Assessment of fetal circulation and mechanisms of heart adaptation during umbilical cord compression: An experimental model in fetal sheep

Abstract

Perinatal asphyxia is a serious health issue with long-term neurologic morbidities. Cerebral lesions are induced by low cardiac output which occurs often during labour without reliable predictive factors. To assess hemodynamic changes during umbilical cord (UC) compression in fetal sheep. Experimental study on chronically instrumented sheep fetuses (surgery at 131 days of gestation, term = 141 days). Under general anesthesia, a hysterotomy is performed. An aortic catheter is inserted via the axillary artery for blood sampling, and a 6 Fr. Sheath is introduced to the left ventricle (LV) through the right carotid artery under pressures and echocardiographic control. Then a 5 Fr. Transonic PV loop catheter (EMKA Technologies, France) is inserted through the sheath into the LV, and the sheath is withdrawn towards the aorta to allow permanent measurement of the aortic pressure. A 16 mm inflatable occlusion device is placed around the UC (OC16, California, USA). Series of complete occlusion of the UC are done with progressive increasing duration to simulate labour. LV pressures and volumes are registered continuously. Pressure-volume loops and blood samples are analyzed before during and after the occlusions. During the first experimentations, short occlusions did not induce significant modifications. Longer occlusions induced progressive systolic and diastolic disorders which appeared before the metabolic acidosis ( Fig. 1 ). Knowledge of foetal heart adaptation could be interesting to prevent neurologic lesions. This hemodynamic model could also be applied in other situations such as congenital diaphragmatic hernia, pulmonary hypertension or aortic coartation.