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MD4001 > Applied physiology: head injury > Flashcards

Applied physiology: head injury Flashcards

1
Q

What is primary brain injury?

A
  • Occurs at the moment of impact
  • Pattern and extent of injury depend on the nature of the impact
  • Not treatable - neurones are poor at regenerating
  • Public health issue- target prevention
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2
Q

What is secondary brain injury?

A
  • Focus of medical intervention is to minimise the secondary brain injury
  • Damage that occurs as a result of secondary processes which occur at the cell and molecular level to exacerbate neurological damage
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3
Q

Describe what happens in secondary brain injury

A
  • Neurones get damaged and become hypoxic and under-refused leading to lactic acid build up due to anaerobic respiration
  • ATP depletes so ion pumps begin to fail and then:
  • (glutamate) neurotransmitter release
  • Free radical generation
  • Calcium mediated damage
  • Inflammatory response
  • Mitochondrial dysfunction
  • Early gene activation
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4
Q

What is the Monroe-kellie doctrine?

A

the sum of the volumes in the brain is consistent (up until the point of compensation ICP is normal)

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5
Q

Describe the physiological processes that occur in primary brain injury to then cause secondary brain injury

A

Pathway 1:
• Activation of bimolecular mediators of injury
• Neuronal damage
• Cytotoxic oedema

Pathway 2:
• Cerebral vessel damage - opening of the BBB
• Increased interstitial fluid and tissue pressure
• Vasogenic oedema

Both feed into and back from: (this goes in a loop) 
• Decreased cerebral perfusion pressure
• Vasodilation 
• Increased Cerebral blood volume 
• Increased intracranial pressure
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6
Q

What happens to intracranial pressure after compensation has been reached?

A

There is an exponential rise in pressure (when looking at its increase with volume)

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7
Q

Describe early management of traumatic brain injury

A
  • Assessment and identification of patient at risk of secondary brain injury - history taking and GCS
  • Pre-emptive investigation (CT scan)
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8
Q

Who should be sent to hospital following a traumatic Brian injury?

A
  • Extremes of age (<5 years (incase non-accidental) and >65 years (drug complications e.g. blood thinners)
  • Amnesia for events before or after injury
  • High energy injury
  • Vomiting
  • Seizure
  • Bleeding/clotting disorder (check platelets)
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9
Q

When is Glasgow coma scale used in the treatment of head injury?

A
  • Initial management
  • Ongoing assessment
  • Best GCS post resuscitation is of prognostic value only
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10
Q

What are the 3 components of GCS?

A
  • Eyes
  • Motor
  • Verbal
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11
Q

Describe the scoring for eyes for GCS

A
  • 4 - eyes open spontaneously
  • 3- eyes open to speech
  • 2- eyes open in response to pain
  • 1- eyes do not open
  • NT is patient is unable to open their eyes e.g. due to swelling
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12
Q

Describe the scoring for verbal response for GCS

A
  • 5- Orientated
  • 4- Confused
  • 3- Inappropriate words
  • 2- Incomprehensible sounds
  • 1- No response despite verbal and physical stimuli
  • NT - dysphasic, T- intubated
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13
Q

Describe the scoring for motor response for GCS

A
  • 6- obeys commands
  • 5- localises to central pain
  • 4- normal flexion towards the source of pain
  • 3- Abnormal flexion
  • 2- Extension to pain
  • 1- response to painful stimuli
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14
Q

What is the maximum GCS score?

A

15 : E4V5M6

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15
Q

What GCS score classes as a minimal head injury?

A

15

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16
Q

What GCS score classes as a mild head injury?

A

13-15

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17
Q

What GCS score classes as a moderate head injury?

A

9-12

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18
Q

What GCS score classes as a severe head injury?

A

8 or less: COMA

19
Q

When should a CT scan be requested immediately?

A
  • GCS>13 on initial assessment in A&E
  • GCS>15 2 hours after injury
  • Suspected open or depressed skull fracture
  • Post traumatic seizure
  • 1 or more episodes of vomiting
  • Amnesia for events more than 30 minutes before impact
20
Q

What are the red flags?

