The intraoperative period follows induction of anaesthesia and is terminated by discharge of the patient from the operating theatre into the recovery area. After leaving the confines of the anaesthetic room the first task is the safe positioning of the patient for surgery and the re-establishment of monitoring and the anaesthesia delivery system as soon as possible.

Positioning the surgical patient

Manipulation of a patient into the desired position for surgery carries its own problems. The main hazards are related to the effects of pressure and the physiological changes associated with a change in posture.

The anaesthetised patient is at risk of developing pressure sores in those areas where perfusion may be compromised. Likely sites are the occiput, the sacrum and the heel, all of which must be padded. External pneumatic compression devices applied to the lower limbs both confer a degree of protection from pressure effects and also improve circulation, which helps to prevent deep vein thrombosis. No patient should ever be allowed to lie with the legs crossed, and where possible an evacuable mattress should be used. Compartment syndrome, usually related to trauma or arterial surgery, and for which immediate fasciotomy is essential to save life or limb, can be a rare complication of prolonged lower limb compression in the lithotomy position.

The physiological effects which result from positioning are posture-related.