Articles: postoperative.
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Spinal clonidine interacts with pre- and postsynaptic alpha(2)-adrenoceptors on afferent neurons in the superficial dorsal horn of the spinal cord: it causes analgesia by inhibition of the synaptic and electrotonic neurotransmission of nociceptive impulses. Epidural doses higher than 4 microg/kg have an analgesic onset time of less than 30 min, reduce pain by more than 70 %; these effects last for 4-5 h. ⋯ The haemodynamic side effects mean close supervision is needed during the first hour after epidural application and limit the use of epidural clonidine to patients who are refractory to the analgesic effects of epidural opioid or local anaesthetics. In these patients excellent results can be achieved either with clonidine alone or with a combination of clonidine and an opioid or a local anaesthetic to exploit the additive or supra-additive interactions of these drugs.
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Journal of anesthesia · Mar 1996
Epidural anesthesia during upper abdominal surgery provides better postoperative analgesia.
Since repeated noxious stimuli may sensitize neuropathic pain receptors of the spinal cord, we tested the hypothesis that the appropriate blockade of surgical stimuli with epidural anesthesia during upper abdominal surgery would be beneficial for postoperative analgesia. Thirty-six adult patients undergoing either elective gastrectomy or open cholecystectomy were randomly allocated to receive either inhalational general anesthesia alone (group G) or epidural anesthesia along with light general anesthesia (group E) throughout the surgery. ⋯ While there was no significant difference in the bupivacaine dose, more patients undergoing gastrectomy in group G required supplemental analgesics than those in group E, and the VAS scores in group E demonstrated significantly better postoperative analgesia compared to group G after both types of surgery. Thus, an appropriate epidural blockade during upper abdominal surgery likely provides better postoperative pain relief.
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The effects of combined spinal administration of alpha(2)-adrenoceptor agonists, local anaesthetics, and opioids have been extensively studied. The motor and the sensory block of spinal and epidural anaesthesia is enhanced and prolonged by the combination of clonidine with the local anaesthetics lidocaine, tetracaine and bupivacaine. Because higher plasma levels of local anaesthetics were measured when clonidine was injected epidurally, the enhancement of the local anaesthetic's effect by clonidine is not due to slowed resorption, but rather to direct spinal and supraspinal effects of clonidine. ⋯ Despite the sedative properties of clonidine, there is no increased risk of respiratory depression when clonidine is given in combination with opioids. The inhibiting effect on the sympathetic nervous system activity regularly observed during spinal administration of clonidine supports the value of this therapy and will support its use in the future. Therefore, the combination of alpha(2)-adrenoceptor agonists with local anaesthetics or opioids is reasonable and may improve anaesthetic practice.