Pediatric Resident Curriculum for the PICU
UTHSCSA
ASTHMA IN THE PICU
Pediatric Resident Curriculum for the PICU
UTHSCSA
Epidemiology
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14-15 million Americans
Nearly 5 million children
5,000 people (mostly adults) die each year
Incidence, hospitalization rate, and death rate
is increasing each year.
• 15-24 year-olds are at higher risk of dying from
asthma than are 0-4 year olds.
• Prior asthma episode requiring mechanical
ventilation is strong predictor of subsequent
asthma death.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Pathogenesis
• Asthma is a chronic inflammatory disease of the
airways.
• Asthma is characterized by bronchospasm, airway
edema, and mucus production
• Asthma has several components:
– Cellular
– Cytokines
– Neurologic
Pediatric Resident Curriculum for the PICU
UTHSCSA
Pathophysiology
• Asthma is an obstructive pulmonary disease.
• Air-trapping and over-expansion of alveoli is a
hallmark of asthma.
• Air-trapping may lead to air-leak, which can be
fatal.
• In addition, active expiration may be required to
return the lung volume to FRC.
• Muscles of expiration are not designed for active
expiration and quickly become fatigued, leading to
respiratory failure and death.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Triggers
• Numerous things can trigger asthma attacks:
– Allergens
– Exercise
– Stress
– Viruses
– Medicines
– Noxious stimuli
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cellular component
• Numerous cells involved:
– Mast cells
– Eosinophils
– Lymphocytes (TH-2 cells)
– Neutrophils
– Epithelial cells
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cytokines
• Numerous soluble products of the cells exacerbate
asthma:
– Interleukins
– Bradykinins
– Histamine
Pediatric Resident Curriculum for the PICU
UTHSCSA
Neurologic
• Parasympathetic
– Stimulation via the vagus leads to airway
constriction.
• Sympathetic
– Plays little role in humans since only pulmonary
vasculature, not airway smooth muscle, is
innervated
• Non-adrenergic non-cholinergic (NANC)
– Role in humans not determined.
– Vasoactive intestinal polypeptide, Substance P,
NO
Pediatric Resident Curriculum for the PICU
UTHSCSA
Receptors
• Beta
– 3 subtypes
– 2 is common in airway smooth muscle
– Activation leads to increase in cAMP
• Alpha: little role
• Cholinergic
– Muscarinic receptors:
• M2 receptor inhibits acetylcholine release,
leading to bronchodilation.
• M3 receptor cause bronchoconstriction
Pediatric Resident Curriculum for the PICU
UTHSCSA
Physical Exam
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Respiratory Rate
Work-of-Breathing
Breath Sounds
Inspiratory:Expiratory Phase
Cyanosis
Mental status
Pediatric Resident Curriculum for the PICU
UTHSCSA
Respiratory rate
• Normal
– Infants: <40
– Toddlers: <30
– Preschoolers: <30
– Elementary School: low 20s
– High school: upper teens
Pediatric Resident Curriculum for the PICU
UTHSCSA
Work-of-breathing
• Nasal Flaring
• Retractions
– Supraclavicular
– Intercostal
– Substernal
• Paradoxical Breathing
Pediatric Resident Curriculum for the PICU
UTHSCSA
Breath sounds
• Lung Fields
• Air flow
– Good, fair, poor
• Expiratory Wheeze
– Polysyllabic vs. Monosyllabic
• Inspiratory Wheeze
– Common, even in non-diseased states
Pediatric Resident Curriculum for the PICU
UTHSCSA
Phases
• Normally, expiratory phase is the same as, or
shorter than the inspiratory phase.
• In asthma, the expiratory phase is prolonged as
airway collapse and air-trapping occur.
• Intrathoracic pressure becomes higher than the
large airway pressure, leading to collapse of the
airways.
• Airway edema, bronchospasm, and mucus
impede air movement.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cyanosis
• Need 5gm/dl of unoxygenated hemoglobin
before cyanosis present
• Cyanosis will be more pronounced in children
with high hematocrits: dehydrated, cyanotic
heart disease
• Cyanosis can be a sign of impending respiratory
failure….or not.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Mental Status
• Hypoxia and hypercarbia can lead to mental
status changes.
• Fatigue can, too.
• Improvement can, too.
• Watch for agitation, delirium, unresponsiveness,
especially to pain.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Laboratory tests
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PEFR
PFTs
Asthma Scores
IgE
Allergy tests
Blood gas
CXR
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatments
• Oxygen
• Steroids
– Inhaled
– Systemic
• Beta Agonists
– Short-acting
– Long-acting
• Anticholinergics
• Leukotriene Inhibitors
• Methylxanthines
• Magnesium
Pediatric Resident Curriculum for the PICU
UTHSCSA
Oxygen/Fluid
• Ventilation/perfusion mismatch can be quite high
• Oxygen lends to patient comfort
• In absence of chronic pulmonary disease, i. e., CO2
retention, supplemental oxygen will not suppress
the respiratory drive
• Most patients with asthma are dehydrated
(increased insensible losses, decreased intake)
• Overhydration can exacerbate pulmonary edema.
• Watch for SIADH.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Steroids
• Only drug that addresses the underlying
pathophysiology
• Solumedrol
– 2mg/kg/day divided q6hr
– Max is 60mg/day “kids,” 180mg/day “adults”
– IV
• Prednisone or Prednisolone
– Oral
Pediatric Resident Curriculum for the PICU
UTHSCSA
Steroids
• No difference between IV and po
• Usually give IV in severe attack because of
nausea and high respiratory rate increases risk
of aspiration
• 5 day course of therapy won’t suppress adrenal
system
• Start to work in 8-12 hours
Pediatric Resident Curriculum for the PICU
UTHSCSA
Steroids
• Complications
– Hypertension
– Hyperglycemia
– Hypokalemia
– Gastritis
Pediatric Resident Curriculum for the PICU
UTHSCSA
Inhaled Steroids
• For long term control
• Fewer side effects than systemic steroids, but
may be associated with long-term growth
suppression.
