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Obstetric Anesthesiology

Anesthetic Management for Percutaneous Minimally Invasive Fetoscopic Surgery of Spina Bifida Aperta: A Retrospective, Descriptive Report of Clinical Experience

Arens, Christoph MD*; Koch, Christian MD; Veit, Mirko MD; Greenberg, Robert Steven MD; Lichtenstern, Christoph MD*; Weigand, Markus Alexander MD*; Khaleeva, Anastasiia§; Schuerg, Rainer MD; Kohl, Thomas MD§

Author Information
doi: 10.1213/ANE.0000000000001896

Since the beginning of fetal surgery, anesthesiologists have relied on high concentrations of volatile agents (≥2 times minimum alveolar concentration [MAC]) to assure adequate uterine relaxation during maternal general anesthesia for both open and minimally invasive fetal surgery.1,2 When Kohl3 introduced the minimally invasive fetoscopic approach (MIFA) for closure of fetal spina bifida aperta (SBA) in 2000, the intraoperative development of maternal pulmonary edema was observed in approximately one-fourth of cases, regardless of an open or minimally invasive surgical approach.2 Although the precise mechanisms are not completely understood, the development of pulmonary edema is facilitated by a combination of liberal volume administration, tocolytic drugs (eg, indomethacin), and the physiologically increased disposition of pregnant women to retain interstitial fluid.4,5 In addition, high concentrations of volatile anesthesia may contribute to pulmonary edema.

During the introduction of the MIFA, Hering and Kohl experimented with reduced concentrations of volatile anesthesia (MAC to 0.5 to 1) and identified a general anesthetic technique that achieved adequate fetomaternal anesthesia, sufficient uterine relaxation, and prevention of uterine contractions.6 This new anesthetic technique appeared to reduce the detrimental side effects of deep anesthesia, including (1) maternal and fetal hemodynamic depression; (2) the need for vasopressor support and intravascular volume administration; and (3) occurrence of pulmonary edema.2,7

In 2010, the fetal surgery center (DZFT) moved to Giessen University, where the “Hering-Kohl-Protocol”6 was further modified. In the most current protocol, fluid and vasopressor management are guided by a pulse contour analysis system (PiCCO) alone instead of in combination with pulmonary artery catheter measurements. In addition, atosiban is selected as the first-line agent for perioperative tocolysis with indomethacin reserved for uterine contractions after surgery.

This retrospective case series describes our clinical experience with the modified protocol in consecutive patients undergoing fetoscopic surgery for SBA. In addition, for the first time the entire protocol is published as Supplemental Digital Content 1, A detailed description of the fully percutaneous MIFA by Kohl is presented in a separate report.3


Please find the detailed description of our anesthesia management protocol as Supplemental Digital Content 1,

Acquisition and Processing

All patients provided written informed consent for percutaneous minimally invasive fetoscopic closure of SBA in their fetuses. They also agreed to the acquisition and publication of their data. The local Ethics Committee at the Medical Faculty of Giessen approved our retrospective secondary analysis of the perioperative data (trial Code Number 173/13, conference date July 18, 2013). The study was performed in accordance to the principles set forth in the Declaration of Helsinki. We included all cases conducted at the University Hospital of Giessen, Germany, between August 2010 and November 2013.

Patients’ data were reviewed and validated manually using the Patient Data Management Systems “ICUData” (IMESO GmbH, Giessen, Germany) and “NarkoData” (IMESO GmbH, Giessen, Germany). The exported data were recorded in an external database.

Baseline parameters including age, weight, high, body mass index, week of gestation, and American Society of Anesthesiologists classification were recorded. Parameters measured during the procedure included uterine insufflation pressure, the total volume administered for both lactated Ringer’s and hydroxyethyl starch solutions, the total dosages of epinephrine and remifentanil, and the durations of anesthesia and the surgical procedure. Heart rate, blood pressure, and hemoglobin were determined preoperatively, intraoperatively, and postoperatively. Values of blood gas analysis (glucose, pH, base excess, arterial partial pressures of carbon dioxide and oxygen, lactate, Horowitz index) as well as PiCCO parameters (continuous cardiac output index, extravascular lung water index [EVLWI]), and temperature were measured intraoperatively and postoperatively.

To determine lung water content, we used the sensitive8 transpulmonary thermodilution method for assessing the EVLWI, which correlates with the gold standard of gravimetric measurement.9 In cases of pulmonary edema, the EVLWI usually clearly exceeds 10 mL/kg.10

Maternal outcomes were recorded, including the length of intensive care unit (ICU) stay, opioid therapy during ICU stay, and clinical occurrence of postoperative pulmonary edema.

