Intracranial Pressure and Cerebral Blood Flow
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Intracranial Pressure and Cerebral Blood Flow

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Questions and Answers

Which management strategy is essential for maintaining adequate cerebral perfusion pressure during cerebral aneurysm clipping?

  • Administering vasopressors to raise systemic vascular resistance
  • Maintaining a BP 15-20% below baseline (correct)
  • Restricting fluid intake to minimize cerebral edema
  • Increasing MAP to above baseline levels

    • What is the primary goal of using controlled hypotension during the clipping of a cerebral aneurysm?

  • To reduce cerebral blood flow and minimize the risk of rupture
  • To achieve a target mean arterial pressure (MAP) of 40-50 mmHg (correct)
  • To ensure excessive brain retraction for easier access to the aneurysm
  • To increase intracranial pressure and facilitate visualization

    • Which complication is most likely to occur during a cerebral aneurysm dissection?

  • Rebound hypertension following rapid fluid administration
  • Intraoperative rupture due to excessive brain retraction (correct)
  • Involuntary vasospasm due to increased blood viscosity
  • Cerebral embolism resulting from coil migration

    • How does the Monro-Kellie hypothesis relate to the management of ICP during cerebral surgery?

    <p>It mandates that ICP remains constant despite changes in blood volume.</p> Signup and view all the answers

    What therapeutic measure is often required to manage complications arising from a cerebral aneurysm rupture during surgery?

    <p>Immediate administration of adenosine at 0.3-0.4 mg/kg</p> Signup and view all the answers

    What is the effect of increased intracranial pressure (ICP) on cerebral perfusion pressure (CPP)?

    <p>CPP decreases as ICP increases.</p> Signup and view all the answers

    Which method is NOT a recommended way to lower intracranial pressure?

    <p>Increase fluid intake.</p> Signup and view all the answers

    Which component is NOT part of the Monro-Kellie hypothesis?

    <p>Electrolyte volume.</p> Signup and view all the answers

    What is the primary goal when managing focal ischemia in the brain?

    <p>Augmenting cerebral perfusion pressure (CPP) while managing reperfusion injury.</p> Signup and view all the answers

    In a patient presenting for tumor resection, which symptom is most indicative of increased intracranial pressure?

    <p>Visual disturbances.</p> Signup and view all the answers

    What is a potential consequence of hyperglycemia in patients with ischemic conditions?

    Signup and view all the answers

    What is a primary concern related to intracranial tumors?

    <p>Elevated intracranial pressure</p> Signup and view all the answers

    Which factor does NOT contribute to the risk of cerebral aneurysm rupture?

    <p>Increased intracranial pressure</p> Signup and view all the answers

    According to the Monro-Kellie hypothesis, what must remain constant in the skull?

    <p>Total intracranial content</p> Signup and view all the answers

    What is indicated by Cushing's triad?

    <p>Hypertension, bradycardia, irregular respirations</p> Signup and view all the answers

    What surgical intervention is suitable for a saccular aneurysm?

    <p>Aneurysm clipping or endovascular coiling</p> Signup and view all the answers

    Which of the following states the relationship defined by transmural pressure?

    <p>TMP = MAP - ICP</p> Signup and view all the answers

    During intracranial surgery, which of the following positioning strategies is NOT typically used?

    <p>Supine position</p> Signup and view all the answers

    What is a common symptom of subarachnoid hemorrhage that should be monitored?

    <p>Worst headache of my life</p> Signup and view all the answers

    What is the primary effect of hyperventilation on intracranial pressure (ICP)?

    <p>It lowers ICP for 4-6 hours.</p> Signup and view all the answers

    In the context of the Monro-Kellie hypothesis, what must happen if the volume of brain tissue increases?

    <p>The volume of cerebrospinal fluid (CSF) must decrease.</p> Signup and view all the answers

    What is a major characteristic of cerebral blood flow during focal ischemia?

    <p>Localized reduction with salvageable tissue surrounding it.</p> Signup and view all the answers

    When preparing a patient for tumor resection, which symptom is critical in assessing for increased intracranial pressure?

    <p>Severe headache</p> Signup and view all the answers

    Which electrolyte solution is advisable to avoid during fluid management for intracranial pressure control?

    <p>Glucose-containing solutions</p> Signup and view all the answers

    What is the expected change in cerebral perfusion pressure (CPP) when intracranial pressure (ICP) is elevated?

    <p>CPP decreases.</p> Signup and view all the answers

    In the management of respiratory support for a patient with increased intracranial pressure, which aspect should be controlled?

    <p>Adjust tidal volume to 6-8 mL/kg.</p> Signup and view all the answers

    What common sign might indicate the presence of Cushing's triad in a patient with increased intracranial pressure?

    <p>Bradycardia</p> Signup and view all the answers

    Study Notes

    Irregular Respirations

    • Compensated by shunting CSF into the spinal cord
    • When exhausted, CPP and CBF begin to decline

    Intracranial Pressure

    • Cranium is a rigid box with three volumes:
      • Brain: 80%
      • Blood: 12%
      • CSF: 8%
    • Increase in one volume requires a decrease in another to maintain the same pressure
    • Increased ICP leads to Cerebral Ischemia, Edema, decreased CBF, and decreased CPP.

