Raised ICP Flashcards
Raised intracranial pressure (ICP) is a common problem in neurosurgical and neurological practice. Its development may be acute or chronic.
What are the normal intracranial pressure values in adults and children?
- adults: <10-15 mmHg
- children: 3-7 mmHg
- term infants: 1.5-6 mmHg
What are the signs and symptoms of raised ICP?
- unequal pupils unresponsive to light
- headache → worse on standing, coughing, sneezing
- reduced alertness / confusion / coma
- nausea + projectile vomiting
- blurred vision
- papilloedema
- Cushing’s reflex → bradycardia, hypertension + irregular respirations
What are causes of raised ICP?
- Localised mass lesions → haematomas, neoplasms, abscess, focal oedema 2o to trauma, infarction or tumour
- Disturbance of CSF circ → obstructive hydrocephalus, communicating hydrocephalus
- Obstruction to major venous sinuses → depressed fractures, cerebral venous thrombosis
- Diffuse brain oedema or swelling → encephalitis, meningitis, diffuse head injury, subarachnoid haemorrhage, Reye’s syndrome, lead encephalopathy, water intoxication, near drowning
- Idiopathic → benign intracranial hypertension
ICP monitoring is used either as a guide to treatment (for example, in the management of closed head injury) or as a diagnostic test (for example, in disorders of CSF circulation).
What are the recommendations for ICP monitoring?
- ICP monitoring is appropriate in patients with severe head injury (GCS between 3 and 8 after cardiopulmonary resuscitation) and an abnormal computed tomographic (CT) scan (haematomas, contusions, oedema or compressed basal cisterns)
- ICP monitoring is appropriate in patients with severe head injury and a normal CT scan if two or more of the following features are noted on admission: age over 40 years, unilateral or bilateral motor posturing, systolic blood pressure < 90 mm Hg
- ICP monitoring is not routinely indicated in patients with mild or moderate head injury; however, a clinician may choose to monitor ICP in certain conscious patients with traumatic mass lesions.
How is ICP measured?
- Intraventricular fluid filled catheter transducer systems represent the “gold standard” for measuring ICP
- Allows checking for zero and sensitivity drift of the measurement system in vivo
- Access to the CSF space provides a method for ICP treatment via CSF drainage
- Placement of these catheters does involve a ventriculostomy with the attendant small risk of infection, haematoma formation, and seizures.
Sites other than the lateral ventricle can be used for ICP recording; these include the subarachnoid and subdural spaces as well as brain parenchyma. Such alternative sites may be associated with lower risks of infection and haemorrhage, but often do not provide reliable measurements.
Primary management is directed, if possible, at the specific process responsible for the rise in ICP.
What is the first-tier management of raised ICP?
- general physiologic homeostasis → maintaining oxygen + fluid balance
- CSF drainage → via ventriculostomy
- head of bed elevation → to 30o, improves jugular venous outflow = lowers ICP
- analgesia + sedation → IV propofol/etomidate/midazolam for sedation and morphine/alfentanil for analgesia
- neuromuscular blockage
- diuretics → mannitol (can cause hyperosmotic state)
- hyperventilation → lowers ICP via hypocapnoeic vasoconstriction
What are second-tier treatments of raised ICP?
- barbiturate coma → depresses cerebral metabolic activity + reduces ICP
- optimised hyperventilation
- hypothermia
- decompressive craniectomy
