JC M WCS 1
RAISED INTRACRANIAL PRESSURE
Dr YW Fan
Neurosurgery
Mon 21-10-02
CONCEPTS
Monro-Kellie-Burrows Doctrine ®
IC contents = blood + brain + CSF
Blood: within BV (a, v, cap)
Eg. if haematoma ® initial ¯ venous vol (preserve arterial vol) ® haematoma expands ® ¯ ABP ® ¯ perfusion pressure
When CSF and venous vol squeezed, IC pressure exponentially
ICP Causes
Mass ® tumour, haematoma
Hydrocephalus ® communicating/ obstructive
Brain swelling ® focal/ diffuse
Hyperaemia/ Venous congestion
Note: CO2 retention
® VD ® bld vol ® hyperaemia
ICP Compensation
¯ Venous bld vol
¯ CSF vol
At first,
vol causes no D ICP; past compensatory limit ® exponential
Head Injury
- Haematoma
- Cerebral oedema:
brain vol
Hyperaemia: VD
Hydrocephalus
Hypoventilation: CO2 retention ® BV VD
Venous sinus thrombosis: rare (eg. frag bone impinges saggital sinus ® impede VR \ removes venous compensation)
IC Pressure
- Adult 5-15 mmHg (> 20 definitely abn)
- Young child 3-7 mmHg
- Infant 1.5-6 mmHg
Children have
¯ ICP cf. adult
Cerebral Perfusion Pressure
Cerebral Perfusion Pressure = Mean Arterial Press - IC Pressure
- Need CPP 70 mmHg to maintain neurones satisfactorily (usu. MAP 80; ICP 10)
- Haematoma (1) Surgically remove to
¯ ICP (2) Artificially MAP to compensate
If multi-injury (eg. ruptured spleen): MAP most important (b/c no matter what you do to ICP, it is no use unless MAP sufficiently high)
Autoregulation
Myogenic theory
¯ BP ® VD ® bld to brain
BP ® VC ® ¯ bld to brain
Prob with autoreg
- Vasomotor paralysis
(BV dilates passively)
® Hyperaemia ® BV ® ICP ® ¯ CPP
CLINICAL APPLICATIONS
Cerebral Ischaemia
90% of head injury
Ischaemia
Acidosis: anaerobic metab
Excitatotoxicity: ¯ E to cells ® Ca++ leak
Free radical generation: n membrane
- Loss of MP (damaged Na/K-ATPase) ® cerebral oedema
Normal Brain Cell Metab
Glucose + O2 ® (bld supply) ® cell ®
Cerebral BF µ Cerebral Metab
- ¯
Cerebral metab: phenobarbitone (barbiturate coma) - rest brain + maintain equilibrium despite ¯ BS
-
Cerebral metab: fever + seizure (\ avoid in Pt's with cerebral metab dysfunc)
Clinical Features
ICP cardinal features
- Headache: stretch dura
- Vomiting: vomiting ctr
- Deterioration in consciousness
- Papilloedema
At first, one-point assessment (does not mean that Pt will not deteriorate) \ monitoring needed (serial) ® deterioration?
