Anesthesia and the child with asthma

1. Anesthesia and the child with asthma Review article Pediatric Anesthesia 2005; vol 15 R3 한진희

2. Introduction • Aim in childhood - asthma 의 prevalence 증가 day-case surgery의 증가 -> the child's medical condition 과 possible anesthetic risk를 assessment 할 수 있는 시간적 제한 during anesthesia of children with asthma 에서 adverse events는 rare But, routine anesthesia 에서도 Complicated or even dangerous

3. Pathophysiology of childhood wheeze • asthma 의 development 에 영향을 주는 인자 : Genetic predisposition, atopy, prenatal, and early-life environment and chronic airway inflammation • atopy and asthma : strong association Atopy: immunoglobin-E (IgE) mediated-hypersensitivity allergy, allergic rhinitis, and atopic dermatitis • But, many children who wheeze do not have atopic asthma

4. the Tucson Children's Respiratory Study classification 1)transient wheezers : reduced lung function in infancy, wheeze in response to viral infections, symptoms resolve after the first few years of life 2)nonatopic wheezers : wheeze beyond the first few years of life, often in response to viral infections, but persistence of wheeze is less likely than in atopic wheeze 3)atopic wheezers : classical asthmatics Early atopic wheezers : severe, persistent symptoms

5. The relevance of this distinction to the anesthetist is unclear -> reactive airways 의 history 를 가진 child 는 increased risk of perioperative bronchospasm. In addition, children with atopy have increased risk of severe allergic reactions. • Asthma : Inflammation of the airways : typically eosinophilic neutrophilic inflammation : severe asthma or acute exacerbations • characteristic changes occur in the airways remodeling and include goblet cell hyperplasia ,the basement membrane의 thickening , thickening of the smooth muscle layer  the anatomy and function of the airway 에 영향  irreversible airway 나 obstruction , bronchial hyperreactivity 를 증가

6. Preoperative assessment • Diagnosis Asthma : 'there is no confirmatory diagnostic blood test, radiographic or histopathological investigation‘ * 특징: variable and intermittent airflow obstruction  frequently as wheeze and cough older children  shortness of breath, or chest tightness or discomfort. • Unremitting wheeze or stridor : fixed obstruction 를 암시 • dry nonproductive cough : often seen in asthma • persistent wet, productive cough : suppurative lung disease (cystic fibrosis, primary ciliary dyskinesia, immunodeficiency, following infection, etc.)를 의심

7. Assessment severity of disease,  how well controlled : important : Mild asthma (poorly controlled) may appear severe, frequent and persistent symptoms. In contrast, a child with severe asthma may currently have well-controlled symptoms but require high doses of inhaled corticosteroids to maintain control • Poorly controlled asthma : frequency of symptoms and use of reliever medication Frequent emergency attendances, hospital admissions or use of oral steroids also indicate inadequate control

8. the British Thoracic Society (BTS) and the National Heart, Lung and Blood Institute -> define the severity of asthma • inhaled steroids:beclomethasone diproprionate (BDP) • difficult asthma (step 4 or 5)

9. difficult asthma 의 원인 : poor compliance with treatment, inadequate inhaler technique or an incorrect diagnosis ofasthma • sudden onset of asphyxiating or anaphylactic type asthmatic attacks - precipitated by nonsteroidal analgesics or irritant gases

10. Investigations ‘Objective testing is not diagnostic but can support a clinical diagnosis.’ • Imaging : chest radiograph, CT scanning :rarely useful  useful only in research excluding other pathology 2. Pulmonary function tests : detect airway obstruction or hyperreactivity * Diurnal variation in peak expiratory flow(PEF)  indicate poor control of asthma, and useful in assessing the severity of an acute exacerbation. * Forced expiratory volume in 1 s (FEV1) • a better measure of obstruction and may be reduced at baseline in poorly controlled asthma; or in response to irritant stimuli such as exercise or methacholine. Reversible airways obstruction: inhaled bronchodilator 후에 PEF or FEV1 증가

11. 3. Inflammatory markers • Peripheral blood eosinophilia: simple measure severity of asthma • Urinary leukotrienes and eosinophil-derived protein X (EPX)  airway inflammation • direct noninvasive measurements of airway inflammation detect : exhaled nitric oxide (ENO) or hydrogen peroxide sensitive marker of airway inflammation • 그 외 total serum IgE levels, antigen-specific IgE levels (RAST) and skin prick

12. Preoperative arrangements atopic asthmatics : allergic reactions : may develop anaphylaxis precipitated by allergens ( drugs, drug excipients or latex) antibiotics or previous anesthetic agents should be sought.

