UTHSCSA Pediatric Resident Curriculum for the PICU ASTHMA IN THE PICU

UTHSCSA Pediatric Resident Curriculum for the PICU Epidemiology million Americans million Americans Nearly 5 million children Nearly 5 million children 5,000 people (mostly adults) die each year 5,000 people (mostly adults) die each year Incidence, hospitalization rate, and death rate is increasing each year. Incidence, hospitalization rate, and death rate is increasing each year year-olds are at higher risk of dying from asthma than are 0-4 year olds 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. Prior asthma episode requiring mechanical ventilation is strong predictor of subsequent asthma death.

UTHSCSA Pediatric Resident Curriculum for the PICU Pathogenesis Asthma is a chronic inflammatory disease of the airways. Asthma is a chronic inflammatory disease of the airways. Asthma is characterized by bronchospasm, airway edema, and mucus production Asthma is characterized by bronchospasm, airway edema, and mucus production Asthma has several components: Asthma has several components: – Cellular – Cytokines – Neurologic

UTHSCSA Pediatric Resident Curriculum for the PICU Pathophysiology Asthma is an obstructive pulmonary disease. Asthma is an obstructive pulmonary disease. Air-trapping and over-expansion of alveoli is a hallmark of asthma. Air-trapping and over-expansion of alveoli is a hallmark of asthma. Air-trapping may lead to air-leak, which can be fatal. 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. 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. Muscles of expiration are not designed for active expiration and quickly become fatigued, leading to respiratory failure and death.

UTHSCSA Pediatric Resident Curriculum for the PICU Triggers Numerous things can trigger asthma attacks: Numerous things can trigger asthma attacks: – Allergens – Exercise – Stress – Viruses – Medicines – Noxious stimuli

UTHSCSA Pediatric Resident Curriculum for the PICU Cellular component Numerous cells involved: Numerous cells involved: – Mast cells – Eosinophils – Lymphocytes (TH-2 cells) – Neutrophils – Epithelial cells

UTHSCSA Pediatric Resident Curriculum for the PICU Cytokines Numerous soluble products of the cells exacerbate asthma: Numerous soluble products of the cells exacerbate asthma: – Interleukins – Bradykinins – Histamine

UTHSCSA Pediatric Resident Curriculum for the PICU Neurologic Parasympathetic Parasympathetic – Stimulation via the vagus leads to airway constriction. Sympathetic Sympathetic – Plays little role in humans since only pulmonary vasculature, not airway smooth muscle, is innervated Non-adrenergic non-cholinergic (NANC) Non-adrenergic non-cholinergic (NANC) – Role in humans not determined. – Vasoactive intestinal polypeptide, Substance P, NO

UTHSCSA Pediatric Resident Curriculum for the PICU Receptors Beta Beta – 3 subtypes –  2 is common in airway smooth muscle – Activation leads to increase in cAMP Alpha: little role Alpha: little role Cholinergic Cholinergic – Muscarinic receptors: M 2 receptor inhibits acetylcholine release, leading to bronchodilation. M 2 receptor inhibits acetylcholine release, leading to bronchodilation. M 3 receptor cause bronchoconstriction M 3 receptor cause bronchoconstriction

UTHSCSA Pediatric Resident Curriculum for the PICU Physical Exam Respiratory Rate Respiratory Rate Work-of-Breathing Work-of-Breathing Breath Sounds Breath Sounds Inspiratory:Expiratory Phase Inspiratory:Expiratory Phase Cyanosis Cyanosis Mental status Mental status

UTHSCSA Pediatric Resident Curriculum for the PICU Respiratory rate Normal Normal – Infants: <40 – Toddlers: <30 – Preschoolers: <30 – Elementary School: low 20s – High school: upper teens

UTHSCSA Pediatric Resident Curriculum for the PICU Work-of-breathing Nasal Flaring Nasal Flaring Retractions Retractions – Supraclavicular – Intercostal – Substernal Paradoxical Breathing Paradoxical Breathing

UTHSCSA Pediatric Resident Curriculum for the PICU Breath sounds Lung Fields Lung Fields Air flow Air flow – Good, fair, poor Expiratory Wheeze Expiratory Wheeze – Polysyllabic vs. Monosyllabic Inspiratory Wheeze Inspiratory Wheeze – Common, even in non-diseased states

UTHSCSA Pediatric Resident Curriculum for the PICU Phases Normally, expiratory phase is the same as, or shorter than the inspiratory phase. 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. 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. Intrathoracic pressure becomes higher than the large airway pressure, leading to collapse of the airways. Airway edema, bronchospasm, and mucus impede air movement. Airway edema, bronchospasm, and mucus impede air movement.

