Gunnarsson G O, Gudmundsson S, Hökegård K, Stale H, Kjellmer I, Hafström O, Marsál K
Department of Obstetrics and Gynecology, University of Lund, University Hospital, Malmö, Sweden.
J Perinat Med. 1998;26(2):107-14. doi: 10.1515/jpme.1998.26.2.107.
The purpose of this study was to assess the effects of hypocapnic hypoxia, acidemia and the combination of hypoxia/acidemia on blood flow velocity variables in the fetal cerebral circulation. Chronically instrumented fetal sheep were used and the ewes were induced to breathe a hypoxic gas mixture for about 90 min. This caused an initial period of hypoxemia followed by a period of mixed hypoxemia/acidemia. When the ewe was reoxygenated, the fetus experienced a period of normoxic acidemia. The fetal cerebral circulation was assessed by recording Doppler blood flow velocity waveform variables in a cerebral vessel and the umbilical artery, using standard ultrasound equipment. External carotid artery blood flow was maintained during hypoxic and hypoxic/acidotic periods despite a fall in cardiac output. In the cerebral vessel, mean maximum velocity (time-averaged maximum velocity), minimum diastolic velocity and maximum systolic velocity manifested increases during hypoxic and hypoxic-acidotic periods, but pulsatility index did not change due to the effect of reduced heart rate on pulsatility index. Umbilical artery pulsatility index increased in the hypoxic and hypoxic-acidotic periods, despite unchanged mean maximum velocity, minimum diastolic velocity and maximum systolic velocity. With acute hemodynamic changes, the measurement of pulsatility index can yield misleading results. For clinical and experimental research on the fetal cerebral circulation, more attention should be paid to the individual Doppler variables, especially to the mean maximum velocity, than to the pulsatility index alone. Changes in mean maximum velocity recorded from the cerebral artery seem to reflect changes in the cerebral arterial flow.
本研究的目的是评估低碳酸血症性缺氧、酸血症以及缺氧/酸血症组合对胎儿脑循环中血流速度变量的影响。使用长期植入仪器的胎羊，诱导母羊呼吸低氧混合气体约90分钟。这导致了最初的低氧血症期，随后是混合性低氧血症/酸血症期。当母羊重新给氧时，胎儿经历了一段常氧性酸血症期。使用标准超声设备，通过记录脑血管和脐动脉中的多普勒血流速度波形变量来评估胎儿脑循环。尽管心输出量下降，但在缺氧和缺氧/酸中毒期间，颈外动脉血流保持稳定。在脑血管中，平均最大速度（时间平均最大速度）、舒张末期最小速度和收缩期最大速度在缺氧和缺氧-酸中毒期间表现出增加，但由于心率降低对搏动指数的影响，搏动指数没有变化。尽管平均最大速度、舒张末期最小速度和收缩期最大速度没有改变，但在缺氧和缺氧-酸中毒期间脐动脉搏动指数增加。对于急性血流动力学变化，搏动指数的测量可能会产生误导性结果。对于胎儿脑循环的临床和实验研究，应更多地关注个体多普勒变量，尤其是平均最大速度，而不仅仅是搏动指数。从脑动脉记录的平均最大速度变化似乎反映了脑动脉血流的变化。
