[Comparative assays of various methods of medullary analgesia. Use of opiates (author's transl)]

Various methods of medullary analgesia are suggested using either the peridural or the subarachnoid technique. Spinal analgesia is much in demand in anaesthesia, in post-operative care or for the alleviation of chronic, mainly neoplastic, pain. Anaesthesia is obtained with a local anaesthetic acting at the level of the membrane. The adjunction of an opiate, acting at the level of the medullary morphinic receptors, enhances local anaesthesia both in depth and duration. This association allows lesser concentrations and volumes of drugs to be used. Various opiates have been tested: their effect depends on the type of administration (I. V., intra-medullary). In the case of intra-medullary injection these is also a difference in the action of the drug according to the technique used (peridural or subarachnoid). The meningeal barrier plays a major function, preventing the diffusion and fixation on the morphinic receptors of some drugs administered peridurally. The action of these drugs, when injected by the subarachnoid technique, is enhanced; this is the case of morphine-base. Others according to their physicochemical characteristics cross easily the dura mater and are very active when injected peridurally. Opiates are also used for the alleviation of chronic pain and are quite as effective as local anaesthetics, steroids or hypertonic saline by peridural injection. The main interest of these techniques lies in the easy reversibility of the analgesia.