UTHSCSA Pediatric Resident Curriculum for the PICU Cyanosis Need 5gm/dl of unoxygenated hemoglobin before cyanosis present Need 5gm/dl of unoxygenated hemoglobin before cyanosis present Cyanosis will be more pronounced in children with high hematocrits: dehydrated, cyanotic heart disease 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. Cyanosis can be a sign of impending respiratory failure….or not.

UTHSCSA Pediatric Resident Curriculum for the PICU Mental Status Hypoxia and hypercarbia can lead to mental status changes. Hypoxia and hypercarbia can lead to mental status changes. Fatigue can, too. Fatigue can, too. Improvement can, too. Improvement can, too. Watch for agitation, delirium, unresponsiveness, especially to pain. Watch for agitation, delirium, unresponsiveness, especially to pain.

UTHSCSA Pediatric Resident Curriculum for the PICU Laboratory tests PEFR PEFR PFTs PFTs Asthma Scores Asthma Scores IgE IgE Allergy tests Allergy tests Blood gas Blood gas CXR CXR

UTHSCSA Pediatric Resident Curriculum for the PICU Treatments Oxygen Oxygen Steroids Steroids – Inhaled – Systemic Beta Agonists Beta Agonists – Short-acting – Long-acting Anticholinergics Anticholinergics Leukotriene Inhibitors Leukotriene Inhibitors Methylxanthines Methylxanthines Magnesium Magnesium

UTHSCSA Pediatric Resident Curriculum for the PICU Oxygen/Fluid Ventilation/perfusion mismatch can be quite high Ventilation/perfusion mismatch can be quite high Oxygen lends to patient comfort Oxygen lends to patient comfort In absence of chronic pulmonary disease, i. e., CO 2 retention, supplemental oxygen will not suppress the respiratory drive In absence of chronic pulmonary disease, i. e., CO 2 retention, supplemental oxygen will not suppress the respiratory drive Most patients with asthma are dehydrated (increased insensible losses, decreased intake) Most patients with asthma are dehydrated (increased insensible losses, decreased intake) Overhydration can exacerbate pulmonary edema. Overhydration can exacerbate pulmonary edema. Watch for SIADH. Watch for SIADH.

UTHSCSA Pediatric Resident Curriculum for the PICU Steroids Only drug that addresses the underlying pathophysiology Only drug that addresses the underlying pathophysiology Solumedrol Solumedrol – 2mg/kg/day divided q6hr – Max is 60mg/day “kids,” 180mg/day “adults” – IV Prednisone or Prednisolone Prednisone or Prednisolone – Oral

UTHSCSA Pediatric Resident Curriculum for the PICU Steroids No difference between IV and po No difference between IV and po Usually give IV in severe attack because of nausea and high respiratory rate increases risk of aspiration 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 5 day course of therapy won’t suppress adrenal system Start to work in 8-12 hours Start to work in 8-12 hours

UTHSCSA Pediatric Resident Curriculum for the PICU Steroids Complications Complications – Hypertension – Hyperglycemia – Hypokalemia – Gastritis

UTHSCSA Pediatric Resident Curriculum for the PICU Inhaled Steroids For long term control For long term control Fewer side effects than systemic steroids, but may be associated with long-term growth suppression. Fewer side effects than systemic steroids, but may be associated with long-term growth suppression. – Beclomethasone – Budenoside – Flunisolide – Fluticasone – Triamcinolone

UTHSCSA Pediatric Resident Curriculum for the PICU Beta-agonists Work via the  2 receptor to bronchodilate Work via the  2 receptor to bronchodilate Albuterol Albuterol Terbutaline Terbutaline Can cause hypokalemia, tremors, nausea, vomiting, tachycardia Can cause hypokalemia, tremors, nausea, vomiting, tachycardia

