Neurosurgery and raised intracranial pressure

What it is

The skull is a rigid box holding brain, blood and cerebrospinal fluid; when one of them grows, as with a tumour, bleed, oedema or blocked fluid, the others are displaced until compensation runs out and intracranial pressure rises steeply (the Monro-Kellie principle). Cerebral perfusion pressure is mean arterial pressure minus intracranial pressure, so both hypotension and raised pressure starve the brain. Cerebral blood flow normally autoregulates against changes in blood pressure, an ability lost in injured brain, and it rises with carbon dioxide, severe hypoxaemia and high temperature. Anaesthesia for craniotomy therefore aims for a smooth induction without coughing, straining or swings in pressure; an arterial line; total intravenous anaesthesia with propofol, which lowers brain metabolism and blood volume, or low concentrations of volatile agents, which dilate cerebral vessels at higher doses; normal oxygen and carbon dioxide; head-up position with a neutral neck; isotonic fluids and normal glucose and temperature; osmotherapy for a tight brain; and a smooth, prompt emergence so the patient can be examined. Awake craniotomy is used when a lesion lies near speech or motor cortex: a scalp block and careful sedation, or an asleep-awake-asleep technique, let the patient talk and move during mapping.

What changes in this patient

• Fixed skull volume: brain, blood and cerebrospinal fluid compensate for a growing lesion until pressure rises steeply.
• Injured brain loses autoregulation, so cerebral blood flow follows blood pressure passively.
• Carbon dioxide, hypoxaemia, fever, seizures and volatile agents at higher doses raise cerebral blood flow and volume.
• Propofol and barbiturates reduce cerebral metabolism, blood flow and intracranial pressure.
• Nitrous oxide raises cerebral metabolism and can expand trapped intracranial air.
• Sitting and head-up positions bring the risk of venous air embolism, because the veins of the head lie above the heart.

Anaesthetic plan (and why)

1. Assess consciousness and focal deficits, and the cause of raised pressure — the baseline guides emergence and the urgency of surgery.
2. Place an arterial line, often before induction — pressure swings at induction and pinning must be seen at once.
3. Induce smoothly, deep enough to block the response to laryngoscopy and pinning — coughing and hypertension raise intracranial pressure.
4. Maintain with propofol-based intravenous anaesthesia or low-dose volatile — both allow a slack brain and a quick wake-up.
5. Keep oxygen normal and carbon dioxide normal to low-normal — hypercapnia swells the brain; deep hypocapnia causes ischaemia.
6. Position head-up with a neutral neck and no tight ties — this helps venous drainage and lowers intracranial pressure.
7. Give isotonic fluids, avoid glucose solutions, and keep glucose and temperature normal — hypotonic fluid and hyperglycaemia harm the brain.
8. For a tight brain: deepen anaesthesia, check the carbon dioxide, give mannitol or hypertonic saline — osmotherapy draws water from the brain.
9. In awake craniotomy, give a scalp block and titrate sedation so the patient can talk — this allows safe mapping of eloquent cortex.
10. Wake up smoothly, controlling blood pressure and coughing, and examine the patient at once — early examination detects a bleed.

What raises and what lowers intracranial pressure

Risks and complications

• Rising intracranial pressure, brain swelling and herniation, with a dilated pupil and Cushing's response.
• Cerebral ischaemia from hypotension or over-hyperventilation.
• Venous air embolism in sitting or head-up positions: a sudden fall in end-tidal carbon dioxide, hypotension and arrhythmia.
• Seizures, including during cortical stimulation in awake craniotomy, usually stopped by cold irrigation of the cortex.
• Airway obstruction, agitation and loss of cooperation during awake craniotomy, with possible conversion to general anaesthesia.
• After surgery: haematoma, hypertension, seizures, and sodium disorders such as diabetes insipidus or hyponatraemia.

Next step

• Admit to neurosurgical high-dependency or intensive care with frequent neurological observations.
• Call the neurosurgeon and a senior at once for falling consciousness, a new deficit or a new dilated pupil: image urgently.
• Control blood pressure, pain, nausea and shivering after surgery: each raises intracranial pressure or bleeding risk.
• Check sodium and fluid balance regularly to detect diabetes insipidus or hyponatraemia.
• Continue seizure prophylaxis and steroids only as the neurosurgical plan states, with a stop date.

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Elsewhere in DurgiPedia

• Cerebral blood flow, brain metabolism and intracranial pressure
• CSF and the blood–brain barrier
• Intracranial hypertension syndrome

Connections

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Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Craniotomy (StatPearls (NCBI Bookshelf), 2026); Anesthesia for Awake Craniotomy (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.