SACCM 85: Intracranial Hypertension

Question 1

What is a normla intracranial pressure in dogs and cats?

Answer 1

5-12 mm Hg

Question 2

What is the Cushing’s triad?

Answer 2

• bradycardia
• hypertension
• irregular breathing

Question 3

What are the 3 mechanisms by which ICP is maintained?

Answer 3

• volume buffering
• autoregulation
• Cushing’s response

Question 4

Explain the steps of volume buffering in intracranial hypertension

Answer 4

1. initial step is to shunt CSF from the intracranial space to the spine
2. after CSF shunting is exhausted –> intracranial blood volume reduced –> compromises blood flow and DO2 –> ischemia

Question 5

Describe the myogenic aspect of ICP autoregulation

Answer 5

changes in transmural pressure cause arteriolar myogenic reflexes –> changes in vascular resistance
works at perfusion pressures/MAP from 50 to 150 mm Hg

Question 6

What part of chemical autoregulation is more potent at changing ICP?

Answer 6

PaCO2 is considered more potent than PaO2

Question 7

What is CMRO2 and how does it affect ICP?

Answer 7

Cerebral metabolic rate of O2 utilization

if high metabolism –> high local lactic acidosis –> higher H+ –> arterial vasodilation –> increased CBF –> increased ICP

Question 8

What fundic exam finding is a reliable sign of intracranial hypertension?

Answer 8

Papilledema

Question 9

How can you clinically identify brain death?

Answer 9

• deep coma
• absence of spontaneous breathing
• loss of brain reflex - fixed dilated pupils

Question 10

What are the most common electrolyte disorders in TBI patients?

Answer 10

• hypo/hypernatremia and hypokalemia in people
• hypernatremia in dogs

Question 11

What are the 3 categoriesd of the MGCS?

Answer 11

• Level of consciousness
• Brainstem reflexes
• Motor activity

Question 12

What are the levels of consciousness on the MGCS?

Answer 12

6. Responsive to environment and occasional periods of alertness
   5 Depressed/Obtunded or delirium, capable of responding but response may be inappropriate
   4 Semicomatose - responsive to visual stimuli
   3 Semicomatose - responsive to auditory stimuli
   2 Semicomatose - responsive to repeated noxious stimuli
   1 Unresponsive and comatose

Question 13

What are the levels of brainstem reflexes on the MGCS?

Answer 13

6. Normal PLR and oculocephalic reflexes
   5 Slow PLR, normal to reduced oculocephalic reflexes
   4 Bilateral unresponsive miosis with normal to reduced oculocephalic reflexes
   3 Pinpoint pupils with reduced to absent oculocephalic reflexes
   2 Unilateral unresponsive mydriasis with reduced to absent oculocephalic reflexes
   1 Bilateral unresponsive mydriasis with reduced to absent oculocephalic reflexes

Question 14

What are the levels of motor activity on the MGCS?

Answer 14

6. Normal gait and normal spinal reflexes
7. Hemiparesis, tetraparesis, or decerebrate rigidity
8. Recumbent intermittent extensor rigidity
9. Recumbent constant extensor rigidity
10. Recumbent constant extensor rigidity with opisthotonus
11. Recumbent, hypotonia of muscles, absent or depressed spinal reflexes

Question 15

What parts of the brain are mainly assessed with PLR and pupil size?

Answer 15

• CN II
• CN III - efferent parasympathetic fibers
• brainstem

Question 16

What parts of the CNS are assessed with the oculocephalic reflexes?

Answer 16

brainstem pathways from the cranial cervical spinal cord and medulla oblongata rostrally to the CN II, III, IV, and VI nuclei via the medial longitudinal fasciculus

Question 17

What structures may be damaged when the corneal reflex is absent?

Answer 17

damage to the afferent CN V, efferent CN VI or VII + brainstem

Question 18

By what osmolality do you need to increase plasma osmolality to have a clinical significant reduction in brain water content?

Answer 18

10 mOsm/kg

Question 19

What are potential indications for corticosteroid administration in veterinary patients with intracranial hypertension?

Answer 19

• vasogenic edema
• primary inflammatory disease
• tumor-associated edema
• acute ischemia