It is well known that epidural infusion of injectate in association with a C6 paratracheal stellate ganglion block (SGB) leads to negative and/or positive side effects for the patient. However, this associated infusion has not been demonstrated experimentally using cadavers. We found that, in postmortem-fixed cadavers, epidural infusion occurred much more frequently in cases of bilateral SGB than in unilateral SGB. The frequency in the bilateral case (36.1%) was far beyond the two times of the unilateral one (7.7%). The injectate (latex resin, 10 ml for one side) was delivered from the prevertebral deposit into the epidural space by way of the spaces around the C8 and/or T1 spinal nerve roots. Thus, the latex spread around and/or in the brachial plexus usually combined with the epidural infusion. We speculate that the amount of injectate spreading into the prevertebral space in the bilateral injection (total 20 ml) was beyond the hypothetical tentative capacity and that the excess amount made the addional, perineural spread. The present results suggests that, in clinical cases, the frequency of epidural infusion depends on the amount of injectate even in the routine unilateral SGB. However, the cadaveric study did not indicate how much amount is the excess for the living patient
