An  Anaesthetist   from  a  provincial  hospital  has  a  20  year  old  man  with suspected fat embolism syndrome following an isolated femoral fracture that was repaired  earlier  that day. The patient  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 mmHg (8.6 kPa), PaCO2  72 mmHg (9.3 kPa), 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)
•    recruitment manoeuvres

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 24/7 (Mention of NO, liquid ventilation, surfactant, TGI – no role in this setting)

Discussion

This is a pretty realistic scenario; as if you were on call and managing a patient over the phone, giving advice to your registrar.

The patient is acidotic, hypoxic and hypercapneic.

What do you do?..

Supportive management:

  • Confirm that the ETT is in the right position and is not blocked up with secretions
  • Confirm diagnosis of ARDS by performing a TTE, looking for significant cardiac dysfunction
  • Exclude immediately reversible problems, eg. pneumothorax

Specific ARDS ventilation strategies and supportive non-ventilation strategies:

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.
  •  

Note how useless it would have been to digress into specifics of management for fat embolism syndrome.