UK EM Field Notes #5
The sickest asthma patients (periarrest or worse), finger thoracostomies, VV ECMO
Causes of cardiac arrest in asthma
There are only likely to be two reversible causes - hypoxia and tension pneumothorax.
Despite this, be in the habit of outwardly considering all the 4Hs & 4Ts in every cardiac arrest. The team leader should call out every H and T and ensure the team discusses each of them - even if obviously not applicable. This process should then be explicitly documented in the clinical note (ie “team discussed all 4Hs & 4Ts”).
Excluding tension pneumothorax in asthmatic cardiac arrest
Whilst we have POCUS (to assess for lung sliding) and a portable CXR at our disposal, they are not perfect—or always practical—especially during chest compressions. In the asthmatic patient in cardiac arrest, to confidently rule out a tension pneumothorax, bilateral finger thoracostomies should be strongly considered. "Take it off the table."
Finger thoracostomy is always recommended over needle decompression in the patient receiving positive pressure ventilation. It almost always works, whereas there is a high failure rate with the needle.
Finger thoracostomy procedure
The patient must be receiving positive pressure ventilation. Ensure you are targeting the Triangle of Safety (aim for 4th intercostal space – which will be higher than you think… close to the axilla). Then just do the first part of a chest drain procedure (make a hole without sticking the drain through).
Here is an excellent instructional video of how to do the procedure most effectively (Geoff Healy, Sydney HEMS).
In a cardiac arrest scenario, the priority is doing the procedure rapidly. There is no finesse. Make a confident incision.
Do the procedure on each side when hands/LUCAS are NOT compressing the chest (ie during pulse checks or temporarily pause compressions).
IM adrenaline is always a reasonable idea in a sick asthma patient
Anaphylaxis and life-threatening asthma can present very similarly. Adrenaline treats both pathologies.
Therefore, if you are in doubt, don’t hesitate to give IM adrenaline.
Bronchodilator treatments that we don’t normally give but should consider in asthma periarrest/arrest
IV aminophylline
IV adrenaline
IV salbutamol (bolus 250mcg, then give 1-20mcg/min)
IV ketamine
Every ED should have a local guideline with clear instructions for the when/how to give the above treatments. Don’t try to remember these drugs, let along the doses, under pressure. I am a huge advocate of getting guidelines/algorithms up on a computer-on-wheels screen/smartphone during the resuscitation.
Mechanically ventilating the bronchospastic patient
Remember the issue is getting the air out of the lungs. If the patient is on a mechanical ventilator and can’t fully expire, they start “breath stacking”.
Therefore, it is crucial to allow adequate time for expiration. Hyperinflated lungs (from breath stacking) obstruct venous return and can ultimately induce cardiac arrest. On top of that the high pressures can cause alveolar rupture and pneumothorax.
Vent setting principles in asthma:
Higher I:E ratio (longer expiratory time)
Lower RR
Don’t give excessive PEEP (perhaps zero PEEP)
Paralyse the patient
Avoid aggressively bagging if manually ventilating
If an asthma patient crashes on the vent your first move must be to immediately disconnect the circuit from the endotracheal tube (leave the tube bare). You should hear a rush of air. Help things along by manually assisting the decompression by pressing down on a patient’s chest to assist expiration.
Here is an excellent lecture on the ventilation strategy for obstructive lung pathology. Both part 1 and part 2 of the “Dominating the Vent” lecture by Scott Weingart are some of the best online MedEd I’ve encountered.
VV ECMO?
VV ECMO is indicated for acute severe but potentially reversible respiratory failure.
There are clear inclusion and exclusion criteria that are fairly consistent across the different ECMO centres in the UK. Prolonged cardiac arrest is a clear contraindication - VV ECMO is NOT the same as ECPR (which is VA ECMO).
If VV ECMO pops into your mind as an option in a periarrest/near fatal asthma case, call the ECMO consultant directly and discuss it. And do it earlier rather than later.
Cheers all,
Robbie
@robbielloyd.bsky.social