Hypoxic Ischemic Encephalopathy

Question 1

Important questions to ask if brain injury

Answer 1

Is there any history of cardiopulmonary arrest?

What was the initial rythym after the arrest?

What has been the best neurological exam after the arrest?

Question 2

What are other common things that can present as coma?

Answer 2

Large ischemic or hemorrhagic stroke

Seizure activity

Systemic infection

Toxins/intoxication

Metabolic abnormalities

Question 3

What is targeted temperature management

Answer 3

also know as the hypothermia/cooling protocol. For patients who are comatose and in whom the initial cardiac rhythm is either ventricular tachycardia or ventricular fibrillation after cardiac arrest, cooling to 32-34C for 24 hours is highly likely to be effective in improving neurologic outcome and survival compared with normothermia.

Question 4

How do you Evaluate mental status

Answer 4

What is the most minimal stimulus that may ellicit a response from the patient? Try first by asking the patient a command, like “open your eyes”, “squeeze my hand”, or “wiggle your toes”. If no response, then try using a tactile stimulus to see if there is any response (like sternal rub).

Question 5

What is the most resistant part of the brain to hypoxic-ischemic injury?

Answer 5

The brainstem.

Brainstem reflexes are often preserved, even in patients with severe brain injury. The absence of brainstem reflexes reflects profound hypoxic injury and severe damage ot all areas of the brain.

Question 6

How do you evealuate brain stem reflexes

Answer 6

Brainstem respiratory centers: Is the patient producing some level of respiration other than that provided mechanically?

CN II: Is there blink to threat?

CN II, III: What are the size of the pupils and are they symmetric? Do the pupils react to light equally?

CN III, IV,VI, VIII: Observe for spontaneous movement of the eyes. Is there nystagmus? Is the there a dysconjugate gaze? Perform a Doll’s Eye Maneuver looking for the oculocephalic reflex. The oculocephalic reflex being tested below is normal. Abnormal would be if both eyes did not move together in the direction that corresponded with the head movement.

CN V & VII: Perform a corneal reflex. This can be done with a wisp of cotton or a drop of saline.

CN VII: Is the face symmetric?

CN VIII: If there is no occulocephalic reflex, then perform cold water calorics. Remember COWS (Cold Opposite, Warm Same).

CN IX, X: Gag & cough reflexes

Question 7

What parts of the brain are most susceptible to hypoxic injury?

Answer 7

The hippocampi, cerebral cortex, and basal gangila.

These parts of the brain are the most metabolically active. These areas play a role in consciousness and would explain why most patients with hypoxic brain injury are comatose.

Question 8

How to perform the motor exam

Answer 8

First observe if there are any sponteneous movements. Then apply peripheral nailbed pressure to see if the patient reacts to the painful stimulus. Some observed responses are as follows in order of decreasing function: Localization>withdrawal>flexor posturing>extensor posturing>no response. Sometimes the patient may look like they are withdrawing, but it is actual something called triple flexion. This is a spinal cord reflex and is not volitional. Is there the presence of seizures or myoclonus (spontaneous, repetetive, non-rythmic movements)?

Question 9

Testing general reflexes for coma

Answer 9

You can check deep tendon reflexes in the arms and legs similarly to a patient who is not comatose. You can also assess plantar responses (Is there a babinski?)

Question 10

Test for sensation in coma

Answer 10

Sensation is assessed by the reaction to sternal rub and peripheral nailbed pressure in all four extremities.

Question 11

What does this show?

Answer 11

Diffuse cerebral edema

Normal:

Question 12

Confounders for brain death evaluation

Answer 12

Hypothermia (<36C)

Other toxins/chemicals (May want to check a urine tox screen, metabolism of sedating medications can be delayed by the hypothermia.)

Severe acid-base, electrolyte, or endocrine abnormality.

Inadequate cerebral perfusion [mean arterial pressure (MAP) < 65 or systolic blood pressure <100 mmhg]

Ongoing/sequelae of seizures (Seizures commonly develop during the first 24 hours and during the rewarming period.)

Question 13

Ancillary brain function tests

Answer 13

Absence of somatosensory evoked potentials, or graphical determination of absence of sensation as it is transmitted to the parietal cortex bilaterally, can suggest poor prognosis if done 1-3 days after arrest.

Elevated serum neuron-specific enolase (NSE) levels at days 1-3 post-CPR accurately predict poor outcome

There is insufficient evidence to determine if newer ancillary tests accurately confirm the cessation of function of the entire brain; however, cereral angiogram, bedside Tc-99m hexamethylpropylene amine oxime scintigraphy, Electoencephalogram (EEG), and Transcranial Doppler (TCD) have all been employed, especially when apnea testing is not feasible.

Question 14

What is an anoxic brain injury

Answer 14

Hypoxic brain injury, or hypoxic ischemic encephalopathy. This type of injury occurs in the setting of prolonged hypotension (like cardiac arrest)

Question 15

Which CN are involved in corneal reflex

Answer 15

Cranial nerves V and VII are involved in the corneal reflex.