Jonker F H, van der Weijden G C, Taverne M A
Department of Herd Health and Reproduction, Faculty of Veterinary Sciences, University of Utrecht, The Netherlands.
Vet Rec. 1991 Nov 9;129(19):423-6. doi: 10.1136/vr.129.19.423.
The effect of an intravenous injection of 0.3 mg clenbuterol on myometrial activity, fetal heart rate and fetal outcome was studied in three groups of animals: six heifers in active labour at term, in which fetal oversize was diagnosed just before the drug was injected and whose calves were delivered by caesarean section within 50 minutes; four cows at the start of the expulsive stage of parturition which had been induced with flumethasone on day 270 of gestation; and in four parturient cows which had had electrodes implanted on the myometrium at least one week before calving was induced with flumethasone on day 270. Electrocardiograph electrodes were placed on the calf and an intrauterine pressure catheter was inserted between the calf and the uterine wall upon rupture of the amniotic membrane. Clenbuterol induced a significant decrease of myometrial activity for at least 20 minutes. Recovery was most rapid in the heifers in which an obstetrical examination had taken place during active labour. There was no significant effect on basal fetal heart rate but decreases in heart rate were absent as long as uterine contractions were inhibited. The fetal outcome, judged either before or at birth by blood pH, base-excess and PCO2 and by a clinical examination, was not adversely affected.
在三组动物中研究了静脉注射0.3毫克克伦特罗对子宫肌层活动、胎儿心率和胎儿结局的影响：六头足月处于分娩活跃期的小母牛，在注射药物前诊断出胎儿过大，其小牛在50分钟内通过剖腹产分娩；四头在妊娠第270天用氟米松诱导分娩的母牛，处于分娩排出期开始时；以及四头在妊娠第270天用氟米松诱导分娩前至少一周在子宫肌层植入电极的分娩母牛。将心电图电极放置在小牛身上，并在羊膜破裂时在小牛和子宫壁之间插入宫内压力导管。克伦特罗使子宫肌层活动显著降低至少20分钟。在分娩活跃期进行过产科检查的小母牛中恢复最快。对基础胎儿心率没有显著影响，但只要子宫收缩受到抑制，心率就不会下降。通过血液pH值、碱剩余和PCO2以及临床检查在出生前或出生时判断的胎儿结局未受到不利影响。