– Beclomethasone
– Budenoside
– Flunisolide
– Fluticasone
– Triamcinolone
Pediatric Resident Curriculum for the PICU
UTHSCSA
Beta-agonists
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Work via the 2 receptor to bronchodilate
Albuterol
Terbutaline
Can cause hypokalemia, tremors, nausea,
vomiting, tachycardia
Pediatric Resident Curriculum for the PICU
UTHSCSA
Beta-agonists
• Give via MDI or nebs
• Dose:
– Depends upon size, severity of disease, and
delivery device. Titrate to heart rate and
response
– Usual neb dose:
• <10kg: 2.5mg/hr
• 10-20kg: 5mg/hr
• 20-30kg: 10mg/hr
• >30kg: 15mh/hr
Pediatric Resident Curriculum for the PICU
UTHSCSA
Anti-cholinergics
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Atropine and atrovent
Bronchodilate and decrease mucus production
Additive effect with beta-agonists.
Use for beta-blocker induced asthma
Complications include drying of the airways
and rarely, increased wheezing
• Atrovent dose: 250-500mcg/dose up to q
20min, usually q2-4hrs.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Leukotriene inhibitors
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Block the actions of leukotrienes
Zafirlukast and zileuton
Used for long-term control
Little use in acute attacks
May be as effective as inhaled steroids
Rare side effects (liver damage)
Pediatric Resident Curriculum for the PICU
UTHSCSA
Methylxanthines
• Theophylline and aminophylline
• Actions are several:
– Phosphodiesterase inhibitor (increases cAMP)
– Stimulates catecholamine release
– Diueresis
– Augments diaphragm contractility
– Prostoglandin antagonist
• May be of little benefit in routine use for acute
asthma
• High risk of side effects: N/V, tachycardia,
agitation, cardiac arrythmias, hypotension,
seizures, death
Pediatric Resident Curriculum for the PICU
UTHSCSA
Magnesium
• Mechanism unclear, but may be a direct
bronchodilator through blocking calcium
• Raising the Mg levels up to 2-4 mg/dL
significantly improved expiratory air flow in
adults
• One study in children showed that MgSO4
25mg/kg over 20 minutes significantly improved
PFTs, but did not change hospitalization rate or
length of stay in the ED.
• Relatively safe. Levels >12 can cause weakness,
areflexia, respiratory depression, and cardiac
arrhythmias
Pediatric Resident Curriculum for the PICU
UTHSCSA
Weaning protocol
• Patients selected by attending/resident
• Physician writes order
• Physician writes initial dose and frequency of
bronchodilator
• Respiratory therapist evaluates patient and
changes therapy in accordance with protocol
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatment levels
• Level 1: Continuous albuterol at > 0.6 mg/kg/hr
• Level 2: Continuous albuterol at 0.3 mg/kg/hr
– (Max 15 mg/hr)
• Level 3: Continuous albuterol at 0.15mg/kg/hr
• Level 4: Albuterol at about 0.3mg/kg q2hours
– Infants <5kg use 1.0 mg
– Infants 5 - 10 kg use 2.5 mg
– Children 10 - 20 kg use 5.0 mg
– Children > 20 kg round to closest multiple of
2.5 mg (2.5, 5.0, 7.5, etc)
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatment levels
• Level 5 : Albuterol q3 hours at same dose as level
4
– When the patient has been stable on q3 hour
treatments for 2 treatment intervals, therapist is
to call the physician to evaluate for possible
transfer out of the PICU (anytime of day or night).
– If the patient is also receiving intermittent Atrovent
nebulizations q2 or q4 hours, the therapist should
make these q3 to coincide with the albuterol
treatments.
• Level 6 : Albuterol q4 hours, same dose as level 4
and 5
• Level 7 : Albuterol q4 hours at about 0.15mg/kg if
dose for previous levels is above 2.5 mg
• Level 8 : Albuterol q6 hours, same dose
Pediatric Resident Curriculum for the PICU
UTHSCSA
Acute Asthma Score
Modified from Woods, et al, AJDC, 1972
Variable
Pulse Oximetry
Cyanosis
0
1
2
>93% in RA
<94% in RA
<94% with
40% FiO2
None
In RA
In 40% FiO2
Inspiratory
Breath Sounds
Normal
Unequal
Decreased to
Absent
Accessory
Muscles Used
None
Moderate
Maximal
None
Moderate
Depressed or
Agitated
Marked
Expiratory
Wheezing
Cerebral
Function
Normal
Coma
Pediatric Resident Curriculum for the PICU
UTHSCSA
Weaning criteria
A. Respiratory therapist has evaluated patient and
feels the patient is not acutely distressed,
AND
B. The asthma score is less than or equal to 3,
AND
C. If the patient is over 6 years and cooperative, the
peak flows are > 70% of predicted,
AND
D. The patient must be stable at these criteria for 3
hours or for two treatment intervals, whichever is
longer.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Failure criteria
A. The therapist (or nurse) judges the patient to
be in increased distress, but not
severe
distress.
OR
B. The asthma score increases to greater than 3
but less than 5.
OR
C. The PEFR drops to less than 70% predicted
but greater than 50% of predicted.
Pediatric Resident Curriculum for the PICU
UTHSCSA
Deterioration criteria
A. The respiratory therapist (or nurse) judges
the patient has developed severe distress.
OR
B. The asthma score increases to more than or
equal to 5.
OR
C. The PEFR drops to less than 50% of
predicted.