Local anesthetic effect of intrathecal normal saline.

The effects of intrathecally administered normal saline have been studied in patients undergoing graduated spinal anesthesia. The injection of 5 or 10 ml volumes resulted in segmental hypesthesia to pin-scratch and cold stimuli extending from the lower thoracic to the sacral dermatomes. There was also partial sympathetic block evidenced by a diminished psychogalvanic skin reflex. The sites and possible mechanisms of action of saline are discussed; its use as placebo in graduated spinal anesthesia is questioned. It is concluded that normal saline acts as a weak local anesthetic when injected intrathecally.