Der Schmerz
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Herpes zoster neuralgia and post-zoster neuralgia (PZN) are common disabling pain syndromes. While pain from acute herpes zoster is self-limited in most cases, as pain may disappear without treatment, post-zoster neuralgia is difficult to manage. Pathological findings in acute herpes zoster include infiltration of ganglia, demyelinization and loss of axons; yet the pathogenesis of pain remains largely unknown. ⋯ The same is true for specific zoster hyperimmunoglobulins and non-specific immunoglobulins; however, there are no definite results. In the future, controlled, double-blind studies on the effect of therapeutic measures in preventing postzosteric neuralgia need to be conducted. So far, the positive effect of sympathetic blocks in preventing the late pain complications of herpes zoster can only be suggested and recommended based on subjective experience.
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Pain prophylaxis is an everyday experience in clinical anaesthesia. There is now considerable experimental evidence that short-term nociceptive stimuli evoke a long-lasting excitatory state of the central nervous system. This excitatory state can be largely prevented by relatively small doses of anaesthetics (local anaesthetics, opioids) given prelesionally. ⋯ Pre-emptive analgesia is advantageous in out-patient surgery as well as for routine clinical anaesthesia, and has proved effective in the prevention of phantom limb pain. Many questions on the nature and clinial application of pre-emptive analgesia are still unanswered. However, its ease of performance and the clear clinical advantages of pain prophylaxis mean that it should have a place in the everyday practice of anaesthesia.
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Systemic analgesia is used in obstetrics to alleviate the pain in labour and to prevent adverse effects on the fetus due to maternal pain and stress and subsequent complications such as prolonged labour. To supplement psychological support tranquillizers such as diazepam are useful in allaying anxiety and increasing patients' acceptance of labour. Possible side-effects include neonatal hypothermia and poor muscle tone of the newborn when large doses are given. ⋯ Thus, in many cases adequate pain relief afforded to parturients by systemic analgesia may result in altered adaptive functions of the newborn. This makes it reasonable to consider alternative methods, including epidural anaesthesia, which is highly effective and fairly unproblematic. Drug administration in the management of labour pain can be recommended if only small doses are needed and in parturients who refuse regional anaesthesia or for whom it is contraindicated or not available.
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Numerous experimental studies have shown that systemic or regional administration of analgesics prior to a nociceptive stimulus results in a significant reduction of analgesic requirements compared with the administration of the same analgesic dose given after the nociceptive stimulus. This phenomenon is called "preemptive analgesia". Recently several clinical studies have been conducted to determine whether "preemptive analgesia" also occurs in humans. ⋯ Most studies have failed to show a significant reduction in postoperative analgesic requirements with preemptive analgesia. Even in studies with positive results the reduction in analgesic requirements was limited and without clinical relevance. Further studies should focus on the questions which analgesics and which administration routes might provide clinically significant "preemptive analgesia" and how long analgesia should be prolonged into the postoperative period.