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CNSLF Surgery: Head Injuries (i) (Medical management (mannitol (don't…
CNSLF Surgery: Head Injuries (i)
Intro
high morbidity + mortality
50% of major trauma deaths are due to head injury
2:1 M:F
2/3 are 15-25 y/o (commonest cause of death in 1-15 y/os)
high costs
commonly caused by falls, RTAs, being struck, assaults
Primary HI
damage that occurs @ time of injury
scalp: blood loss, laceration, foreign body, portal of infection
skull: linear fractures, basilar fractures, depressed fractures
perforating + penetrating: ICH, vasc injury
focal: EDH, acute/chronic SDH, ICH, contusion, laceration, SAH, IVH (inter ventricular)
can affect hypothalamus, pit, brainstem + cranial Ns
diffuse: contusion, diffuse axonal injury
Monro-Kellie Doctrine
skull can only hold a fixed vol - problems if brain/blood/CSF expands - raised ICP - only way out through foramen magnum
comps of raised ICP
herniation (e.g. uncle - ant extremity of parahippocampal gyrus)
reduced cerebral perfusion (blood flow) - tissue hypoxia - high pCO2 - low pH - cerebral vasodilation + oedema
ICP should be < 20 mmHg - NB to monitor as guides tx
Cerebral perfusion pressure (CPP)
MAP - ICP
MAP = dias BP + 1/3 PP
should be >65mmHg (no upper value)
Secondary HI
systemic: hypoxia, hypotension, hypercapnia, hyperthermia, poor glycaemic control
intracranial: brain swelling, brain shift + herniation, raised ICP, post-traumatic fits, intracrhail infection
prevention of secondary injuries can prevent death + disability
EDH
usually blunt trauma
often a/w linear fracture
usually temporal (70-80%)
tear of middle meningeal art (weakest point in skull = pterion)
biconvex (lemon) due to attachment of dura to skull sutures
lucid interval
tx - requires emergency craniotomy
Acute SDH
venous tear / brain lacerations
covers enteric cerebral surface
crescent shaped
associated parenchymal injury
morbidity/mortality due to underlying brain injury
mortality = 30-90%
requires emergency craniotomy
banana/crescent shaped
Chronic SDH
hx of minor trauma
risk factors
age (brain shrinks with age, bridging veins more exposed)
male
anticoags
coagulopathy
thrombocytopenia
alcoholism
Tx = early burr hole drainage in the presence of raised ICP or lateralising signs (hemispheric seizures)
ICH
15% of fatal HIs
a/w contusions, diffuse axonal injury, SDH
tx = usually conservative but evacuation of haematoma in the presence oft raised ICP or marked midland shift
Diffuse axonal injury
35% of all fatal HIs
prolonged unconsciousness in the absence of a mass lesion
petechial haemorrhage
basal cisterns effaced (expansions of subarachnoid space)
ventricles compressed
sulci invisible
loss of grey-white differentiation
management: conservative or decompressive craniectomy
Penetrating injuries
1/3 have vasc injury
1/3 result in infection
universally fatal of cross midline
management: wound debridement, foreign body removal, angiography
e.g. gunshot
GCS
best eye response
open spontaneously = 4
open to verbal command = 3
open to pain = 2
doesn't open eyes = 1
best verbal response
orientated = 5
confused speech = 4
inappropriate words = 3
incomprehensible sounds = 2
no speech = 1
best motor response
obeys commands = 6
localises pain = 5
normal flexion to pain = 4
abnormal flexion to pain = 3
extension to pain = 2
no movement = 1
8 or less - unable to maintain airway - intubate
Indications to scan patient
GCS < 15
base of skull fracture
penetrating HI
post-trauma seizures
Medical management
head position - 30-40 degrees head up
mannitol
don't use if patient haemodynamically unstable
has an osmotic effect as doesn't cross BBB (extracts fluid from brain)
diuretic
frusemide
hypertonic saline
ensure theres no compression around neck
paralysis
sedation
analgesia
hyperventilation to lower PCO2
causes cerebral vasoconstriction - reduces oedema
don't lower PCO2 below normal as this will cause ischaemia (secondary HI)