TBI Anesthetic Considerations
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Questions and Answers

Which induction agent is known to decrease cerebral perfusion pressure (CPP) due to its effects on reducing mean arterial pressure (MAP) and systemic vascular resistance (SVR)?

  • Ketamine
  • Propofol (correct)
  • Etomidate
  • Phenylephrine

    • What common anesthetic agent is associated with increasing cerebral blood flow (CBF) despite decreasing cerebral metabolic rate for oxygen (CMRO2) i.e. uncoupling?

  • Fentanyl
  • Ketamine
  • Volatile anesthetics (correct)
  • Nitrous Oxide

    • Which neuromuscular blocker should be administered with a defasciculating dose to prevent an increase in intracranial pressure (ICP)?

  • Succinylcholine (correct)
  • Rocuronium
  • Vecuronium
  • Pancuronium

    • Why are steroids considered detrimental in the management of traumatic brain injury (TBI)?

    <p>They increase blood glucose and exacerbate secondary brain injury</p> Signup and view all the answers

    What is the preferred fluid type in TBI management to minimize the risk of cerebral edema?

    <p>Normal Saline</p> Signup and view all the answers

    Which maintenance anesthetic agent poses a risk of elevating intracranial pressure (ICP) through increased CMRO2 and cerebral vasodilation?

    <p>Nitrous Oxide</p> Signup and view all the answers

    Why is the sitting position contraindicated in patients with a right-to-left intracardiac shunt?

    <p>Facilitates air embolism</p> Signup and view all the answers

    What is the target arterial CO2 level (PaCO2) during ventilation for TBI patients?

    <p>PaCO2 ~30</p> Signup and view all the answers

    Which primary components are involved in the Monroe-Kellie Doctrine?

    <p>CSF, tissue, blood</p> Signup and view all the answers

    What occurs if there is an increase in one component of the cranial compartment without compensation?

    <p>Herniation occurs due to increased ICP</p> Signup and view all the answers

    Which method is recognized as the gold standard for measuring intracranial pressure (ICP)?

    <p>Intraventricular catheter</p> Signup and view all the answers

    Where is cerebrospinal fluid (CSF) primarily produced in the body?

    <p>Choroid plexus in the ventricles by ependymal cells</p> Signup and view all the answers

    What does a Glasgow Coma Scale (GCS) score of ≤7 typically signify?

    <p>Requirement for ICP monitoring</p> Signup and view all the answers

    Which technique is effective in reducing intracranial pressure (ICP)?

    <p>Use hyperventilation to induce vasoconstriction</p> Signup and view all the answers

    Which of the following methods is directly related to improving venous drainage to lower ICP?

    <p>Elevating the head of the bed &gt;30 degrees</p> Signup and view all the answers

    What physiological phenomenon may be observed in diffuse brain injury despite decreased cerebral blood flow (CBF)?

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

    What is the typical range for normal cerebral autoregulation?

    <p>60-160 mmHg</p> Signup and view all the answers

    What triggers Cushing's reflex in response to physiological disturbances?

    <p>ICP exceeding MAP</p> Signup and view all the answers

    What is a potential consequence of having a low cerebral perfusion pressure (CPP)?

    <p>Brain ischemia due to reduced blood flow</p> Signup and view all the answers

    Which treatment goal is most appropriate when managing low cerebral perfusion pressure?

    <p>Increase mean arterial pressure or decrease intracranial pressure</p> Signup and view all the answers

    What defines excitotoxicity in the context of secondary brain injury?

    <p>Metabolic and inflammatory changes that increase glutamate levels</p> Signup and view all the answers

    Which condition is characterized by increased intracranial pressure with no identifiable cause?

    <p>Pseudotumor cerebri</p> Signup and view all the answers

    What kind of brain injury is notably associated with symptoms of 'walk and drop'?

    <p>Epidural hematoma</p> Signup and view all the answers

    Which statement accurately describes diffuse axonal injury?

    <p>Involves shearing of nerve cells leading to prolonged unconsciousness &gt; 6 hours</p> Signup and view all the answers

    What characterizes a coup-contrecoup brain injury?

    <p>Injury occurring at both the site of impact and opposite side of the brain</p> Signup and view all the answers

    Which skull fracture is most serious and commonly associated with cerebrospinal fluid leaks?

    <p>Basilar skull fracture</p> Signup and view all the answers

    Which drug combination is recommended to manage acute increases in ICP?

    <p>Furosemide followed by mannitol</p> Signup and view all the answers

    Which hematoma is caused by tearing of bridging veins between the cerebral cortex and draining sinuses?

