Reddy V M, Liddicoat J R, Klein J R, Wampler R K, Hanley F L
Division of Cardiothoracic Surgery, University of California San Francisco, USA.
J Thorac Cardiovasc Surg. 1996 Mar;111(3):536-44. doi: 10.1016/s0022-5223(96)70305-7.
Earlier work suggests that fetal cardiac bypass is technically feasible but results in significant placental dysfunction. Many of the stimuli that initiate this placental dysfunction have been identified in the past several years and these involve fetal stress, extracorporeal surfaces, priming substances (maternal blood), and flow characteristics. Fetal survival with conventional methods of bypass has been far less than optimal. A novel fetal bypass circuit requiring no priming volume was designed incorporating an in-line axial flow pump (Hemopump, Johnson & Johnson Interventional Systems, Rancho Cordova, Calif.) and was demonstrated to have a marked beneficial effect on placental function.
The purpose of this study was to investigate the effect of this newly developed customized fetal bypass circuit on fetal survival and developing fetal organs.
Nine fetuses at 122 to 126 days of gestation were subjected to fetal cardiac bypass via a transsternal approach, with a 16F single right atrial venous cannula and a 12F arterial cannula. Normothermic cardiac bypass was continued for 30 minutes at flow rates of 320 +/- 32 ml/kg. Of the nine fetuses, one fetus was stillborn 4 days after bypass and eight (89%) were delivered alive after progressing to term gestation. One lamb died of blunt trauma 1 day after birth. All other lambs (n = 7) thrived normally, and at 1 week of age they were subjected to autopsy. No gross hemorrhagic or thromboembolic lesions were detected in the organs examined including the brain. Microscopic examination of representative sections from all organs revealed mild pleural reaction in two lambs, and in two other lambs the hepatocytes showed evidence of mild increase in glycogen content, the significance of which is unknown in relation to fetal bypass. In one fetus that was aborted there was evidence of mild to moderate neuronal loss in the cerebral cortex.
This study demonstrates that with improvements in fetal extracorporeal circuitry and techniques very favorable fetal outcome can be achieved. Further studies are necessary to evaluate the effects of bypass on fetal brain in an appropriate animal model. Advances in extracorporeal circuitry to suit the unique fetal physiology increase the possibility of future clinical application.
早期研究表明胎儿心脏搭桥在技术上是可行的，但会导致显著的胎盘功能障碍。在过去几年中，引发这种胎盘功能障碍的许多刺激因素已被确定，这些因素包括胎儿应激、体外表面、预充物质（母体血液）和血流特性。采用传统搭桥方法的胎儿存活率一直远低于理想水平。设计了一种新型的无需预充液的胎儿搭桥回路，该回路包含一个在线轴流泵（Hemopump，强生介入系统公司，加利福尼亚州兰乔科尔多瓦），并被证明对胎盘功能有显著的有益影响。
本研究的目的是调查这种新开发的定制胎儿搭桥回路对胎儿存活及发育中的胎儿器官的影响。
9只妊娠122至126天的胎儿通过经胸骨途径进行胎儿心脏搭桥，使用16F单根右心房静脉插管和12F动脉插管。常温心脏搭桥以320±32毫升/千克的流速持续30分钟。9只胎儿中，1只胎儿在搭桥后4天死产，8只（89%）在足月妊娠后存活分娩。1只羔羊在出生后1天死于钝性创伤。所有其他羔羊（n = 7）正常生长，在1周龄时进行解剖。在包括大脑在内的检查器官中未检测到明显的出血或血栓栓塞性病变。对所有器官的代表性切片进行显微镜检查发现，两只羔羊有轻度胸膜反应，另外两只羔羊的肝细胞显示糖原含量有轻度增加迹象，其与胎儿搭桥的关系尚不清楚。在1只流产的胎儿中，大脑皮质有轻度至中度神经元丢失的证据。
本研究表明，随着胎儿体外循环回路和技术的改进，可以实现非常良好的胎儿结局。有必要在合适的动物模型中进一步研究搭桥对胎儿大脑的影响。适合独特胎儿生理学的体外循环回路的进展增加了未来临床应用的可能性。
