Deranged Physiology ยป Content

Viva 1

Created on Thu, 06/04/2015 - 05:27
Last updated on Wed, 02/07/2018 - 03:13

You are the Consultant Intensivist in charge for the day with a new registrar in their first week working in ICU. You are called about a 53-year-old man with hypotension 30 minutes after elective admission post coronary artery bypass grafts and mitral valve repair. He had an acute myocardial infarction 4 weeks ago; his pre-operative echo showed moderate left ventricular dysfunction and moderate to severe mitral regurgitation. His blood pressure is now 70/45 and the registrar requests your
immediate help at the bedside.

Describe your management approach to this problem, including the major differential diagnoses you would consider.
 

(I have changed the script somewhat to more closely reflect the logical approach to an unstable post-op cardiac patient)

  • History from OT staff and anaesthetist, regarding why the pump time was so prolonged, what the last ACT was and what other complications there were.
  • Examination, including dynamic manoeuvres to assess for fluid responsiveness
  • ECG to exclude STEMI
  • CXR to exclude pneumothorax
  • Arterial blood gas
  • Mixed venous blood gas
  • Formal TTE to examine valve function and exclude tamponade
What are the possible causes of shock in this patient?

This is a standard list of causes of haemodynamic instability in a patient returng from cardiac surgery.

Causes of cardiovascular instability after bypass

Immediately recognisable on direct inspection

  • Artifactual - check your lines, zero to recalibrate
  • Anaphylaxis
  • Arrhythmia, eg. AF
  • Valve failure - eg. mitral regurgitation of sudden onset

Immediately recognisable on routine investigations

  • Myocardial ischaemia should not be left unrecognized
  • Pneumothorax or tension pneumothorax
  • Cardiac Tamponade
  • Haemorrhage
  • LV outflow tract obstruction

Excluded by inspection and investigations

  • Rewarming-related vasodilation
  • Excessive sedation with propofol
  • Post-bypass vasoplegia
  • Post-bypass myocardial depression
 

 

Disclaimer: the viva stem above is the original CICM stem, acquired from their publicly available past papers. However, because the college do not make the rest of the viva text or marking criteria available, the rest has been confabulated. It sounds like a plausible viva and it can be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station.