Halothane exerts a more potent depressant effect on newborn rabbit myocardium compared to adult myocardium, which may explain its hypotensive effects in human neonates.
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May explain halothane hypotension in neonates; leaves open translation from rabbit data to clinical practice.
The effect of halothane on myocardial contractility was studied in isolated right ventricular muscle preparations from newborn and adult rabbits. Right ventricular strips were mounted in oxygenated Krebs' solution and stimulated with supramaximal voltages at 1.0 Hz, while isometric force of contraction was continuously recorded. Halothane (0.4, 0.7, and 1.1%) caused a significant dose-dependent depression of both peak developed tension (42, 61, and 70%, respectively) and maximum rate of rise of isometric tension (40, 56, and 64%, respectively) of newborn myocardium. Newborn myocardial preparations exhibited approximately 20% greater depression of contractility than adult myocardium at each concentration studied (P less than 0.05), thus a parallel shift of the dose-response curves was observed. It was concluded that halothane exerts a potent depressant effect on newborn myocardium that is greater than that on adult myocardium. The depression effect of halothane on the newborn myocardium may contribute to its hypotensive effect in newborn infants.
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Krane et al. (1987) studied this question.
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