Neuroanaesthesia Flashcards
Incidence of neurological damage during scoliosis correction
0.5%
SSEP stimulation electrodes placement
Pair of stimulating electrodes placed bilaterally: 1) Posterior Tibial Nerves (Lumbar surgery) 2) Median Nerves (Cervical surgery)
Frequency of SSEP stimulation
30mA at 5Hz
SSEP recording electrode placement
Proximal to site of surgery: 1) 2 or more scalp electrodes (frontal and cervical) 2) Reference electrode 3) ground electrode
Band filter width for SSEP
20-1000 Hz
Shape of characteristic response in SSEP
W
Changes seen in SSEP with spinal cord compromise
Increased latency Decreased amplitude
Critical change in SSEP
50% increase in latency
What is an MEP?
Motor Evoked Potential
What is a SSEP?
Somatosensory Evoked Potential
What does MEP monitor?
Territory of the anterior spinal cord artery (corticospinal tracts)
What does SSEP monitor?
Dorsal column integrity
Source of stimulation for MEP
Transcranial electrical stimulation Transcranial magnetic stimulation Direct rostral spine stimulation
Risk of transcranial electrical stimulation
Injury secondary to mandibular contraction
How are MEPs recorded?
S/C / IM needle electrodes in arm and leg muscles
Time taken for MEP response
Less than 1 minute
Define Serious Traumatic Brain Injury
GCS less than 9 post resuscitation
List some primary prevention strategies for STBI
Helmets, airbags, reducing alcohol consumption, speed limits
Define secondary brain injury
A hypoxic insult to the brain from oedema, haematoma or low systemic pressure following a primary insult
Indications for CT head within 1 hour of TBI
GCS less than 13 at any time GCS 13-14 2 hours post injury Open fracture Skull base fracture More than 1 episode of vomitting Seizure Coagulopathy Event amnesia Focal deficit
Oxygen targets in TBI
PaO2 great than 13
CO2 targets in TBI
ETCO2 4.5-5
MAP target in TBI
great than 80
Glucose targets in TBI
6 - 10
Describe the features of diabetes insipidus
Raised sodium Polyuria Low urine osmolality
CPP target in neuroprotection
greater than 60
ICP target in neuroprotection
Less than 20
Rescue therapies in TBI
ABC Approach Ensure good venous drainage Increase sedation Hyperventillate to ETCO2 4-4.5 150 mL 5% NaCl Barbiturate Coma (Burst Suppression)
What causes the blown pupil in a decompensating head injury?
Falsely localising nerve injury (CNIII)
How should you treat seizures in TBI?
Thiopental or Benzodiazepine immediately. Phenytoin loading immediately afterwards
The role of steroids in TBI
Generally none
Why early fixation in unstable spinal injury?
allows for proper nursing care, PT, cough etc.
Classical timing for early complications of SAH
Hydrocephalus - Day 1 Rebleed - Day 1-7 Ischaemia - More than day 7
SAH risk factors
Smoking HTN Alcohol Polycystic kidney Family history Female gender Age 40-50
SAH incidence
6/100,000 patient years
SAH outcomes
10% die before hospital 40% die within 1 month
Fisher Scoring System
CT
Hunt and Hess Scoring System
Arrival clinical
WFNS Scoring System
GCS and motor
What are the hallmarks of a cholinergic crisis?
- Flaccid paralysis
- Respiratory failure
- Salivation
- Excess bronchial secretions
- Miosis
- Sweating (sweat glands are the exception to the rule of SNS innervation)
What are the indications for urgent (within 1 hour) CT head?
- 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
- Post-traumatic seizure
- Focal neurological deficit
- > 1 episode of vomiting
Cerebral ischaemia monitoring in CEA
- Awake
- Transcranial doppler
- Stump pressure
- EEG
- SSEP
- NIRS
What are the diagnostic criteria for SIADH?
- 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.
How do you treat SIADH
- Conservatively
- Fluid restrict (1000mL/day)
- Consider Hypertonic saline (1.8%), but stop at around Na 120 mmol/L
- Consider diuretics
- Consider demeclocycline/lithium to inhibit renal response to lithium
- Consider lixivaptan
Cerebral Salt Wasting Syndrome biochemical diagnostic criteria
- low or normal serum sodium;
- high or normal serum osmolality;
- high or normal urine osmolality;
- increased haematocrit, urea, bicarbonate, and albumin as a consequence of hypovolaemia.
