Thank you to Salman and Jin from our stellar ICU team for presenting a great case about severe asthma exacerbation management. We talked about a middle aged man with moderate persistent asthma, who present with progressively worsening SOB in s/o of a respiratory virus; his severe asthma exacerbation required intubation, and heliox among other standard therapies.
Toolkit for Management of Severe Asthma
See the table below for recommendations from the Thoracic society on management of severe asthma exacerbations (2009), but the mainstays are:
- Supplemental oxgyen
- Short Acting Beta Agonist (SABA) ie albuterol, consider adding inhaled ipratropium in severe exacerbation
- Systemic corticosteroids (ie solumedrol in ED, followed by prednisone 40-60mg daily)
- IV magnesium
How do you determine appropriate response to therapies?
It is critically important to have frequent examination and monitoring of these patients. Pay attention to accessory muscle use, tripod-ing, and mental status – if these are worsening, very low threshold to have patient in the ICU for possible intubation! Also helpful to follow serial ABGs. ABG is more helpful than VBG to determine the A-a gradient, and also to carefully watch the pCO2. With an increasing pCO2, you should be concerned the pt is tiring out and may require intubation.
What is Heliox?
Salman explained this so beautifully with a throwback to the Poiseuille equation (A calling in physics perhaps?) — big picture idea is that Heliox allows increased oxygen delivery through bronchoconstricted airways. Heliox, is made up of helium + oxygen in ratios of either 70-30 or 80-20. Heliox is lower density than our typical nitrogen rich air, and therefore has increased laminar flow (and decreased turbulent flow) through airways. This ultimately helps with delivery of oxygen past constricted airways.
Clinical applications of heliox in adults are most commonly in setting of severe asthma, though there have been smaller studies of heliox use in COPD, and case reports of its use for upper airway obstructions.