Coma / Neurology

    .

    Bedside Evaluation

    • Pupils
      • neuromuscular blockade does not affect pupil size/reactivity
      • Systemic atropine causes pupil dilation (but remain reactive)
      • High-Dose dopamine causes fixed dilated pupils
      • If pupils remain non-reactive for > 6-8hrs after resuscitation from an arrest, cahnces of satisfactory neurologic recovery are very poor.
    • Ocular Reflex
      • Brainstem Evaluation
      • Oculocephalic Reflex
        • Rotate head from side-to-side 
        • If lower brainstem is intact --> eyes deviate away from direction of rotation.
        • If lower brainstem impaired --> eyes follow direction of motion
      • Oculovestibular Reflex
        • 50mL of cold saline into external auditory canal
        • If brainstem intact --> both eyes deviate towards cold injection
        • If brainstem impaired --> conjugate movement lost.
    • Sensorimotor Exam
      • Clonic Movements?
        • Elicit by flextion of hands or feet (asterixis)
        • Sign of metabolic encephalopathy
      • Focal motor or sensory defect?
      • Pain Response
        • Injury to thalamus --> painful stimuli provoke flexion of upper extremity
          • This is called Decorticate Posturing --> POOR prognosis
        • Injury to midbrain and pons --> arms+legs extend and pronate in response to pain.
          • This is called Decerebrate Posturing --> VERY POOR prognosis

     

    • OcularReflexes.jpg

    • (Source: "The Little ICU Book" by Paul Marino 2008)

     

    Glasgow Coma Scale

    • Eye Opening

         4 - Spontaneous

         3 - To Speech

         2 - To Pain

         1 - None

      Verbal Communication

         5 - Oriented

         4 - Confused

         3 - Inappropriate but recognized words

         2 - Incomprehensible sounds

         1 - None

      Motor Response

         6 - Obey Commands

         5 - Localizes to pain

         4 - Withdraws to pain

         3 - Abnormal flexion (decorticate response)

         2 - Abnormal extension (decerebrate response)

         1 - No movement

     

    • Clinical Applications:
      •    
        1.  To define coma GCS ≤ 8
        2.  To stratify severity of head injury

        13-15 = MILD

        9 - 12 = MODERATE

            ≤ 8 = SEVERE

        3.  To identify candidates for intubation GCS ≤ 8
        4.  To predict likelihood of recovery from coma

        if GCS < 6 @ 72hrs

        = No chance of satisfactory

           neurologic recovery
           (Edgren et al (1994))

     

    Brain Death

    • BraindeathChecklist.jpgIrreversible cessation of function in all areas of the brain, with permanent loss of automatic breathing.
    • Most often as a result of traumatic head injury, intracranial hemorrhage and cardiac arrest.
    • Clinical Diagnosis of Breath Death

       

      1.  Irreversible Coma

      2.  Absence of brainstem reflexes

      3.  Absence of spontaneous breathing efforts

       

      Two confirmatory evaluations 6-8hrs apart are required

    • Apnea Test
      • Observe patient for spontaneous breathing in presence of hypercapnia (powerful breathing simulus)
      • 100% O2 breathing --> separate from ventilator --> O2 insufflated into ET tube (prevent hypoxemia)
        • Patient observed for spontaneous breathing efforts for 8-10min.  At that point ABG is obtained + ventilator resumed. 
        • Arterial pCO2 rises by 2-3mmHg/min of apnea
        • If arterial pCO2 increases by > 20 mmHg without breathing efforts --> confirms dx of brain death.
      • Note: Apnea test brings hypotension, cardiac arrhythmias (abort if develop this, and test is never repeated once confirmed brain death)
      • Note: spontaneous movement bursts head/torso/upperExtremities are "Lazarus' sign", neuronal bursts from C-spine, not manifestations of brain activity.
    • May not be possible to diagnose brain death in following:
      • Severe facial trauma or C-spine cord injury
      • Pre-existing pupillary abnormalities
      • End-stage pulmonary disease with high CO2
      • Drugs that interfere with evaluation (i.e. paralytics)
    • In above cases, may need confirmatory test such as EEG, brain scan with Tc-99m, transcranial doppler, or somatosensory evoked potentials.

     

    Organ Donor

    • Measures to maintain organ viability:
      • Hemodynamics
        • Urine output < 1mL/kg/hr --> give volume to a CVP of 10-15mmHg
        • Dopamine 5-15 mcg/kg/min (avoid alpha-adenergic vasoconstriction --> can cause anoxic organ injury)
      • Pituitary Failure (50% of brain dead pts)
        • Diabetes Insipidus
        • Adrenal Insufficiency
          • ACTH stim test is not useful
          • If suspected due to hypotension --> give IV hydrocortisone 50mg q6h
    Tag page (Edit tags)
    • No tags
    Page statistics
    6237 view(s), 3 edit(s) and 7078 character(s)

    Comments

    You must login to post a comment.

    Attach file

    Attachments