11. Hypertension

Question 1

What are the causes of intra- operative hypertension?

Answer 1

> Patient factors:

• Pre-existing uncontrolled hypertension:

essential hypertension (90% of cases)

secondary hypertension

(e.g. Conn’s syndrome, phaeochromocytoma,
renal artery stenosis or pre-eclampsia in pregnant patients).

• Disease states exacerbated by surgery
(e.g. thyroid storm or the
Cushing’s reflex in the head-injured patient
with raised intracranial pressures).

> Anaesthetic factors:

• Inadequate depth of anaesthesia
• Inadequate analgesia

• Inadequate ventilation causing
hypercapnia or hypoxia

• Overdosing of vasopressor drugs
causing iatrogenic hypertension

• Malignant hyperpyrexia (rare)

Question 2

How would you manage such a case?

Answer 2

> Pre-operative:

An assessment should identify and optimise patient
factors prior to elective surgery.

> Intra-operative:
This requires an assessment to

identify the cause followed by the required intervention,

e.g.

increase depth of anaesthesia,

supplemental analgesia.

Administration of antihypertensive medications
may be required intra-operatively.

Drugs that can be used to bring down BP in the acute setting include:

• β-Blockers –

esmolol is an ultra-short-acting agent given by infusion.

Labetalol has α and β effects and is typically given as slow boluses titrated to effect.

• Hydralazine – a directly acting
vasodilator (arteries > veins) that can be
administered if β-blockers are contraindicated.

• GTN –
a short-acting vasodilator (veins > arteries), and tolerance develops within 24 hours.

• Sodium nitroprusside –

an arteriolar vasodilator. It is light sensitive and
prolonged use can lead to cyanide accumulation.

• Remifentanil – a synthetic opioid that causes a decrease in mean arterial pressure and heart rate.

Profound bradycardia can limit its use.