Articles: postoperative.
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Nociceptive stimuli are modulated at the dorsal horn of the spinal cord. This modulation is performed by various systems working independently complementarily, additively or supra-additively. Non-opioid analgesics relieve pain without a motor blockade. ⋯ Lysine acetylsalicylic acid (L-ASA) has been given intrathecally for the therapy of severe cancer pain and chronic back pain. In most patients good analgesia was observed up to 2 months after a single injection. If neurotoxity can be excluded, L-ASA may be an alternative in the therapy of cancer pain before neurodestructive therapy is done.
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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.
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Pain and pain-related sympathoadrenergic reactions (hypertension, tachycardia) accompanied by nausea, vomiting and shivering are the most common side effects of recovery from anaesthesia. The alpha(2)agonist clonidine acts as a sedative, anxiolytic, antihypertensive, antiemetic, antisialogogue and decreases the incidence of shivering. Thus, we studied the effects of intraoperatively administered clonidine on the recovery period and the postoperative analgesic requirements in patients undergoing maxillofacial surgery. ⋯ Opiates are frequently used as analgesics after maxillofacial surgery, even though their most common side effect-respiratory depression, nausea and vomiting-are particularly dangerous in these patients because of the obstruction of the upper respiratory tract. Self-titration of the opiate dosage on demand can decrease the incidence of serious side effects. Clonidine administered intraoperatively caused a profound reduction in analgesic requirements in this study. Additional opiate administration in the postoperative period was unnecessary in nearly all clonidine-treated patients. The attenuating effect on sympathoadrenergic reactions leads to lowering of the rate-pressure product and may be of advantage for patients suffering from arterial hypertension, angina pectoris or bronchial asthma. The slower emergence from anaesthesia following clonidine administration is probably caused by double-blind study properties preventing full consideration of the decreased isoflurane requirements after clonidine.
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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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Interpleural analgesia is a method of postoperative analgesia that was developed by Kvalheim and Reiestad in 1984. The main indication is postoperative pain after unilateral thoracic and upper abdominal surgery. Many authors report good analgesic effects and better postoperative lung function following cholecystectomy. ⋯ The local anaesthetic of choice is bupivacaine (in concentrations of 0.25-0.75%, injection volumes of 10-40 ml, with or without epinephrine, applied as bolus or infusion), but others, such as lidocaine or morphine, are also being tested. Risks involved in this method are pneumothorax when the catheter is placed blind and the systemic toxicity of the local anaesthetic. This review provides information on the mechanism of action, the technique, the clinical use to date and possible risks.