FRCA Notes

Prone Positioning for Neurosurgery

Resources

Indications
Posterior fossa neurosurgery
Cervical spine surgery e.g. PCDF
Spinal surgery e.g. scoliosis correction
Management of refractory hypoxaemia e.g. due to ARDS
Some general surgeries e.g. sacral nerve stimulator insertion

  • Requires 6 people to safely prone a patient
  • Patient is usually log-rolled into position

Body support while prone

  • Specialised tables:
    • Allen/Jackson table
    • Montreal mattress (foam mattress with abdominal cut-out)
    • Wilson frame (for lumbar surgery)

  • Pillows
  • Chest/pelvic bolsters
  • Knee-chest position

Head and neck

  • In neutral position or minimally turned to one side
  • Minimal flexion
  • ± pinned to a Mayfield frame
  • Ensure no pressure on eyes, ears

Arms and legs

  • Arms placed iether:
    • Beside the head on arm boards, which can avoid overstretch the lower trunks of the brachial plexus
    • By sides
  • Be careful not to force the joint when raising arms
  • Ensure elbows padded and no pressure in axilla
  • Forearms lower than torso to avoid stretching neurovasculature

  • Legs extended, although slightly bent to reduce sciatic nerve injury

Trunks & torso

  • Displace breasts laterally
  • Ensure male genitalia hang freely without torsion or compression

  • Adequate personnel to turn patient prone (and back) = 6 people
  • Risk of disconnection or accidental removal of IV lines, monitoring wires, tubing

Airway & breathing

  • Airway obstruction
  • Accidental extubation
    • First sign would be 'low-pressure' alarm, reservoir bag emptying or surgeon admitting accidental extubation
    • Managed with insertion of LMA or bag-mask ventilation
    • Inserting a supraglottic device is likely to be the easiest temporising measure
  • Endobronchial intubation due to tube moving

  • See: Physiology of prone ventilation from the ICM Respiratory section for beneficial ventlatory effects
  • May get reduced chest wall compliance/splinting of diaphragm if abdominal contents are impeded

Cardiovascular

  • Reduced preload from:
    • Positive pressure ventilation
    • IVC compression
    • Blood pooling
  • This reduces cardiac output (∽20%) and may cause hypotension

  • Reduced LV compliance due to raised intra-thoracic pressure
  • Intra-operative venous bleeding during spinal surgery due to raised epidural venous pressure
  • Femoral artery compression

Ophthalmic

  • Special consideration should be given to eye protection
    • The position of the head and eyes should be checked before | during | after surgery
    • The frequency of eye injury during anaesthesia is low (<0.1%) but the injury may be significant e.g. permanent loss of vision
    • Corneal abrasions are most common and avoidable with eye protection
  • Raised IOP - direct pressure on the eye in the prone position may raise IOP above MAP and lead to retinal ischaemia
  • Nerve injuries from pressure (see below)

Neurological

  • Raised ICP ± reduced CBF due to rotation or over - flexion/extension of the neck
  • Peripheral nerve injuries including supra-orbital nerve, brachial plexus, femoral nerve & lateral cutaneous nerve of the thigh (see below)

Intra-abdominal

  • Raised intra-abdominal pressure
  • Reduced splanchnic blood flow
  • AKI
  • Acute liver injury / metabolic acidosis

Musculoskeletal

  • Backache
  • C-spine hyper extension
  • Shoulder dislocation during arm movement

  • Major pressure points include:
    • Head: ears, eyes, cheeks, nose
    • Torso: acromial processes, breasts
    • Abdomen: iliac crests, ASIS, male genitalia
    • Lower limb: patellae, toes

Nerve injuries

  • Higher risk if:
    • Male
    • Obese/severely underweight
    • Diabetic
    • Prolonged hospital stay
Nerve injury Note
Brachial plexus Compression in the axillae from Montreal mattress
Excessive head turning
Shoulder AB-ducted >90°
Ulnar nerve At the elbow
Femoral nerve
Lateral cutaneous n. of thigh
Sciatic nerve Excessive leg extensor tension
Avoided by bending legs and raising feet
Spinal cord From over-extension or -flexion of the C-spine
From rolling unstable vertebral column
Post-operative visual loss Peri-operative ischaemic optic neuropathy
Central retinal artery occlusion
Raised ICP Obstruction of cerebral venous drainage if head not in midline
Spinal cord ischaemia
Ischaemic stroke		 From intra-operative hypotension


  • Avoid prone positioning; anaesthetise in lateral position
  • When turning prone, disconnect lines and wires temporarily

Airway & breathing

  • Intubate with cuffed armoured tube
  • Secure tube with particular attention
  • Disconnect tube from breathing circuit when turning prone
  • Re-auscultation once re-connected to ensure no endobronchial intubation

Cardiovascular

  • Large bore IV access
  • Check peripheral pulses once prone

Ophthalmic

  • Tape and pad eyes
  • Avoid direct pressure i.e. ensure not compressed by headrest
  • Check eyes every 30mins
  • Normal BP and oxygenation

Neurological

  • Avoid stretching brachial plexus e.g arms by side or <90° Abduction at shoulder
  • Avoid ulnar nerve injury with adequate padding, <90° flexion at elbow or arms by side
  • Avoid direct pressure on peripheral nerves e.g. padding legs under straps
  • Slight bend in legs to avoid sciatic nerve stretch

Intra-abdominal

  • Avoid abdominal compression with specialised mattress e.g. Montreal, Allen-Jackson frame, Wilson table
  • If signs of acidosis and raised LFT's consider turning supine to avoid acute liver injury

Musculoskeletal

  • Avoid neck hyper extension
  • Position face on soft pillow or other support
  • Controlled log roll with limbs in neutral position
  • Adequate padding of pressure points
  • Ensure BP maintained to prevent ischaemia of pressure points

Head-up prone position

  • Head is held in pins and elevated above the heart by tilting whole table head-up
  • Improves venous drainage of the head and neck
  • Requires strapping across/under the buttocks to prevent the body sliding down the table
  • The knees are flexed with a wedge/pillow beneath the lower legs

  • Can lead to pressure on the chin
  • Can lead to excessive traction on the cervical vertebrae

Concorde

  • The Concorde position is similar to the prone position but with a hyper-flexed C-spine, which carries similar risks as regular proning but additional difficulties with airway issues