Der Schmerz
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The gate-control theory of pain, as originally proposed by Melzack and Wall [8], is nothing but a hypothesis concerning the spinal processing of non-noxious and noxious afferent information. Its basic tenant is that the P cells (projecting neurons) convey noxious information to supraspinal pain systems only after a critical threshold of excitation has been passed, and that access to the P cells is controlled by the SG cells (cells of the substantia gelatinosa Rolandi) or, in other words, the SG cells act as the gate. Since the primary afferent fibres have monosynaptic connections with the P cells the gate can only operate-and this is the critical point of the whole hypothesis-via presynaptic inhibition exerted by axoaxonic contacts on these afferents (Fig. 1). ⋯ As a consequence, Melzack and Wall [9] have now modified their hypothesis considerably. Its present formulation is not much more than a very general statement to the effect that all kinds of afferent input, including noxious input, is under the modulating influence of various mechanisms operating both at the spinal level and from supraspinal (descending) structures. No implications for therapy can be derived directly from such an undefined, in many ways trivial, assumption.
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Abdominal pain is an important and the most frequent symptom of acute gastrointestinal diseases; crucial hints on the diagnosis can be gleaned from its location and from associated symptoms and signs. As symptomatic therapy the treatment of pain plays a major role in acute gastrointestinal diseases, e.g. the acute abdomen, acute pancreatitis, biliary colic, peptic ulcer disease and diverticulitis. ⋯ Acute severe pain arising from biliary colic and acute pancreatitis should be treated with an opioid that does not influence the sphincter of Oddi or the pressure in the common bile duct, e.g. buprenorphine, nalbuphine or tramadol. An effective but not widely known therapy for colic pain is parenteral administration of a nonsteroidal anti-inflammatory drug, e.g. indomethacin or diclofenac.
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The spectrum of perioperative pain treatment is discussed in the present review. The analgesic efficacy of various drugs and the dosage methods of administration and side effects reported for them in such reference works as the practical guide on the management of acute pain recently published by the International Association for the Study of Pain (IASP) are described. Effective postoperative analgesia can diminish stress reactions following surgery. ⋯ Investigations performed by the author of this review have shown that epidural infusion of highly diluted mixtures of bupivacaine/fentanyl is highly effective in the analgesic treatment of patients undergoing prostatectomy, providing excellent physical mobilization. The potential dangers of drug combinations and contraindications are also discussed. The concept of using balanced analgesia to induce additive or synergistic effects following the administration of analgesic drugs requires further clinical studies.