Neurologic and Neurosurgical Emergencies in the ICU

Posted by e-Medical PPT Saturday, January 7, 2012
Altered Consciousness and Coma
Consciousness requires arousal (coming from the brainstem reticular formation) and content (the cerebral hemispheres)
Alterations in consciousness stem from:
Disorders affecting the reticular formation
Disorders affecting both cerebral hemispheres
Disorders affecting the connections between the brainstem and the hemispheres

Definitions
Delirium: classically, altered awareness with motor and sympathetic hyperactivity, often with sleeplessness, hallucinations, and delusions
-    More recently used to describe any acute change in consciousness short of coma, as a synonym for encephalopathy
Obtundation: the patient appears to sleep much of the day but has some spontaneous arousals

Stupor: the patient lies motionless unless aroused but     will awaken with stimulation; localizes or withdraws from     noxious stimuli

     Coma: the patient makes no understandable      response to stimulation but may display abnormal flexor     (decorticate) or extensor (decerebrate) posturing

The purpose of the coma examination is to determine whether the upper brainstem is functioning.
Brainstem dysfunction means immediate imaging.
Bilateral hemispheral dysfunction leads initially to metabolic or toxic diagnoses.

Four domains to examine:
Pupillary responses
Extraocular movements
Respiratory pattern
Motor responses

Assessing Eye Movements
Spontaneous horizontal conjugate eye movements prove that the brainstem centers for eye movement are intact.
These overlap the portion of the reticular formation necessary for consciousness.
Therefore, coma in a patient with roving horizontal conjugate eye movements is not due to brainstem dysfunction.

If there are no spontaneous eye movements, attempt to trigger them.
In the absence of cervical spine disease, test cervico-ocular reflexes (“dolls’ eyes”):
-    Turning the head to the right should cause the eyes to go left, and vice versa.
-    Same meaning as spontaneous movements regarding the brain stem
-    Partial responses mean a problem involving the brainstem or cranial nerves (use the diagram to determine where the problem lies).

Vestibulo-ocular testing (“cold calorics”)
Check for tympanic membrane perforation first
50 - 60 mL ice water in one extra-ocular canal using soft tubing (e.g., from a butterfly; do not use an IV catheter, which can penetrate the tympanic membrane)
Tonic deviation of both eyes toward cold ear indicates intact brainstem function.
Wait for one ear to warm up before testing the other ear.

Nystagmus away from the cold ear is due to cortical correction of the brainstem-induced eye movement and means the patient is not comatose.

Respiratory Patterns in Coma
Cheyne – Stokes respiration: bilateral hemispheral dysfunction
or congestive heart failure
Central reflex hyperpnea: midbrain dysfunction causing neurogenic pulmonary edema
rarely see true central neurogenic hyperventilation with this lesion; central hyperventilation is common with increased ICP

Apneustic respiration (inspiratory cramp  lasting up to 30 sec): pontine lesion
Cluster breathing (Biot breathing): pontine lesion
Ataxic respiration: pontomedullary junction lesion...

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