Cold Sensitivity Test Cannot Eliminate Epidural Catheter Misplacement-Minimal Perception Current Measurement as a Novel Technology to Quantitatively Evaluate an Epidural Blockade

Interpleural misplacement is a rare complication of epidural catheter insertion. We report a case in which the combination of catheter placement in an awake patient, loss of resistance technique, negative aspiration as well as cold sensitivity test failed to identify epidural catheter misplacement. The possible reasons for the failure to diagnose the misplacement of the epidural catheter are discussed. A novel technique to quantitatively evaluate an epidural blockade which may aid in early diagnosis of epidural catheter misplacement was introduced. While evaluating an epidural blockade by cold sensitivity test, the decrease in cold sensitivity may reflect the effect of blockade or preexisting sensitivity variation, as in the case. A more reliable method was mandatory to evaluate epidural blockade and may aid in confirmation of epidural catheter placement. At the 2007 annual meeting of the American Society of Anesthesiologists, Yamakage et al presented their study on skin sensitivity and aging by measuring minimal perception current (MPC) with Painvision . While there was no studies regarding the application of MPC to quantitatively evaluate epidural neural blockade been published, we suggest that by comparing the MPC measured by Painvision before and after epidural blockade, the intensiveness and the coverageof se ns or y blockade could be quantitatively measured. Unexplained weak or ineffective block which may resulted from a misplaced epidural catheter could be identified before a failed block does happen.