Neurosurgery

Question 1

Outline the Glasgow Coma Scale

Answer 1

Scale 3-15
Comprises Motor, Verbal and Eye

E1 = no response
E2 = open pain
E3 = open voice
E4 = spontaneous eye opening

V1 = no response
V2 = incomprehensible
V3= inappropriate words
V4= confused
V5 = orientated

M1= no response
M2 = extension to pain
M3 = Flexion to pain
M4= withdrawl to pain
M5 = Localising pain
M6 = Obeys command

Question 2

Discuss the causes of hydrocephalus

What is the treatment?

Answer 2

Broadly TWO groups:
OBSTRUCTION CSF outflow (non-communicating)
Space occupying lesion
SAH
Arnold Chiari malformation
Spina Bifida

Failure of absorption of CSF by arachnoid villi
(non communicating)
SAH
Meningitis
Head Injury

Surgeons will place a EVD (usually into the frontal horn of the lateral ventricle) - Temporary due to risk of ventriculitis

Question 3

Discuss issues of anaesthesia for posterior fossa surgery

Answer 3

Posterior fossa houses -> cerebellum, pons, medulla, lower cranial nerves and fourth ventricle. Tight rigid compartment. Small pressure increases can cause life threatening brainstem complications

PRE OP
Evaluate cerebellar and cranial nerve dysfunction ?cough and gag reflex
Evaluate for signs of hydrocephalus and raised ICP
Evaluate hydration and electrolyte status
Evaluate for intraoperative positioning (check TTE)
evaluate airway and neck movement

IntraOp

POSITIONING
Dependant on position of lesion - includes supine, sitting, lateral, prone, park bench

SITTING - improves access to midline tumours, gravity assisted drainage of blood and CSF - decreasing ICP.
Decreases retraction needed to access deeper structures.

Monitoring - 2x ivc, IAL, ?CVC, Temp probe, Sp02, ECG, BIS, ETCO2

Technique - TIVA (prop & remi) - consideration given if also using SSEP , MSEP
goals of anaesthetic management
avoid significant increase in ICP,
maintain cerebral perfusion pressure, avoid haemodynamic instability,
enable intraoperative neuro-monitoring and
ensure the early detection and management of complications.

POSTOPERATIVE
Extubation depends on preoperative status and the intraoperative course.

Recheck Airway after prolonged positioning

Aim for smooth extubation

PONV can be severe due to operating near vomiting centre

Pain esp occipital and infratentorial approaches can be painful due to muscle dissection and spams post.

The posterior fossa syndrome can complicate the postoperative course in children. This syndrome is defined as temporary and complete loss of speech after posterior fossa surgery and risk factors include medulloblastoma and midline location of tumours. Early diagnosis is important to facilitate speech and language therapy and to promote parental understanding and coping with the syndrome.

Question 4

Discuss issues of SITTING POSITION for posterior fossa surgery

Answer 4

CVS Instability :
venous pooling in legs can lead to significant hypotension particularly in the elderly.
Surgical stimulation of lower pons, upper medulla can have variable effects such as hypo/hyper tension, brady cardia , tachy cardia and arrthymias.
- AVSD, R to L shunt absolute contraindication to this position

VAE
Incidence 25-75%
Dependant on rate and volume entrained.
increase RAP, hypotension shock to obstuction of RV outlet leading to RV failure and arrest,

Pneumocephalus
Once cranial vault closes - mass effect
delayed recovery, raised ICP, headache , confusion, agitation,

MACROGLOSSIA
venous and lymphatic obstruction of the tongue , may possible obstruction risk at end of case.

Quadriplegia
Prolonged pressure on spinal cord due to neck flexion. Exacerbated by periods of hypotension leading to cord ischaemia.

Question 5

Discuss Management of Venous Air Embolism

Answer 5

1. Inform surgeons - flood field with saline
2. 100% Oxygen
3. Raise venous pressure by Level Patient
4. Aspirate CVL if present

Question 6

Discuss complications of prone positioning

Answer 6

Occular - post operative visual loss, corneal abrasions

Peripheral never injury ulnar nerve at elbow, brachial plexus

Difficult access to airway - potential extubation

Pressure Injuries - skin necrosis, breast/genital injury

Abdominal compression ( venous congestion in epidural veins, organ ischaemia, impaired ventilation and reduced cardiac output)

Question 7

Discuss anaesthesia issues for spinal surgery

Answer 7

1. Trauma, 2. Infection, 3. Malignancy, 4. congenital, 5. Degenerative