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Board Questions

1. Your patient was a pedestrian struck by a motor vehicle yesterday leading to a parietal fracture, subdural hematoma, and significant cerebral edema. Her ICP is 25mmHg and the waveform has been steady over the last 4 hours. Which of the following is an accepted treatment for intracranial hypertension in this setting? 

a) Dexamethasone
b) Therapeutic hypothermia 
c) Hyperventilation to a PaCO2 of 25
d) Craniectomy

2. Which of the following is true? 

a) Mannitol is superior to hypertonic saline
b) Hypertonic saline cannot be given through a peripheral IV
c) The reflection coefficient of sodium is nearly 1
d) The use of hypertonic saline has been reported to lead to central pontine myelinolysis

3. Your 6 yo patient has a cerebral abscess with secondary intracranial hypertension. They have an ICP monitor in place with an ICP noted to be 30 mmHg. Their blood pressure is 140/90. What treatment is most indicated?

a) isradipine PO
b) nicardipine infusion
c) hydralazine IV 
d) none of the above


ANSWERS & EXPLANATIONS

1. D- If other less invasive methods of controlling ICP have been exhausted, craniectomy is a viable option to reduce persistently elevated ICP. None of the other choices are accepted methods of reducing the ICP in this case. Therapeutic hypothermia has not been shown to be effective after TBI (Cool Kids Trial). Nonetheless, one should still aim for normothermia as hyperthermia is associated with worse outcomes. Dexamethasone is not used with cytotoxic edema but is used in the case of vasogenic edema, for example with brain tumors or potentially meningitis. Hyperventilation can be used to acutely reduce ICP in the patient at risk for herniation. However, as hyperventilation leads to cerebral vasoconstriction, persistent hyperventilation and subsequent vasoconstriction is likely detrimental for the injured brain in the long term. This patient has had persistently elevated ICP for the last 4 hours, making hyperventilation not an ideal treatment modality (assuming a currently normal PaCO2 of 35-40 mmHg).

2. C. Hypertonic saline is at least equivalent to mannitol in terms of control of intracranial hypertension (if not better). HTS has a reflection coefficient of nearly 1, meaning it stays within intact vasculature and retains its osmotic effect. The reflection coefficient of mannitol is approximately 0.75 which although is still high, means eventually some mannitol diffuses across the capillary membrane potentially leading to a reverse osmotic effect. HTS can be bolused safely through a peripheral IV. However, due to its high tonicity, continuous infusions should probably be run through a central vein to avoid sclerosis of smaller veins. Despite theoretical concerns, HTS has not been reported to cause central pontine myelinolysis.

3. D. Due to elevated ICP, your patient is likely autoregulating blood pressure in an attempt to increase cerebral blood flow in the face of increased ICP. Hence, antihypertensive treatment is not indicated at this time. Efforts should be made to reduce the ICP (ie via HTS bolus, mannitol, mild hyperventilation if neurological changes are occurring, or other methods)


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