Question 2

College answer

This question was answered well, as most candidates were able to outline sufficient potential differential diagnoses. Candidates are reminded that is a question asks for 4 likely causes, only the first four causes listed will be taken into consideration. Candidates were required to demonstrate a stepwise logical approach
to for the immediate management.

Discussion

This question is basically the same as Question 13 from the first paper of 2012, which demonstrates to exam candidates that they need to reach at least ten years back into historical papers in order to capture all potential repeat SAQs. 

Differential diagnosis for this hypotension can be organised in a number of different ways (see the discussion section of Question 13), but the one which 

• Preload
  • Inadequate intraoperative fluid
  • Haemorrhage
  • Valve failure (mitral / tricuspid)
• Rate
  • Bradycardia (or excessive tachycardia!)
• Rhythm
  • AF or other arrhythmia
• Contractility
  • Post-bypass myocardial depression
  • Myocardial ischaemia
• Afterload
  • Artifact: art line is incorrectly zeroed
  • LVOT obstruction
  • Anaphylaxis
  • Vasoplegia
  • Valve failure (aortic or pulmonic)

Considering this was weighted only 20% of the total mark, one should be expected to produce a laconic pointform list rather than a paragraph of text, which means the use of this classification system might be a bit excessive. 

Four likely causes of excessive post-operative bleeding in this setting:

One could pick any from the following list of factors:

• incomplete surgical haemostasis
• residual heparin effect after cardiopulmonary bypass
• platelet abnormalities (platelet dysfunction and thrombocytopenia – from bypass circuit consumption, antiplatelet agents etc)
• hypothermia 
• postoperative hypertension
• clotting factor depletion
• haemodilution (dilutional thrombocytopenia and coagulopathy)

Immediate management here would have to be structured and detailed to earn full marks. Examples of what that means abound in the past papers, but the best one is probably again in the college answer to Question 13 from the first paper of 2012. A mutant version of that structure is offered here:

• Maintain  SpO2 ~ 100%
• Adjust positive pressure, with two goals in mind:
  • Enhancement of preload by controlling the intrathoracic venous flow
  • Enhancement of afterload by increasing LV transmural pressure
  • Perhaps some sort of tamponade effect - the college answer recommends a PEEP of 10, which ( a reader has helpfully pointed out) probably comes from Ilabaca et al (1980).
• Assess the drains to make sure they are not blocked
• Maintain satisfactory diastolic pressure with noradrenaline and/or vasopressin
• Give a fluid bolus
• Check for a cardiovertable rthythm disturbance
• Consider increasing pacing rate to 90
• Organise a TOE or TTE to assess the need for inotropes
• Check bloods and TEG to see what further factors/platelets the patient might require
• Alert the surgeons to the deterioration, in case you need to reopen the chest