Week 8 ICP

Question 1

What percentage of the body’s oxygen does the brain consume?

Answer 1

The brain uses 20% of the body’s oxygen, with 60% dedicated to neuronal ATP production.

Question 2

How quickly can irreversible brain injury occur after interrupted perfusion?

Answer 2

Irreversible brain injury can occur within 3-8 minutes of interrupted perfusion.

Question 3

What is the normal Cerebral Blood Flow (CBF) rate?

Answer 3

Normal CBF is 50 mL/100g/min.

Question 4

What CBF rate indicates irreversible neuronal injury?

Answer 4

CBF <10 mL/100g/min indicates irreversible neuronal injury.

Question 5

What is the normal range for Intracranial Pressure (ICP) in adults?

Answer 5

Normal ICP in adults is 5–15 mmHg.

Question 6

What ICP level indicates intracranial hypertension?

Answer 6

ICP >20–25 mmHg indicates intracranial hypertension.

Question 7

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

Answer 7

CPP = MAP – ICP.

Question 8

What is the normal range for CPP?

Answer 8

Normal CPP is 80–100 mmHg.

Question 9

What is the Brain Trauma Foundation goal for CPP and ICP?

Answer 9

The goal is CPP 50–70 mmHg and ICP <20 mmHg.

Question 10

What are the components of the skull’s total volume?

Answer 10

The skull contains 80% brain, 12% blood, and 8% CSF.

Question 11

What does the Monro-Kellie Doctrine state?

Answer 11

The total volume is fixed; any increase in one component must be offset by a decrease in another to prevent ICP from rising.

Question 12

What happens during the Compensation Phase of ICP-Volume Relationship?

Answer 12

A small increase in volume is offset by displacement of CSF/blood, keeping ICP stable.

Question 13

What occurs during the Decompensation Phase of ICP-Volume Relationship?

Answer 13

Compensation is exhausted, leading to an exponential rise in ICP and decreased CPP, increasing herniation risk.

Question 14

What are transient triggers for increased ICP?

Answer 14

Coughing, Valsalva maneuver, and Trendelenburg positioning can transiently increase ICP.

Question 15

What are common signs and symptoms of intracranial hypertension?

Answer 15

Headache, nausea, vomiting, papilledema, pupillary changes, hemiplegia, seizures, and Cushing’s Triad.

Question 16

What is Cushing’s Triad?

Answer 16

Cushing’s Triad is characterized by hypertension, bradycardia, and irregular respirations.

Question 17

What are the indications for ICP monitoring?

Answer 17

Severe TBI with GCS ≤8 and abnormal CT, or GCS ≤8 with normal CT and 2 or more risk factors.

Question 18

What are some risk factors for ICP monitoring?

Answer 18

Age >40, decorticate/decerebrate posturing, and SBP <90 mmHg.

Question 19

What are the current guidelines for CPP and ICP in severe head injury?

Answer 19

Maintain CPP between 50-70 mmHg and ICP at less than 20 mmHg.

Question 20

What is the gold standard method for ICP monitoring?

Answer 20

Intraventricular Catheter (EVD) is the gold standard for ICP monitoring.

Question 21

What are the risks associated with ICP monitoring?

Answer 21

Risks include infection, hemorrhage, CSF leak, brain herniation, and malposition.

Question 22

What does P1, P2, and P3 represent in ICP waveforms?

Answer 22

P1 represents SBP transmission, P2 represents brain compliance, and P3 represents aortic valve closure.

Question 23

What indicates critically low intracranial compliance in ICP waveforms?

Answer 23

Plateau Waves (A waves of Lundberg) lasting 5-20 minutes indicate critically low intracranial compliance and ischemia risk.

Question 24

What is the mechanism of action for Mannitol in ICP management?

Answer 24

Mannitol draws water out of the brain via osmotic gradient, reducing ICP for up to 6 hours.

Question 25

What is a risk associated with Mannitol use?

Answer 25

Risks include hyperosmolality, dehydration, and electrolyte loss.

Question 26

What is the target serum sodium level when using Hypertonic Saline?

Answer 26

The target serum sodium level is 145–155 mEq/L.

Question 27

What is the goal for fluid management in ICP management?

Answer 27

The goal is to maintain euvolemia using isotonic or slightly hypertonic fluids.

Question 28

What should be avoided in fluid management for ICP?

Answer 28

Avoid hypotonic solutions and glucose-containing fluids.

Question 29

What is the effect of loop diuretics like furosemide in ICP management?

Answer 29

Loop diuretics reduce CSF production and cerebral edema.

Question 30

What is the role of corticosteroids in ICP management?

Answer 30

Corticosteroids like dexamethasone are used for vasogenic edema but not in TBI due to increased mortality.

Question 31

What is the purpose of barbiturate coma in ICP management?

Answer 31

Barbiturate coma is used in refractory ICP to achieve EEG burst suppression and reduce CMRO₂.

Question 32

What is the goal for PaCO₂ in controlled ventilation for ICP management?

Answer 32

The goal is to maintain PaCO₂ at 30–35 mmHg.

Question 33

What is the effect of volatile anesthetics on CBF and ICP?

Answer 33

Most volatile anesthetics increase CBF and ICP.

Question 34

What is the preferred anesthetic agent for neurosurgery?

Answer 34

Sevoflurane is preferred for neurosurgery due to the least vasodilation.

Question 35

What should be monitored during the maintenance phase of anesthesia in ICP management?

Answer 35

Monitor SSEP/MEP if needed and maintain CPP.

Question 36

What is the role of hypothermia therapy in ICP management?

