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Difficulty: HardNeurosurgery

While recovering in the surgical intensive care unit, a 35-year-old male patient demonstrates a precipitous decline in his level of consciousness. He sustained a severe traumatic brain injury in a high-speed vehicular collision 4848 hours prior. Current vital signs reveal a blood pressure of 185/110 mmHg185/110 \text{ mmHg}, a heart rate of 46 min−146 \text{ min}^{-1}, and an irregular respiratory rate of 8 min−18 \text{ min}^{-1}. Neurologic evaluation reveals that the right pupil is 8 mm8 \text{ mm} and nonreactive to light, whereas the left pupil is 3 mm3 \text{ mm} and briskly reactive. The right globe is deviated inferiorly and laterally. Application of a painful stimulus elicits rigid extension of the left arm and leg. What is the most appropriate immediate pharmacologic or procedural intervention for this patient?

  1. Intravenous infusion of an osmotic diureticAnswer
  2. B
    Initiation of empiric broad-spectrum antimicrobial therapy
  3. C
    Acquisition of cerebrospinal fluid via the L3-L4 interspace
  4. D
    Administration of high-dose intravenous glucocorticoids
  5. E
    Aggressive mechanical hyperventilation to a target PaCO2\text{PaCO}_2 of 20 mm Hg20 \text{ mm Hg}

Answer

The correct intervention is the intravenous infusion of an osmotic diuretic to rapidly lower intracranial pressure.
The patient's clinical presentation of Cushing's triad (hypertension, bradycardia, and irregular respirations) combined with an ipsilateral blown pupil and contralateral posturing is the hallmark of uncal (transtentorial) herniation. In this acute neurosurgical emergency, the immediate goal is to reduce intracranial pressure (ICP) to prevent irreversible brainstem ischemia and death. Intravenous infusion of an osmotic diuretic, such as mannitol, creates an intravascular osmotic gradient that draws water out of the brain parenchyma, rapidly lowering ICP. This is a critical temporizing measure while preparing the patient for definitive surgical decompression.

Step-by-Step Solution

1
Analyze the patient's vital signs.
Hypertension (185/110 mmHg185/110 \text{ mmHg}), bradycardia (46 min−146 \text{ min}^{-1}), and irregular respirations (8 min−18 \text{ min}^{-1}) are identified.
These findings constitute Cushing's triad, which is a classic reflex response to severely elevated intracranial pressure.
2
Interpret the focal neurologic deficits.
The patient exhibits a dilated, nonreactive right pupil with a 'down and out' gaze, alongside left-sided extensor posturing.
These signs represent right oculomotor nerve (CN III) palsy and compression of the right cerebral peduncle, indicating right-sided uncal herniation.
3
Determine the optimal immediate intervention.
Select a therapy that rapidly draws fluid out of the brain parenchyma.
Osmotic agents (such as mannitol) lower intracranial volume immediately, providing a critical bridge to definitive neurosurgical decompression.

Key Concept

Uncal herniation presents with Cushing's triad, ipsilateral CN III palsy, and contralateral hemiparesis. Immediate management requires temporizing measures to rapidly lower intracranial pressure, such as osmotic therapy, prior to definitive surgical intervention.
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Topics

Neurosurgery

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