Objectives Describe basic intracranial physiology

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 = 14–15

• History

• Exclude systemic injuries

• Neurologic exam

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

• Controlled ventilation

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