All that wheezes is not asthma…except it often is
Myron Yaster MD and Justin L. Lockman MD, MSEd
For over 40 years, I taught and continue to teach a voluntary oral board review course for fellows and young faculty members taking the test. Last weekend, I used one of my favorite questions which involves an adult patient undergoing a thoracotomy who acutely developed intraoperative wheezing. Invariably, the answer given by pretty much every student: “I’d give albuterol 1-X (where X = 2-100) puffs, steroids, yada yada.” I nod and tell them the patient is deteriorating…more albuterol…the patient continues to deteriorate and dies. Why? because the patient had a kinked endotracheal tube and all the albuterol in the world wont fix that problem…“Not all that wheezes is asthma”. Of course, they assumed the cause was asthma. We then review the differential for intraoperative wheezing, namely, mechanically-obstructed tracheal tubes (kinking or secretions), pulmonary edema, tension pneumothorax, aspiration, anaphylaxis, etc. This month’s edition of the Journal of Pediatric Anesthesia has a focus on pulmonary issues. Over the next couple of weeks, we’ll review a bunch of the articles in this issue. Today’s article involves the perioperative management of pediatric asthma – when it really is asthma. Myron Yaster MD
Original article
Regli A, Sommerfield A, von Ungern-Sternberg BS. Anesthetic considerations in children with asthma. Paediatr Anaesth. 2022 Feb;32(2):148-155. PMID: 34890494
From the introduction in today’s Pediatric Anesthesia Article of the Day: “Children with asthma and those with reactive airway diseases are at higher risk for perioperative respiratory adverse events including bronchospasm, laryngospasm, perioperative cough, desaturation, or airway obstruction.” And because “respiratory adverse events are responsible for more than 75% of all critical perioperative incidents and 30% of all perioperative cardiac arrests, optimization of anesthesia management for the asthmatic child is vital.”(1) In today’s PAAD we’ll review some of the highlights and compare them to the advice given in SPA’s PediCrisis v2 app (if you haven’t yet downloaded the app onto your phone, what are you waiting for?).
Regli et al. work from the basic assumption that wheezing is reactive airways disease. As noted in my (MY) opening statement, this may or may not be true. We encourage you to take a moment to open your PediCrisis app to bronchospasm right now and look at the differential diagnosis tab. As discussed previously, the app’s value is not limited to crises. It can (and should) be used as a teaching tool as well. But for purposes of today’s PAAD, we will assume the diagnosis is correct: bronchospasm.
According to the authors, the 3 triggers of intraoperative bronchospasm: (1) Mechanical (intubation, light anesthesia), (2) Non-immunologic anaphylaxis [anaphylactoid reaction] caused by mast cell and basophil degranulation (e.g., due to neuromuscular blocking agents or morphine), and (3) immunologic/IgE-mediated anaphylaxis (e.g., due to latex). Not discussed in the article, is how to diagnose bronchospasm. This is found in the PediCrisis app: Bronchospasm may be diagnosed by auscultation, decreasing ETCO2 and SpO2, an upsloped stage III on capnography, and increased airway pressure.
Preoperative Management. All asthma medications, including oral and inhaled steroids as well as any regular beta-2 agonists, should be continued. In preop, administer beta-2 agonists 10 to 30 min before induction (e.g., albuterol via a spacer.) Remember, pressurized-metered-dose inhalers require priming (a few puffs into the air) and a spacer to deliver the intended dose to the site of action. How to best do this in the OR in an intubated patient is unclear, particularly when a spacer is not available.(2) Indeed, how much albuterol actually gets to its site of action when a spacer is not used?
Intraoperative. Prior to airway management, consider IV and/or topical lidocaine to blunt airway reflexes. In children before endotracheal intubation without neuromuscular blockade, topical lidocaine may or may not be helpful. In one study it was “associated with increased desaturations without reducing the incidence of bronchospasm or laryngospasm.”(3) Whenever possible “less invasive airway devices and less airway manipulation generally led to a lower risk of perioperative laryngo- or bronchospasm.”(4) When tracheal tubes are required, a cuffed tube allows for application of higher peak airway pressures during mechanical ventilation and if bronchospasm develops”.(1) Deep extubation is also preferred for severe asthmatics.
Anesthetic agents: The most potent bronchodilators known to man are the vapor anesthetics. We can count on one hand the number of times we’ve ever used albuterol for an intubated patient in the OR with asthma, because vapor anesthetics DO get to the site of action and are so potent. Sevoflurane is preferred, isoflurane is also safe, and desflurane should be avoided. Of the IV agents, propofol is best at blunting airway reflexes, ketamine also works well but is a second choice because of the increased secretions it generates. Avoid light anesthesia as it will not be tolerated well by asthmatics.
