Abstract
The aim of the present study was to examine whether changes in temperature alter the effects of halothane and isoflurane on isolated left atria. Concentrationresponse curves for inotropic effects at different temperatures (30° C, 37° C, 40° C) on electrically stimulated left atria of the rat were obtained. The change of temperature modified the maximal negative inotropic response to halothane. The maximal decrease induced by halothane was 12 ± 2.3 per cent at 37° C and 18 ± 2.5 per cent at 30° C. When the temperature increased up to 40° C the maximal decrease of atrial inotropism was 46 ± 2.1 per cent — significantly higher than obtained at 37° C. However, the maximal effect obtained by isoflurane was not significantly affected by temperature (30° C = 7 ± 1.6 per cent; 37° C = 8 ± 1.8 per cent; 40° C = 2 ± 0.8 per cent). Furthermore the potency of halothane (expressed as the concentration which produced 50 per cent inhibition — IC 50 per cent), decreased significantly at 30° C (IC 50 = 1.34 ± 0.18) and increased at 40° C (IC 50 = 0.44 ± 0.17) when compared with its potency at 37° C (IC 50 = 0.96 ± 0.08). On the other hand changes in temperature did not significantly modify the IC 50 for isoflurane obtained at 37° C. These data demonstrated that the maximal effects of halothane but not those of isoflurane on the left atria preparation were modified by change in temperature; the potency of halothane but not of isoflurane increased significantly with increases in temperature of the organ bath.
Résumé
Le but de la présente étude était d’examiner si les changements de la température altèrent les effets de l’halothane et de l’isoflurane sur l’oreillette gauche isolée. Les courbes de concentration- réponse pour les effets inotropes à différentes températures (30° C, 37° C, 40° C) sur l’oreillette gauche de rat stimulé électriquement furent obtenues. Le changement de température a modifie la réponse inotropique négative maximale à l’halothane. La diminution maximale induite par l’halothane était de 12 ± 2,3 pour cent à 37° C et 18 ± 2,5 pour cent à 30° C. Quand la température augmenta jusqu’à 40° C la diminution maximale de l’inotropisme de l’oreillette était de 46 ± 2,1 pour cent significativement supérieure que celui obtenu à 37° C. Cependant l’ effet maximal obtenu par l’isoflurane n’était pas significativement affecté par la température (30° C = 7 ± 1,6 pour cent; 37° C ± 1,8 pour cent; 40° C = 2 ± 0,8 pour cent). De plus la puissance de l’halothane (exprimé comme étant la concentration qui produit 50 pour cent d’inhibition — IC 50 pour cent), diminua significativement à 30° C (IC 50 = 1,34 ± 0,18) et augmenta à 40° C (IC 50 = 0,44 ± 0,17) lorsque comparée à sa puissance à 37° C (IC 50 = 0,96 ± 0,08). D’autre part les changements de temperature n’ont pas modifié significativement le IC 50 pour l’isoflurane obtenu à 37° C. Ces donnés démontrent que les effets de l’halothane et non ceux de l’isoflurane sur la préparation d’oreillette étaient modifiés par les changements de température; la puissance de l’halothane et non celle de l’isoflurane augmenta significativement avec l’augmentation de la température.
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This work was supported by Grant PB 85-0323 from CAYCIT (Comisión Asesora de Investigación y Ciencia), Spain.
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Laorden, M.L., Miralles, F.S., Cárceles, M.D. et al. Temperature-dependent effects of halothane and isoflurane on the isolated left atrium. Can J Anaesth 37, 482–485 (1990). https://doi.org/10.1007/BF03005633
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DOI: https://doi.org/10.1007/BF03005633