A more detailed review of noradrenaline is available, where its many virtues are gleefully explored. The generic approach to the haemodynamically unstable cardiac surgical patient  is also discussed elsewhere; noradrenaline forms a small part of the overall approach.

However, in Question 7 from the first paper of 2013, , the candidate was expected to reason throughtfully about the advantages and disadvantages of using a α-1 agonist specifically in the management of a post-bypass patient.

The summary below, therefore, relates only to this specific use of noradrenaline.

Rationale

  • Hypotension in the post-cardiothoracic surgery patient can be due to a multitude of factors.
  • Noradrenaline theoretically addresses at least some of them, namely:
    • Improves preload (by venoconstriction)
    • Improves vasoplegia (by arterioconstriction)
    • Improves cardiac contractility (β-1receptor effect increases with increasing dose)
    • Improves diastolic filling of coronary arteries (by increasing diastolic pressure)
    • Improves diastolic filling of the ventricles (by producing a reflex bradycardia)

Advantages of noradrenaline

  • Cheap, by the standards of a developed country
  • Short half life: easily titrated
  • Relatively pure α-1 agonist effect; thus, no lactic acidosis due to its use
  • Relatively linear dose-response relationship; predictable effects.

Disadvantages of noradrenaline

  • Expensive, by the standards of a developing country (dopamine is still in use in many places owing to its gentle effect on the ICU budget)
  • Increased afterload increases LV workload and decreases subendocardial perfusion, potentially worsening ischaemia
  • In hypotension due to cardiogenic shock, noradrenaline will do little to improve blood pressure
  • Temporary improvement in hemodynamic variables may obscure another cause of hemodynamic instability, eg. haemorrhage, infarction or cardiac tamponade.

Evidence for its use

References

Maas, Jacinta J., et al. "Cardiac Output Response to Norepinephrine in Postoperative Cardiac Surgery Patients: Interpretation With Venous Return and Cardiac Function Curves*." Critical care medicine 41.1 (2013): 143-150.

Hajjar, L., et al. "Vasopressin Versus Norepinephrine for the Management of Shock After Cardiac Surgery (VaNCS study): a randomized controlled trial." Critical Care17.Suppl 2 (2013): P222.

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