Negative inotropy of halogenated anesthetics in ferret ventricular myocardium
P. R. Housmans Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905. The effects of the volatile anesthetics halothane, enflurane, and isoflurane on amplitude and time variables of contraction and relaxation in isometric, isotonic, and zero-load clamped twitches of is...
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Veröffentlicht in: | American journal of physiology. Heart and circulatory physiology 1990-09, Vol.259 (3), p.H827-H834 |
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Zusammenfassung: | P. R. Housmans
Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
The effects of the volatile anesthetics halothane, enflurane, and
isoflurane on amplitude and time variables of contraction and relaxation in
isometric, isotonic, and zero-load clamped twitches of isolated right
ventricular ferret papillary muscles (n = 24) were compared with those of
changing extracellular Ca2+ concentration [( Ca2+]o). Contraction and
relaxation variables were compared at equal contraction amplitudes to
determine whether the studied anesthetics exert specific effects on
contraction and relaxation other than those that may exist as a consequence
of their negative inotropic effect. Both changes in [Ca2+]o and anesthetic
concentrations had quantitatively and qualitatively similar effects on the
following variables of contraction amplitude: peak isometric developed
force (DF), maximal extent of shortening (DL), and maximal unloaded
velocity of shortening (MUVS). Analysis of anesthetic concentration-effect
curves normalized for effects to changes in [Ca2+]o demonstrated that
anesthetic effects relative to those of changes in [Ca2+]o were greater on
DF greater than DL greater than MUVS. When compared with twitches of equal
amplitude in low [Ca2+]o, halothane, enflurane, and isoflurane accelerated
isometric and isotonic relaxation. These data are consistent with the
hypothesis that the negative inotropic effects of halothane, enflurane, and
isoflurane are mostly a consequence of a reduction of intracellular Ca2+
availability and that anesthetic-induced decreases in myofibrillar Ca2+
responsiveness play only a minor role. |
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ISSN: | 0363-6135 0002-9513 1522-1539 |
DOI: | 10.1152/ajpheart.1990.259.3.h827 |