for arrhythmias, tachycardia, hypertension, cardiac ischemia[18]

Epinephrine

  • 1:1000 0.01 mg/kg (max 0.5mg) subQ or IM Q20min x3
  • Nebulized racemic epinephrine 0.03 mL/kg (2.25% solution) diluted in 3-5 mL NS via jet nebulizer q3-4hr PRN shown to be as safe as nebulized albuterol[19]
  • In severe, life-threatening asthma, IV epinephrine may be safe to consider, substantiated only by a case series of adults in 2003, however[20]
  • Epinephrine infusion for adults at 5mcg/min (0.05mcg/kg/min for pediatrics) after requiring multiple epinephrine doses.

Terbutaline

  • Longer-acting beta2-agonist promoting bronchodilation
  • Caution in elderly/CHF with greater potential for cardiotoxicity
  • 0.25mg subQ/IM q20min x 3
    • Then followed by infusion at 1 µg/kg/min, titrated up by increments of 1 to max of 10 1 µg/kg/min
    • Elevated troponins q4hrs during infusion, more common in cTnI vs. cTnT, with EKG changes of ischemia should prompt re-evaluation for stopping infusion[21]
  • Some experts have nebulized IV form[22][23]
    • 5 mg of IV form terbutaline
    • However, significantly higher cost than albuterol

Non-invasive ventilation

  • Consider as alternative to intubation
  • Alleviates muscle fatigue which leads to larger tidal volumes
  • May drive nebulized treatments deeper into airways
  • Maximize inspiratory support
    • Inspiratory pressure 8
    • PEEP 0-3, only enough to match patient's auto-PEEP

Intubation and Invasive Ventilation

A-B) Breath stacking and mounting lung volumes, C-D) Normal tracing
  • Relative indications include worsening hypercapnea, exhaustion, altered mental status, CO2 narcosis without any specific number endpoint on blood gases, refractory hypoxemia, status asthmaticus
  • Consider induction with Ketamine
    • Provides bronchodilation and sedation however it does promote secretions
    • Ketamine is the preferred induction agent for intubation in an asthmatic.
    • Dosing 1-2mg/kg
  • Ventilation of asthmatic patients requires deep sedation
    • Benzos, propofol, or ketamine (1mg/kg/hr)
    • Avoid long-term administration of neuromuscular blocking agents such as succinylcholine for prolonged periods in ICU (>12 hours), if possible, given higher rates of complication[24]
    • A large ET tube is preferred (>8.0 mm)
  • Initial ventilation settings - severe asthma
    • Assist-control ventilation
    • Resp rate
      • Start slow to avoid air-trapping
      • RR ~ 8-10 in adults
    • Goal: obtaining a pH above 7.2 and plateau pressure below 30 cmH2O[25]
    • If Pplat >30 must lower respiratory rate
      • If Pplat under 30 cannot be maintained, other causes of decreased respiratory system compliance must be considered (i.e. pneumothorax, misplaced endotracheal tube, pulmonary edema, etc.)
    • May require "permissive hypoventilation"
      • Sacrifice MV for full exhalation
      • Lower I:E ratio
      • Low peak pressure/avoidance of breath stacking more important than correcting CO2 [26]
    • Tidal volume 6-8mL/kg ideal wt
    • PEEP 0-5 cmH2O
    • Flow rate 80-100L/min
    • Keep FiO2 minimum to achieve SpO2 > 90%
  • Use bronchodilators even when intubated
  • Monitor for breath stacking (inspiratory holds, plateau pressures)
    • Most common cause of post-intubation hypotension[27]
    • Check ventilator tracing

Asthma Arrest

  • Disconnect ventilator
  • Decompress chest
  • Consider empiric bilateral chest tubes or rapid ultrasound to identify pneumothorax
  • IVF bolus

Antibiotics

  • Administration of antibiotics only when physical exam or ancillary testing supportive of bacterial infection
  • Antibiotics may be considered for select patients and may improve symptoms and peak expiratory flow, further understanding needed to identify which patients may be most likely to benefit [28]

Heliox

  • 60 to 80% helium is blended with 20 to 40% oxygen
  • Heliox improves laminar flow and may increase the diffusion of carbon dioxide by improving ventilation[29]

Leukotriene Modifiers

  • Not indicated for acute treatment
  • Zafirlukast (20 mg bid) and montelukast (10 mg/day)

Outpatient Treatment

New guidelines by Global Initiative for Asthma (GINA) 2019 endorse the use of an ICS-LABA combined product as both rescue and maintenance inhaler based off of a 2018 meta analysis [30]

  • GINA recommends budesonide or beclomethasone as the inhaled corticosteroid, and formoterol as the long acting beta agonist. The only U.S. formulation meeting this recommendation is Symbicort (budesonide-formoterol).
Severity Day Sx Night Sx Treatment (WHO 2008 Formulary)[31]
Mild intermittent, > 80% peak flow < 2/wk < 2/mo Albuterol MDI 100-200 mcg PRN QID
Mild persistent, > 80% peak flow >2/wk >2/mo Albuterol MDI 100-200 mcg PRN QID AND

Beclometasone 100-250 mcg bid

Moderate persistent, 60-80% peak flow Daily with exacerbations weekly > 1/wk Albuterol MDI 100-200 mcg PRN QID AND

Beclometasone 100-500 mcg BID AND

Salmeterol inhaled 50 mcg bid

Severe persistent, < 60% peak flow Continuous daily Frequent Albuterol MDI 100-200 mcg PRN QID AND

Beclometasone 1mg BID (high dose) AND

Salmeterol inhaled 50 mcg BID AND (if needed)

theophylline, leukotriene antagonist, or PO prednisolone with taper

Disposition

Discharge

  • If symptoms resolve
    • Often, patients will still have mild wheezing, but should have complete resolution of tachypnea, hypoxia, and work of breathing if being discharged
    • A short course of glucocorticoids decreases chance of relapse[32] - prednisone in adults (40-60 mg/day for 5-10 days without tapering) or dexamethasone (0.6mg/kg) in children

Admit

  • If symptoms persist or are severe
  • Classically disposition is based on peak flow measurements - however, these measurements are often not available in the ED
    • Predicted = (30 x age (yrs)) + 30
    • PEF >70% predicted → high likelihood of successful discharge
    • PEF <40% predicted → should be admitted

See Also

External Links

References

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