Anesthetic goals included adequate fetal anesthesia, uterine relaxation, and avoidance of maternal pulmonary edema, maternal or acute fetal deaths, placental abruption, or spontaneous labor. Adequate fetal anesthesia was defined by (1) the absence of sustained periods of fetal tachycardia or bradycardia as determined by Doppler ultrasound; and (2) the absence of active fetal movements during surgical dissection of the malformation. Sufficient uterine relaxation was determined clinically by (1) enough uterine work space for the intervention; (2) the absence of uterine contractions during intervention; (3) uterine insufflation pressures ≤20 mm Hg; and (4) no requirement for postoperative indomethacin for tocolysis. Maternal pulmonary edema was identified by (1) clinical evaluation and (2) measurement of EVLWI ≥10 mL/kg.

Statistical Analysis

Data are reported as mean ± standard deviation, minimal and maximum value, medians, and interquartile range (25th–75th percentiles).


Sixty-one cases underwent therapy of SBA by the MIFA. In 2 cases, surgery was discontinued prematurely (Supplemental Digital Content 2,, so 59 procedures are summarized in Table 1 and described subsequently. Most patients were classified as American Society of Anesthesiologists I (39%) and American Society of Anesthesiologists II (59%). The procedure was feasible in patients up to body mass index of 44.6 kg/m2. Duration of anesthesia and surgery both became shorter as experience with this technique increased.

Table 1.
Table 1.:
Patients’ and Anesthesia Characteristics: Preoperative, Intraoperative, and Postoperative Data

Adequate fetal anesthesia was uniformly achieved. No fetus developed sustained tachycardia or bradycardia or continued active movements during surgical dissection of the malformation.

Uterine relaxation was uniformly sufficient to allow the surgeons to complete the intervention with complete absence of intraoperative uterine contractions. The goal for uterine insufflation pressures was exceeded in 3 of 46 cases (6.5%). No patient developed postoperative uterine contractions or required indomethacin.

No patient developed intraoperative pulmonary edema. Restrictive intraoperative hydration was achieved with a mean crystalloid infusion rate of 3.64 mL/kg/h Ringer’s solution and 500 mL of hydroxyethyl starch (6% per 130,000) solution added in all but 3 patients. All women were extubated immediately after the procedure. On the first postoperative day, EVLWI exceeded 10 mL/kg in 6 of 40 cases (15%). One patient developed dyspnea after discharge from the ICU to the general ward; clinical records at that time documented Spo2 96% on room air and normal heart rate and blood pressure. Symptoms resolved rapidly after administration of 10 mg furosemide IV and 2 L/min O2 via a nasal cannula.

There were no maternal or acute fetal deaths, placental abruption, or evidence of spontaneous labor. Four neonates died after delivery: 1 as a result of complications of prematurity (24.6 weeks of gestation) and chorioamnionitis, 2 as a result of severe brainstem dysfunction attributed to Chiari II malformation, and 1 as a result of Trisomy 13 that was diagnosed at birth.


Our retrospective case series describe the modified “Hering-Kohl-Protocol”6 for percutaneous minimally invasive fetoscopic surgery for SBA in 61 maternal–fetal dyads. In contrast to previous assumptions,1,2 anesthetic maintenance with <1 MAC of desflurane was sufficient to achieve both adequate fetal and maternal anesthesia and uterine relaxation when combined with preoperative atosiban for tocolysis and remifentanil infusion. The combination of reduced volatile anesthesia and goal-directed fluid and vasopressor therapy guided by the PiCCO system (Pulse Contour Cardiac Output, Pulsion Medical Systems, Feldkirchen, Germany) ensured stable perioperative hemodynamics and mitigated the risk of pulmonary edema. No patients developed intraoperative pulmonary edema, and only 15% of patients experienced elevated EVLWI (10–10.5 mL/kg). A single postoperative case of mild pulmonary edema was easily treated. The modified Hering-Kohl protocol provides a guide for safe general anesthesia during complex minimally invasive fetoscopic interventions.


Name: Christoph Arens, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

Name: Christian Koch, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

Name: Mirko Veit, MD.

Contribution: This author helped acquire and interpret the data, and write the manuscript.

Name: Robert Steven Greenberg, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

Name: Christoph Lichtenstern, MD.

Contribution: This author helped acquire and interpret the data, and write the manuscript.

Name: Markus Alexander Weigand, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

Name: Anastasiia Khaleeva.

Contribution: This author helped conduct the study, acquire and interpret the data, and prepare the manuscript.

Name: Rainer Schuerg, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

Name: Thomas Kohl, MD.

Contribution: This author helped design and conduct the study, acquire and interpret the data, and write the manuscript.

This manuscript was handled by: Jill M. Mhyre, MD.


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