Carbon dioxide insufflation for percutaneous fetoscopic spina bifida repair [Neurosurgery Wiki]

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====== Carbon dioxide insufflation for percutaneous fetoscopic spina bifida repair ======


Partial amniotic carbon dioxide insufflation (PACI) involves insufflating the amniotic sac with carbon dioxide (CO2 ) and, in some cases, draining some of the amniotic fluid. The creation of a gaseous intra-amniotic compartment improves visualization, even in the presence of limited bleeding, and creates the work space required for complex fetoscopic procedures. Clinically, PACI is mostly used to perform fetoscopic myelomeningocele (MMC) repair, enabling a minimally invasive alternative to open fetal surgery. However, evidence of the fetal safety of PACI is limited. Previous animal experiments in sheep demonstrate that PACI induces fetal hypercapnia and acidosis with largely unknown short and longer term implications. In this review, we examine the literature for the physiological effects of intrauterine insufflation pressure, duration, humidity, and the role of maternal hyperventilation on fetal physiology and well-bein
((Skinner S, DeKoninck P, Crossley K, Amberg B, Deprest J, Hooper S, Hodges R.
Partial amniotic carbon dioxide insufflation for fetal surgery. Prenat Diagn.
2018 Dec;38(13):983-993. doi: 10.1002/pd.5362. Epub 2018 Oct 28. PMID: 30238473.)).


===== Case series =====
In a prospective study from  [[Los Angeles]] of patients who underwent [[percutaneous fetoscopic spina bifida repair]] from 2/2019 to 7/2020. Fetal [[cordocentesis]] of the [[umbilical vein]] was performed in cases with favorable access to the umbilical cord. The umbilical vein cord blood samples were obtained under ultrasound guidance immediately at the conclusion of the OSB repair. Simultaneous maternal arterial blood gas samples were also obtained. Results are reported as median (range).

Of 20 patients who underwent percutaneous fetoscopic OSB repair during the study period, 7 patients (35%) underwent fetal blood sampling. Gestational age at time of surgery was 27.4 (24.0 - 27.9) weeks and operative time was 183 (156 - 251) minutes. The CO2 exposure time was 122 (57 - 146) minutes with maximum pressure of 13.5 (12.0 - 15.0) mmHg. Fetal umbilical vein results were: pH 7.35 (7.30 - 7.39), pO2 56.2 (47.1 - 99.9) mmHg, pCO2 43.8 (36.2 - 53.0) mmHg, HCO3 23.9 (20.1 - 25.6) mmol/L and base excess (BE) -2.2 (-4.5 to -0.4) mmol/L. Simultaneous maternal arterial blood gas results were: pH 7.37 (7.28 - 7.42), pO2 187.5 (124.4 - 405.2) mmHg, pCO2 36.6 (30.7 - 46.0) mmHg, HCO3 21.3 (18.0 - 22.8) mmol/L and BE -3.2 (-5.9 to -1.8) mmol/L.

Despite prolonged [[Carbon dioxide insufflation]] of the [[uterus]], fetal [[umbilical vein]] [[pH]] and base excess values did not approach those associated with potentially pathologic fetal acidemia
((Sangara RN, Chon AH, Speybroeck ALV, Chu JK, Llanes MAS, Kontopoulos EV, Quintero RA, Chmait RH. Fetal blood gases after in utero carbon dioxide insufflation for percutaneous fetoscopic spina bifida repair: Fetal blood gases after intrauterine partial CO2 insufflation. Am J Obstet Gynecol MFM. 2021 May 28:100409. doi: 10.1016/j.ajogmf.2021.100409. Epub ahead of print. PMID: 34058420.)).
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Baschat et al. performed umbilical venous cord blood sampling in three patients during fetoscopic MMC repair at 25 + 1, 25 + 3 and 24 + 0 weeks' gestation, respectively. Fetal venous pH at the beginning of CO2 insufflation was 7.36, 7.46 and 7.37, respectively in the three fetuses, and repeat values were 7.28, 7.35 and 7.36 after 181, 159 and 149 min, respectively. The partial pressure of oxygen and CO2 was maintained in the normal range during these times, and pH decrease was less in Patient 3 who received humidified CO2 insufflation. Our observations suggest that, in contrast to sheep experiments, CO2 insufflation during fetoscopic myelomeningocele repair does not cause acidemia in human fetuses
((Baschat AA, Ahn ES, Murphy J, Miller JL. Fetal blood-gas values during
fetoscopic myelomeningocele repair performed under carbon dioxide insufflation.
Ultrasound Obstet Gynecol. 2018 Sep;52(3):400-402. doi: 10.1002/uog.19083. Epub
2018 Jul 18. PMID: 29750436.)).