Prediction of successful epidural catheter placement by a 'cold test'.

We tested the hypothesis that the patients' feeling of cold sensation down the back during epidural drug administration through the epidural catheter was a reliable predictor of correct epidural catheter placement. In a prospective study of 80 patients, an epidural catheter was placed in the lumbar epidural space. During epidural drug injection, patients were asked to report feeling of the cold sensation in their back by pressing a bell. After 15 minutes, the patients were assessed for cold sensation in the thoracic to sacral dermatomes bilaterally and the dermatomal block recorded. Of 80 patients, three had inadvertent dural puncture. Seventy-two of 77 patients reported feeling cold sensation in their back during local anaesthetic injection, and all had successful epidural blockade. Of the five patients who did not report any cold sensation, three had failed epidural block and two successful epidural block. There were no false positive results. Of three patients who had inadvertent dural puncture and had normal saline 5 ml injected through the Tuohy needle, none reported cold sensation. The perception of cold sensation in the back during epidural administration of a test dose and/or subsequent full dose of local anaesthetic is useful in predicting successful epidural catheter placement.