Reduction of isoflurane MAC by fentanyl or remifentanil in rats

The Effects of the Toll-Like Receptor 4 Antagonist, Ibudilast, on Sevoflurane’s Minimum Alveolar Concentration and the Delayed Remifentanil-Induced Increase in the Minimum Alveolar Concentration in Rats

“…Analgesic treatment with opioids has a major effect on anesthetic requirements by reducing them. 23,24 This reduction can be measured by determining the associated change in the MAC and has clinical relevance. However, the observed changes in the MAC cannot be considered a measure of analgesia but just the interaction of these drugs with inhaled anesthetics.…”

Amitriptyline, minocycline and maropitant reduce the sevoflurane minimum alveolar concentration and potentiate remifentanil but do not prevent acute opioid tolerance and hyperalgesia in the rat

“…Fresh gas flow to the T piece was adjusted to 1 l min À1 of oxygen (100%), and the sevoflurane concentration was adjusted to 1.5 Â MAC (3.5 to 4%vol.). The rats were kept under spontaneous ventilation during the entire experiment because remifentanil at the doses administered did not produce significant hypercapnia, 15 which might have modified the MAC. However, when signs of hypoventilation occurred, spontaneous ventilation was stimulated by softly touching the rat's thorax.…”

Remifentanil and Other Opioids

“…This is probably related to the very rapid onset of effect the drug (Nieuwenhuijs et al 2003;Habib et al 2002;Dimitriou et al 2006;Lecomte et al 2006;Bilgin et al 2006;Chanavaz et al 2005;Locala et al 2005;Pleym et al 2004;Ouattara et al 2004;Godet et al 2004;Heijmans et al 2004;Joo et al 2004;Unlugenc et al 2003;Jellish et al 2003;Manyam et al 2006;Albertin et al 2006;Mustola et al 2005;Albertin et al 2004;Bouillon et al 2004;Kern et al 2004;Drover et al 2004;Mertens et al 2003;Milne et al 2003;Fechner et al 2003;Criado and Gomez e Segura 2003;Bothtner et al 2002).…”

“…Without opioid, the hypnotic concentration required for loss of consciousness is lower than the one to prevent response to noxious stimulations (around 1/3 MAC). It is moderately reduced by low-dose opioids: for example, propofol concentration for loss of consciousness is reduced by 25% in the presence of remifentanil 6 ng/ml (Nieuwenhuijs et al 2003;Manyam et al 2006;Albertin et al 2006;Mustola et al 2005;Albertin et al 2004;Bouillon et al 2004;Kern et al 2004;Drover et al 2004;Mertens et al 2003;Milne et al 2003;Fechner et al 2003;Criado and Gomez e Segura 2003;Bothtner et al 2002). Consequently, at high opioid concentrations the hypnotic needs for loss of consciousness may be higher than those to prevent response to noxious stimuli, and a patient might show no response to surgery and be completely awake, especially if he cannot move to signal his awareness because of neuromuscular blockade.…”