Managing Severe Refractory Asthma Episodes

Educational Objectives

The goal of this program is to improve management of severe asthma exacerbations. After hearing and assimilating this program, the clinician will be better able to:

1. Choose appropriate settings for use of bilevel positive-airway pressure (BiPAP) for a patient with an episode of severe refractory asthma.
2. Administer medications to improve tolerance of BiPAP for a patient with an episode of severe refractory asthma.

Summary

Bilevel positive-airway pressure (BiPAP) for noninvasive ventilation: can be a helpful adjunct for patients with episodes of severe asthma refractory to medical management; may prevent intubation, but evidence is not as strong as that for steroids, ipratropium, and magnesium; in patients with asthma, airways are constricted and filled with mucus, which increases the work required to inhale and necessitates active (as opposed to passive) exhalation; muscles of the diaphragm and chest are overextended; bronchioles collapse; patients can become fatigued and deteriorate; BiPAP offloads the work of breathing and alters the breathing pattern; short, rapid breathes in severe asthma (40/min) lead to inadequate exchange of gas and an increase in PCO₂; management should focus on pressure support; assess the patient’s baseline clinical appearance, respiratory rate, tidal volume, oxygen saturation, pH, and PCO₂; initiate BiPAP at low settings, ie, inspiratory positive-airway pressure (IPAP) of ≈10 cm H₂O and positive end-expiratory pressure (PEEP) of 5 cm H₂0 (higher PEEP does not help in the early phases); if the patient does not improve, try to offload the work of breathing by increasing IPAP; few patients easily tolerate BiPAP; as steroids and BiPAP require time for onset of effect, it is important to remain calm, present a relaxed demeanor, and try to keep the patient and family members in a calm state; low-dose opioids can be helpful for air hunger; monitor the patient’s mental status and clinical progression, and avoid excessive administration of opioids

Other options for calming the patient: include dexmedetomidine, which is not readily available; however, it is effective for this purpose, without causing sedation; although benzodiazepines are typically discouraged, benefits may outweigh risks in this setting; opioids, benzodiazepines, and dexmedetomidine could be considered procedural sedation; no specific “cocktail” is recommended; rather, this is a staged approach, with the goals of keeping the patient as interactive as possible, continuing the targeted asthma-directed therapy through the BiPAP machine, keeping the patient relaxed so that treatment is tolerate, and preventing further deterioration; ketamine — not typically used to promote tolerance of BiPAP; may be used for induction of anesthesia or intubation in patients with asthma; data in adults is lacking

Interventions for the persistent nonresponse: administer continuous nebulized β-agonist (albuterol) at 20 mg/hr; BiPAP is preferred, but a high-flow nasal cannula or nebulizer mask can be used; if albuterol is not reaching the lungs, consider parenteral medications (eg, epinephrine infusion; terbutaline has been used successfully in some institutions); although epinephrine infusion is associated with elevated lactic acid levels, tachycardia, ectopy, and hypokalemia, benefits (bronchodilation) outweigh risks in this setting; helium-oxygen (heliox) therapy — if available, can be used for patients who are not excessively hypoxemic; more typically used for proximal airway problems, but worth trying when other options have been exhausted

Intubation: absolute indications include cardiac or respiratory arrest; clinical judgment is needed when considering intubation for physical exhaustion or altered sensorium (ie, to distinguish between effects of medication vs the physiological effects of hypoxemia as the cause of obtundation)

Ventilator settings: patients with asthma die because of hypoxemia or dynamic hyperinflation (air becomes trapped and tamponades off the superior and inferior vena cava and right atrium, leading to cardiovascular collapse); the goal is to oxygenate and manage dynamic hyperinflation; patients intubated for asthma have severe bronchoconstriction, high airway resistance, and high inspiratory peak pressures; adjust the peak pressure alarms; clinicians should refrain from increasing the respiratory rate to counter high PCO₂, as doing so worsens air trapping and dynamic hyperinflation; start with a respiratory rate of 8 to 12 breaths/min (<8 breaths/min sacrifices minute ventilation) and tidal volume of 8 mL/kg ideal body weight; maintain low PEEP, set inspiratory time at 0.8 to 1 sec, and continue medical therapy; continue nebulizer treatments after intubation; monitor for dynamic hyperinflation using plateau pressure at end-inspiration with an inspiratory hold maneuver (shows the volume of air remaining in the chest cavity); lower respiratory rates increase expiratory time; decreasing the inspiratory time is not helpful (leads to inadequate ventilation); high peak pressure is acceptable if plateau pressure is reasonable because peak pressure does not equal alveolar pressure

Readings

Green E, Jain P, Bernoth M. Noninvasive ventilation for acute exacerbations of asthma: A systematic review of the literature. Aust Crit Care. 2017;30(6):289-297. doi:10.1016/j.aucc.2017.01.003; Hashemian SM, Fallahian F. The use of heliox in critical care. Int J Crit Illn Inj Sci. 2014;4(2):138-142. doi:10.4103/2229-5151.134153; La Via L, Sanfilippo F, Cuttone G, et al. Use of ketamine in patients with refractory severe asthma exacerbations: systematic review of prospective studies. Eur J Clin Pharmacol. 2022;78(10):1613-1622. doi:10.1007/s00228-022-03374-3; Sellers WF. Inhaled and intravenous treatment in acute severe and life-threatening asthma. Br J Anaesth. 2013;110(2):183-190. doi:10.1093/bja/aes444

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Roginski was recorded at Emergency Medicine Update 2023, held January 22-25, 2023, in Stowe, VT, and presented by Larner College of Medicine at the University of Vermont. For information about upcoming CME activities from this presenter, please visit med.uvm.edu/cmie. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0.50 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0.50 CE contact hours.

Lecture ID:

EM410501

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.