Impact of partial amniotic carbon dioxide insufflation (PACI) on middle cerebral artery blood flow in mid‐gestation human fetuses undergoing fetoscopic surgery for spina bifida aperta

During last year's international fetal surgery meeting in Crete, Greece, concerns were raised by some colleagues about the potential deleterious effects of partial amniotic carbon dioxide insufflation (PACI). This technique improves visualization of intra-amniotic contents during technically complex fetoscopic procedures. The first clinical application of PACI was by Bruner et al. after maternal laparotomy and transuterine trocar placement during fetoscopic surgery for spina bifida aperta1. A more complex, percutaneous insufflation approach that involves both amniotic and peritoneal cavities was pioneered by our group2. The concerns with PACI may have been prompted by the observation of the development of progressive fetal acidosis during early insufflation studies in sheep3, 4. Before and during the clinical introduction of PACI, our group also studied its safety in this species5-7. We concluded that the progressive fetal acidosis in sheep observed by other investigators was more likely the result of impaired intercotyledonal blood flow by uterine overdistension associated with maternal laparotomy, too high insufflation pressure, and the uterine-relaxing effects of anesthesia. Given the different anatomy of the human uterus and placenta, and the percutaneous approach which makes it easier to avoid hyperinsufflation, we deemed the finding of these studies not necessarily applicable to the human situation. Because of technical restraints and safety issues, we have not performed fetal blood gas measurements during PACI. Therefore, we prospectively sampled, by pulsed-Doppler interrogation before surgery and within 2 min following deflation of the amniotic cavity, the middle cerebral artery flow of two human fetuses undergoing fetoscopic closure of spina bifida. Surgery was performed in both cases using PACI during the 26th week of gestation, at Bilim University in Istanbul, Turkey, following informed consent and patient approval. Pregnancy outcome was spontaneous labor at 36 + 5 weeks of gestation in one case and the other was delivered electively at 37 + 0 weeks of gestation. The insufflation times were 210 and 150 min, respectively (Table1). The Doppler-velocity-time-integrals in the middle cerebral artery before and within 2 min following deflation of the amniotic cavity were almost identical (Figure1), suggesting that fetal hypercarbia is unlikely. This observation may result because not much carbon dioxide is absorbed by the fetal skin and/or placenta during surgery and/or that the fetal concentration of carbon dioxide can be lowered effectively by maternal ventilatory adjustments8. Unfortunately, normal middle cerebral artery flow integrals may not prove sufficient oxygen delivery to the fetal brain because the cardiovascular and biophysical responses of a preterm fetus to induced hypoxemia may be less pronounced than those of older fetuses9, 10. It is reassuring that, in our clinical experience of almost 150 human fetuses, no significant direct ill effects on the fetal brain or on postnatal neurological development of treated children could be attributed to the use of PACI in mid-gestation. Further evidence pointing to its safe clinical application stems from a study in sheep that did not show any postnatal neurological and brain histological abnormalities after PACI11. Yet, given the early clinical experience with PACI, continued caution, flow studies and assessments of clinical outcomes in a larger number of patients are desired. Furthermore, consideration should be given to the use of gases or gas mixtures other than carbon dioxide for this purpose. T. Kohl German Center for Fetal Surgery & Minimally Invasive Therapy (DZFT), University Hospital Giessen-Marburg, Klinikstr. 33, 35592 Giessen, Germany (e-mail: thomas.kohl@uniklinikum-giessen.de)