Continuos microinfusion intrathecal local anesthetics: real or perceived effectiveness?

In this review the knowledgements about the mechanisms underlying thelocal anesthetics action, the validity of their efficacy, the relationship among the anesthetic effect duration, the doses used, the administration pathways, particularly as concerns the continuousintrathecal infusion, and their sites of action are presented.It is evidenced that among the various sites described, the action at sinaptic level could explain results obtained with the very low doses that can be reached through systemic or spinal slow administration. Furthermore this kind of action could explain also the plurimetameric effect comparable to that of morphine knownto act at synaptic level, other than the potentiating action on the opioid effects intrathecally administered and the usual observation of a control of non incident pain and not of “incident pain”