Coma/Raised ICP Flashcards
Four main causes of coma
Supratentorial mass lesions
Infratentorial mass lesions
Metabolic encephalopathy
Psychogenic coma
What is needed to maintain consciousness?
One cerebral hemisphere and the brain stem RAS (failure of both hemispheres OR the brain stem RAS results in coma)
How can you try to reverse coma (3 reversible etiologies)
Naloxone
Thiamine
Dextrose
Decorticate posturing
Upper extremity flexion, lower extremity extension
Decerebrate posturing
Extension of all four limbs
Does flexion or extension imply higher level of brain functioning?
Flexion
Verbal responses in Glasgow Coma Scale
Oriented 5 Confused 4 Inappropriate words/ not coherent 3 No words, only sounds 2 None 1
Eye Opening in Glasgow Coma Scale
Spontaneously 4
To speech 3
To pain 2
None 1
Motor responses in Glasgow Coma Scale
Obeys commands 6 Localizes to pain 5 Withdraws to pain 4 Abnormal flexion 3 Abnormal extension (decerebrate) 2 None 1
Dose of thiamine that should be given in comatose pt who is receiving glucose?
100 mg IV
What do pupils look like in coma due to metabolic reason?
Small and reactive
What do pupils look like in coma due to a tectal lesion
Large, fixed, hippus
What do pupils look like in coma due to lesion in pons
Pinpoint pupils
What do pupils look like in coma due to a midbrain lesion
Mid position, fixed
What do pupils look like in coma due to CN III (uncal) lesion
Dilated, fixed
What do pupils look like in coma due to diencephalic lesion
Small and reactive
Vestibulo-ocular reflex (dolls eye reflex)
Reflex eye mvmt that stabilizes the image on the retina during head movements, such that eye moves in direction opposite to head movement in order to keep image in centre of retina - mediated by CN VIII and CN 3,4,6
What are the brainstem reflexes to check in comatose pt
Pupillary reflex Corneal reflex VOR dolls eye Caloric testing Gag reflex
In comatose pt, if you find asymmetric focal signs in CN exam what is next step in diagnosis and what do you suspect?
Order urgent non contrast head CT
- suspect structural cause of decreased consciousness such as stroke, abscess, tumor or ICH
Cerebral perfusion pressure
CPP = MAP - ICP
- normally > 60 torr
What cerebral perfusion pressure is considered “too low” and results in inadequate cerebral blood flow
< 40 torr
Uncal herniation
Ipsilateral CN III palsy
Contralateral hemiparesis
Central (transtentorial) herniation
Progressive rostral-caudal loss of brain stem function due to pressure on entire brain stem
Transfalx (subfalcial) herniation
May cause infarction of anterior cerebral artery that lies in interhemispheric fissure
Cerebellar tonsillar herniation
Compression of the medulla by the cerebellar tonsils
Physical exam findings in pt with ICP
Altered mental status
Headache
Papilledema - hallmark but rare
Cushing reflex
Cushing reflex
Elevated systemic BP with bradycardia - seen in setting of increased ICP; seen when the pressure is transmitted to the medullary autonomic centres
what is a false localizing sign seen in pts with diffusely elevated ICP
CN 6 palsy
- paralysis of lateral gaze
Diagnostic study of choice for raised ICP
Head CT
What position should pt be placed in if they have raised ICP
Head and neck elevated at 30 degrees
Hyperventilation as tx of increased ICP
Tracheal intubation to lower pco2 to 25-30 torr
- works within minutes by causing vasoconstriction of cerebral blood vessels but the effect only lasts 8 hours
Mannitol as tx for increased ICP
Osmotic diuretic, dose 1/2 to 1 g/kg IV, repeat every 4-6 hours
- acts within minutes but do not exceed 325 mOsm
Dexamethasone as tx for increased ICP
10 mg IV initially, then 4 mg every 4-6 hrs
- stabilizes vascular membranes and prevents vasogenic brain edema; acts within 24 hours and is only helpful if brain edema is due to expanding mass lesion
Barbiturate therapy in tx of ICP
325 mg/kg
- reduces cerebral blood flow and intracranial pressure by decreasing the cerebral metabolic rate
