[Effect of the combination of the beta-1-blocker metoprolol with the tocolytic fenoterol on uteroplacental hemodynamics and fetal cardiovascular sensitivity with particular consideration of intrauterine fetal malnutrition. Results of animal experiments].

7 merino sheep in an advanced state of pregnancy received oxytocin for labour induction under the conditions of control, monotherapy with the beta 2-adrenergic tocolytic fenoterol, combination of the latter with the beta 1-blocking substance metoprolol (Beloc). Likewise, the effect of labour induction was investigated when putting an artificial stenosis around the a. uterina during simultaneous application of fenoterol alone and combined with metoprolol. The following parameters were measured: aortic pressure and heart rate both in dam and fetus, maternal left ventricular pressure rising velocity, intrauterine pressure, uterine blood flow, uterine vascular resistance and regional myometrial contraction patterns by means of an ultrasonic transit time method. Measurement of maternal cardiovascular parameters once more showed, that maternal cardiovascular derangements could excellently be antagonised by metoprolol. Intrauterine pressure measurements as well as regional myometrial contraction patterns proved evidence, that there is no counteraction between the beta 2-mimetic substance and the beta 1-blocking agent concerning the tocolytic effect. When artificially stenosing the a. uterina, a rise in uterine contraction status could be observed; this hypoxic augmentation of myometrial tone could almost completely be reverted when combining fenoterol and metoprolol. Finally, no difference could be observed in the reaction of fetal cardiovascular parameters to reduced uterine blood flow before and after application of the beta 1-blocking substance metoprolol.