    <p>Subdural hematoma</p> Signup and view all the answers

    Which anesthetic induction agent promotes hemodynamic stability but should be avoided in acute trauma due to adrenocortical suppression?

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

    What positioning technique minimizes the risk of midcervical injury in the sitting position?

    <p>Maintaining 3 fingerbreadths between chin and chest</p> Signup and view all the answers

    What systemic effect is commonly seen in response to traumatic brain injury?

    <p>Tachycardia and hypertension</p> Signup and view all the answers

    How does hyperventilation reduce ICP?

    <p>By lowering PaCO2, leading to cerebral vasoconstriction</p> Signup and view all the answers

    CSF is LIT AF = lateral ventricles, intraventricular foramen, third ventricle, cerebral aqueduct, fourth ventricle

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

    Where does cerebrospinal fluid (CSF) travel after exiting the fourth ventricle from the lateral apertures?

    <p>Foramen of Luschka</p> Signup and view all the answers

    Where does cerebrospinal fluid (CSF) travel after exiting the medial apertures?

    <p>Foramen of Magendie</p> Signup and view all the answers

    What is the normal cerebrospinal fluid (CSF) volume and rate of production?

    <p>150 mL and 30 mL/hr</p> Signup and view all the answers

    What is the site of absorption of cerebrospinal fluid (CSF)?

    <p>Arachnoid villi in the superior sagittal sinus</p> Signup and view all the answers

    What is CSF absorption dependent on?

    <p>The pressure gradient between CSF and venous circulation</p> Signup and view all the answers

    What does ICP measure?

    <p>Supratentorial CSF pressure</p> Signup and view all the answers

    What is the normal range for intracranial pressure (ICP)?

    <p>5-15 mmHg</p> Signup and view all the answers

    What are signs and symptoms of intracranial hypertension? (Select all that apply)

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

    What should be avoided in treating increased intracranial pressure (ICP)?

    <p>All of the above</p> Signup and view all the answers

    Which of the following methods are used to reduce cerebrospinal fluid (CSF)?

    <p>All of the above</p> Signup and view all the answers

    What methods can reduce cerebrovascular blood volume (CBV)?

    <p>All of the above</p> Signup and view all the answers

    Which of the following factors affects cerebral blood flow (CBF)? (Select all that apply)

    <p>Cerebral perfusion pressure (CPP)</p> Signup and view all the answers

    What is the correct equation for cerebral blood flow (CBF)?

    <p>CBF = CPP / CVR</p> Signup and view all the answers

    Which of the following best describes Poiseuille's Law?

    <p>It describes resistance in terms of the relationship between length, viscosity, and radius</p> Signup and view all the answers

    What is the equation for Cerebral Perfusion Pressure (CPP)?

    <p>CPP = Mean Arterial Pressure - Intracranial Pressure</p> Signup and view all the answers

    Which factors lead to decreased flow? (Select all that apply)

    <p>Increased blood viscosity</p> Signup and view all the answers

    What does it mean that cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) are coupled?

    <p>Blood flow will vary to match metabolic activity.</p> Signup and view all the answers

    Which of the following would lead to an increase in cerebral metabolic rate for oxygen (CMRO2) and cerebral blood flow (CBF)? Select all that apply

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

    Which of the following would lead to a decrease in CMRO2 and CBF? (Select all that apply)

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

    With TBI, cerebral autoregulation can be disrupted by which of the following factors? (Select all that apply)

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

    When cerebral autoregulation is disrupted, what changes would you see?

    <p>CPP becomes dependent on MAP.</p> Signup and view all the answers

    What occurs when Mean Arterial Pressure (MAP) is too high outside of autoregulation?

    <p>All of the above</p> Signup and view all the answers

    What occurs when Mean Arterial Pressure (MAP) is too low outside of autoregulation?

    <p>Ischemia and hypoperfusion</p> Signup and view all the answers

    What is an adverse outcome indicator in TBI?

    <p>SBP &lt; 90</p> Signup and view all the answers

    What occurs to cerebral blood flow (CBF) in areas of focal brain injury?

    <p>Decreased in injured areas</p> Signup and view all the answers

    What is the primary physiological effect of acute brain swelling and edema? Select all that apply

    <p>Increase in tissue volume</p> Signup and view all the answers

    What are some causes of intracranial hypertension? (Select all that apply)

    <p>Acute brain swelling</p> Signup and view all the answers

    What is the normal range for Cerebral Perfusion Pressure (CPP)?

    <p>60-100 mmHg</p> Signup and view all the answers

    What is the goal cerebral perfusion pressure (CPP) during anesthesia?

