Acute neurosciences

Question 1

Respiratory control centre

Answer 1

Medulla oblangata
- controlls most of breathing
- Dorsal Respiratory Group: integrates peripheral signals
- Ventral Respiratory Group: Excites inspiratory muscle to contract

Pons
- Controls smooth transition from inspiration to expiration

Question 2

Neural control of respiration…

Answer 2

Automatic (metabolic) respiration – to maintain acid-base balance

Voluntary (behavioural) respiration – allows modulation of ventilation in response to voluntary acts such as speaking, singing, breath hold and straining.

Limbic (emotional) control – allows respiratory modulation to emotion such as laughing, coughing and anxiety

Question 3

Automatic (metabolic) respiration

Answer 3

To maintain acid-base balance

Question 4

Voluntary (behavioural) respiration –

Answer 4

Allows modulation of ventilation in response to voluntary acts such as speaking, singing, breath hold and straining.

Question 5

Limbic (emotional) control

Answer 5

Allows respiratory modulation to emotion such as laughing, coughing and anxiety

Question 6

CNS respiratory considerations

Answer 6

Impaired neurological control of respiration (altered rate, depth and pattern)

Muscle weakness / fatigue

Dysfunction in gas exchange leading to respiratory failure

Impaired neurological control of swallow, cough and secretion clearance leading to reduced airway protection and increased risk of aspiration

Question 7

Monroe-Kellie hypothesis

Answer 7

“The total volume of intercranial contents must remain constant”

Brain tissue, CSF, blood

An increase in one should cause a reciprocal in one or both of the remaining two.

Question 8

Intercranial pressure (ICP)

Answer 8

ICP depends on volume of intercranial contents. Normally 1.4kg brain, 50-70ml blood and 50-120ml CSF.

Common causes of raised ICP = brain swelling e.g. after TBI or as a result of tumour.

Raised ICP means both neural and vascular tissues are compressed and if left untreated can be fatal.

Elevated ICP can be treating with medication, drainage of CSF or changing ventilator settings.

Question 9

Cerebral perfusion pressure (CPP)

Answer 9

Pressure at which the brain is perfused (approx. 15-20% of cardiac output)

Normal CPP = 60-80mmHg

CPP > 50mmHg results in cerebral ischaemia and tissue death

Question 10

Symptoms of raised ICP

Answer 10

Dilated pupils
Headache
Drowsiness
Hyper or hypotension
Loss of reflexes or increased reflexes
Seizures
Shortness of breath or rapid breathing
Abnormal posturing, rigid body movements and abnormal positions of the body
Cardiac arrest
Loss of consciousness
Coma

Question 11

Factors affecting ICP

Answer 11

• Hypercapnia
• Hypoxia
• Obstruction to venous outflow from the brain
• Increased intrathoracic or abdominal pressure
• Uncontrolled systemic BP
• Pyrexia
• External stimuli

Question 12

Cushing’s triad

Answer 12

• 3 primary signs that often indicate an increase in ICPIncreased Systolic BP
  Decreased Pulse
  Decresed Respiration

Question 13

Diagnosis of death using neurological criteria

Answer 13

Completed by two doctors on two occasions

Evidence of irreversible brain damage of known aetiology

Exclusion of reversible causes of coma and apnoea

Test for absence of brain stem reflexes

Apnoea test

Mitigation for ‘Red Flags’

Question 14

Disorders of consciousness

Answer 14

**Coma **(usually acute and short term)

Prolonged disorders of consciousness (PDOC) (unconscious >4 weeks)
Vegetative state (VS)
Minimally conscious state (MCS)

Question 15

Disordered consciousness occurs in two main contexts:

Answer 15

• Prolonged disorder of consciousness (PDOC) following sudden onset acquired brain injury – from which the patient may or may not regain consciousness
• Terminal decline of consciousness (TDOC) towards the end of life in patients with progressive degenerative brain damage (for example due to dementia, Parkinson’s disease or multiple strokes)