Intrathecal normal saline without preservative does not have a local anesthetic effect.

The effects of intrathecally administered normal saline (preservative-free) were studied in patients undergoing differential spinal block anesthesia for evaluation of chronic pain below the waist. The injection of 5 ml saline did not significantly change the sensitivity to pinprick measured in the lower back and both lower extremities. Temperature measurement in both the lower extremities and psychogalvanic skin reflex did not show evidence of sympathetic block; the psychogalvanic skin reflex was abandoned because of inconsistent results. These findings refute the earlier conclusion of Urban and McKain who found that normal saline acts as a weak local anesthetic when injected intrathecally. We recommend use of normal saline (preservative-free) in 5 ml doses as a placebo for differential spinal block anesthesia.