1. The knee-chest position offers the surgeon excellent conditions for operations on lumbar intervertebral discs.

2. Hypotension on resumption of the prone or supine position is common: it is influenced by the anaesthetic technique, the physical state of the patient, the operation time and the extent of surgical bleeding.

3. The hypotension is thought to be due to poor perfusion of the lower limbs while the patient is in the knee-chest position.