Raised ICP Flashcards
What is the normal intracranial pressure
0-10mmHg
What processes regulate ICP
Autoregulation:
vasoconstriction
Vasodilation
Chemoregulation:
Vasodilation in response to low pH
What compensatory processes maintain ICP
Reduced venous blood volume
Reduced CSF volume
Why do we need compensatory processes
Cranium is an inextensible cavity containing brain+blood+CSF
Increased volume of one structure causes decreased volume of another
Venous blood/CSF needs to be reduced to maintain ICP and blood supply
What is the pathophysiology of raised ICP
RICP causes compression of cerebral arteries Reduced blood supply Hypoxia + inhibit Na/K ATPase Increased intracellular Na Cellular oedema Further RICP and compression
What are the clinical features of RICP
Headache Reduced consciousness level N+V Visual disturbance Double vision Cushings reflex
What is the characteristic headache in RICP
Generalised
Worse in mornings (sleep+hypoventilation causes vasodilation)
Worse on bending, coughing (obstruct SVC)
Why do you get N+V in RICP
Stimulate Area Postrema - vomiting centre
With compression of medulla
What visual disturbance do you get
Blurry vision
Transient blindness on bending
Papilloedema
Why do you get double vision
Compression of CN VI on petrous part of temporal bone with downward displacement of brainstem
False localising sign
Why do you get altered conscious level
Compression of midbrain and depression of reticular formation
What is Cushing’s reflex
Physiological response to RICP that leads to triad of: Hypertension + Bradycardia + Respiratory depression
What are the stages of cushings reflex
Hypertension - cerebral ischaemia activations SNS
Bradycardia - increased aBP activates baroreceptors
Respiratory depression - RICP causes herniation and compression of brainstem
What are causes of RICP
Blood volume: venous obstruction, venous sinus thrombosis
CSF: hydrocephalus, choroid plexus papilloma
Brain: meningitis, encephalitis, diffuse brain injury, infarction
SOL: tumour, abscess, haematoma
idiopathic intracranial hypertension
What is idiopathic intracranial hypertension
When does it typically occur
RICP in absence of evidence of hydrocephalus of mass lesions
In obese young women after weight gain
What are causes of hydrocephalus
What are the findings on CT
Communicating: post SAH, Post meningitis
All ventricles equally enlarged
Non-communicating: congenital atresia, stenosis, tumour
Third ventricle enlarged, fourth ventricle normal
What are the steps in acute management of RICP
- Recognise signs:
Reduced GCS, focal neurological sign, Papilloedema (late), htn+bradycardia, seizures - Do NOT perform lumbar puncture
- Stabilise patient:
ABC + O2, mannitol or 3% saline, treat shock, anaesthetist to intubate + ventilate - Neurointensive care:
Elevate head, sedation, prevent hyperthermia, consider CT
How do you manage RICP caused by increased blood volume
Anticoagulation
Tenting of venous sinus
How do you manage RICP caused by cerebral oedema
Treat cause: antibiotics, alteplase
Mannitol / 3% Saline: fluid shift from interstitium into vessels
How to you manage RICP caused by hydrocephalus
Ventriculoperitoneal shunt
Tumour resection
Diuretics: furosemide, carbonic anhydrase inhibitor
How do you manage RICP caused by SOL
Surgical resection - craniotomy
Abscess drainage