Intraoperative ventilation strategy: This is not discussed in the current PediCrisis app. “A slow respiratory rate and a decreased inspiratory to expiratory (I:E) ratio is preferred, while “permissive hypercapnia” should be tolerated. In children with exacerbations of asthma, the suggested initial ventilation settings are tidal volume 8–12 mL/kg, respiratory rate of 12–16 (<5 years) and 10 to 12 (>5 years) breaths/min, I:E ratio around 1:4, PEEP of 0–4 cm H2O, driving pressure (inspiratory plateau pressure – PEEP) of 25 to 30 cm H2O (<5 year), and 30 to 35 cm H2O (>5 year), maximum inspiratory pressure of <50 cm H2O.”(1). It’s worth noting that there is some controversy around the question of PEEP management for asthmatics; many ICU physicians including me (JL) would never use such a low PEEP because it can lead to increased air trapping because of midsized airway collapse. In fact, in my (JL) experience, patients with severe bronchospasm sometimes benefit from higher than anticipated PEEP to match their intrinsic PEEP and allow improved exhalation.
Intraoperative bronchospasm crisis: The first step should be to deepen the anesthetic with sevoflurane, after all, we are in the operating room and not the emergency room! The authors suggest ePHEDrine if an immunologic cause is suspected. We, and the PediCrisis app, recommend EPINEPHrine 1-2 MICROgrams/kg IV instead as an intravenous bronchodilator. We are unsure if ephedrine also works or if this was an error. Although not rapidly acting, we think corticosteroids should be given (different centers prefer methylprednisolone, dexamethasone, or hydrocortisone – follow local guidance/practice). The PediCrisis app also suggests this and does not recommend a dose for the same reason. Regli et al. recommend that IV magnesium should be administered to improve respiratory function in children with an asthma exacerbation, and it should be considered prophylactically in children with poorly-controlled asthma. A recommended regimen is IV magnesium sulfate 75 mg/kg (max 2.5 g) given over 20 min for children over 5 years old.(5,6) The PediCrisis app recommends “IV magnesium 50-75 mg/kg (maximum 2 grams) as part of the intraoperative treatment algorithm for refractory bronchospasm.” Importantly, we have found that magnesium works best when given quickly (over 20 minutes, which is much faster than the “electrolyte repletion” dose) AND that it is best to give a fluid bolus (i.e., 20 mL/kg LR or NS) for most patients before administering it because of the hypotension associated with vascular smooth muscle relaxation as the magnesium works.
Postoperative: Finally, Regli et al. recommend avoiding nonsteroidal anti-inflammatory drugs (NSAIDS) for post operative pain management because these drugs increase leukotriene production which may exacerbate asthma. This is not discussed in the app. Although this may be true in vitro, pain should be expected after surgery. Is the alternative use of opioids a better option in asthmatic patients? We aren’t convinced but hope our readers will send in some responses as to their practice. Myron Yaster MD and Justin Lockman MD, MSEd
References
1. Regli A, Sommerfield A, von Ungern-Sternberg BS. Anesthetic considerations in children with asthma. Paediatr Anaesth 2022;32:148-55.
2. Anderson N, Schultz A, Ditcham W, von Ungern-Sternberg BS. Assessment of different techniques for the administration of inhaled salbutamol in children breathing spontaneously via tracheal tubes, supraglottic airway devices, and tracheostomies. Paediatr Anaesth 2020;30:1363-77.
3. Hamilton ND, Hegarty M, Calder A, Erb TO, von Ungern-Sternberg BS. Does topical lidocaine before tracheal intubation attenuate airway responses in children? An observational audit. Paediatr Anaesth 2012;22:345-50.
4. von Ungern-Sternberg BS, Boda K, Chambers NA, Rebmann C, Johnson C, Sly PD, Habre W. Risk assessment for respiratory complications in paediatric anaesthesia: a prospective cohort study. Lancet 2010;376:773-83.
5. Craig SS, Dalziel SR, Powell CV, Graudins A, Babl FE, Lunny C. Interventions for escalation of therapy for acute exacerbations of asthma in children: an overview of Cochrane Reviews. Cochrane Database Syst Rev 2020;8:Cd012977.
6. Griffiths B, Kew KM. Intravenous magnesium sulfate for treating children with acute asthma in the emergency department. Cochrane Database Syst Rev 2016;4:Cd011050.