PEDBASE.org - The Pediatric Database - Detailed information of ACUTE ASTHMA

ACUTE ASTHMA

DEFINITION:

An acute exacerbation of asthma characterized by airway obstruction and respiratory distress.

EPIDEMIOLOGY:

incidence: 10-20% of children have asthma
age of onset:
- any
risk factors:
- see below

PATHOPHYSIOLOGY:

1. Early Phase

rapid onset
begins almost immediately after the initial challenge and is characterized by airway hyperresponsiveness to a specific stimulus
characteized by smooth muscle bronchoconstriction
beta-2 agonists rapidly reverse
prevented by cromolyn but not steroids

2. Late Phase

gradual onset
begins 6-8 hours after the initial challenge and is characterized by non-specific airway hyperresponsiveness to a variety of stimuli lasting several days or weeks
characterized by airway inflammation with increased neutrophils and eosinophils
beta-2 agonists do not reverse
prevented by cromolyn and steroids

3. Risk Factors for Severe Asthma

1. On History

1. Poorly Controlled Asthma

frequent asthma attacks (more than 2 per week)
recent attack of severe asthma
recent emergency room visit, hospitalization, and/or ICU admission for asthma

2. Severe Present Attack

duration of current symptoms for greater than 24 hours
greater than 10 puffs of ventolin in past 24 hours
recent use of high dose steroids
long delay in seeking medical care

2. On Physical

1. Pulsus Paradoxus

represents the drop in systolic blood pressure with inspiration
a pulsus paradoxus of greater than 15-20 mmHg indicates severe asthma when correlated with pulmonary function tests (FEV1 less than 60% of predicted; PEFR 10% of predicted) and blood gas analysis (PaCO2 greater than 40 mmHg) - Rebuck and Tomarken, CMAJ 112:710 (1975); Galant et al., Pediatrics 61(1): 46 (1978)

2. Sternocleidomastoid (SCM) Contraction

SCM contraction and supraclavicular indrawing indicate severe asthma when correlated with pulmonary function tests (FEV1 less than 60% of predicted) - Commey and Levison, Pediatrics 58(4): 537 (1976)

CLINICAL FEATURES:

1. Mild Acute Asthma

cough, wheeze, some dyspnea
SaO2 greater than 95% in room air
Peak Flow les than 75% of personal best or standard level

2. Moderate Acute Asthma

cough, wheeze, dyspnea
intercostal indrawing, tracheal tug
SaO2 92-95% in room air
Peak Flow 40-75% of personal best or standard level

3. Severe Acute Asthma

anxiety, confusion, fatique, decreased level of consciousness
dyspnea with inability to speak and/or eat
respiratory rate greater than 2 standard deviations for age
signs of severe airway obstruction:
- nostril flaring, tracheal tug, intercostal indrawing
- supraclavicular indrawing
- accessory muscle use
- pulsus paradoxus greater than 20 mmHg
- absent or faint breath sounds (lack of air entry)
- marked expiratory wheeze
SaO2 less than 91% in room air
Peak Flow less than 40% of personal best or standard level

INVESTIGATIONS:

1. Pulse Oximetry

see above

2. Pulmonary Function Tests

see above

3. Blood Gases

ominous signs include a normal or elevated PaCO2 and/or a PaO2 less than 60 mmHg in room air

4. Chest X-Ray

hyperinflation with air trapping
rule out pneumothorax

MANAGEMENT:

1. Criteria for Hospital Admission

critically ill (severe airway obstruction with respiratory distress)
poor response to Emergency Room Therapy:
- greater than 3-4 ventolin treatments
- post treatment PEFR less than 40% of predicted
- post treatment PaCO2 greater than 40 mmHg
social considerations:
- unreliable parents
- home far distance from hospital

2. Supportive

humidified oxygen by mask, nasal prongs, or hood box
if dehydrated, start IV and rehydrate

3. Medications

1. Early Phase

1. Salbutamol (Ventolin)

0.04cc/kg (up to 1cc) per dose of inhalation solution diluted in 2cc normal saline q20m or continuously if necessary (or 0.5cc for children less than 10 years of age and 1.0cc for children greater than 10 yrs of age)
if admitted to hospital give same dose q2-4h with q1-2h prn depending upon clinical status
if admitted to the ICU continue with nebulized ventolin and add intravenous salbutamol:
- loading dose - 10 ug/kg IV over 10 minutes
- maintenance dose - 0.2-4.0 ug/kg/min IV (to maximum of 10ug/kg/min)
- watch for side effects - tachycardia, hypokalemia, hyperglycemia

2. Ipratropium Bromide (Atrovent)

250-500 ug in 2cc normal saline or with ventolin q4-8h

3. Aminophylline

use only if admitted to the ICU and must moniter level
loading dose - 6 mg/kg IV
maintenance dose - 0.8-1.5 mg/kg/hr IV

2. Late Phase

1. Corticosteroids

1. Oral

Prednisone 1-2 mg/kg/day od or bid x 5 days
use whether or not admitted to hospital

2. Intravenous

for admission to hospital or the ICU

1. Hydrocortisone (Solu-Cortef)

loading dose: 5-10 mg/kg IV
maintenance dose: 5-10 mg/kg/dose q6h IV x 5 days then taper

2. Methylprednisolone (Solu-Medrol)

loading dose: 1-2 mg/kg IV
maintenance dose: 0.5-1 mg/kg/dose q6h IV x 5 days then taper

Pediatric Database - ACUTE ASTHMA

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