TBI

Question 1

Primary brain injury involves:

injury includes

Direct vascular damage also occurs leading to

Laceration is the most severe form of primary brain

axial hematomas
extraaxial hematomas in the

leading to compression of the brain and severe neurologic dysfunction

Historically it has been believed that extraaxial hemorrhage is rare in dogs and cats suffering from TBI. However, more recent evidence suggests that this type of hemorrhage occurs in up to _____% of animals with mild head injury and in >_____% with severe injury

Answer 1

physical disruption of intracranial structures

contusions, hematomas, lacerations

intracranial hemorrhage and vasogenic edema

within the brain parenchyma
subarachnoid, subdural, and epidural spaces

10%
>80%

Question 2

excitatory neurotransmitters:

which excitatory NT should you remember and what does it do?:

Answer 2

1. massive release of excitatory NT
2. influx of Na & Ca
3. depolarization, further release of excitatory NT ie (glutamate)
4. glutamate mediates accum. of Ca activates numerous intracellular enzymes =ultimately cell death
5. depletion of ATpP = cell death

glutamate - increase intracell. Ca

Question 3

ROS
3 main triggers:
MoA:

Answer 3

acidosis
hypoperfusion
hemorr./iron triggering Haber-Weiss reaction

1. local tissue acidosis and hypoperfusion trigger ROS formation
2. ROS preferentially damaging to cell membranes w high levels of polyunsaturated fats and cholesterol .:. brain tissue
3. hemorrhage may serve as an iron source
4. which favors the production of OH (hydroxyl) radicals via the Haber‐Weiss reaction of the xanthine oxidase pathway

Question 4

NO/CK

NO contributes to ROS‐ & glutamate‐med tissue damage

Answer 4

1. release of inflammatory CK
2. followed by accum. inflammatory cells
3. activate AA andcoagulation cascades, disrupting the BBB, and …
4. inducing nitric oxide (NO) production
   =excessive vasodilation leading to the loss of pressure autoregulation

Question 5

worse primary injury ranked

Answer 5

laceration>contusion>concussion

Question 6

Systemic insults that contribute to secondary brain injury:

Answer 6

HHHHH
hypotension, hypoxemia, hyperglycemia, hypoglycemia, hypercapnia, hypocapnia, hyperthermia
electrolyte imbalances, and acid-base disturbances

Question 7

ICP explained via Monroe‐Kellie doctrine holds that the skull is a rigid compartment that contains 3 components:

normal circum, these components exist in state of:

increase occurs in the volume of one component:

accommodation is known as:
and accomplished by:

limit to intracranial compliance results in:

severe increases in ICP trigger the:

Answer 7

brain parenchyma
arterial and venous blood
CSF

balanced dynamic equilibrium

one or more of the other components must decrease or an elevation in ICP will result

intracranial compliance
fluid shifts in the brain vasculature and CSF pathways

= ICP
= ischemia of brain tissue

cerebral ischemic response, or Cushing reflex

Question 8

Cushing reflex MoA:

why the increased MAP:
why the decreased HR:

CPP equation:

cushing’s reflex occurs when:

Answer 8

1. > ICP result in decreased cerebral blood flow (CBF)
2. increased CO2
3. sensed at the vasomotor center
4. initiates a SNS response leading to massive catecholamine release and > MAP

attempt to increase cerebral perfusion pressure (CPP)

hypertension is detected by baroreceptors
= reflex bradycardia

CPP = MAP - ICP

late = life‐threatening elevation in ICP

Question 9

Blood flow to the brain per unit time, or cerebral blood flow (CBF), is a function of CPP:

normal brain CBF autoreg.:
How does this change with trauma:

“Monro-Kellie Doctrine,” developed in the early nineteenth century to describe intracranial dynamics:

Answer 9

CPP is driving pressure in brain

MAP 50 to 150 mm Hg
loses much of this autoregulatory capacity
=susceptible to ischemic injury w small decreases in MAP

V intracranial = V blood + V parench + Vcsf + V lesion

Question 10

primary determinant of CBF:
Blood flow to the brain per unit time, or cerebral blood flow (CBF), is a function of CPP:

normal brain CBF autoreg.:
How does this change with trauma:

“Monro-Kellie Doctrine,” developed in the early nineteenth century to describe intracranial dynamics:

Answer 10

CPP
CPP is driving pressure in brain

MAP 50 to 150 mm Hg
loses much of this autoregulatory capacity
=susceptible to ischemic injury w small decreases in MAP

V intracranial = V blood + V parench + Vcsf + V lesion

Question 11

Tx priorities:

Answer 11

ABC the systemic stuff first

Question 12

Tx priorities:

Answer 12

1. ABC the systemic stuff first

2. vertebral, skull

Question 13

Initial neurologic assessment includes evaluation of (5):

Answer 13

level of consciousness
pupil size and responsiveness/ocular position & movem.
skeletal motor responses
breathing pattern

