›No taper required for courses less than 7 days
›Initiate or step up ICS before or at discharge
›IV magnesium sulfate
›Indications
›Severe exacerbation not responding to initial bronchodilators
›SpO2 < 92% after first-line therapy
›Dosing
›2 g IV over 20 minutes in adults
›Pediatric dose 40 to 50 mg/kg IV over 20 to 30 minutes
›Maximum 2 g pediatric dose
›Mechanism and evidence
›Smooth muscle relaxation via calcium channel antagonism
›Modestly reduces hospitalizations in severe exacerbations
›ACEP Level B recommendation
›Monitoring
›Blood pressure monitoring during infusion
›Renal function assessment before administration
›Risk of flushing and hypotension at rapid infusion rates
Epinephrine and systemic beta-agonists
›Epinephrine indications
›Severe refractory bronchospasm
›Failure of inhaled SABA plus ipratropium plus magnesium
›Anaphylaxis-associated bronchospasm
›IM epinephrine dosing
›Adults 0.3 to 0.5 mg IM in anterolateral thigh
›Children 0.01 mg/kg IM maximum 0.5 mg
›IV terbutaline or epinephrine for ICU setting
›Terbutaline 0.25 to 0.5 mcg/kg/min IV continuous infusion
›Titrate to bronchodilator effect and tolerable tachycardia
›Continuous cardiac monitoring mandatory
Refractory and rescue therapies
›Ketamine
›Role and evidence
›Bronchodilatory and anti-inflammatory properties
›Preferred induction agent when intubation required
›Limited evidence for routine use in non-intubated patients
›Dosing for refractory bronchospasm
›0.5 to 2 mg/kg/h continuous IV infusion
›Sub-dissociative doses may provide bronchodilation
›Systematic review shows benefit in prospective studies
›Heliox
›Indications
›Refractory bronchospasm with inadequate response to standard therapy
›May improve nebulized drug delivery
›Mixture and delivery
›70:30 or 80:20 helium to oxygen ratio
›Non-rebreather mask or ventilator circuit
›Not suitable when FiO2 requirement > 0.4
›Evidence
›Reduces airway resistance via laminar flow
›Not routinely recommended but may be considered as rescue therapy
›Inhaled anesthetics
›Sevoflurane or isoflurane
›Last-line therapy for intubated patients with refractory bronchospasm
›Anesthesiology involvement required
›Bronchodilation via direct smooth muscle relaxation
›ECMO consideration
›Absolute last resort for refractory respiratory failure
›ECMO team consultation in tertiary centers
Mechanical ventilation strategy
›Ventilator settings for intubated asthmatic
›Rate and volumes
›Respiratory rate 10 to 12 breaths per minute
›Tidal volume 6 to 8 mL/kg ideal body weight
›Long expiratory time to minimize air trapping
›Permissive hypercapnia
›Accept PaCO2 up to 70 to 80 mmHg
›Target pH > 7.2 rather than normal PaCO2
›ACEP Level C recommendation
›PEEP strategy
›Start with zero PEEP or very low extrinsic PEEP
›Auto-PEEP monitoring via expiratory hold
›Extrinsic PEEP titrated to 80% of measured auto-PEEP if needed
›Monitoring for barotrauma
›Peak and plateau pressure trending
›Sudden desaturation or hypotension triggers pneumothorax screen
›Sedation and paralysis
›Sedation priorities
›Deep sedation reduces patient-ventilator dyssynchrony
›Propofol preferred for bronchodilatory properties
›Ketamine as alternative with bronchodilation benefit
›Neuromuscular blockade
›Short-term NMB for severe dyssynchrony
›Prolonged NMB plus steroids increases critical illness myopathy risk
›Minimize duration to lowest effective period
›HFNC and NIV considerations
›HFNC role
›May reduce work of breathing in pre-intubation phase
›Not standard of care but increasingly used
›Close monitoring for failure to improve within 1 hour
›BiPAP considerations
›Limited evidence base in acute asthma
›May reduce intubation rates in select patients
›Contraindicated if unable to cooperate or altered mental status
›NIV failure criteria
›Worsening acidosis or hypoxemia despite NIV
›Inability to tolerate interface
›Proceed to intubation without further delay