    Ways to Lower ICP

    • Hyperventilation: Lasts 4-6 hours
    • Mannitol: 0.25-1 g/kg
    • Furosemide: 0.5-1 mg/kg
    • Corticosteroids
    • Restrict Fluids
    • Elevate Head Of Bed (HOB)
    • Hypothermia: Not recommended for Cerebral Haemorrhage Injury (CHI)
    • Normotensive to slightly hypertensive

    Cerebral Blood Flow Summary

    • Arterial vessel diameter is related to Mean Arterial Pressure (MAP)
    • ICP influences blood flow

    Cerebral Protection: Ischemic & Reperfusion

    • Rapid ischemic injury due to
    • High rate of oxygen and glucose consumption
    • Inability to store substrates
    • Inability to dispose toxic metabolites quickly
    • Global ischemia results from severe hypotension or anemia
    • Focal ischemia is a regional insult
    • A “penumbra” of salvageable tissue usually surrounds the necrotic core

    Cerebral Protection: Ventilation Management

    • Tidal volume (Vt): 6-8 mL/kg
    • Peak pressure < 40 cmH2O
    • No Positive End Expiratory Pressure (PEEP) unless needed for oxygenation
      • PEEP decreases cerebral venous drainage and cardiac output
    • Positive Pressure Ventilation (PPV) to control ventilation and PaCO2
      • Further decreases risk for Venous Air Embolism (VAE) in a sitting position

    Cerebral Protection: Fluids & Electrolytes

    • Euvolemia with isotonic or slightly hypertonic solutions
    • Avoid glucose-containing solutions
      • Glucose is metabolized quickly and not osmotically active, can lead to Cerebral Edema
      • Ideal Blood Glucose: 90-280 mg/dL
        • Hypoglycemia: no glucose for ATP production
        • Hyperglycemia: more glucose converted to Lactic Acid (LA) if ischemia present
    • Hypotonic solutions are acceptable if diabetes insipidus (DI) is present
    • Excessive NaCL leads to hyperchloremic metabolic acidosis

    Preoperative Evaluation of Intracranial Tumors

    • Identify problems to plan appropriately
      • Intracranial mass lesion and increased ICP
      • Headache, dizziness, visual and gait disturbances, nausea and vomiting, seizures, altered level of consciousness, confusion, papilledema, loss of strength and sensation, cranial nerve dysfunction etc.
      • Coughing and vomiting can be deleterious
      • Control pain: short-acting opioids, IV acetaminophen, local anesthetic infiltration by surgeon, dexmedetomidine etc.

    Intracranial Tumors

    • Supratentorial lesions are more common in adults
    • Most commonly arise from Central Nervous System (CNS) support cells (gliomas, astrocytomas, oligodendrogliomas etc.
    • Most common metastatic tumors to the brain include melanoma or those that originate in the lung, breast, or kidney

    Infratentorial and Posterior Fossa Tumors

    • Close proximity to the brainstem
      • Increased risk of hemodynamic distress, changes in respiratory control and arousal
      • Altered respiratory patterns, cardiac dysrhythmias, or cranial nerve dysfunction
    • Require postoperative intubation and mechanical ventilation
    • Positioning can be prone, lateral, or sitting
    • Particular risk for VAE

    Cerebral Aneurysm

    • Saccular aneurysm is the most common cause of subarachnoid bleeding
    • Arterial bleeding into Subarachnoid space
    • Venous bleeding into Subdural space
    • ↑ aneurysmal distention pressure is essential for aneurysm rupture
    • ↑ Mean Arterial Pressure (MAP) = ↑ distention = ↑ aneurysm radius = ↑ wall tension
    • ↓ intracranial pressure (ICP) = ↓ distention = ↓ aneurysm radius = ↓ wall tension
    • Most common sign of subarachnoid hemorrhage (SAH) is “worst headache of my life”
    • Symptoms include: Syncope, nausea and vomiting, photophobia, fever, obstructive hydrocephalus

    Aneurysm and Transmural Pressure

    • Transmural Pressure = MAP - ICP
    • Perfusion pressure is affected by transmural pressure

    Cerebral Aneurysm Location

    • Anterior cerebral artery (ACA): 40%
    • Middle cerebral artery (MCA): 25%
    • Posterior cerebral artery (PCA): 25%
    • Basilar artery (BA): 10%

    Cerebral Aneurysm Rupture Risk

    • ↑ transmural pressure (TMP = MAP – ICP)
    • Diameter > 2.5 cm (Laplace)
    • Smoking
    • Excessive Alcohol
    • Recreational drugs
    • Age > 40
    • Female
    • Systemic hypertension

    Cerebral Aneurysm Surgical Options

    • Aneurysm clipping or endovascular coiling
    • Intervention should take place within 48 hours of initial bleeding

    Cerebral Aneurysm Anesthesia Considerations

    • Preinduction
      • Total Intravenous Anesthesia (TIVA) vs Volatiles
      • Limit sedation (hypercapnia)
    • Maintenance
      • Blood Pressure 15-20% below baseline
      • Prevent vasospasm
      • Decrease Estimated Blood Loss (EBL)
    • Emergence
      • Need rapid wake up for neurologic assessment
      • Similar considerations as intracranial mass

    Cerebral Aneurysm: Intraoperative Rupture

    • Most likely during
      • Dural incision (decreases ICP)
      • Excessive brain retraction
      • Aneurysm dissection
      • Clipping or clip release
    • Treatment
      • Immediate, aggressive volume replacement (Packed Red Blood Cells (PRBC))
      • Decrease MAP: 40-50 mmHg
      • Visualization
        • Surgeon will attempt to clip the feeder vessel
        • Adenosine: 0.3-0.4 mg/kg may be needed

    Cerebral Aneurysm: Surgical Techniques

    • Clipping: involves placing a clip at the base of the aneurysm
    • Endovascular coiling: involves threading a coil into the aneurysm sac transarterially

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    Description

    This quiz covers important concepts related to intracranial pressure (ICP) and its effects on cerebral blood flow (CBF). It discusses compensation mechanisms for irregular respirations, ways to lower ICP, and the relationship between arterial diameter and mean arterial pressure. Test your understanding of these critical neurological principles!

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