A
  • Loss of consciousness, drowsiness, confusion, fits
  • Painful headache that doesn’t settle, vomiting or visual disturbance
  • Clear fluid from ear or nose, bleeding from the ears, new deafness
  • Problems understanding or speaking, loss of balance, difficulty walking or weakness in arms or legs
21
Q

Oxygenation and head injury

A

• If they are hypoxic, their head injury is not causing it:
- may be intoxicated, interfering with respiration
- airway may be closed
• Open their airway but remember the cervical spine: if suspected fracture, immobilise and until immobilised: jaw thrust

22
Q

Breathing and head injury

A
  • Administer oxygen
  • Monitor spO2
  • Monitor ABGs
  • If GCS<8, intubate
  • You want to avoid hypoxia as the cerebral arteries will dilate, increasing blood flow and therefore intracranial pressure
23
Q

How can you minimise oxygen demand?

A
  • Convusions occur in 15% of head injuries, treat with phenytoin
  • Treat pyrexia: brain metabolic rate increases 6-9% for every degree rise in temperature
  • Think about sedation (propofol/midazolam) - surpasses the metabolic rate but means you can’t assess GCS
24
Q

Carbon dioxide and head injury

A
  • Cerebral vessel diameter and CBF changes over a wide range of PaCO2
  • Target directed therapy: PaCO2: 4.5-5.0kPa
25
Q

BP and head injury

A
  • When assessed 25% are hypotensive

* Low blood pressure is not caused by head injury

26
Q

How can you calculate cerebral perfusion pressure?

A

Mean arterial pressure - intracranial pressure

27
Q

How can you calculate mean arterial pressure?

A

Diastolic + 1/3 pulse pressure

28
Q

Describe auto regulation in the brain

A
  • Cerebral arterioles react to local changes in the environment (pressure and chemical)
  • Normally auto regulation maintains MAP of 50mmHg and 150mmHg
  • Traumatised or ischaemic brain, CBF may become blood pressure dependent
29
Q

Pressure target goals after severe head injury

A
  • Maintain Cerebral perfusion pressure above 60-70mmHg
  • Maintain the systolic blood pressure higher than 90mmHg (preferably higher than 120mmHg)
  • ICP is less than 20mmHg (invasive pressure monitor)
30
Q

What is a normal intracranial pressure?

A

10mmHg

31
Q

What should you do if a patient is hypotensive?

A
  • Look for other causes: not due to head injury: chest trauma, pelvic fracture
  • Stop bleeding
  • Intravenous fluids (n. saline)
32
Q

How can you encourage venous drainage?

A
  • Nurse tilts head up 15-30 degrees

* Check straps and ties are not obstructing venous flow

33
Q

What are the features suggesting an intracranial mass?

A 
From their history: 
• High impact injury 
• Significant retrograde amnesia 
• History of coagulopathy 
• post traumatic seizure

Examination:
• GCS 12/15 or less, 13-14/15 and failing to improve after 2 hours
• Clinical signs of skull fracture

34
Q

Peri orbital bleeding

A

Possible anterior cranial fossa fracture

35
Q

Battle’s sign

A
  • Possible petrous temporal bone fracture
  • Bruising may take time to develop
  • Bruising behind the ear
36
Q

Extradural haematoma

A
  • Relatively uncommon
  • Strongly associated with skull fracture
  • Middle meningeal artery
  • 1/3 due to venous drainage
  • Classically a lucid interval
  • Good outcome if it is treated
  • Biconvex
37
Q

Subdural haematoma

A
  • Common
  • Complicates 20-30% of head injuries
  • Rupture of veins travelling from the brain surface to the saggital sinus
  • Prognosis is worse
  • Crescenteric shape
38
Q

Subarachnoid haemorrhage

A
  • Associated with a ruptured berry aneurysm

* More commonly caused by head injury

39
Q

Intercerebral haemorrhage

A
  • Stretching and shearing skull injury
  • Impact on the side of the skull
  • Often contra coup injury (high impact, brain strike other side of the skull)
40
Q

Clinical herniation

A
  • Dilated or unreactive pupils
  • Extensor posturing
  • Decrease in GCS of 2 or more points
41
Q

Physiological Principe - CO2

A

Temporary hyperventilation can decrease ICP and buy time, it brings the CO2 levels down

42
Q

Drugs used in head injury treatment

A
  • 20% mannitol to decrease blood viscosity, osmotic diuretic
  • Hypertonc saline
  • Tranexamic acid
43
Q

Control of Glucose

A

• Dangers of unrecognised hypoglycaemia

44
Q

When contacting neurosurgeons, what information should you give?

A
  • Mechanism of injury
  • Age of patient
  • Respiratory and cardiovascular status of patient
  • GCS score and pupil response
  • Alcohol and drugs
  • Associated injuries
  • Result of CT scan

MD4001 (28 decks)

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