Posture and isobaric subarachnoid anaesthesia. The influence on spread of spinal anaesthesia with 'isobaric' 0.5% bupivacaine plain.

Twenty-five patients had subarachnoid anaesthesia induced with 3.0 ml 0.5% bupivacaine plain. A study of the spread of analgesia demonstrated a small (2-3 segments) but significant (p less than 0.001) rise in analgesic levels when the patients were turned from a lateral to the supine position, and from the supine to prone positions.