Neurological Emergencies - brain Flashcards
Primary Brain Injury
physical damage to brain tissue - contusion, haematoma, laceration, vasogenic oedema
Secondary brain injury
Associated with excitatory neurotransmitter release, inflammation and increased ICP
Vasogenic oedema
Disrupted BBB - extracellular accumulation of serum proteins - oedema
Cytotoxic oedema
Swelling of cells due to energy depletion - ion pumps fail
Cerebral blood flow is dependant on
Cerebral perfusion pressure
= mean arterial pressure - intracranial pressure
cerebral perfusion pressure can be reduced by either
Decreased MAP, increased intracranial pressure
Blood flow in the brain is usually protected by
auto regulation
Initial actions with a potential head trauma
Check ABC - airways breathing, circulation
Ensure adequate oxygenation - pulse ox or blood gas if available.
Check MAP
Head trauma can lead to a temporary severe dyspnoea & tachypnoea due to
Neurogenic pulmonary oedema.
Doesn’t normally require specific tx
Levels of alertness
Comatose - non-responsive even to noxious stimuli
Stuporous - basically asleep but rousable by noxious stimuli e.g. pinching toe
Obtunded - depressed response to normal stimulation
Decerebellate posture
Extreme dorsal extension of the head and neck, thoracic limb extension and pelvic limb flexion.
Indicates cerebellar damage.
Decrebrate posture
Similar to decerebellate but pelvic limbs extended and reduced mentation
Indicates more severe damage at the forebrain level
Pupil changes seen with increased ICP
initial constriction followed by dilation.
Anisocaria can result from asymmetrical ICP
Modified Glasgow coma scale takes into account
Motor activity
Brainstem reflexes
Level of consciousness
Signs of elevated ICP
Reduced level of mentation
Altered pupil function - constricted then dilated ± unequal
Loss of vestibule-ocular reflex
Cushing response
Increased MAP and bradycardia occurring simultaneously - response to end-stage, life threatening ICP
Auto-regulatory mechanisms increase MAP to try and maintain cerebral perfusion pressure - reflex bradycardia
Investigating/monitoring head trauma
Modified Glasgow coma scale - esp. if done by the same person.
Monitor MAP, oxygenation, HR, RR, urine output.
CT > MRI as faster
Treating head trauma (6 points)
Goal = maintaining cerebral blood flow
- elevate head 30 degrees to ensure no occlusion of jugular veins.
- may need IVFT - many animals in shock
- oxygenation - aim >95% on pulse ox
- analgesia - usually methadone
- treat any seizure activity aggressively - diazepam and phenobarbitone
- nutritional support if prolonged
IVFT in severe head trauma
Hypertonic saline bolus followed by maintenance crystalloids - restore normovolaemia - restoring MAP.
Mannitol - high molecular weight osmotic diuretic diuresis - use once normovolaemia is achieved to reduce ICP
Mannitol
A high molecular weight osmotic diuretic - if BBB intact can work in the brain to decrease ICP.
Risk of rebound ICP
If there are concerns regarding head trauma and increased ICP you can administer
Mannitol & hypertonic saline - induce osmotic diuresis in the brain (provided BBB intact). Lowering ICP.
Also act to restore normovolaemaia improving cerebral blood flow.
If seizure activity
Treat aggressively
Diazepam and phenobarbitone
