The Unconscious Patient Flashcards
What is consciousness?
Awareness of self and surroundings, combination of awareness and wakefulness
What is awareness?
Ability to have and having experience of any kind
What is wakefulness?
is a state in which the eyes are open and there is a degree of motor arousal, contrasts with sleep – a state of eye closure and motor quiescence
What is consciousness regulated by?
Regulated by ascending reticular activating system – comes up through brainstem, triangulates thalamus
Intralaminar nuclei of the thalamus maintains arousal
ARAS contains cholingeric neurons
Monosminergic neurons project from upper brainstem to thalamus, basal forebrain and cortex
What does stimulation of the posterior hypothalamus result in ?
arousal
What is abulia and what can cause it?
Abulia – lack of motivation due to anterior cingulate lesions (distinct from unconsciousness)
What possible conditions cause LoC?
Problem in brainstem stopping ARAS
Problem in thalamus – at junctions of ARAS
Bilateral hemispheres – must be bilateral
Was is the definition of coma?
Unrousable Unresponsive >6 hours Cannot be wakened Lacks normal sleep-wake cycle No voluntary actions (can have reflex actions e.g. withdrawal from pain
What is the definition of vegatative state?
Can be diagnosed after 4 weeks – continuing vegetative state
Considered permanent if >1 year following TBI (given longer time as increased prospect of improvement following TBI), >6 months in other mechanisms
What is the definition of minimally conscious state?
Severely altered consciousness
Minimal evidence of self and environmental awareness at best
Inconsistent but reproducible responses to surroundings e.g. everytime a relative comes in the patient cries
Follow simple commands – areas of cortex preserved
Emotional responses to emotional stimuli e.g. crying, smiling, laughing
Reaching for objects with intent
Eye movement pursuit
Can be diagnosed after 4 weeks – ‘continuing’
Permanent if >5 years
Permanent if >3-4 years if diffuse injury seen on scans etc. and no improvement seen
What are the preconditions for diagnosis of VS or MCS?
Need to know cause of condition
Reversible causes excluded e.g. medications, metabolic disorders, structural causes such as haemorrhage/haematoma that can be treated.
Also Guillain-Barre Syndrome, a demyelination syndrome and if it affects the brainstem white matter can cause unconsciousness
Careful assessment
What are possible causes of prolongued disorders of consciousness?
Trauma – direct impact or deceleration injury
Vascular – ICH, SAH, CVA
Drugs/alcohol – generally reversible
Metabolic - severe hypoglycaemia that is unknown until on brink of coma – generally bad outcome as every neuron effected
Hypoxic – Cardiac arrest, shock
Inflammation/infection – encephalitis, vascuclitis §
What are some chronic states of altered conciousness and coma mimics?
Dementia
Hypersomnia
Akinetic mutism
Silent, alert, immobile, sleep wake cycles, no external evidence of mental activity and no spontaneous motor activity.
Apallic syndrome
Absent neocortical and preserved brainstem activity
Locked in syndrome
What is locked in syndrome? What can cause it?
Conscious and aware of self and the environment
No voluntary movement
High brainstem pathology with retention of blinking or vertical eye movement – sometimes not, this makes it almost impossible to diagnose
Central pontine myelinolysis most likely cause
Rapid over correction of hyponatraemia is also a cause– normally at hospital as patient would not think to correct hyponatraemia
What must be taken to assess PDOC?
collateral history
General examination
Neurological examination
What is included in a general examination of PDOC
Skin Temp BP Breath CVS Abdomen
What is included in a neurological examination of PDOC
GCS
Meningism – nuchal rigidity
Trauma?
Fundoscopy/pupils – papilledema = raised ICP
Tone – increased tone and brisk reflexes = UMN
Reflexes
Brainstem – breathing, gaze, eye movements and oculocephalic reflex
What are some examples of how a breath assessment can indicate cause of PDOC
Bitter almonds – cyanide Garlic – phosphorus Burnt Rope – opium Fruity – paralehyde Hay – phosgene Pear drops – ketones
What indications of drugs need to be checked in assessment of PDOC?
Skin bullae – barbituates Tracks – opium Sweating – cholinergics Flushing – amphetamines Dry – Anti-Ch Hot - Tricyclics
What are the components of the GCS, what is the lowest possible?
Eyes, vocal and motor
Motor is the most important aspect
Need to give breakdown of E, V, M
Lowest possible is 3
What does uncal herniation cause?
Causes third nerve palsy – eyes down and out
Causes blown pupil due to disruption of parasympathetic fibres of third nerve
If bilateral that is bad – immediate action needed
What can be told from a vertical or lateral gaze?
Vertical gaze: Rostral brainstem Hydrocephalus Lateral gaze: Structural Irritative Brainstem
What are some examples of eye movements that indicate certain location of lesion in the brain?
Roving (eyes not fixating) – associated with toxic or bi-hemispheric Ping Pong – extreme roving Retraction nystagmus – tegmental Ocular bobbing - pontine Nystagmoid jerks – pontine
What are signs of brainstem localisation in coma?
Asymmetric Eye movement disorder Large pupils – downward shift Small pupils – upward shift ‘Normal CT’ = basilar artery occlusion
What are signs of metabolic cause of coma?
Normal pupils Roving eye movements Absent VOR and OCR Multifocal myoclonus Asterixis Odd forms of rigidity
What investigations would be done for losing consciousness?
Lab tests
Acidosis, anion gap, osmolar gap - antifreeze
Abnormal Na, Ca, CO2 or Glu
Drug screen – early otherwise will have washout
Blood cultures
Imaging, EEG and CSF – infection
Check for epilepsy
what is the immediate management for PDOC patients?
Oxygenation ABC Correct BP, temperature 50 ml 50% glucose Naloxone (opiods), flumenazil (benzo) Correct Na, Ca and eliminate toxins Neurosurgery and ICP Infection
What is the long term management for PDOC patients?
Tracheostomy, PEG, bladder, bowel, infection and DVT prevention Wean from ventilator Avoid MRSA and vancomycin resistance Prevent contractures Protect skin Avoid neurostimulation including drugs
What are indicators of poor prognosis
Myoclonic status Absent corneal / pupil at 3 days Absent motor at 3 days Absent SEP –sensory evoked potentials Increased serum neurone specific enolase – not in clinical practice atm
What is needed for the diagnosis of brain death?
Known cause No drugs and >36.5C > SPB 100 mmHg Eu-volaemia, capnia, oxaemia, BP Absent brain stem reflexes Apnoea with no CO2 response when off ventilator