    <p>greater than 70 mmHg</p> Signup and view all the answers

    Which of the following is defined as the pressure gradient between systemic blood pressure (BP) and pressure in the cranial compartment?

    <p>Cerebral Perfusion Pressure (CPP)</p> Signup and view all the answers

    What can cause low Cerebral Perfusion Pressure (CPP)? (Select all that apply)

    <p>Decreased Mean Arterial Pressure (MAP)</p> Signup and view all the answers

    What causes high cerebral perfusion pressure (CPP)?

    <p>Systemic hypertension without increased in ICP</p> Signup and view all the answers

    What can result from high cerebral perfusion pressure (CPP)?

    <p>Leaky capillaries and edema</p> Signup and view all the answers

    What is the mechanism of the cerebral ischemic response when mean arterial pressure (MAP) is less than 20 mmHg?

    <p>CNS directly stimulates the sympathetic nervous system (SNS) to cause vasoconstriction, prioritizing blood flow to the brain.</p> Signup and view all the answers

    What are the signs and symptoms of Cushing's triad?

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

    Cushing's triad are ___ signs that are the result of Cushing's reflex.

    <p>late clinical</p> Signup and view all the answers

    What is the most common site of brain herniation?

    <p>Uncal and temporal uncus herniation</p> Signup and view all the answers

    What causes a fixed, dilated pupil in traumatic brain injury (TBI)?

    <p>Increased intracranial pressure and/or herniation affecting CN3</p> Signup and view all the answers

    ____ brain injury tends to be worse than primary brain injury

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

    What are common features of secondary brain injury? (Select all that apply)

    <p>Cardiopulmonary dysfunction</p> Signup and view all the answers

    What is a common cause of epidural hematomas?

    <p>Skull fracture and laceration of the middle meningeal artery</p> Signup and view all the answers

    Where are intracerebral hematomas usually found?

    <p>Frontal and temporal lobes</p> Signup and view all the answers

    What typically causes subarachnoid hematomas?

    <p>Small arterial tears during primary injury</p> Signup and view all the answers

    What type of skull fracture is the most common and typically does not require surgical intervention?

    <p>Linear fracture</p> Signup and view all the answers

    Where do diastatic fractures typically occur?

    <p>Along normal suture lines</p> Signup and view all the answers

    What nerve is at risk of being injured due to overstretching in the park bench position?

    <p>Brachial plexus</p> Signup and view all the answers

    Which of the following nerves are at increased risk of injury in the sitting position? (Select all that apply)

    <p>Sciatic nerve</p> Signup and view all the answers

    How do most induction agents decrease cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF)?

    <p>By causing vasoconstriction</p> Signup and view all the answers

    Which of the following anesthetic agents cause cerebral vasodilation? (Select all that apply)

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

    What effect does dexmedetomidine have on cerebral perfusion?

    <p>Decreases cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2), while slightly decreasing or maintaining intracranial pressure (ICP) and cerebral perfusion pressure (CPP)</p> Signup and view all the answers

    What is a risk of using nitrous oxide (N2O) as an anesthetic agent?

    <p>It diffuses into airspaces, increasing the risk of pneumocephalus and venous air embolism (VAE).</p> Signup and view all the answers

    Which opioid is popular in neuroanesthesia due to its short context-sensitive half-time (CSHT)?

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

    How does an increase in intrathoracic pressure typically affect cerebral perfusion pressure (CPP)?

    <p>Reduces CPP by increasing ICP and decreasing MAP</p> Signup and view all the answers

    How does a decrease in intrathoracic pressure typically affect cerebral perfusion pressure (CPP)?

    <p>Improve CPP by lowering ICP and enhancing venous return.</p> Signup and view all the answers

    What is the primary mechanism by which increased intrathoracic pressure reduces cerebral perfusion pressure (CPP)?

    <p>Increases cerebral venous congestion, leading to higher intracranial pressure (ICP)</p> Signup and view all the answers

    Why are ETCO2 and PaCO2 different?

    <p>Physiological dead space causes some alveoli to be ventilated but not perfused, resulting in lower CO2 in exhaled air compared to arterial blood.</p> Signup and view all the answers

    Why are lactated Ringer's solution and 5% albumin not recommended in patients with traumatic brain injury (TBI)?

    <p>It is slightly hypotonic, which can lead to cerebral edema.</p> Signup and view all the answers

    Why are colloids not recommended in traumatic brain injury (TBI)?

