Pain threshold and subjectively perceived epidural sensory blockade with 0.5% bupivacaine

We investigated the relationship between patients' pain thresholds and the quality of the subjectively perceived epidural sensory blockade (SPESB). The pain thresholds of 50 patients were evaluated with a modification of the submaximum effort tourniquet technique. There was a significant correlation between pain threshold and the number of subjectively perceived anesthetic and analgesic segments, the likelihood of developing an extensive SPESB being greater in patients with higher pain thresholds. Forty-one percent of patients with pain scores of less than 10 mm on the visual analogue scale, but no patient with a pain score of 20 mm or more, developed anesthesia in ten or more spinal segments.