impaired consciousness and coma Flashcards
what are the 2 components of conciousness
- arousal;
- awareness
what brain structures is arousal dependent on
- the ascending reticular activating system (RAS - part of the midbrain and pons)
- diencephalon (thalamus, hypothalamus, subthalamus, and the epithalamus)
what can cause diminished arousal (3)
damage to RAS/thalamus by:
1. brain shift;
2. brainstem displacement;
3. direct destruction
what brain area maintains awareness
cerebral cortex
what is a coma
a state of being where one is unaware and un-awake
initial management of unconciouss/coma pt (7)
- ABCDE
- Improve oxygenation (face mask 40% oxygen aiming at a pulse oximeter saturation of >95%);
- Intubate if patient cannot protect the airway (ie, increased work of breathing, pooling secretions, gurgling sounds, GCS<8);
- Intubate any comatose patient with irregular ineffective respiratory drive and poor oxygenation;
- Correct hypotension or extreme hypertension;
- early recognition and treatment of the cause (e.g. hypoglycemia, increased ICP, untreated seizure, infection etc.)
- neurological examination
when should glucose be administered in a coma pt
if <2.5mM
what should be done if raised ICP/herniation suspected as cause for coma (2)
- ventilation
- mannitol (0.5-1.0g/kg)
what should be given if come + BM <2.2mM (2)
- thiamine (100g)
- glucose
what should be given for opioid overdose
naloxone (0.4-2mg IV)
what should be given for benzodiazepine overdose
flumazenil
what should be done if coma due to drug intoxication suspected (3)
- intubate
- gastric leverage
- activated charcoal
5 important questions when taking hx of a coma pt (from fam/witnesses)
- onset (gradual/abrupt);
- recent complains (headache, focal weakness, vertigo, depression etc.);
- medical comorbidities (diabetes, heart disease);
- recent injury;
- access to drugs;
3 categories of coma
- coma without focal signs or meningism;
- coma with meningism but no focal signs;
- coma with focal/ raised pressure signs;
breathing patterns in unconscious pts + describe them (5)
- cheyne-stokes (a period of fast, shallow breathing followed by slow, heavier breathing and moments without any breath at all);
- neurogenic (deep and rapid breaths at a rate of at least 25 breaths per minute);
- apneustic (regular deep inspirations with an inspiratory pause followed by inadequate expiration);
- cluster (clusters of breaths followed by apneic episodes of variable duration);
- ataxic (complete irregularity of breathing, with irregular pauses and increasing periods of apnea)
damage to what area can cause cluster breathing
low pontine or high medullary lesions
damage to what area can cause apneustic breathing
upper pons (usually due to stroke/trauma)
what can cause neurogenic respiration
metabolic acidosis - renal failure, CKA, aspirin etc.
asymmetrical pupils vs symmetrical pupils indication for coma cause
asymmetrical - structural cause (i.e. brain lesion);
symmetrical - metabolic cause more likely
3 eye movements to note when examining coma pt
- primary eye position (corneal light reflex test - light should appear as a pin point in the center of both eyes if they are aligned);
- roving eye movements (slow random predominantly horizontal conjugate eye movements -> indicates brainstem preservation);
- Dolls eyes (occulo-cephalic refelx -> head is moved side to side and the eyes should move in the opposite direction to the head i.e. the eyes always look at the same point despite which way the head is turned)
3 stimuli for eliciting a motor response
- supraorbital nerve;
- nailbed;
- sternum
decortate (cortical lesion) vs decerebrate (brainstem lesion) posturing
decortate - curled wrists and balled hands against chest, pointed + turned in toes;
decerebrate - straight tense arms parallel to the body, curled fingers, flexed wrists, pointed + turned in toes
what does myoclonus indicate
hypoxic cortical injury
how to differentiate “locked in” vs comatose
ask pt to blink, look up/down
7 signs of psychiatric unresponsiveness (rather than coma)
- lids close actively;
- pupils reactive;
- physiologic oculovestibular responses (nystagmus);
- motor tone is inconsistent/normal;
- normal breathing/hyperventilation;
- no pathological reflexes;
- normal EEG;
what does coma without focal signs/meningism usually arise from (5)
neuronal depression due to:
1. hypoxia;
2. metabolic derangement;
3. toxic + drug induced;
4. infection;
5. post seizure states
8 features for metabolic derangement
C - CO2
O - O2
A - ammonia
T- temp
P - pH
E - electrolytes
G - glucose
S - serum osmolality
causes for coma with meningism but no focal signs (2)
- meningitis
- SAH
coma with focal signs causes
structural brain injury to RAS/thalami (bilaterally)/ cortex (bilaterally) due to:
1. ICH
2. infarction
3. tumour
4. abscess
symptoms/sign of raised ICP (4)
- headache
- vomiting
- progressive drowsiness
- swollen optic nerve (papilloedema)
what might post-traumatic amnesia be a marker for
diffuse axonal injury
3 areas of herniation (brain)
- sub falcine
- trans-tentorial
- tonsillar
see ppt
Management of acute supratentorial mass with brain shift – raised ICP (6)
Stabilising measures:
1. Intubation and mechanical ventilation
2. Correct hypoxaemia/hypercarbia
3. Elevate head to 30o
4. Treat extreme agitation with lorazepam 2mg IV or propofol
5. Mannitol 20%, 1g/kg
6. Dexamethasone, 100mg IV (in tumours only)
Specific surgical measures for acute supratentorial mass with brain shift (3)
- Evacuation of haematoma
- Drain abscess
- Decompressive craniectomy for mono-hemispheric swelling
when should a CT head be performed within 1 hr (7)
Within 1 hour if any of:
1. GCS <13/15 on A&E assessment
2. GCS <15/15, 2 hours after injury
3. Suspected skull #
4. Focal neurological deficit
5. Any sign of basal skull fractrure
(Haemotypanum, panda eyes, CSF from nose or ears, Battle’s signs)
6. Post-traumatic seizure
7. > 1 vomiting episode
when should a CT head be performed within 8 hrs (3)
- On anticoagulants with evidence of head injury
- Any loss of consciousness or amnesia since injury and one of:
- Retrograde amnesia > 30 mins
-Clotting or bleeding disorder
-Age > 65 - Dangerous mechanism of injury e.g. Fall from a height of > 1m or 5 stairs, Pedestrian/ cyclist hit by motor vehicle, Ejection from motor vehicle
