Correct positioning of the surgical patient facilitates comfortable surgical access to the operative site, reduces bleeding (mostly by avoiding venous congestion), prevents pressure damage to skin, nerves, joints and muscles, minimises adverse cardiac and respiratory problems, and provides good access for the anaesthetist.
Flexion of the cervical spine and extension of the atlanto-occipital joint gets you the classical 'sniffing' position. On a normal bed, the patients chest wall sinks into the mattress, flexing the neck to some degree, even if no pillow is used. A single standard pillow will usually prove too thin when used on a much firmer operating table. Grogono's GasNet tip was to use more than one pillow. Michael Bookallil uses one pillow folded in half. I use a foam rest over a standard pillow.
Usually prone, with risk of eye, ulnar nerve, neck and brachial plexus injury. A GasNet tip suggested that extubation while prone has advantages and another emphasises the importance of ETT fixation when prone. Always securely close the eyelids to avoid corneal abrasions, and avoid pressure on the globe and hypotension. Pads over the eyes will only increase pressure on the eye if any exists.
The WFSA summary of anatomic and physiological changes in pregnancy, with an update, on their obstetric udpate pages. Comments on positioning for anaesthesia such as lateral tilt are made in several articles.
Make sure the table is able to take the weight. Get lots of assistance with movement.
Take care not to compress the calves if the patient is steeply head down (pressure in the muscle compartment can exceed perfusion pressure). Reduced lung volume leading to atelectasis is common. See Nick Robson's notes on gynaecologic surgery.
This GasNet abstract discusses use of PEEP to reduce venous air embolism in the sitting position. Hypotension due to venous pooling in dependent limbs and bibliography neuropraxias need to be carefully managed. Intra-arterial direct blood pressure monitoring is essential. The arterial transducer should be zeroed to air at the tap on the transducer, and then attached to the table at mid-head level. Table anglulation or rotation may raise or lower the transducer with respect to the centre of the head, and may require re-positioning of the transducer. SNACC Web has an extensive bibliography.
Cerebral ischaemia due to inadequate cerebral perfusion pressure is a significant hazard.
If a non-invasive cuff at mid-arm level is used, arterial pressure at the head will be significantly less, and the arterial blood pressure should be maintained with vasopressor infusions at say 20mmHg to 30mmHg above 'normal' - where 'normal' means the blood pressure number that you'd ordinarily deem appropriate for that particular patient if they would be supine. The actual offset required can be calculated more precisely as three-quarters of the vertical distance from mid-arm to mid-head measured in cm. For example, if mid-head level is 40cm above mid-arm level, then arterial blood pressure should be maintained 30mmHg above 'normal'.
There is a strong case for direct intra-arterial blood pressure monitoring with the transducer set at mid-head level in these cases.