You are the leader on the retrieval team for a patient with cerebral arterial gas embolism (CAGE) following a scuba diving accident to your regional Hyperbaric Centre, 300 km away. The patient is intubated, ventilated and on vasopressors.

Outline the strategies needed in preparation, planning and implementation to ensure safe transport of the patient, including the necessary strategies for the patient's specific condition.

[Click here to toggle visibility of the answers]

College answer

A. General; compliance with CICM/ANZCA/ACEM guideline;

 Possible clinical impact of the transport environment (in this case flight environment may be particularly deleterious if patient is exposed to sub-atmospheric pressure).

  • Urgency of intervention – urgent
  • Road transport times and road conditions  
  • Weather conditions and aviation restrictions for airborne transport  
  • Aircraft landing facilities  
  • Range and speed of vehicle                                

 a) Team with suitable training and experience

  • Clinical – adequate seniority
  • Logistic – aircraft safety training and familiarity with transport equipment/environment 

 
b) Equipment- appropriate ventilator, monitors, alarms, devices for manual handling, pumps to maintain infusions. Full list from the CICM guideline not required but key elements needed

  • Respiratory support equipment (doesn’t need extensive expansion other than ventilator, manual ventilation equipment, appropriate gear for reintubation)
  • Circulatory support equipment:
    • Monitor/defibrillator/external pacer combined unit  
    • Multifunction monitor including capnograph
    • Intravenous fluids and pressure infusion set  
    • Infusion pumps
    • Syringes and needles
    • Pericardiocentesis and thoracostomy equipment
  • Other equipment:  
    • Personal protective equipment
    • Nasogastric tube and bag
    • Urinary catheter and bag
    • Thermal insulation and temperature monitor  
  • Consideration should be given to alternative vascular access such as intraosseous devices  

 
c) All drugs should be checked and clearly labelled prior to administration. The range of drugs available should include all drugs necessary to manage acute life-threatening medical emergencies and those specific to the patient’s clinical condition 
 
d) Liaison with the receiving centre ensuring key details have been conveyed, especially relevant in this case 
 
e) Final preparation of the patient should be made prior to transport, with anticipation of clinical needs. Examples include giving appropriate doses of muscle relaxants or sedatives, replacing  near-empty inotrope and other intravenous solutions with fresh bags, and emptying drainage bags


 B. Specific to condition;  Need to consider mode of transport

  • 300km essentially obviates road  
  • Fixed wing has potential for sea level cabin but requires increased handling
  • Helicopters not pressurised and may not be suitable unless terrain allows low-level flight 

The candidates needed to be aware that minimal cabin altitude is a key part of management. 

  • Airway
    • ETT secured, CXR to confirm the position
    • May need suctioning if prolonged delay to retrieval
  • Ventilation
    • 100% FiO2
    • Minimise PEEP (5cm H2O)
    • Check ABG, and ventilate at TV 6-ml/kg, SIMV, rate to maintain normocarbia
    • CAGE may be associated with other barotrauma so CXR to exclude pneumothorax •
  • Circulation
    • Try to maintain euvolaemi
    • As on vasopressors will need CVC. CVC needs to be well secured. Probably dilute vasopressors according to retrieval regimen to ensure smooth transition
  • Neurological
    • Maintain normothermia
    • Will need sedation and paralysis for transport, again dilutions as per retrieval
    • Regular check of BSL, aim 6-10
    • Should have CT to exclude differential diagnosis.
    • Copy will need to go with patient (hard copy or digital copy) 

 C. Interim management in liaison with hyperbaric unit

Additional Examiners’ Comments: This answer template is long and detailed and it was not expected that candidates needed to reproduce it all to obtain a pass. Important points were the awareness and compliance with guidelines on transport of critically ill patients, and the awareness that minimising flight altitude is essential. 

Discussion

Preparation, planning and implementation of transfer sounds a lot like a question on aeromedical retrieval. However, for some reason this gas embolism question ended up in the Trauma category.

Administrative/logistic planning of the transfer:

  • Consider the urgency of transfer, depending on clinical need.
  • Transfer options which are available in this scenario all have some advantages and disadvantages:
    • The timing of the transfer is less important than the safety of the patient, as recompression therapy still has a role to play even 24-48 hrs after the injury; therefore there is no imperative to transfer by air immediately.
    • If the dive was recent (within the last 24 hrs), exposure to altitude in a commercial aircraft cabin could give rise to new gas emboli.
    • One may use a pressurised cabin instead. The additional weight and the need to fly at a lower altitude increases the amount of fuel required by up to 30%, and the travel time is longer.
    • Travel by road may be up to 4 hrs. During this time, vibration in the vehicle may give rise to increased tribonucleation, whereby gas bubbles precipitate out of a solution. 
  • Which of the possible options are chosen (road, fixed wing, helicopter, pressurised vs. depressurised cabin) depends on the clinical state of the patient.
  • If the patient is stable on vasopressors and mechanicaly ventilated, road transport may be the safest option (i.e. one which does not promote any new neurological injury). The next best option is retrieval by an aircraft with a sea-level pressurised cabin.

Preparation of the patient

  • Secure the airway with immobiliser devices to ensure the patient is not accidentally extubated in transit
  • Trial the patient on the retrieval transport ventilator for ~ 30 minutes prior to transfer, to ensure that this is well tolerated
  • The patient will be on 100% FiO2 throughout this transfer; there should be no hiatus in therapy. Ensure that the transport vehicle has enough oxygen supply to last for two such trips  
  • Ensure all vascular access is established before transfer, and all ports easily accessible.
  • Administer thiopentone - ensure the cerebral metabolic rate is lowest in the event of worsening cerebral ischaemia. This also protects against seizures.
  • Administer long-acting muscle relaxant
  • Perform one last pre-transfer assessment.

Preparation of personnel and family

  • Brief senior retrieval staff (this complex job is not for the junior trainees)
  • Ensure accepting hospital have received a detailed handover about the patient
  • Next of kin need to be updated about the trasnfer
  • Medical documentation travels with the patient
  • Receiving unit receives updates on transfer status (i.e. call them as you are about to leave)

References

References

ANZCA "Guidelines for Transport of Critically Ill Patients

CICM "Minimum Standards for Transport of Critically Ill Patients" (IC-10, 2010)

Warren, Jonathan, et al. "Guidelines for the inter-and intrahospital transport of critically ill patients*." Critical care medicine 32.1 (2004): 256-262.

Bennett, P. B., and R. E. Moon. "Final summary of recommendations: diving accident workshop." Diving Accident Management: Undersea and Hyperbaric Medical Society, Bethesda, MD (1990): 366-369.

Stephenson, Jeffrey C. "Pathophysiology, treatment and aeromedical retrieval of SCUBA-related DCI." Journal of Military and Veterans Health 17.3 (2009): 10.