Key result
Halothane and isoflurane induced greater negative inotropic effects in cardiomyopathic hamsters compared to healthy ones, though differences resolved when corrected for minimum alveolar concentration.
Why the study?
Does halothane or isoflurane differentially affect myocardial contraction and relaxation in cardiomyopathic versus healthy hamsters?
Does halothane or isoflurane differentially affect myocardial contraction and relaxation in cardiomyopathic versus healthy hamsters?
Absolute Event Rate: 19% vs 28%
p-value: p=< 0.05
Halothane and isoflurane exert greater negative inotropic effects in cardiomyopathic hamsters compared to healthy ones, but this difference is abolished when concentrations are adjusted for minimum alveolar concentration.
May indicate heightened sensitivity in cardiomyopathy models at fixed doses; hypothesis-generating for human anesthetic selection.
BACKGROUND: The effects of halothane and isoflurane on myocardial contraction and relaxation in diseased myocardium are not completely understood. METHODS: The effects of equianesthetic concentrations of halothane and isoflurane on inotropy and lusitropy in left ventricular papillary muscles of healthy hamsters and those with genetically induced cardiomyopathy (strain BIO 14.6) were investigated in vitro (29 degrees C; pH 7.40; Ca2+ 2.5 mM; stimulation frequency, 3/min) in isotonic and isometric conditions. RESULTS: Halothane induced a negative inotropic effect that was greater in cardiomyopathic than in healthy hamsters (1.5 vol%, active isometric force (AF): 19 +/- 8% vs. 28 +/- 11% of control values; P < 0.05). Isoflurane induced a negative inotropic effect that was greater in cardiomyopathic than in healthy hamsters (2.0 vol%, AF: 64 +/- 13% vs. 75 +/- 11% of control values; P < 0.01). However, the negative inotropic effects of halothane and isoflurane were not different for cardiomyopathic or healthy hamsters when their concentrations were corrected for minimum alveolar concentration (MAC) values in each strain. Halothane induced a negative lusitropic effect under low load, which was more important in cardiomyopathic hamsters, suggesting a greater impairment in calcium uptake by the sarcoplasmic reticulum. In contrast, isoflurane induced a moderate positive lusitropic effect under low load in healthy but not in cardiomyopathic hamsters. Halothane and isoflurane induced no significant lusitropic effect under high load. CONCLUSIONS: Halothane and isoflurane had greater negative inotropic effects in cardiomyopathic than in healthy hamsters. Nevertheless, no significant differences in their inotropic effects were noted when concentrations were correlated as a multiple of MAC in each strain.
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Vivien et al. (1997) studied Hypertrophic Cardiomyopathy. Halothane and Isoflurane vs. Healthy hamsters was evaluated on Active isometric force (AF) as a percentage of control values (p=< 0.05). Halothane and isoflurane induced greater negative inotropic effects in cardiomyopathic hamsters compared to healthy ones, though differences resolved when corrected for minimum alveolar concentration.
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