Answer 36

Hypothermia therapy decreases CMRO₂ by 7% per 1°C drop and is considered experimental for refractory ICP.

Question 37

What are the risks associated with surgical decompression for ICP?

Answer 37

Risks include herniation through the craniectomy defect, post-operative cerebral edema, and infection.

Question 38

Which of the following is the primary determinant of cerebral perfusion pressure (CPP)? A) Intracranial pressure (ICP) alone B) Mean arterial pressure (MAP) alone C) The sum of ICP and MAP D) The difference between MAP and ICP

Answer 38

Answer: D) The difference between MAP and ICP Rationale: Cerebral perfusion pressure (CPP) is the difference between MAP and intracranial pressure (ICP) (or central venous pressure [CVP], if it is greater than ICP). MAP – ICP (or CVP) = CPP. CPP is normally 80 to 100 mm Hg. Moreover, because ICP is normally less than 10 mm Hg, CPP is primarily dependent on MAP. (Butterworth et al., 2022, p. 587)

Question 39

Which anesthetic agent is preferred for neuroanesthesia due to its ability to reduce ICP, cerebral blood flow, and cerebral metabolic rate of oxygen (CMRO₂)? A) Isoflurane B) Nitrous Oxide (N₂O) C) Propofol D) Ketamine

Answer 39

Answer: C) Propofol Rationale: Propofol is a popular induction and maintenance agent for neurosurgical patients. It is very useful in patients with intracranial pathologic conditions, provided that hypotension is prevented. The cerebral effects are a dose-dependent reduction in CBF and CMRO2. The reductions are approximately 40% to 50%. CPP may decrease because of reductions in blood pressure after bolus induction doses; however, the reduction in CBF appears to be independent of systemic hemodynamic changes. They are most likely due to the metabolic depressant effect and cerebral vasoconstriction. Reductions in systemic blood pressure produce corresponding reductions in CPP. (Nagelhout et al., 2023. pp 718)

Question 40

Which of the following is a contraindication for the use of succinylcholine in neurosurgical patients? A) History of difficult intubation B) Severe traumatic brain injury (TBI) C) Need for rapid sequence induction D) Refractory intracranial hypertension

Answer 40

Answer: B) Severe traumatic brain injury (TBI) Rationale: As mentioned previously, succinylcholine is contraindicated in patients with neurologic or denervated muscle because of the potential for life-threatening hyperkalemia. Succinylcholine should be avoided in patients with cerebrovascular accident, upper and lower motor neuron lesions, coma, encephalitis, closed head injury, and after severe burns and prolonged bed rest. (Nagelhout et al., 2023. pp 720).

Question 41

Which intravenous anesthetic agent is known to cause adrenal suppression and is therefore avoided in patients with traumatic brain injury (TBI) and sepsis? A) Propofol B) Dexmedetomidine C) Etomidate D) Ketamine

Answer 41

Answer: C) Etomidate Rationale: Many clinicians feel that etomidate should be avoided in brain-injured patients. Although it is considered an induction drug of choice in situations of hemodynamic compromise, prolonged adrenal insufficiency is a major concern. Adrenal insufficiency is of special concern in critically ill patients with sepsis and traumatic brain injury (TBI). For these reasons, it may be prudent to replace etomidate with an amnestic dose of a benzodiazepine in combination with an opioid or ketamine to facilitate endotracheal intubation. If etomidate is used, empirical adrenal replacement therapy for 24 hours should be considered. (Nagelhout

Question 42

Which of the following describes the pathophysiology of plateau waves (A waves of Lundberg) seen in intracranial pressure monitoring? A) Slow oscillations in ICP due to venous congestion B) Persistent ICP elevation (40-100 mmHg) lasting 5-20 minutes, indicating critically low intracranial compliance C) Fluctuations in ICP due to transient vasodilation D) Rapid ICP decline following CSF drainage

Answer 42

Answer: B) Persistent ICP elevation (40-100 mmHg) lasting 5-20 minutes, indicating critically low intracranial compliance. Rationale: Intracranial pathology leading to sustained elevations of ICP may produce plateau waves, also known as A waves of Lundberg. These waves reflect a sudden dramatic rise in ICP to levels of40 to 100 mm Hg, often lasting 5 to 20 minutes. Plateau waves indicate critically low intracranial compliance, leading to marked changes in ICP, even with very small variations in intracranial volume. (Nagelh

Question 43

In patients with elevated ICP, which of the following ventilatory strategies optimally balances ICP reduction while avoiding the risk of cerebral ischemia? A) Permissive hypercapnia with a PaCO₂ target of 45–50 mmHg to promote cerebral vasodilation and oxygen delivery B) Tight PaCO₂ control (30–35 mmHg) to induce mild vasoconstriction and reduce cerebral blood volume while preserving perfusion C) Aggressive hyperventilation with PaCO₂ < 25 mmHg to maximize cerebral vasoconstriction and ICP reduction D) Maintaining tidal volumes > 10 mL/kg and PEEP > 10 cmH₂O to improve oxygenation and limit secondary injury

Answer 43

Answer: B) Tight PaCO₂ control (30–35 mmHg) to induce mild vasoconstriction and reduce cerebral blood volume while preserving perfusion. Rationale: When the physiologic control is intact, hyperventilation lowers PaC02, resulting in respiratory alkalosis and subsequent vasoconstriction. When vasoconstriction is pronounced, intracranial blood volume will decrease and lower ICP. This is particularly important in known low-CBF conditions, such as severe TBI or vasospasm. To avoid cerebral ischemia, Paco2 should be lowered to approximately 30 to 35 mm Hg.