Sequence of return of neurological function and criteria for safe ambulation following subarachnoid block (spinal anaesthetic).

Twenty-three adult men were studied during and after subarachnoid block anaesthesia for elective surgery. Measurements were obtained of mean arterial pressure and pulse, both supine and after standing for five minutes, core body (tympanic) and peripheral skin (toe) temperatures and blood flow in the leg. Time of measurements included one hour after the injection of tetracaine and after regression of the block. Results obtained indicate that the sequence of return of neurological activity following tetracaine subarachnoid block is sympathetic nervous system activity, pinprick sensation, somatic motor function followed by proprioception in the feet. This progression provides the basis for recommended criteria which indicate when it is safe for patients who have been subarachnoid block anaesthesia to become ambulatory. These criteria include: (1) return of pinprick sensation in the peri-anal area (sacral 4--5); (2) plantar flexion of the foot (while supine) at pre-anaesthetic levels of strength; and (3) return of proprioception in the big toe, always provided that the patient is not hypovolaemic or sedated.