MONITORING
- Clinical: GCS
- ICP
- Jugular oxygen saturation
- Transcranial Doppler
- Metab study
1. CLINICAL MONITORING
- GCS: eye, verbal, motor response (score 3-15)
|
Score |
Eye opening |
Verbal response |
Motor response |
|
6 |
|
|
Obey |
|
5 |
|
Oriented |
Localise |
|
4 |
Spontaneous |
Confused |
WD |
|
3 |
To speech |
Words |
Flexor (decorticate) |
|
2 |
To pain |
Sounds |
Extensor |
|
1 |
None |
None |
None |
2. ICP MONITORING
Used: no clinical monitoring (sedation, m paralysis), GCS £ 8
GCS cut-off 8 ® ¯ sensitivity of scale at lower scores
Fibre-optic transducer-tip (v small)
a. Ventricular ICP monitor
- Hydraulic system, gold standard, CSF drainage/ monitoring
- Infective, invasive, difficult with cerebral oedema
b. Parenchymal ICP monitor
c. Subdural ICP monitor
d. Epidural ICP monitor: eg. Bleeding tendency
MANAGEMENT
- Targeted therapy: ID 1o cause + remove it
Modalities to ¯ ICP
- Mechanical
- Hyperventilation
® ¯ CO2 ® VC ® ¯ ICP (if XS ® ¯ perfusion ® ischaemia) \ start with normal PaCO2 (4-5 kPa) ® then KEEP PaCO2 AT 3.0-3.5 kPa
- Mannitol
: osmotic diuretic, 0.25-2.0 g/kg Q4-5H bolus, start 20% mannitol 200ml, monitor serum osmolality/ electrolytes, Foley
- Diuretics
: eg. Frusemide (Loop)
- CSF drainage
- Evacuation
of mass lesion ® haematoma, brain tumour, abscess, decompressive craniotomy (v severe: neurones burst, impeded VR)
- Barbiturates
: barbiturate coma, ¯ cerebral metab/ BF \ ¯ ICP, cerebral protection effect (eg. sodium thiopentone, pentobarbitone), S/E: hT, myocardial depression (\ give inotropes A, NA), monitor EEG (burst suppression)
- Steroids
: ¯ oedema (tumour, abscess), NOT for trauma, control bacteria first (otherwise sepsis), S/E: GDU, imm-supp, Cushings, nosomcomial infection
- Enhance venous drainage (1) No neck rot (2) Head elevation (3) No neck collar if poss
Slides
- Brain tumour ® remove
- Subdural haematoma ® craniotomy, remove clot
- Cerebellar tumour w/ hydrocephalus ® drain CSF, buy time for definitive tumour surgery
- Brain abscess ® catheter to drain pus, steroid to ¯ oedema
- Brain swelling ® diuretics (eg. Hepatic encephalopathy)
HYDROCEPHALUS
Aetiology
CSF production: eg. choroid plexus papilloma
¯ CSF absorption (granulations): eg. subarachnoid haemorrhage, newborn (arachnoid granulation not well-dev)
CSF obstruction: multiple levels of CSF p'way
- Children: congenital (structural, granulation absorption problem)
- Adults: acquired (tumour, haematoma), late-onset, obliged to find cause
CSF Circulation
- Choroid plexus (lateral, 3rd, 4th ventricles - 500 ml/day, 0.35 ml/min)
- (IV foramen)
- 3rd ventricle
- (cerebral aqueduct)
- 4th ventricle
- (median and lateral apertures)
- Subarachnoid space
- Superior saggital sinus (arachnoid granulations)
Rate of production same for adults + children
CSF DRAINAGE
EXTERNAL VENTRICULAR DRAINAGE
- Temporary
- eg. Cerebellar haematoma that will eventually lyse
- Permanent
- CSF shunt to recipient area with
¯ press
- Ventriculo-atrial: atrial press = central venous press (0-5 mmHg), can drain extra fluid, avoid in congestive heart failure (
atrial press)
Ventriculo-pleural: -ve press, avoid in children (¯ absorption ® pleural effusion)
Ventriculo-peritoneal: -ve press, absorption (SA), 1st choice, infections loculated in ab cavity, shunt revision every 5y
Lumbo-peritoneal: only communicating hydrocephalus (NOT obstructive - coning)
- Pressure control valve: one end to ventricular catheter, other to peritoneal catheter. Patency: if can compress CSF reservoir, distal end patent (cannot retrograde), if recoils upon release, proximal end patent (cannot refill from distal). DO NOT perform regularly - risk of sucking choroid plexus into ventricular cavity holes
COMPLICATIONS
- Infection
- Blockage
- Over-shunt - subdural haematoma (deflate brain mass
® shrink cortical sinus ® pull on bridging veins ® subdural haematoma)
Dislodgement
Abdominal pseudocyst - eg. ventriculo-peritoneal shunt
\
CSF shunt NOT 1st choice in hydrocephalus