Neuroanaesthesia

Question 1

Incidence of neurological damage during scoliosis correction

Answer 1

0.5%

Question 2

SSEP stimulation electrodes placement

Answer 2

Pair of stimulating electrodes placed bilaterally:
1. Posterior tibial nerves (lumbar surgery)
2. Median nerves (cervical surgery)

Question 3

Frequency of SSEP stimulation

Answer 3

30mA at 5Hz

Question 4

SSEP recording electrode placement

Answer 4

Proximal to site of surgery:
1. 2 or more scalp electrodes (frontal and cervical)
2, Reference electrode
3. Ground electrode

Question 5

Band filter width for SSEP

Answer 5

20-1000 Hz

Question 6

Shape of characteristic response in SSEP

Answer 6

W

Question 7

Changes seen in SSEP with spinal cord compromise

Answer 7

Increased latency
Decreased amplitude

Question 8

Critical change in SSEP

Answer 8

50% increase in latency

Question 9

What is an MEP?

Answer 9

Motor Evoked Potential

Question 10

What is a SSEP?

Answer 10

Somatosensory Evoked Potential

Question 11

What does MEP monitor?

Answer 11

Territory of the anterior spinal cord artery (corticospinal tracts)

Question 12

What does SSEP monitor?

Answer 12

Ascending sensory pathways (dorsal columns)

Question 13

Source of stimulation for MEP

Answer 13

Transcranial electrical stimulation Transcranial magnetic stimulation Direct rostral spine stimulation

Question 14

Risk of transcranial electrical stimulation

Answer 14

Injury secondary to mandibular contraction

Question 15

How are MEPs recorded?

Answer 15

SC / IM needle electrodes in arm and leg muscles

Question 16

Time taken for MEP response

Answer 16

Less than 1 minute ???

Question 17

Latency of SSEP

Answer 17

20 ms upper limb
37 ms lower limb

Question 18

Define Serious Traumatic Brain Injury

Answer 18

GCS < 9 post resuscitation → mortality 40%

Question 19

List some primary prevention strategies for serious traumatic brain injury

Answer 19

Helmets
Airbags
Reducing alcohol consumption
Speed limits

Question 20

Define secondary brain injury

Answer 20

A hypoxic insult to the brain from oedema, haematoma or low systemic pressure following a primary insult

Question 21

Indications for CT head within 1 hour of TBI

Answer 21

GCS <13 at any time
GCS 13-14 2 hours post-injury
Open fracture
Skull base fracture
More than 1 episode of vomiting Seizure
Coagulopathy
Event amnesia
Focal deficit

Question 22

Oxygen targets in TBI

Answer 22

PaO₂ >13

Question 23

CO₂ targets in TBI

Answer 23

ETCO₂ 4.5-5

Question 24

MAP target in TBI

Answer 24

> 80

Question 25

Glucose targets in TBI

Answer 25

6-10 mmol/L

Question 26

Describe the features of diabetes insipidus

Answer 26

Raised sodium Polyuria Low urine osmolality (Caused by lack of ADH / lack of response to ADH → polyuria + dehydration)

Question 27

CPP target in neuroprotection

Answer 27

>60

Question 28

ICP target in neuroprotection

Answer 28

<20

Question 29

Rescue therapies in TBI

Answer 29

ABC Ensure good venous drainage Increase sedation Hyperventillate to ETCO₂ 4-4.5 Hypertonic saline (1-3ml/kg 5%, 3-5ml/kg 3%) or mannitol (0.25-2g/kg) Barbiturate coma (burst suppression)

Question 30

What causes the blown pupil in a decompensating head injury?

Answer 30

Falsely localising nerve injury (CN III) - due to uncal herniation → mechanical compression of CN III → subsequent brain stem compromise

Question 31

How should you treat seizures in TBI?

Answer 31

Thiopental or benzodiazepine immediately Phenytoin or levetiracetam loading immediately afterwards

Question 32

The role of steroids in TBI

Answer 32

Generally none

Question 33

Why early fixation in unstable spinal injury?

Answer 33

Allows for proper nursing care, PT, cough etc.

Question 34

Classical timing for early complications of SAH

Answer 34

Day 1: hydrocephalus Day 1-7: rebleed Day 7+: ischaemia

Question 35

SAH risk factors (7)

Answer 35

Smoking HTN Alcohol Polycystic kidney Family history Female gender Age 40-50

Question 36

SAH incidence

Answer 36

6/100,000 patient years

Question 37

SAH outcomes

Answer 37

10% die before hospital 40% die within 1 month

Question 38

Modified Fisher Scoring System

Answer 38

Grade 0: - No SAH - No IVH Grade 1: - Focal or diffuse, thin SAH - No IVH - Incidence of symptomatic vasospasm: 24% Grade 2: - Focal or diffuse, thin SAH - IVH present - Incidence of symptomatic vasospasm: 33% Grade 3: - Thick SAH - No IVH - Incidence of symptomatic vasospasm: 33% Grade 4: - Thick SAH - IVH present - Incidence of symptomatic vasospasm: 40%

Question 39

Hunt and Hess Scoring System

Answer 39

Clinical grading system Grade 1: asymptomatic/mild headache Grade 2: moderate-severe headache or nuchal rigidity, or cranial nerve palsy Grade 3: lethargy, confusion, or mild focal deficit Grade 4: stupor and/or hemiparesis Grade 5: deep coma, decerebrate posturing, or moribund appearance

Question 40

Modified WFNS Scoring System

Answer 40

Grade I: GCS 15 Grade II: GCS 14 Grade III: GCS 13 Grade IV: GCS 7-12 Grade V: GCS 3-6

Question 41

What are the hallmarks of a cholinergic crisis?

Answer 41

SLUDGE + other Salivation Lacrimation Urination Defecation GI upset Emesis Miosis Muscle weakness Flaccid paralysis (initially spasm) Respiratory failure

Question 42

What are the indications for urgent (within 1 hour) CT head?

Answer 42

GCS < 13 when first assessed in emergency department GCS < 15 when assessed in emergency department 2 hours after the injury Suspected open or depressed skull fracture Sign of fracture at skull base haemotympanum, ‘panda’ eyes, cerebrospinal fluid leakage from ears or nose, Battle’s sign (bruise behind ear) Post-traumatic seizure Focal neurological deficit > 1 episode of vomiting

Question 43

Cerebral ischaemia monitoring in CEA

Answer 43

Awake Transcranial doppler Stump pressure EEG SSEP NIRS

Question 44

What are the diagnostic criteria for SIADH?

Answer 44

Hypotonic hyponatraemia - Serum sodium <135 mmol/l - Serum osmolality <280 mOsm/kg Urine osmolality > serum osmolality Urine sodium concentration >18 mmol/l Normal thyroid, adrenal, and renal function Clinical euvolaemia - absence of peripheral oedema or dehydration

Question 45

How do you treat SIADH?

Answer 45

Conservatively Fluid restrict (1000mL/day) Hypertonic saline (1.8%) if Na <120 mmol/L Consider diuretics (furosemide) Consider demeclocycline (inhibits ADH)

Question 46

Cerebral Salt Wasting Syndrome biochemical diagnostic criteria

Answer 46

Low/normal serum sodium; High/normal serum osmolality; High/normal urine osmolality High urine sodium Increased haematocrit/urea/bicarbonate/albumin as a consequence of hypovolaemia