A previously fit and well 24 year old man sustained an isolated C5-C6 spinal injury following  a  diving  accident  resulting  in  a  tetraplegia.  The  spinal  fracture  was surgically fixed the following day and the patient was extubated on Day 6 of his ICU admission. Within 4 hours of extubation, the patient developed respiratory distress requiring urgent rapid sequence induction and reintubation. The patient sustained a cardiac arrest soon after intubation.

18.1.   List five (5) likely causes of cardiac arrest in this patient.

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College Answer

•    Oesophageal intubation
•    Hypoxic cardiac arrest (unrelated to oesophageal intubation due to delayed or unanticipated difficulty with intubation)
•    Suxamethonium induced hyperkalemia
•    Incidental PE
•    Autonomic dysfunction from the spinal injury.
•    Tension pneumothorax
•     Anaphylaxis


This question relies on the candidate being able to generate a list of differential causes for cardiac arrest.

A good systematic framework for this is the "Four Hs and four Ts" mnemonic:

  • Hypoxia (thus, oesophageal intubation or delayed oxygenation)
  • Hypovolemia (thus, cardiovascular collapse due to vasodilation by an induction agent like propofol, or due to the autonomic dysfunction of spinal cord injury)
  • Hyper/hypokalemia (thus, the effects of suxamethonium)
  • Hyper/hypothermia (probably irrelevant in this case)
  • Tension pneumothorax (due to overvigorous bag-mask ventilation, or due to tracheobronchial disruption by violent use of the bougie)
  • Tamponade (unlikely in this setting)
  • Toxins (eg. anaphylactic reaction to induction agents)
  • Thrombus (eg. the PE which the college for some reason offer as a valid differential)