UMEM Educational Pearls

 

Despite ongoing research and efforts to improve our care of patients with ARDS, it remains an entity with high morbidity and mortality. Early recognition of the disease process and appropriate management by emergency physicians can have profound effects on the patient's course, especially in centers where ICU boarding continues to be an issue.

 

Recognition of ARDS (Berlin criteria)

• Acute in onset
• Bilateral infiltrates on chest imaging not due to cardiac failure/volume overload
• PaO2 : FiO2 < 300 despite PEEP of at least 5cmH2O 
• This is the standard ED patient who gets intubated with multifocal pneumonia and has continued hypoxemia

*An ABG should be obtained in the ED if physicians are unable to wean down FiO2 from high settings, if oxygenation by pulse ox is marginal, or if the patient is in a shock state.

 

Tenets of ARDS Management:

• Low tidal volume ventilation (6-8ml/kg ideal body weight*)
• Maintain plateau pressures (Pplat) < 30 cmH2O
• Driving pressure (Pplat – PEEP) < 15 cmH2O
• Goal PaO2 > 55-60 
• Permissive hypercapnia to pH >7.2

*IBW Males = 50 + 2.3 x [Height (in) - 60]   /  IBW Females = 45.5 + 2.3 x [Height (in) - 60]

 

Strategies for Refractory Hypoxemia in the ED:  You can't prone the patient, but what else can you do? 

1. Escalate PEEP in stepwise fashion

• ex: 2cmH20 every 10 minutes
• can use ARDSnet PEEP/FiO2 table as guide

2. Recruitment maneuvers

• "20 of PEEP for 20 seconds" or "30 for 30"
• if patient is "PEEP responsive," leave PEEP on a higher setting than when you started (ex: 10 instead of 5, 16 instead of 10)
• Risk of barotrauma with higher PEEPs and hypotension in underresuscitated or hemodynamically unstable patients due to decreased venous return

3. Appropriate sedation and neuromuscular blockade

• promotes patient synchrony with lung protective settings
• can result in improved oxygenation by itself

4. Inhaled pulmonary vasodilators (inhaled prostaglandins, nitric oxide) if known or suspected right heart failure or pulmonary hypertension

 

Bottom Line: Emergency physicians are the first line of defense against ARDS. Early recognition of the disease process and appropriate management is important to improve outcomes AND to help ICU physicians triage which patients need to be emergently proned or even who should potentially be referred for ECMO. 

 

References

Fielding-Singh V, Matthay MA, Calfee CS. Beyond Low Tidal Volume Ventilation: Treatment Adjuncts for Severe Respiratory Failure in Acute Respiratory Distress Syndrome. Crit Care Me.. 2018;46(11):1820-31.