13. Premedication - midazolam(can safely receive) - inhaled β2-agonists,  LABA or LTRA, - Corticosteroids : prevent perioperative bronchospasm : avoid adrenal crisis - inhaled topical lidocaine : intubation시 bronchoconstrictive effect 약화 :Paradoxically, induce irritation and bronchospasm  negated by the administration of β2-agonists.

14. Induction of anesthesia • Intravenous induction : choice of route or agent may be influenced by a history of asthma : ketamine - in patients with severe asthma: the intravenous agent of choice for induction of anesthesia  bronchodilator effect (possibly mediated by direct relaxation of airway smooth muscle, inhibition of vagal pathways and augmentation of catecholamine release.) :Propofol – produce less bronchoconstriction than other agents, idiosyncratic reactions (there are case reports of severe bronchospasm with the use of propofol) : histamine release bronchospasm Morphine - induce histamine release more easily than fentanyl atracurium - more so than suxamethonium

15. Gaseous induction : Volatile anesthetic agents – well known as bronchodilating drugs unresponsive status asthmaticus에도 사용 intubation 에 의한 bronchoconstrictive response 을 막지 못함 : Halothane-과거에 쓰임 : Sevoflurane : less pungent and less irritant than isoflurane small increase in airways resistance seen  premedication with an inhaled β2-agonist로 예방 fewer cardiac arrhythmias than halothane

16. Intubation : Tracheal intubation more likely to produce adverse respiratory events the incidence of complications with the LMA was significantly less than with tracheal intubation For very short procedures (children with reactive airways)  use of a facemask only.

17. Recognizing and treating complications • Bronchospasm : increased airway reactivity, or secondary to an anaphylactic reaction. : polyphonic, bilateral expiratory wheeze, prolonged expiration, active expiration with increased respiratory effort, increased airway pressures, rising endtidal CO2, and possibly hypoxemia. Tx. : inhaled β2-agonists, a metered-dose inhaler (MDI) via the tracheal tube : IV salbutamol or aminophylline may be used to treat severe bronchospasm.

18. aminophylline : In acute exacerbations of asthma, more effective : increased risk of cardiac arrhythmia especially in conjunction with some volatile anesthetics Hypokalemia is a side-effect of almost all anti-asthmatic medications Other options : intravenous magnesium, increasing concentrations of volatile anesthetics It is safer to over-treat bronchospasm as anaphylaxis than to delay treatment of true anaphylaxis.

20. 2. Anaphylaxis the most common precipitants : Neuromuscular-blocking drugs (NMD), antibiotics or latex(more closely associated with atopy) Latex allergy : encountered this antigen before For example, children who have had previous surgery or have required intermittent bladder catheterization may have been sensitized. * cross-reactivity may exist between latex and various fruit antigens (such as avocado, kiwi, and banana)) - Premedication : intravenous steroids, and H1 and H2-receptor antagonists, latex-free environment

21. Anaphylaxis Sign : angioedema, flushing or urticaria, and tachycardia, reduced perfusion and hypotension secondary to hypovolemia. • Angioedema (the face or lips) :the upper airway - stridor. in the anesthetized patient, prodromal symptoms(perioral tingling, urticaria or angioedema) may be absent. The most common presentation is cardiovascular collapse (with an absent pulse noted) or bronchospasm (with difficulty in ventilating the patient). • Treatment : intramuscular adrenaline, nebulized salbutamol, and fluid resuscitation : Corticosteroids and antihistamines

23. 3. Adrenal crisis steroid therapy : the hypothalamic–pituitary–adrenal (HPA) axis 를 suppression . Adrenal crisis : precipitated by a stress such as surgery  hypotension, hypoglycemia , seizures. ; Tx. : intravenous hydrocortisone : fluid resuscitation (saline or colloid) : dextrose (∵ hypoglycemia)

24. * Short courses of prednisolone :can affect HPA function ( up to 10 days but dysfunction is unlikely to be prolonged) * High doses, prolonged therapy (>3 weeks) : increase suppression of the HPA axis and therefore delay recovery of function, which may take up to a year * inhaled steroids may be associated with adrenal insufficiency. * Perioperative steroid cover : recently requiring systemic steroids, high-dose inhaled steroids

25. Postoperative care • Nonsteroidal analgesics : sudden deterioration of asthma • aspirin (NSAID) hypersensitivity appears much less common in children than in adults (rarely used) • Cross-reactivity between NSAID is also common • Ibuprofen : usually safe • diclofenac : used safely in asthmatic children * avoid NSAID :전에 NSAID 를 투여 받지 않거나, NSAID 에 대한 adverse reaction Hx. 를 가진 severe asthmatics Postoperative lung function is reduced -preexisting pulmonary disease such as asthma