Pediatric Anesthesia: Case Report
The ex utero intrapartum treatment (EXIT) procedure maintains a period of uteroplacental gas exchange for fetal oxygenation during delivery to provide time to explore and secure the airway of the fetus (1–8) or to perform fetal operations before the umbilical cord is clamped. The procedure is established for multiple indications, including fetal neck masses, congenital high airway obstruction syndrome, reversal of tracheal occlusion for congenital diaphragmatic hernia, fetal hydrothorax, and EXIT-to-extracorporeal membrane oxygenation for severe pulmonary or cardiac defects (1,5,6,9–22). We describe the airway management using the EXIT procedure in a fetus with a large cystic neck mass and the use of end-tidal carbon dioxide (ETco2) measurement for verification of tracheal intubation.
A 32-yr-old G2P1 woman was referred to our hospital with a 21-6/7-wk gestation complicated by a fetus with a large cystic neck mass (D × G 33.4 × 35.8 mm). Consecutive magnetic resonance imaging and 3-dimensional computed tomography reconstruction showed tracheal and partial esophageal obstruction by a cystic mass of unknown etiology (Fig. 1). At 29 wk gestation total occlusion of the esophagus by the growing mass was diagnosed. Maternal tocolysis with IV fenoterol and fetal lung maturation were initiated. The decision for cesarean delivery and EXIT of the fetus was made at 32-2/7 wk gestation. At that time the estimated weight of the fetus was 2080 g.
Preoperatively, the mother received 25 mL sodium bicitrate orally and 20 mg famotidine IV. The patient was positioned on her left side to achieve uterine displacement. Standard monitoring (electrocardiogram, pulse oximetry, and noninvasive arterial blood pressure reading) and external fetal heart rate monitors were applied to the patient. After administration of 100% oxygen, a rapid sequence anesthetic induction was achieved by administering 500 mg thiopental, 100 mg succinylcholine, and 0.4 mg fentanyl IV. Oral intubation was performed with a 7.0-mm ID endotracheal tube. Anesthesia was maintained with isoflurane at an initial end-tidal concentration of 0.8 to 1.2 vol% in a 50% oxygen-air mixture. At the time of hysterotomy the end-tidal concentration of isoflurane was increased to 2.5 vol% and the Fio2 was 1.0. Uterine relaxation was sufficiently obtained with 2.5 vol% of isoflurane. Her mean arterial blood pressure was kept normotensive between 55 and 65 mm Hg. The maternal blood loss was minimized to 900 mL by sutures at the edges of the relaxed uterus. Two L of lactated Ringer's solution and 1 L of 6% hydroxyethyl starch were administered for fluid replacement. After delivery of the infant the mother received 25 mg of rocuronium, 0.2 mg of fentanyl, and 20 IU of oxytocin IV. The isoflurane concentration was decreased to 0.8 vol%. Immediately after completion of the surgical procedure, anesthesia was discontinued and the patient's trachea was extubated. The mother stayed for 2 h in the postoperative care unit and was then transferred to the normal ward.
A hysterotomy was performed 14 min after anesthesia induction. The head, neck, left shoulder, and left arm of the fetus were delivered by the obstetric surgeon and the fetus was given 10 mg of ketamine and 0.05 mg of atropine in the left deltoid muscle. The fetus was monitored by a pulse oximeter probe, which was attached to the cleaned left hand. The pulse oximeter showed a reliable signal with oxygen saturations ranging between 61% and 72% and heart rates between 142 and 176 bpm. There was no decrease in fetal heart rate to less than 140 bpm during the procedure. After delivery of the fetus's head, neck, shoulder and arm, the otorhinolaryngology surgeon palpated the cystic mass in the pharynx of the fetus and incised the cyst. The contents of the cyst, blood and parts of the cystic wall were suctioned from the fetus's mouth and pharynx. Laryngoscopy reveals an easily visible epiglottis, but visualization of the vocal cords was obstructed by blood and other fluids. Even with continuous suction it was not possible to advance the endotracheal tube through the glottis under direct vision. However, an uncuffed 3.0-mm inner diameter endotracheal tube was blindly advanced beyond the epiglottis. Flexible bronchoscopy to confirm the correct position of the endotracheal tube was hampered by fluids and blood. The decision was then made to attempt to ventilate the fetus with 100% oxygen via the endotracheal tube with simultaneous measurement of ETco2. A gas humidifier with a CO2 probe was connected between the endotracheal tube and the resuscitation bag (Fig. 2). The CO2 probe absorbed gas at a constant rate of 200 mL/min and was connected to the monitor of a Draeger® (Drägerwerk AG, Lübeck, Germany) ventilator. Immediately after initiating ventilation of the fetus, a capnographic wave with an ETco2 signal of 18 to 27 mm Hg and oxygen saturation between 80 and 90% was noted. With confirmation of an appropriate position of the endotracheal tube, the tube was taped at 8 cm, the fetus was fully delivered, the umbilical cord was clamped and the infant was brought to the newborn resuscitation table. The time between hysterotomy and complete delivery was 26 min. A peripheral IV access was established and standard monitoring was applied. The oxygen saturation was more than 90% and the heart rate was 145 bpm. The newborn weighed 2290 g, was sedated with lorazepam and fentanyl, and was transferred to the neonatal intensive care unit. The infant stayed for several weeks in hospital and underwent three further resections of the neck mass. The histopathological features of the mass were compatible with a teratoma. The infant was discharged home at the 15th week of life without any sequelae from the EXIT procedure.
The EXIT procedure is an established technique to secure the airway of a fetus while maintaining feto-placental circulation (1–5). It is essential that the airway be established before the fetus is completely delivered and the feto-placental circulation is impaired (1–3,7,8,12,13,19). Auscultation or palpation of the tip of the tube is not a reliable method to verify correct endotracheal intubation. Measurement of ETco2 concentration is an easy way to detect correct placement of the airway. Because uteroplacental blood flow might be reduced after the start of ventilation, this method should only be used if no further feto-placental circulation is needed. It is unlikely that the uteroplacental blood flow would be disturbed by inadvertent temporary ventilation of the esophagus or stomach as a result of accidental esophageal intubation.
During EXIT procedures, it might be impossible to place an endotracheal tube under direct vision because of pharyngeal masses. In this case, the measurement of ETco2 concentration to confirm the endotracheal placement of the tube proved easy to perform in EXIT procedures. A capnographic wave form and a measurable ETco2 value can help to confirm a tracheal position for a fetal endotracheal tube during an EXIT procedure.
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