Acute asthma exacerbation: Difference between revisions
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==Background==
==Background==
*3 questions
Three questions:
*#Does this pt have asthma?
#Does this pt have asthma?
*#*Most wheezing in pt <3yr is not asthma
#*Most wheezing in patient <3yr is not asthma
*#What is the severity?
#What is the severity?
*#Is there a treatable preciptant?
#Is there a treatable preciptant?


==Clinical Features==
==Clinical Features==

Revision as of 00:23, 22 September 2015

Background

Three questions:

  1. Does this pt have asthma?
    • Most wheezing in patient <3yr is not asthma
  2. What is the severity?
  3. Is there a treatable preciptant?

Clinical Features

  • Dyspnea, wheezing, and cough
  • Prolonged expiration
  • Accessory muscle use
  • Sign of impending ventilatory failure
    • Paradoxical respiration
      • Chest deflation and abdominal protrusion during inspriation
    • Altered mental status
    • "Silent chest"

Differential Diagnosis

Acute dyspnea

Emergent

Non-Emergent

Diagnosis

Consider CXR if:

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

ED Treatment

Albuterol

Favor continuous nebulization to decrease the chance of admission when compared to intermittent dosing[1]

  • Nebulizer
    • 2.5-5mg q20min x3, then 2.5-10mg q1-4hr as needed OR
    • Continuous = 0.15mg/kg/hr (max 25mg/hr)
  • MDI
    • 4-8 puffs q20min up to 4h, then q1-4hr as needed

Ipratropium

  • 0.5mg q20min x3

Steroids

Should be given in the first hour with effects to reduce admission[2]

  • Dexamethasone
    • As effective as prednisone especially in children [3]
    • 0.6mg/kg IV or PO (max 16mg); 2nd dose 24hr later
  • Prednisone
    • 40-60mg/day in one or two divided doses x5d
  • Methylprednisolone
    • 1mg/kg IV q 4–6hr
    • Only use IV if cannot tolerate PO since equal effectiveness between dosing routes[4]

Magnesium

  • 1-2gm IV over 30min
  • Duration of action approx 20 min
  • In patients with moderate to severe asthma there is a decreased rate of admission with an NNT of 2[2]

Parenteral beta-agnonist

Epinephrine

  • 1:1000 0.01mg/kg (max 0.5mg) subQ or IM Q20min x 3

Terbutaline

  • Longer-acting beta2-agonist promoting bronchodilation
  • 0.25mg subQ/IM q20min x 3
  • Caution in elderly/CHF

Non-invasive ventilation

  • Consider as alternative to intubation
  • Alleviates muscle fatigue which leads to larger tidal volumes
  • Maximize inspiratory support
    • Inspiratory pressure 8
    • PEEP 0-3

Heliox

  • 60 to 80% helium is blended with 20 to 40% oxygen
  • Heliox improves non laminar flow and may increases the diffusion of carbon dioxide by improving ventilation[5]

Intubation

  • 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 pts requires deep sedation
  • Ventilation settings[6]
    • Assist-control ventilation
    • Resp rate
      • Start slow to avoid air-trapping
      • RR ~ 8-10 in adults
    • Make sure plateau pressure <30
    • If >30 must lower resp rate
    • May require "permissive hypoventilation"
      • Low peak pressure/avoidance of breath stacking more important than correcting CO2 [7]
    • Tidal volume 6-8cc/kg ideal wt
    • PEEP 0
    • Flow rate 80-100L/min
    • Keep FiO2 minimum to achieve SpO2 > 90%
  • Use bronchodilators even when intubated

Outpatient Treatment

Severity Day Sx Night Sx Treatment (WHO 2008 Formulary)[8]
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

PLUS Beclometasone 100-250 mcg bid

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

PLUS Beclometasone 100-500 mcg bid

PLUS Salmeterol inhaled 50 mcg bid

Severe persistent, < 60% peak flow Continuous daily Frequent Albuterol MDI 100-200 mcg prn qid

PLUS Beclometasone 1 mg bid (high dose)

PLUS Salmeterol inhaled 50 mcg bid

PLUS (if needed) SR theophylline, leukotriene antagonist, or PO prednisolone with taper

Disposition

  • A short course of glucocorticoids (prednisone in adults or dexamethasone in children (0.6mg/kg) decreases change of relapse [9]
  • Although classically disposition is based on peak flow measurements such results are often not available in the ED
    • Predicted = (30 x age (yrs)) + 30
    • Discharge if symptoms resolved and PEF >70% predicted
    • Admit if symptoms persist and PEF <40% predicted
    • Discharge versus admit based on physician judgment if some symptoms persist and adequate home support
  • Often patient will still have mild wheezing should have resolution of tachypnea, hypoxia, and work of breathing if they are being discharged.

See Also

References

  1. ↑ Camargo CA et al. Continuous versus intermittent beta- agonists for acute asthma. Cochrane Database Syst Rev. 2003;(4):CD001115. PMID: 14583926.
  2. ↑ 2.0 2.1 Rowe BH et al. Magnesium sulfate for treating exac- erbations of acute asthma in the emergency depart- ment. Cochrane Database Syst Rev. 2000;(2):CD001490. PMID: 10796650.
  3. ↑ Keeney, et al. Dexamethasone for Acute Asthma Exacerbations in Children: A Meta-analysis. Pediatrics. 2013-2273
  4. ↑ Rowe BH, Keller JL, Oxman AD. Effectiveness of steroid therapy in acute exacerbations of asthma: a meta-analysis. Am J Emerg Med. Jul 1992;10(4):301-10
  5. ↑ Kass JE: Heliox redux. Chest 2003; 123:673.
  6. ↑ EMCrit *15 http://emcrit.org/podcasts/severe-asthmatic/
  7. ↑ Darioli, et al. Mechanical Controlled hypoventilation in status asthmaticus. Am Rev Respir Dis. 1984; 129 (3) 385-7
  8. ↑ Stuart MC et al. WHO Model Formulary 2008. http://www.who.int/selection_medicines/list/WMF2008.pdf.
  9. ↑ Chapman K. Effect of a short course of prednisone in the prevention of early relapse after the emergency room treatment of acute asthma. NEJM. 1991;324(12):788
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