Raised intracranial pressure Flashcards
What is an extradural haematoma?
An extradural (or ‘epidural’) haematoma is a collection of blood that is between the skull and the dura, almost always caused by trauma, typically low-impact trauma.
Where is an extradural haematoma most commonly located?
The collection is often in the temporal region, particularly at the pterion where the middle meningeal artery is vulnerable to injury.
What is the classical presentation of an extradural haematoma?
A patient initially loses, briefly regains, and then loses consciousness after a low-impact head injury, with the brief regain termed the ‘lucid interval’.
What happens as an extradural haematoma expands?
As the haematoma expands, the uncus of the temporal lobe herniates around the tentorium cerebelli, leading to a fixed and dilated pupil due to compression of the third cranial nerve.
How does an extradural haematoma appear on imaging?
It appears as a biconvex (or lentiform), hyperdense collection around the surface of the brain, limited by the suture lines of the skull.
What is the management for patients with no neurological deficit due to extradural haematoma?
Cautious clinical and radiological observation is appropriate.
What is the definitive treatment for an extradural haematoma?
The definitive treatment is craniotomy and evacuation of the haematoma.
What is idiopathic intracranial hypertension?
A condition classically seen in young, overweight females, also known as pseudotumour cerebri.
What are the risk factors for idiopathic intracranial hypertension?
Risk factors include obesity, female sex, pregnancy, drugs (combined oral contraceptive pill, steroids, tetracyclines, retinoids, lithium).
What are the common features of idiopathic intracranial hypertension?
Headache, blurred vision, papilloedema, enlarged blind spot, and possible sixth nerve palsy.
What are the management options for idiopathic intracranial hypertension?
Weight loss, carbonic anhydrase inhibitors (e.g., acetazolamide), topiramate, repeated lumbar puncture, and surgery (optic nerve sheath decompression).
What is papilloedema?
Papilloedema describes optic disc swelling caused by increased intracranial pressure, almost always bilateral.
What features may be observed during fundoscopy in papilloedema?
Venous engorgement, loss of venous pulsation, blurring of the optic disc margin, elevation of optic disc, loss of the optic cup, and Paton’s lines.
What are common causes of papilloedema?
Space-occupying lesions, malignant hypertension, idiopathic intracranial hypertension, hydrocephalus, and hypercapnia.
What are rare causes of papilloedema?
Hypoparathyroidism, hypocalcaemia, and vitamin A toxicity.
Fundoscopic demonstrating papilloedema
Fundoscopic demonstrating papilloedema
What is raised intracranial pressure?
Raised intracranial pressure occurs when additional volume (e.g. haematoma, tumour, excessive CSF) leads to a rise in intracranial pressure (ICP) due to the rigid skull’s limited ability to accommodate it.
What is the normal ICP range in adults?
The normal ICP is 7-15 mmHg in adults in the supine position.
What is cerebral perfusion pressure (CPP)?
CPP is the net pressure gradient causing cerebral blood flow to the brain.
CPP = mean arterial pressure - ICP.
What are some causes of raised intracranial pressure?
Causes include idiopathic intracranial hypertension, traumatic head injuries, infection, meningitis, tumours, and hydrocephalus.
What are the features of raised intracranial pressure?
Features include headache, vomiting, reduced levels of consciousness, papilloedema, Cushing’s triad, widening pulse pressure, bradycardia, and irregular breathing.
What investigations are used for raised intracranial pressure?
Neuroimaging (CT/MRI) is key to investigate the underlying cause, along with invasive ICP monitoring.
How is invasive ICP monitoring performed?
A catheter is placed into the lateral ventricles of the brain to monitor pressure, collect CSF samples, and drain small amounts of CSF to reduce pressure.
What is the cut-off for ICP that indicates treatment may be needed?
A cut-off of > 20 mmHg is often used to determine if further treatment is needed to reduce the ICP.
What is the management for raised intracranial pressure?
Management includes investigating and treating the underlying cause, head elevation to 30º, IV mannitol as an osmotic diuretic, controlled hyperventilation, and removal of CSF.
What is the aim of controlled hyperventilation in managing ICP?
The aim is to reduce pCO2, leading to vasoconstriction of the cerebral arteries and reduced ICP.
Caution is needed as it may reduce blood flow to already ischaemic parts of the brain.
What techniques can be used to remove CSF?
Techniques include draining from an intraventricular monitor, repeated lumbar puncture, and ventriculoperitoneal shunt for hydrocephalus.
What are two simple positional maneuvers to open the airway?
Head tilt / chin lift and jaw thrust (preferred if concern about cervical spine injury).
What is an oropharyngeal airway?
An airway device that is easy to insert and use, requiring no paralysis, ideal for very short procedures, and often used as a bridge to more definitive airway.
What are the characteristics of a laryngeal mask?
Widely used, very easy to insert, sits in pharynx to cover the airway, poor control against reflux of gastric contents, and paralysis is not usually required.
When is a laryngeal mask commonly used?
Commonly used for a wide range of anaesthetic uses, especially in day surgery.
Not suitable for high-pressure ventilation.
What is the purpose of a tracheostomy?
Reduces the work of breathing and dead space, may be useful in slow weaning, and percutaneous tracheostomy is widely used in ITU.
What are the requirements for humidified air with a tracheostomy?
Dries secretions, humidified air is usually required.
What is the function of an endotracheal tube?
Provides optimal control of the airway once the cuff is inflated and may be used for long or short-term ventilation.
What are the risks associated with endotracheal tube insertion?
Errors in insertion may result in oesophageal intubation, accounting for around 5% of major airway complications.
Therefore, monitor end-tidal CO2 (capnography).
What is often required for endotracheal tube use?
Paralysis is often required, and higher ventilation pressures can be used.
