Articles: opioid-analgesics.
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Cahiers d'anesthésiologie · Jan 1991
Review[Mechanism of action and clinical use of opioids administered by the peripheral perineural route].
Experimental studies have shown that opioids could produce two types of effect on neuronal excitability. The first one, aspecific, is a local anesthetic action on the nerve fiber with a diminution of sodium and potassium conductance. ⋯ Clinical studies have proved that opioid injection in peripheral nervous trunks and specially in the brachial plexus produce a prolonged analgesia status in the post operative period but also and mostly in the chronic pain. The more liposoluble opioids like fentanyl and buprenorphine are the more effective.
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Cahiers d'anesthésiologie · Jan 1991
Review[Opioids by the perimedullary route: mechanisms of opioid analgesia].
The identification of multiple opioid receptors and opioid peptides in the 1970 was the starting point of an increasing knowledge on opioid physiology and pharmacology. The mechanisms of action of spinally supraspinal levels. At the spinal level, opioids act by a modulation of specific supraspinal effect is the consequence of the migration of opioids, other in the bloodstream or in the cerebrospinal fluid, towards the encephalon. ⋯ At the receptor level, opioid agonists act, hypothetically via the system of adenylcylase, more certainly via a modulation of membrane tonic channels. Thus, opioids modify sodium, calcium and potassium currents, and modify the successives phases of the membrane action potential. The result is an hyperpolarization which is responsible of an inhibition of the release of various neurotransmitters such as P substance.
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Anaesthesiol Reanim · Jan 1991
ReviewPain control with intrathecally and peridurally administered opioids and other drugs.
Sharp pain is conducted rapidly by myelinated delta A fibers and diffused pain slowly by nonmyelinated C fibers to pseudobipolar neurons in the posterior ganglion and from there to neurons located in the posterolateral horn of the spinal cord. From here on nociferous impulses are transmitted by excitatory peptides (e.g. substance P) or amino acids (e.g. glutamate, aspartate) through interconnecting neurons of the pain pathways, primarily on the contralateral side, to the brain stem and from there to the sensory cortex, where they are appreciated and acted upon. There are specific inhibitory receptors located on axon terminals, near to the release sites of the excitatory amino acids and peptides. ⋯ Several different approaches are being investigated for the production of selective spinal analgesia without side effects. They include: a. the use of more lipophilic, long-lasting opioids (e.g. lofentanil) which would be almost completely absorbed by the spinal cord and therefore would not reach the medullary centers; b. the development of opioids with specific affinity to kappa- and for delta- and little or no affinity to mu-receptors, primarily responsible for side effects; and c. combining lower doses of opioid agonists with alpha 2-adrenergic agonists (e.g. clonidine) or with somatostatin. It is conceivable that in the not-too-distant future, it will be possible to achieve through these measures, selective spinal analgesia without side effects.
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Cahiers d'anesthésiologie · Jan 1991
Review[The use of opioids by the regional route in obstetrics].
Epidural and spinal administration of opioids in obstetrics can be used during labour and for cesarean section. Although these routes of administration are of limited use when opiates are employed as sole agents, the association with local anesthetics may improve the characteristics of analgesia. The administration of a local anesthetic-opiate mixture allows a reduction of the total amount of local anesthetics, thus reducing the incidence of maternal hypotension and the percentage of instrumental extraction. ⋯ Opioids may also be used for postoperative analgesia after cesarean section. Since they could be responsible for an opioid-related respiratory depression in the mother and the neonate, a strict supervision is absolutely necessary following this particular mode of administration of opiates. If human and technical means of supervision failed to bring into operation, it would be better not to use opioids by the spinal route in such a context.
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The postoperative care of patients usually is characterized by the fact that the individual need of pain killers is not sufficiently recognized. An opioid given only when asked for, results in an underdosage as the patient does not receive the analgesic in time, so that he suffers pain. As there is insufficient knowledge with regard to the pharmacology of opioids which can be used for postoperative pain therapy, physicians and nurses usually tend to give a lower dose in order to avoid any possible side-effects. ⋯ Piritramide has a fast onset of action, 2-5 minutes after intravenous injection and a peak action after 10 minutes. In comparison to pethidine it has no cardiovascular effects, in particular no myocardial depression or increased myocardial oxygen demand (MVO2). Last but not least, the cost-effectiveness is a financial factor of increasing importance to the institution that runs the hospital.