UTHSCSA Pediatric Resident Curriculum for the PICU Beta-agonists Give via MDI or nebs Give via MDI or nebs Dose: Dose: – Depends upon size, severity of disease, and delivery device. Titrate to heart rate and response – Usual neb dose: <10kg: 2.5mg/hr <10kg: 2.5mg/hr 10-20kg: 5mg/hr 10-20kg: 5mg/hr 20-30kg: 10mg/hr 20-30kg: 10mg/hr >30kg: 15mh/hr >30kg: 15mh/hr

UTHSCSA Pediatric Resident Curriculum for the PICU Anti-cholinergics Atropine and atrovent Atropine and atrovent Bronchodilate and decrease mucus production Bronchodilate and decrease mucus production Additive effect with beta-agonists. Additive effect with beta-agonists. Use for beta-blocker induced asthma Use for beta-blocker induced asthma Complications include drying of the airways and rarely, increased wheezing Complications include drying of the airways and rarely, increased wheezing Atrovent dose: mcg/dose up to q 20min, usually q2-4hrs. Atrovent dose: mcg/dose up to q 20min, usually q2-4hrs.

UTHSCSA Pediatric Resident Curriculum for the PICU Leukotriene inhibitors Block the actions of leukotrienes Block the actions of leukotrienes Zafirlukast and zileuton Zafirlukast and zileuton Used for long-term control Used for long-term control Little use in acute attacks Little use in acute attacks May be as effective as inhaled steroids May be as effective as inhaled steroids Rare side effects (liver damage) Rare side effects (liver damage)

UTHSCSA Pediatric Resident Curriculum for the PICU Methylxanthines Theophylline and aminophylline Theophylline and aminophylline Actions are several: 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 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 High risk of side effects: N/V, tachycardia, agitation, cardiac arrythmias, hypotension, seizures, death

UTHSCSA Pediatric Resident Curriculum for the PICU Magnesium Mechanism unclear, but may be a direct bronchodilator through blocking calcium 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 Raising the Mg levels up to 2-4 mg/dL significantly improved expiratory air flow in adults One study in children showed that MgSO 4 25mg/kg over 20 minutes significantly improved PFTs, but did not change hospitalization rate or length of stay in the ED. One study in children showed that MgSO 4 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 Relatively safe. Levels >12 can cause weakness, areflexia, respiratory depression, and cardiac arrhythmias

UTHSCSA Pediatric Resident Curriculum for the PICU Weaning protocol Patients selected by attending/resident Patients selected by attending/resident Physician writes order Physician writes order Physician writes initial dose and frequency of bronchodilator Physician writes initial dose and frequency of bronchodilator Respiratory therapist evaluates patient and changes therapy in accordance with protocol Respiratory therapist evaluates patient and changes therapy in accordance with protocol

UTHSCSA Pediatric Resident Curriculum for the PICU Treatment levels Level 1: Continuous albuterol at > 0.6 mg/kg/hr Level 1: Continuous albuterol at > 0.6 mg/kg/hr Level 2: Continuous albuterol at 0.3 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 3: Continuous albuterol at 0.15mg/kg/hr Level 4: Albuterol at about 0.3mg/kg q2hours Level 4: Albuterol at about 0.3mg/kg q2hours – Infants <5kg use 1.0 mg – Infants kg use 2.5 mg – Children kg use 5.0 mg – Children > 20 kg round to closest multiple of 2.5 mg (2.5, 5.0, 7.5, etc)

UTHSCSA Pediatric Resident Curriculum for the PICU Treatment levels Level 5 : Albuterol q3 hours at same dose as level 4 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 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 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 Level 8 : Albuterol q6 hours, same dose

UTHSCSA Pediatric Resident Curriculum for the PICU Acute Asthma Score Modified from Woods, et al, AJDC, 1972

UTHSCSA Pediatric Resident Curriculum for the PICU 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.

UTHSCSA Pediatric Resident Curriculum for the PICU 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.

UTHSCSA Pediatric Resident Curriculum for the PICU 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.