Question 14

In human patients TBI is graded as mild, moderate, or severe based on the Glasgow coma scale

MGCS for TBI has been evaluated with respect to survival over a 48‐hour period:

MGCS incorporates 3 categories:

assigns a score from:

Answer 14

• estimate of prognosis for the veterinarian and owner
• higher better px
• **better utilized as obj assessment of progression of neurologic signs rather than as a prognostic indicator (SIS for individual vs group)

level of consciousness
motor activity
brainstem reflexes

1 to 6, total score of 3–18

Question 15

motor activicty:
-affected by the animal’s level of consciousness

decerebrate rigidity

decerebellate rigidity

main determination between cerebral and cerebellar injury is ____

decerebrate patient, results in a comatose state = damage to ____ & associated w grave prognosis

Answer 15

opisthotonus with hyperextension of all four limbs
= cerebral damage

variable flexion and extension of the hind limbs
= cerebellar damage

level of consciousness

RAS within the midbrain

Question 16

brainstem reflexes:

Pupils that respond appropriately to light indicate adequate function of:

Miotic pupils indicate:
Progression to mydriasis may indicate:

Transtentorial herniation places pressure on:
resulting in:

Fixed, unresponsive and midrange pupils are seen with:

Brain herniation is associated with severe disability and death if not treated rapidly and aggressively

Repeated neurologic assess recommended every ____

Answer 16

rostral brainstem, optic chiasm, optic nerves, and retinae

diffuse forebrain injury
brain herniation

CN III, interrupting parasympathetic input to the eye resulting in a dilated pupil

cerebellar herniation

30–60 minutes to monitor tx efficacy/assess deterior.

Question 17

Tx:
1.
2.

Answer 17

Extracranial stabilization: correction perfusion, optimizing systemic oxygenation and ventilation

Intracranial stabilization: optimizing cerebral perfusion, decreasing ICP, and minimizing elevations in the cerebral metabolic rate

Question 18

Initial Extracranial Therapy
Fluid therapy:

restoration of intravascular volume to ensure ___

discuss hx recommendations for fluid restriction:

hypotension has been shown to be associated with:

In 1 prospective study, hypotension was associated with a ____% increase in mortality

Answer 18

adequate CPP

little/no data to support idea that dehydration diminishes cerebral edema and these recommendations for fluid restriction are firmly contraindicated

significant increases in morbidity and mortality in human TBI patients

150% increase in mortality

Question 19

fluid type controversy:
It is the _____, rather than the plasma _____ pressure, that determines water movement between the vascular and extravascular compartments

.:. uninjured brain, minimal concern that aggressive crystalloid resuscitation may produce cerebral edema b/c

injured brain the BBB may be disrupted regionally or globally. This disruption may result in increased permeability to both ions and _____ particles

regaurdless, benefit obtained by the restoration of CPP with either crystalloids or colloids outweighs the potential risks

Answer 19

osmolality vs oncotic pressure

isoosmolar .:. no fluid shifts

colloidal

Question 20

Hypertonic saline is superior why?

Answer 20

> osmolarity promotes transcapillary shift of interstitial and intracellular fluid into the vasculature
marked volume expansion exceeds the volume infused
4mL/kg of 7.5% sodium chloride
< ICP and >MAP

Question 21

after resusc. then what?

Answer 21

continued fluid therapy is mandatory
hypertonic solutions act to dehydrate

maint. + ongoing

Question 22

Oxygenation and ventilation

decreased oxygen delivery is a main perpetrator of:

human studies in TBI patients have shown that mortality for patients with documented hypoxia after injury is ____that of patients w.out doc. episodes of hypoxia

lethal level of hypoxemia - pulse os 75% = PaO2

Nasal oxygen cannulas and transtracheal oxygen catheters supply approximately 40% inspired oxygen concentration with flow rates of:

Answer 22

secondary brain insult

double

40mmHg

50–100mL/kg/min

Question 23

what is the most imortant fctor controlling CBF?:

Plasma CO2 tension regulates cerebral blood vessel diameter -
hypercapnia vs hypocapnea:

most accurate method to monitor PaCO2 levels:
rak VBG, ABG, ETCO2 highest to lowest CO2:

Answer 23

PaCO2

dilation vs constriction

ABG
VBG > ABG > ETCO2

Question 24

hypoventilating patients may require:

Hyperventilation has traditionally been viewed as a method of decreasing ICP. Hyperventilation:

However, it has been shown that even moderate hypocapnia (CO2 <34mmHg) leads to excess vasoconstriction, perpetuating cerebral hypoperfusion

When can aggressive hyperventilation be considered:

Answer 24

MV

cerebral vasoconstriction < CBV < ICP

brief periods of time in patients with acute deterioration but still not below a PaCO2 of 30

Question 25

Initial Intracranial Therapy
Minimizing increases in ICP

Positioning the head such that it is elevated:
must prevent:

