Inpatient / Pulmonology and critical care

Asthma Exacerbation

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If You Remember Nothing Else

When patients present with an acute asthma exacerbation the standard of care is duonebs, steroids, and O2. Be fearful of a blood gas not suggesting respiratory alkalosis from tachypnea  (would see low pH or rising PCO2 - implies worse retaining and that the patient is tiring out). Check on their home regimen - ICS-LABA is the mainstay of outpatient management, and you can update the regimen for patients who have not been seen in the outpatinet setting in some time and are still prescribed just albuterol rescue inhaler. It's okay to to diagnose people clinically with asthma, but being diagnosed as an adult is very rare.

Clinical Pearls

• Exacerbation is a reversible episode of lower airway obstruction (bronchospasm); Status Athmaticus is an old term used to mean an exacerbation that progresses rapidly and does not respond to standard acute therapies
• PEF (peak expiratory flow rate) <80% of personal best means we can manage them better with chronic therapies in the outpatient setting, <50% is a severe exacerbation
• If the patient is If chronically SOB, then its not just asthma - asthma is intermittent SOB
• GERD (acid reflux) is a very common trigger for asthma OR an alternative diagnosis for chronic cough other than asthma
• Note - recent guidelines from 2019 make PRN ICS-LABA (budesonide-formoterol or Symbicort) the mainstay, and should not have albuterol only treatment (which was the previous mainstay); some patients who have been lost to follow-up may have outdated regimens and could benefit from changes
• Severe chronic management includes the addition of tiotropium, leukotriene receptor antagonists, biologics (anti-IL4, anti-IgE, anti-IL5)
• ICS may be less effective in phenotypes with lower eosinophils
• If the patient is If chronically SOB, then its not just asthma - asthma is intermittent SOB
• On VBG should expect to see respiratory alkalosis (tachypnea blowing out CO2), if you see pH normal or decreased, may indicate impending respiratory failure and patient tiring out
• If someone needs to get intubated (resp failure defined as PaO2 <60 or PaCO2 >45 despite treatments, also use clinical judgment) - things to know include the reason for intubation (one-liner, clinical and data), code status, decision-makers, previous intubations, known difficult airway (obese, OSA, no teeth, huge beard, small mouth, obstruction or anatomically unique airway), time of last meal, co-morbid conditions that can complicate ventilation settings (pHTN, ARDS, etc), and function of the patient’s right heart (and their echo in general)
• If need to intubate and mechanically ventilate - low Vt (6-8cc/kg), low RR (10-14), paralyze with goal to maximize expiratory phase with permissive hypercapnia (this helps avoid breath stacking and worsening hyperinflation which can reduce venous return and cause hypotension)
• Intubation can be dangerous in asthma because it doesn't fix the underlying problem and can make things worse via lung hyperinflation which leads to decreased pulmonary venous return, which can lead to hypotension; mechanical ventilation converts negative pressure ventilation to positive pressure ventilation and increased intrathoracic pressure which decreases venous return
• If there is a COPD/asthma overlap, can continue COPD home regimen (ICS-based therapies) when a patient presents with an exacerbation in the hospital
• “PFTs” have multiple components, it’s not just one test - spirometry (flow), volume assessments, diffusion studies, exercise challenges, etc.
• When going through PFTs in the chart, you don’t have to have FEV1/FVC <0.70 to diagnose asthma (only when they are actually having an exacerbation! Or if their disease is poorly controlled at baseline), but traditionally obstructive disease is characterized by <0.70; an FEV1 increase >12% indicates a response to bronchodilator, FEV1 20% worse with methacholine also used to diagnose, but really not often done - usually only if high suspicion for asthma, but ratio is normal; DLCO should be normal to high in asthma
• Adult diagnosis of asthma is rare and should prompt some questions and further workup including ABPA, EGPA, systemic mastocytosis, occupational (more common), aspirin or NSAID induced (would see nasal polyps)
• Consider vocal cord dysfunction in patients who have frequent asthma-like exacerbations requiring intubation but are quickly extubated - would need to be seen by ENT

Trials and Literature

• 4x dose of controller ICS can help patients abort a mild exacerbation - (NEJM 2018)
• Steroids in asthma exacerbation - Cochrane Review 2016
• Mild Asthma - PRN ICS-LABA > PRN SABA (NEJM 2019; NEJM 2018) and non-inferior to maintenance ICS to prevent exacerbations (NEJM 2018, though increased side effects associated with steroids) - guidelines

Other Resources

• Core EM - Life-Threatening Asthma
• Run the List - Asthma and Social Determinants of Health
• Curbsiders Podcast - #71 Asthma Made Simple