Pressure monitoring devices may undetect epidural space: a report on the use of Compuflo® system for epidural injection.

Lumbar epidural infiltration (EI) is a feasible procedure performed in pain therapy. Even though epidural analgesia is widely applied, it remains a blind technique, based on the operator's hand sensations, and it is associated with significant failure rate and several potential complications. Compuflo® (Compuflo, Milestone Scientific, Livingston, NJ) is a computerized injection pump which precisely detects the real time pressure at the tip of a Tuohy needle when placed in human tissues, thanks to a continuous fluid path. In our institution, we usually perform EI for chronic back pain guided by the Compuflo device, especially for expected difficult procedures. However, we report 6 false negative cases on a total number of 60 procedures in which the Compuflo system didn't meet the criteria of epidural space entry, even though the epidural space was actually reached. A mild pressure decrease (less than 50%) which lasted for more than 5 s was reported on the monitor, and the acoustic signal changed in a little bit lower sound, without a clear indication on stopping or not the needle advancement. This unspecific drop in monitored pressure gives false negatives using the Compuflo® system and may lead to excessive advancing of the needle. In conclusion, we consider the epidural pressure monitoring device Compuflo as a tool which may be able to ease the correct positioning of an epidural needle. The percentage of 10% false negative identifications of the epidural space in our case series however suggests more investigations on adequate or specific settings for this epidural system. In the meantime, in chronic pain patients, this anesthetic technique should only be used by experienced hands.