    <p>They impair platelet function and coagulation.</p> Signup and view all the answers

    What is the trigger to transfuse blood in TBI patients? select 2

    <p>Hgb &lt; 9</p> Signup and view all the answers

    Match the following conditions with their effects on cerebral blood flow (CBF):

    <p>Acidosis = Increased CBF Alkalosis = Decreased CBF Hypovolemia = Decreased CBF and hypoperfusion Hypervolemia = Increased CBF and edema</p> Signup and view all the answers

    If a patient comes in with increased ICP, which actions can be taken to reduce it? (Select all that apply)

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

    What is the relationship between cerebral blood flow (CBF) and arterial oxygen tension (PaO2)?

    <p>Inversely proportional when PaO2 is less than 50 mmHg</p> Signup and view all the answers

    How does Ohm's Law relate to blood flow?

    <p>Blood flow is directly proportional to pressure and inversely proportional to resistance.</p> Signup and view all the answers

    Study Notes

    Monroe-Kellie Doctrine

    • Primary components: Tissue, blood, cerebrospinal fluid (CSF), and oxygen
    • Compensation: Increase in one component must be compensated by a decrease in another to maintain normal intracranial pressure (ICP)

    Cranial Compartment Imbalance

    • Result: Herniation occurs due to increased intracranial pressure (ICP)

    Intracranial Pressure (ICP) Measurement

    • Gold standard: Intraventricular catheter

    Cerebrospinal Fluid (CSF) Production

    • Typical site: Choroid plexus in the ventricles

    Glasgow Coma Scale (GCS) Score

    • Score ≤7: Indicates brain death

    Intracranial Pressure Reduction Techniques

    • Hyperventilation: Reduces PaCO2, leading to vasoconstriction and decreased ICP
    • Head elevation: Improves venous drainage, reducing ICP
    • Medications: Acetazolamide (carbonic anhydrase inhibitor), mannitol (osmotic diuretic)

    Cerebral Autoregulation

    • Normal range: 40-80 mmHg
    • Disruptors: Hypoxia, Ischemia, Hypercapnia, Hypothermia, Vasoconstriction, Anemia, Hyperglycemia, Low ICP, Hyperoxia, Alkalosis, Hypoperfusion, Steroids

    Cushing's Reflex

    • Triggered by: Increased ICP exceeding mean arterial pressure (MAP)
    • Clinical signs (Cushing's Triad): Bradycardia, Hypertension, Irregular respiration (or Cheyne-Stokes respirations)

    Brain Herniation Types

    • Common: Temporal uncus into brainstem
    • Other types: Cerebellum into foramen magnum, etc.

    Excitotoxicity

    • Key change: Elevated glutamate levels

    Treatment Goal for Low CPP

    • Maintain ICP above 20 mmHg
    • Increase MAP (mean arterial pressure) or Decrease ICP

    Secondary Brain Injury

    • Characterized by: Metabolic and inflammatory changes
    • Examples: Coup-contrecoup injury, Excitotoxicity, Traumatic subarachnoid hemorrhage

    Idiopathic Intracranial Hypertension

    • Cause: Unknown
    • Condition: Increased intracranial pressure
    • Related symptoms: Pseudotumor cerebri

    Brain Injury Symptoms

    • "Walk and drop" symptoms: Epidural hematoma

    Cerebral Edema Reduction

    • Methods: Vasoconstrictors, Hypertonic saline, Reduced intrathoracic pressure

    Diffuse Axonal Injury Hallmark

    • Prolonged Loss of Consciousness (LOC) >6 hours, due to nerve cell shearing

    Coup-Contrecoup Injury Distinction

    • Bilateral injuries: Occur at both the site of impact & opposite site

    Anesthetic Agents and ICP

    • Agents to avoid in acute trauma: Due to adrenocortical suppression (e.g., Ketamine)
    • Agents decreasing CBF and cerebral oxygen metabolism (CMRO2): Propofol, barbiturates, etomidate

    Steroid Use in TBI Management

    • Detrimental effects: Glucose increases, exacerbates secondary brain injury, and impairs immune response

    Fluid Choice in TBI Management

    • Preferred: Isotonic saline (0.9% NaCl) or Lactated Ringer's solution
    • Avoid solutions that can increase intracranial pressure, such as hypotonic or hyperglycemic solutions.

    Anesthetic Considerations

    • Important use: Hyperventilation decreases intracranial pressure by decreasing cerebral blood flow

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    Description

    This quiz explores the Monroe-Kellie Doctrine and its implications on intracranial pressure (ICP). Test your knowledge on factors affecting ICP, measurement techniques, and cerebral autoregulation. Additionally, understand the consequences of cranial compartment imbalance and the implications of the Glasgow Coma Scale.

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