Positioning

Principles

1. Provide optimal exposure
- begin after induction of anaesthesia when most relaxed.

2. Prevent complications
- know the patients medical problems / arthropathies etc.
- proper electrical insulation
- pad all pressure points adequately.
- do not stretch or compress nerves - esp brachial plexus, ulnar, com peroneal.

3. Ensure optimal ergonomics
- elbow at 90o for incision, without wrist bent upward.

Positions & Complications

Supine
- Pressure sores, focal baldness
- Ulner nerve compression from inner aspect elbow vs table edge.

Trendelenburg
(Head-down tilt, eg for moving upper abdo viscera cephalad).
- Cerebral oedema (CVP)
- Bronchial relocation of ETT
- Atelectasis due to lung base compression
- Positional pulmonary oedema (greater blood volume in thorax)
- Hypovolaemia masking.

Lithotomy
Note: take legs up and down together, helps avoid stretch injuries to muscles / nerves.
- Venous stasis by compression against equipment
- Nerve ischaemia (obturator, saphenous, common peroneal)
- Knee / Hip damage due to exteme flexion / abduction
- Rarely compartment syndromes

Lat Decubitus
- Dependent lung at risk: atelectasis.
- Shoulder limitation
- Brachial plexus tension

Prone
- Ventilatory compromise: place pillows longitudinally under both sides of chest to allos diaphragmatic movement
- Loss of airway / vascular access while prone is dangerous.
- Ocular oedema
- Compression of eye, ear, facial nerves, unseen.
- Resp compromise in the obese is common
- Neuro injury: brachial / sciatic
- Vascular disturbance: altered venous return
- Compression injury to genitalia.

References
Deitch EA.  Tools of the trade.