Comparison of the analgesic potency of xenon and nitrous oxide in humans evaluated by experimental pain

Abstract

We have compared the analgesic potency of MAC-equivalent concentrations of xenon (10, 20, 30 and 40%) and nitrous oxide (15, 30, 45 and 60%) in humans using a multimodal experimental pain testing and assessment technique. We tested 12 healthy volunteers in a randomized, single-blind, crossover study. The following experimental pain tests were used: nociceptive reflex to repeated stimuli; pain tolerance to maximal effort tourniquet ischaemia; electrical stimulation; mechanical pressure; and cold. Reaction time was also measured. Xenon and nitrous oxide produced analgesia to ischaemic, electrical and mechanical stimulation, but not to cold pain. There was no difference in MAC-equivalent concentrations of xenon and nitrous oxide. Both increased reaction time in a similar manner. Xenon and nitrous oxide evoked nausea and vomiting in a large number of volunteers.

Xenônio: farmacologia e uso clínico

“…Estudo mostra que ao administrar-se 1,3 CAM de anestésico geral inalatório, considerando que os valores de CAM do xenônio, do óxido nitroso e do sevoflurano são aditivos (1,3 CAM de sevoflurano versus 0,7 CAM de xenônio + 0,6 CAM de sevoflurano versus 1 CAM de xenônio + 0,3 CAM de sevoflurano versus 0,7 CAM de óxido nitroso + 0,6 CAM de sevoflurano), verificou-se que a pressão arterial e a freqüência cardíaca, medidas antes da indução da anestesia assim como antes e um minuto após a incisão, apresentaram alterações significativas no grupo 1,3 CAM de sevoflurano, quando comparado com os outros três grupos, o que sugere que o xenônio e o óxido nitroso têm efeitos analgésicos 24 . Em estudo prospectivo, aleatório e encoberto, verificou-se potência analgésica 1,5 vezes maior do xenônio quando comparado com o óxido nitroso 25 . Outros estudos têm confirmado a maior potência analgésica do xenônio 26,27 .…”

Is there a future for xenon anesthesia?

“…However, this is probably unrealistic because xenon often causes nausea and vomiting. 9,10 Recently, investigators have started to recognize another very appealing characteristic of xenon, i.e., its lack of cardiac depression. The study of Nakayama et al in this issue of the Journal 1 is important because it convincingly supports this.…”

“…The results are consistent with xenon's lack of action on some important cardiac ion channels, 11,12 and also with its lack of hemodynamic depression in healthy humans, 13 in patients with ischemic heart disease, 14 and in dogs with normal hearts and with cardiomyopathy. 15 Furthermore, xenon produces analgesia 10,16 and thereby suppresses hemodynamic and catecholamine responses to surgical stimulation, 17,18 further contributing to hemodynamic stability. In addition, unlike other analgesics, xenon is a potent hypnotic.…”

“…Ce qui n'est sans doute pas réaliste, puisqu'il cause souvent des nausées et des vomissements. 9,10 Récemment, des chercheurs ont commencé à entrevoir une autre caractéristique vraiment intéres-sante du xénon, il n'entraîne pas de dépression cardiaque. De ce point de vue, l'étude de Nakayama et coll.…”

“…Les résultats cadrent avec l'absence d'action du xénon sur d'importants canaux ioniques cardiaques, 11,12 et aussi avec l'absence de dépression hémodynamique chez des sujets en bonne santé 13 ou qui présentent une cardiopathie ischémique 14 et chez des chiens dont le coeur est normal ou qui sont atteints de cardiomyopathie. 15 De plus, le xénon produit de l'analgésie 10,16 et, donc, supprime les réponses hémo-dynamiques et de la catécholamine à la stimulation chirurgicale, 17,18 contribuant davantage à la stabilité hémodynamique. De plus, contrairement à d'autres analgésiques, le xénon est un puissant hypnotique.…”