Asthma

 Introduction

The Global Initiative for Asthma Global Burden of Asthma (2004) estimates there are 300 million people worldwide with Asthma.  Prevalence is highest in the developed world, and rates of asthma increase as "communities adopt western lifestyles and become urbanised".

Asthma is the 3rd most common Respiratory diagnosis in US EDs (NHAMCS 2006-2008), and account for 146 000 ED visits a year in Canada (based on 1994 data, as reported by the Asthma Society of Canada). A recent Canadian Study from Alberta revealed similar results:

During the 6-year study period, 93 146 patients made 199 991 ED visits for asthma. Crude rates in 2004/05 were 7.9/1000, 6.5/1000 and 15.4/1000 in the Edmonton, Calgary and NMU regions, respectively. The Edmonton and Calgary regions had consistently lower visit rates than the NMU regions. The ED visits were followed by low rates of follow-up visits in a variety of non-ED settings, at different intervals. (CJEM 2010;12(4):339-346)

Asthma (Wikipedia) is a chronic inflammatory diesease whose acute exacerbations have 3 pathophysiologic features - 1. Bronchocnostriction secondary to airway hyperresponsiveness  2. Airway inflammation leading to narrowing and airflow restriction and obstruction  3. Mucus plugs from increased secretions secondary to the acute on chronic inflammation.  These lead to the diagnostic hallmarks of Wheezing, Cough, Difficulty Breathing, and Chest Tightness.  They are also the primary therapeutic targets of both maintenance and acute treatment strategies.

 

 Approach

The Guideline Links below contain most of the following information, and more details besides.  The following is a bare bones review of the Assessment and Treatment of Asthma.

ABCDE Primary Survey should always be your first steps when seeing an asthmatic, or anyone with respiratory distress.  As part of the Primary Survey you should be able to classify the severity of the Asthma attack.

In cases where asthma is clearly the diagnosis, treatment should begin simultaneously with your Primary Assessment.  Further assessment can be done once treatment is underway.

 

PEFR = Peak Expiratory Flow Rate [This is a surrogate measure for FEV1 (Forced Expiratory Volume in 1 second), which is usually impractical in the ED setting, though considered a more acurate measure.]  Predicted PEFR is calculated (MDCalc), or found in tables like this (By Mikael Häggström [Public domain], via Wikimedia Commons), or these (from sphemerg.ca) - Males, Females, Children.

 

 History

The initial history should be aimed at determining the patient's baseline Asthma Severity (Academic Life in EM Paucis Verbis Card).

Important questions to ask early:

  • When did the wheezing/this attack begin?
  • Have you been prescribed medication for you asthma?
  • Are you taking these medications?
  • Which ones, and how often? SABAs are often blue of green MDIs, while ICS are often orange, red, or brown.  Patients will often refer to their puffers by the color and have little understanding of what they do.  Pay attention to the common colors of MDIs in you area.
  • Have you been taking your medications more often in the last few days or weeks?
  • Have you ever been:
    1. to the Emergency Department for your Asthma before?
    2. admitted to hospital for your Asthma before?
    3. been intubated or admitted to the ICU for your Asthma before?

Answers to these questions can help you better understand how THIS patient's asthma MAY progress/respond to therapy.

Other important things to ask:

  • Do you have particular triggers for you asthma, and have you been exposed to any of those?
  • Do you or anyone you live with/closely associate with smoke?
  • Have your symptoms been worse at night?
  • Have you had a recent cough, or worsening of a chronic cough?

 Exam

Look - is there cyanosis? are they using accesory muscles? how fast are they breathing? do they appear scared/distressed?

Listen - are they wheezing? is the chest quiet? is the expiratory phase prolonged? are there other, or localized abnormal sounds

Feel - are they hot or cool?  are they sweating? is there pulsus paradoxis (a stretch on the 'feel' motif…)

These things will help you determine severity, and point at alternate diagnoses (infection, pneumothorax etc)

 Investigations

Peak Expiratory Flow Rate (see above) serially

ECG - Arrhythmias can accompany severe and life-threatening asthma

Arterial Blood Gases.  Low PaO2, and high PaCO2 are indications of life-threatening cases

Chest XRay, CBCDiff, Electrolytes.  These can point to alternate diagnoses, and help guide therapy.

 Treatment

Acute Exacerbation

  • Inhaled Short Acting ß2 Agonist (SABA) (Wikipedia)(American Thoracic Society) therapy is the 1st line therapy in all cases. SABAs can be delivered by MDI (best with a spacer device) or by nebulizer.  Therapy may be intermittent in Mild or Moderate cases, but continuous nebulized therapy is best for severe and life-threatening cases (NNT).  Intravenous SABAs are a last resort therapy.
  • The addition of Inhaled Anticholinergics is advised. Using these medications more than q4-6hours does not add any benefit.
  • Supplemental Oxygen is indicated to get oxygen saturation to or above 90%.  Where practical nebulized therapy should be driven by oxygen rather than air.
  • Systemic corticosteroids (oral or IV) are indicated in all acute exacerbations (NNT).
  • IV magnesium may be of benefit in severe or life-threatening cases (NNT).
  • Antibiotics should be reserved for those with clear evidence of bacterial infections.
  • Leukotriene Receptor Agonists.  One recent study seems to suggest a benefit to the addition of LRAs to standard therapy in acute exacerbations (Thorax. 2011 Jan;66(1):7-11).  This is not a practice changing paper, as pointed out by Cliff Reid of Resus.me
  • For severe cases responding poorly to therapy consider Non-Invasive Ventilation (NIV) - CPAP or BiPAP (see the reviews below for more complete discussion of NIV).

 Admission

  • Admission is indicated in those who can not reach PEFR 75-80% of predicted/personal best.
  • ICU admission is appropriate in those  worsening despite optimal therapy, or severe/life-threatening asthmas that shows no improvement despite optimal therapy.

Good Reviews

Discharge treatment

 

 Guidelines

Most Countries (and major jurisdictions) have published Asthma guidelines covering both chronic and acute asthma. While all very similar, they all differ in various ways reflecting variations in medical practice, and the variable epidemiology of asthma in different parts of the world.

Despite all of these Guidelines they are not stricly followed in many clinical situations.  A Canadian study looked at Asthma guideline compliance (all of these guidelines existed in an earlier form at the time of the study).  Overall compliance was 65-75%, highest with mild asthma and lowest with severe asthma (CJEM 2004;6(5):321-326)

 

Deeper Learning

Landmark Papers

 

  

Science Based Medicine

 

 

 Physiology

Respiratory Physiology (Wikibooks)

Respiratory Physiology (Wikipedia)

 

 Pathophysiology

 

 

 Pharmacology

 

 

 Biochemistry

 

 

 Other

 

 

Textbook Links/References

Google Books has a Preview of Tintinalli's Emergency Medicine: A Comprehensive Study Guide with sections on Asthma.

 

Areas of Controversy

The Buteyko Method (Wikipedia) is a method of slow and/or shallow breathing purported to cure asthma.  The Wikipedia artlice is relatively even-handed, indicating little or no support for the utility of the method.  You can visit the Buteyko Breathing Centre site for the PRO view, and visit the Science Based Medicine blog for a more scientific assessment.  The bottom line is that it MAY reduce the sensation of breathlessness in some asthmatics, reducing their use of rescue inhalers, but has no effect on objective measures of asthma.

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