Question 10

Last updated Fri, 07/17/2015 - 15:26
 Topic: Cardiothoracic Intensive Care
Pass rate
62%
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A 56 year old woman 1 hr post cardiac surgery has a high blood pressure in the ICU. Give likely causes for her high blood pressure and the potential complications this may cause in the early post operative period.

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College Answer

Causes: 
Previous hypertension
Pain
Inadequate analgesia or sedation vs paralysis
Measurement error
Hypercarbia
Endotracheal tube intolerance
Wrong dosing of inotropes/vasopressors
Blocked IDC
Post AVR for AS

Potential complications:

Bleeding from aortic cannulation site
Generalised ooze 
Heart failure 
Myocardial ischaemia 
Arrhythmias
Graft dislodgement 
Extension of a dissection 
Hypertensive crises

Discussion

Apparently, hypertension can occur in 15-40% of post-cardiac surgery patients. It receives a little less interest than hypotension. Note how the college answer has few points which are actually specific to cardiothoracic surgery. And where is hypothermia? That surely plays a role.

The college answer then goes on to mention arrhythmias and hypertensive crises as potential complications. I would have added the effects of increased afterload on myocardial oxygen consumption, the additional stress on new valve components, increase of pre-existing mitral regurgitation, increased sedation demands and thus potentially a delay of extubation, and complications related to the use of antihypertensive polypharmacy.

Anyway; the complete list of causes and consequences looks like this:

Causes

  • Pain
  • Inadequate sedation in a partially paralysed patient
  • Pre-existing hypertension, and the perioperative cessation or regular medications
  • Artifactual hypertension (measurement error)
  • Unintelligent use of vasopressors
  • The sudden improvement of aortic flow following the repair of a stenotic aortic valve, which exposes the systemic circulation to being bullied by a massively hypertrophied left ventricle.

Consequences

  • Increased bleeding risk - particularly from the aortic cannulation site
  • Extension of an arterial dissection
  • Increased afterload and thus increased LV workload
    • Thus, increased risk of ischaemia
    • Increased risk of cardiac failure due to decompensated LV failure
  • Increased stress on grafted valves or repaired aortic root
  • Worsening of existing mitral regurgitation
  • Increased need for sedation
  • Bleeding from aortic cannulation site

References

Estafanous, Fawzy G., and Robert C. Tarazi. "Systemic arterial hypertension associated with cardiac surgery." The American journal of cardiology 46.4 (1980): 685-694.

Roberts, A. J., et al. "Systemic hypertension associated with coronary artery bypass surgery. Predisposing factors, hemodynamic characteristics, humoral profile, and treatment." The Journal of thoracic and cardiovascular surgery 74.6 (1977): 846-859.

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