Prophylaxis Against Postoperative Pain After Orthopedic Surgery: Does it Help to Give Fentanyl Before Start of Remifentanil/Propofol Based Anesthesia?
Prophylaxis Against Postoperative Pain After Orthopedic Surgery: Does it Help to Give Fentanyl Before Start of Remifentanil/Propofol Based Anesthesia?
The aim of this trial is to examine the possibility that fentanyl 1,5 µgr/kg given intravenously (i.v.) before the start of remifentanil infusion for anesthesia gives less development of tolerance/hyperalgesia postoperative than fentanyl given at the end of surgery (the traditional method).
Postoperative pain can contribute to reduction in the patient's well-being and, if it is pronounced, delayed rehabilitation and an increase in the total cost for nursing and treatment.
Experimental studies has shown that infusion of remifentanil over some period of time, can result in acute opioid tolerance and hyperalgesia (1-2).
One clinical trial has shown that intraoperative infusion of remifentanil gives acute opioid tolerance with subsequent increased postoperative pain and increased opioid consume postoperative (3).
The development of opioid tolerance probably has several mechanisms. One topical mechanism is opioid induced influence of N-methyl-d-aspartate (NMDA)-receptor and its intracellular second-messenger-systems. This results in central sensitization to pain stimulus in the dorsal horn and the brain (4-5), with following development of hyperalgesia.
Several strategies can be successful to reduce or prevent opioid induced hyperalgesia, for example NMDA-receptor antagonists, alfa-2 agonists, opioid rotation or combination of opioids with different receptor selectivity (6-8).
The theoretical background for pre-treating the opioid receptor with an other opioid (fentanyl) that gives less tendency to hyperalgesia than remifentanil, is that it can reduce the development of tolerance and hyperalgesia of remifentanil.
The aim of this trial is to examine the possibility that i.v. administration of fentanyl 1,5 µgr/kg before start of remifentanil infusion for anesthesia gives less development of tolerance/hyperalgesia postoperative than fentanyl given in the end of surgery (the traditional method).
This is to be measured by less pain postoperative (VAS, visual analog scale, and a five point verbal rating scale) and less fentanyl consumed (measured by using PCA).
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