An anaesthetist from a provincial hospital appears on the video-link seeking advice.  He has a 20 year old man with suspected fat embolism syndrome following an isolated femoral fracture that was been repaired earlier that day. He has become increasingly hypoxic and difficult to ventilate, but transfer to a metropolitan centre has been delayed for 12 hours due to bad weather.

His arterial blood gases on SIMV mode of ventilation are as follows: FiO2  1.0, pH
7.21, PaO2  65 mm Hg (8.6kPa), PaCO2 72 mm Hg (9.3kPa), HCO3  28 mmol/L.  He 
has a four quadrant infiltrate on his Chest X-Ray.

Outline the advice that you would give to help your colleague manage this patient’s ventilation.

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College Answer

General 
Confirm Diagnosis

- ARDS criteria: CXR, PF ratio, Etiology, no overload

•    exclude other etiologies - where is the ETT (not RMB), no pneumothorax, aspiration etc.
•    What ventilator is he using, are you familiar with it’s modes (such as pressure control, volume control)
•    Ventilatory strategy –pressure and volume limitation to minimise barotrauma)
•    PEEP increments to effect, ensuring Plateau Pressure < 30 cm H20
•    Heavy sedation and paralysis to minimize O2 consumption and CO2 generation to
GCS 3 and no spontaneous ventilation
•    Targets for ventilation SpO2 > 90-95 and PO2 > 60
- permissive hypercapnia as long as pH > 7.1
•    prone position probably not appropriate (if staff not experienced)

•    Fluids

- CVP only to ~PEEP+2 as maximum
- Consider frusemide if CVP PEEP +5
- Use inotrope to maintain MAP > 60 - suggest noradrenaline
- Transfuse only for Hb approaching 7

•    Reassure him and make yourself available for advice

NO, liquid ventilation, surfactant and tracheal gas insufflation – no role in this setting)

Discussion

This question is very similar to Question 13 from the first paper of 2011.

Initial ventilator strategy:

Additional ventilator manoeuvres to improve oxygenation:

Non-ventilator adjunctive therapies for ARDS:

Ventilator strategies to manage refractory hypoxia

  • Prone ventilation, for at least 16 hours a day (PROSEVA, 2013)
  • High frequency oscillatory ventilation may not improve mortality among all-comers (OSCAR, 2013) or it may actually increase mortality (OSCILLATE, 2013) but some authors feel that there were problems with methodology.

Non-ventilator adjuncts to manage refractory hypoxia

  • Nitric oxide was a cause for some excitement, but is no longer recommended.
  • Prostacyclin is still a cause for excitement, and is still vaguely recommended.
    • Neither agent improves mortality, but prostacyclin can improve oxygenation.
  • ECMO may improve survival (CESAR, 2009) but again there were problems with methodology.