Sensory blockade of S3 dermatome prevents pain during bladder catheterization

Purpose: We often encounter patients who do not complain of pain on undergo ing invasive urogenital or rectal procedures, despite incomplete epidural b lockade of sacral cutaneous sensation. To clarify whether or not urethral p ain is blocked faster than sacral cutaneous sensation during lumbar epidura l anesthesia, we investigated the correlation between occurrence of urethra l pain and loss of cold sensation in the Sl-3 dermatomes, Methods: In 46 gynecological patients, Group A (n = 22) received 15 mi of 2 % mepivacaine via an epidural catheter inserted cephaladly. Group B (n=24) received 5 mi of 2% mepivacaine directly in the epidural needle directed ca udally and 10 mi of 2% mepivacaine via the epidural catheter inserted cepha ladly. A Foley catheter was inserted into the urethra 30 min after the inje ction. Results: Urethral pain, which was defined as a pained facial expression and /or complaint of pain, was observed in seven patients in Group A, and none in Group B. The caudad level of epidural block ade was significantly lower in patients without urethral pain (S3, median) than with urethral pain (L4) (P <0.05). In 39 patients without urethral pain, 19 (49%) experienced loss of cold sensation in the S I dermatome, 27 (69%) in the 52 and 38 (97%) in the S3 25 min after the injection. Conclusion: Blockade of urethral visceral pain often occurs before complete sacral somatosensory blockade, and 53 somatosensory blockade is the import ant sacral level as an indicator of successful urethral sensory blockade.