Objectives Describe basic intracranial physiology



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tarix13.03.2017
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Objectives

  • Describe basic intracranial physiology.

  • Recognize the importance of limiting secondary brain injury.

  • Perform a focused neurologic exam.

  • Stabilize and arrange for definitive care.



Key Questions

  • What are the unique features of brain anatomy and physiology and how do they affect patterns of brain injury?

  • What is a focused neurologic exam?

  • What is optimal management of the brain-injured patient?

  • How do I diagnose brain death?



Anatomy and physiology effects?

  • Rigid, nonexpansile skull filled with brain, CSF, and blood

  • CBF autoregulation

  • Autoregulatory compensation disrupted by brain injury

  • Mass effect of intracranial hemorrhage



Monro-Kellie Doctrine



Volume – Pressure Curve



Intracranial Pressure (ICP)

  • 10 mm Hg = Normal

  • > 20 mm Hg = Abnormal

  • > 40 mm Hg = Severe

  • Many pathologic processes affect outcome

  • Sustained  ICP leads to  brain function and outcome



Cerebral Perfusion Pressure*



Autoregulation

  • If autoregulation is intact, CBF is maintained with a mean BP of 50 to 160 mm Hg.

  • Moderate or severe brain injury: Autoregulation often impaired

  • Brain more vulnerable to episodes of hypotension  secondary brain injury



GCS Score = 14–15



GCS Score = 9–13

  • GCS Score = 9–13

  • Initial evaluation same as for mild injury

  • CT scan for all



Severe Brain Injury

  • GCS Score = 3–8

  • Evaluate and resuscitate

  • Intubate for airway protection

  • Focused neurologic exam

  • Frequent reevaluation

  • Identify associated injuries



Classification of Brain Injury



Classification of Brain Injury



Classifications of Brain Injury



Diffuse Brain Injury

  • Mild concussion  Severe, ischemic insult



Contusion / Hematoma

  • Coup / contracoup injuries

  • Most common: Frontal / temporal lobes

  • CT changes usually progressive

  • Most conscious patients: No operation



Contusion / Hematoma



Epidural Hematoma

  • Associated with skull fracture

  • Classic: Middle meningeal artery tear

  • Lenticular / biconvex

  • Lucid interval

  • Can be rapidly fatal

  • Early evacuation essential



Epidural Hematoma



Subdural Hematoma

  • Venous tear / brain laceration

  • Covers cerebral surface

  • Morbidity / mortality due to underlying brain injury

  • Rapid surgical evacuation recommended, especially if > 5 mm shift of midline



Subdural Hematoma



Priorities

  • ABCDE



Focused Neurologic Exam?

  • GCS Score



Indications for CT Scan?



Medical Management



Medical Management



Medical Management

  • Other medications



Surgical Management



Surgical Management



Diagnose brain death?

  • Clinical





Summary: What should I do?

  • Maintain mean BP > 90 mm Hg

  • Maintain Paco2 near / at 35 mm Hg

  • Use isotonic solution for euvolemia

  • Frequent neurologic exams

  • Liberal use of CT scans

  • Early neurosurgical consult



Summary: What should I not do?

  • Allow patient to become hypotensive

  • Over-aggressively hyperventilate

  • Use hypotonic IV fluids

  • Use long-acting paralytics

  • Paralyze before performing complete exam

  • Depend on clinical exam alone



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