Answer 25

15–30° angle
-reduce CBV by increasing venous drainage
bending of neck .:. stiff board

Question 26

Hyperosmotic agents
Mannitol:
____is considered the first‐line therapy
dose ____

Answer 26

mannitol
0.5 to 1.5g/kg over 15–20 minutes
study showed that high‐dose (∼1.4g/kg) = significant neurologic improv. vs (∼0.7g/kg) therapy

Question 27

Hyperosmotic agents
Mannitol:
____is considered the first‐line therapy
dose ____

MoA

rheologic mechanism:
onset
duration

Osmotic mechanism:
onset
duration
limit in trauma:

Free radical scavenging properties:

furosemide + mannitol?

Answer 27

mannitol
0.5 to 1.5g/kg over 15–20 minutes
study showed that high‐dose (∼1.4g/kg) = significant neurologic improv. vs (∼0.7g/kg) therapy

controversy exists MoA

-transient plasma expansion decreasing blood viscosity
=cerebral vascular vasoconstriction to maint. CBF
.:. ICP decreases secondary to a decreased CBV despite maintained CBF
- rheologic mechanism most profound effect on ICP
- occurs immediately, persists for approx 75 min

-osmotic effects delayed for 15–30 min
-nontraumatized brain mannitol promotes the shift of water ICS, ISS to IVV
= osmotic diuresis, reducing cerebral edema
-peaks 1 hour - persist for 6–8 hours
-traumatized brain decreased perfusion of parenchyma

• reported to have free radical scavenging properties
• limit secondary oxidative injury

-addition of furosemide has no effect + risk of worsening hypovolemia

Question 28

Mannitol administration is contraindicated in:

being freely filtered, it retains fluid within the renal tubules resulting in wasting of _____

Answer 28

hypovolemic patients
electrolytes and water
only to normo‐volemic followed w crystalloid

Question 29

exacerbation of ongoing intracranial hemorrhage:
- by its osmotic effect. However, there is no clinical evidence to prove this theory and, as the benefits of treatment far outweigh the theoretical risks, it may be:

Mannitol may cause increased permeability of the blood-brain barrier:

Answer 29

disregaurded

worse when in circ long time .:. no CRI rather boluses

Question 30

reverse osmotic shift:
-In situations of prolonged contact (multiple bolus doses or continuous infusions) mannitol can accumulate in the extravascular compartment exceeding the intravascular concentration and leading to brain edema and an increase in ICP. However:

Answer 30

reverse osmotic shift is less likely to occur with appropriate bolus use of mannitol

Question 31

Hypertonic saline
intact BBB is relatively ______ to sodium and chloride

hyperosmolar concentrations:

1. creates a driving force shifting
2. improves regional CBF via
3. excitotoxicity by promoting reuptake of excitatory amino acids, such as:

duration:

must exclude ____ before treatment:

Risk of aggravating _____:
risk exists for mannitol as well and may be worse than hypertonic saline in the patient with pulmonary contusions

Studies comparing mannitol and hypertonic saline

When equimolar doses of mannitol, 3% NaCl, and 23.4% NaCl were compared in a ovine model of intracerebral hemorrhage, ICP reduction was most prominent after:

However, after 2 hours only ___ had a sustained effect on ICP and the ICP in the ____ animals exceeded the pretreatment ICP

• this study suggests that hypertonic saline may actually be favored over mannitol
• rodent model = 23.4% hypertonic greater ICP decrease and a more sustained effect than mannitol
• human patients w increased ICP = hypertonic saline‐dextran solution lowered ICP more effectively and longer than mannitol

Answer 31

impermeable

-shifting water from the interstitial and intracellular spaces of the brain into the intravascular compartment thus reducing brain water content and ICP

-dehydration of cerebrovascular endothelial cells
reduction of endothelial edema = increase in vessel diameter = improving CBF
-reduction in ICP
-and enhanced cerebral oxygen delivery

• glutamate, into the intracellular space

l- reducing adhesion of polymorphonuclear cells to microvasculature modulating the inflammatory response

volume expansion 15–75 minutes
beneficial effects on ICP are maintained far longer

hyponatremic

pulmonary edema or contusions

prominent after 23.4% NaCl administration

3% NaCl had a sustained effect
mannitol‐treated animals exceeded the pretreatment ICP

Question 32

At this time The Brain Trauma Foundation Guidelines still consider ______to be first line treatment for ICP TBI

recent studies support the growing clinical literature that hypertonic saline may in fact be superior to mannitol in controlling ICP with fewer untoward effects

especially valuable in situations of shock and hypotension when administered with an artificial colloid.

Answer 32

mannitol

untoward effects

Question 33

NaCl similar rheologic and osmotic effects to mannitol

-hypotension is a less likely sequela why?:

Answer 33

Na reabsorbed in the kidneys