Editing Patient positioning

== Goals: ==

* Facilitate surgical access
* Facilitate anaesthesia
* Reduce risk of injury to anaesthetised patient

== Complications ==

* Peripheral nerve injuries
** Likely multifactorial, and can occur despite optimal positioning, but we should be active in preventing them
*** Pre-op
**** Identify at-risk patients
**** Correct positioning
**** Attention to body alignment
**** Padding/gel pads over bony prominences
**** Arm abduction <90 degrees
*** Intra-op
**** Reduce tourniquet duration
**** Minimise retractors
**** Avoid hypotension/hypothermia
** Risk factors
*** Obese or cachectic patients
*** Diabetics
*** Smokers
*** Surgery lasting >4 hours
** Stretch, compression, generalised ischaemia, metabolic derangement and surgical section
** Ulnar neuropathy - most common, but might not be related to positioning. Seems to occur without apparent cause in some patients.
** Brachial plexus - most common in cardiothoracic procedures requiring median sternotomies. Avoid excessive neck rotation in the supine patient.
** Lower limb - most common is peroneal nerve in lithotomy, especially with long surgery and thin patients. Also obturator, lateral femoral cutaneous, and sciatic.
** Classification
*** Seddon's classification
*** Neuropraxia (Sunderland 1) - damaged myelin with intact axon
*** Axonotmesis (Sunderland 2-4) - axonal disruption, but with intact endoneurium and other supportive connecting tissue
*** Neurotmesis (Sunderland 5) - nerve is completely severed
** Management
*** Assess with history and examination, and early neurology involvement
*** EMG and NCS can be done, but should be done after two weeks, to allow the process of demyelination to complete and an accurate picture of injury to be gained
** Prognosis
*** Mostly reach full recovery with 6-12 weeks

== Supine ==

* Physiological changes:
** Lung volume reduced
** Higher cardiac output due to increased venous return from legs
** Central redistribution of blood - beware in CCF
** Regurgitation
* Setup:
** Arms strapped out on boards or wrapped at sides
** Protect calcaneus: pillow under knees or gel pads behind ankles
* Vulnerable:
** Occiput, scapulae, olecranon, thoracic vertebrae, sacrum, coccyx, and calcaneum
* Injuries:
** Ulnar nerve - can be compressed at olecranon
** Radial nerve - can be compressed between edge of table and humerus, especially if arm is abducted beyond 90 degrees
** Brachial plexus - stretch, especially with abduction >90 degrees


== Lithotomy/Lloyd Davies ==

* Lloyd-Davies - lesser degree of hip and knee flexion, with some Trendelenburg - allows longer operating than lithotomy
* Setup
** Move patient down so GT is level with the bottom table break (I think)
** Top of stirrup at ASIS
** Aim the back of the boot, toe and knee to opposing shoulder
** Top of the boot level with knee
** One or two-hourly leg checks - correct leg alignment with no internal rotation, no pressure on legs, SCDS are working
** Ideally, maximum of four hours in this position
* Physiological changes:
** Similar to supine
* Injuries:
** Lower limb nerve injuries
*** Hip flexion stretches sciatic and obturator nerves, and compresses femoral nerve under inguinal ligament
*** Common peroneal nerve - compressed against fibular head
*** Saphenous nerve can be injured at medial tibial condyle


== Trendelenburg (head down) ==

* Physiological changes:
** Abdominal viscera can severely impair diaphragm movement
** Increased CVP
** Increased intracranial pressure
** Passive regurgitation increased

== Reverse Trendelenburg ==

* Physiological changes:
** Venous pooling - hypotension
* Injuries
** Venous air embolism

== Lateral ==

* Dependent lung is relatively underventilated and overperfused whereas the non-dependent lung is overventilated and underperfused
* Setup
** Lower leg flexed and upper leg straight
** Protect common peroneal and saphenous nerves by placing padding between the legs
** Both arms slightly flexed
* Injuries:
** Common peroneal nerve can be compressed between table and fibular head


== Prone ==

* Improved oxygenation
* Increased abdominal pressure, reducing venous return and cardiac output
* Can create space for diaphragmatic excursion using chest and pelvis supports
* Can be harder to drive breathing with reduced chest compliance
* Setup
** Anaesthetic induction on trolley, then log-roll onto table
** Can use Gillespie pillow or Doig frame and head supports
** Turn head to one side on a pillow, ensuring no pressure behind the ear
* Injuries:
** Eye injuries - corneal abrasions, ischaemic optic neuropathy, central retinal artery thrombosis
** Bruising of chest wall/hips, including breasts
** Lateral cutaneous nerve of the thigh - 90% resolve in 3/12
** Male genitalia can be twisted

[[Category:Oncology]]