Hypertension (fitness for anaesthesia)

Drug-controlled hypertension is not a contraindication to general anaesthesia. Medication should be maintained throughout the operative period as there is a risk of rebound hypertension causing a cerebrovascular accident. Also, a sustained rise in end diastolic pressure reduces the inflow of blood to the myocardium during diastole.

Untreated hypertension discovered at the preoperative anaesthetic assessment necessitates a systematic approach. The following algorithm is one possibility. Three diastolic blood pressure readings are taken. If the average value is:

• >120mmHg:
  • cancel the operation
  • investigate and treat the hypertension during admission
  • reschedule the operation once the blood pressure is controlled for four to six weeks time
• 105-115mmHg with signs of end-organ damage: follow the same course as for blood pressure >120mmHg
• 105-115mmHg without signs of end-organ damage:
  • continue with operative plan
  • consider treating pre-operatively with an oral beta-blocker, e.g. atenolol, or alpha-2-agonist, e.g. clonidine

A blood pressure of the magnitude of, for example, 240/80 mmHg in an elderly patient may be due to arteriosclerosis. It is important to avoid perioperative hypotension in these patients as they need an elevated blood pressure to maintain tissue perfusion.