Adjunctive Strategies for Severe ARDS

- 1) There is no single right answer as to which strategies should be used in severe ARDS. Each approach may or may not be feasible due to the resource constraints of the austere environment. If unfamiliar with these techniques, obtain teleconsultation.
- 2) Pressure Control – may include Inverse Ratio Ventilation (PC-IRV):
  - EMV+ 731 with the most recent software package has the capability to do PC-IRV. While using AC-P mode, PC-IRV is achieved by increasing the Inspiratory-to-Expiratory (I:E) ratio above 1:2 (i.e. 1:1, 2:1, 3:1 and higher).
  - PC-IRV cannot fully approximate Airway Pressure Release Ventilation (APRV), but is still the best available salvage mode using EMV+ 731.
  - Once PEEP is maximized (or limited by peak inspiratory pressure) and oxygenation is still not yet at goal, increase the I:E ratio incrementally.
  - Tidal volume goal remains the same as with conventional ventilation; adjust cycle time (60/RR) to optimize minute ventilation.
  - Higher I:E ratios are not physiologic, so PC-IRV will likely require increased depth of sedation for patient comfort and synchrony.
- 3) Paralysis for Patient-Ventilator Synchronization
  - Adequate depth of sedation is essential prior to starting a paralyzing medication; recommend RASS greater than -2.
  - SCCM and DoD COVID-19 Practice Management Guide recommend intermittent paralytics over continuous infusions, if possible. Continuous infusion can result in prolonged paralysis if not closely monitored, especially if muscle twitch monitor is not available.
  - Paralysis with Vecuronium:
    - Bolus: 5mg to 10mg every 60-90 minutes as needed.
    - Infusion: 0.8 to 1.2mcg/kg/min (approx. 80mcg/min for 80kg).
    - Without pump: 40mg vecuronium in 250mL bag (50mL wasted) of normal saline yields 40mg/250mL = 160mcg/mL. For 80mcg/min = 0.5mL/min ~ 1gt every 12 seconds in 10gt tubing.
  - Monitoring Goal:
    - Absence of muscle movement and no evidence of spontaneous breathing on the ventilator. If possible, titrate to 2/4 TOF (testing device likely only available for surgical teams).
    - Increased HR and BP may suggest inadequate sedation and should be empirically treated by increasing sedation.
    - Once the patient is stabilized, consider holding the paralytic at least once every 24 hours to provide for assessment of sedation depth.
    - DO NOT hold sedation until paralytic wears off unless absolutely necessary (e.g., sudden hypotension).
- 4) Prone Positioning
  - “Awake Self-Proning” with high flow nasal cannula devices has been successfully used in patients with moderate to severe COVID-19 lung disease. If patients are unable to tolerate prone positioning (i.e. strong desire to remain in a tripod position), DO NOT force them into the prone position.
  - Reference DoD COVID-19 Practice Management Guide for full details on prone positioning precautions and procedures.
  - Placement of either a central line or additional peripheral access is strongly encouraged PRIOR to prone positioning.
  - Have push-dose vasopressor medication available during the process of prone positioning and un-positioning, as hypotension frequently occurs.
  - Proning cycle is generally 16 hours of prone positioning each 24 hours. Match the proning cycle to the daily care plan as much as possible.
  - Prone positioning may not be feasible or safe during evacuation.