the patient was a healthy 29-year - old multigravida . in week 28 , the fetus was found to have an anterior neck mass and polyhydramnios was also detected by prenatal ultrasound . during the last four weeks prior to delivery , the neck mass grew substantially , had a broad base , and was 7 cm in diameter .
an exit procedure was performed at week 38 of gestation by a multidisciplinary team of experts including a pediatric otorhinolaryngologist , neonatologist , obstetrician , two anesthesiologists , and nurses .
the patient was placed in a supine position with a left lateral tilt to avoid aortocaval compression .
an arterial line for continuous arterial pressure monitoring and two peripheral intravenous lines ( 16-gauge ) were placed before induction .
endotracheal intubation ( 6.5 cuffed ) was done after thiopental sodium ( 3 mg / kg ) and succinylcholine ( 1.5 mg / kg ) administration by a rapid sequence induction .
general anesthesia was maintained with sevoflurane 2 - 3 vol% and nitrous oxide in oxygen ( 50 - 50 ) combined with an additional dose of remifentanil ( 0.1 - 0.5 g / min / kg ) and rocuronium ( 50 mg in total ) . an end - tidal ( et ) concentration of sevoflurane was maintained at 1 - 1.5 minimum alveolar concentration ( mac ) for proper uterine relaxation until the umbilical cord was clamped .
prior to uterine incision , the patient was given two boluses of intravenous nitroglycerine ( 30 g ) , followed by an infusion at 0.5 - 1 g / kg / min to ensure uterine relaxation . to maintain a maternal systolic blood pressure of 100 - 120 mmhg ,
the following treatments were required : four boluses of intravenous phenylephrine ( 50 g ) , followed by an infusion at 0.05 - 0.1 g / kg / min , an infusion of dopamine at 5 g / kg / min , and rapid infusion of volume expander ( 500 ml ) .
, the obstetrician confirmed that the uterus was fully relaxed and inserted an angiocatheter ( 20-gauge ) into the uterus under the guidance of ultrasound for decompression by slow reduction of the amniotic fluid volume .
then , the fetal head and the part of the torso just above the nipple were partially delivered .
a sterile pulse oxymetry was applied at the left ear lobe of the fetus after removal of amniotic fluid , but reliable readings could not be obtained .
ultrasound - guided monitoring was done by an obstetrician for the early detection of placental detachment until the fetal airway was secured .
the fetus was intubated with a 2.5 endotracheal tube by a pediatric anesthesiologist at the second attempt ( fig .
the stylet of the endotracheal tube was not removed by an assistant due to the slipperiness of the vernix caseosa .
the position of the endotracheal tube was confirmed by a sterile end - tidal co2 monitor . once the fetal airway was established and the positive - pressure ventilation was satisfactory , the umbilical cord was severed and the neonate was fully delivered from the uterus .
the 1-min apgar score of the neonate was 7 ; the 5-min score was 9 .
after delivery , the infusions of nitroglycerine , dopamine , and phenylephrine were all discontinued , and the et concentration of sevoflurane was also lowered to 0.8 - 1.0 vol% .
then , five units of oxytocin were injected intravenously by bolus , and 20 units / l was infused continuously .
the estimated blood loss was 1,100 ml . the total intake of fluid during the operation was 1,800 ml .
three days later , the neck mass of the neonate was completely excised by a pediatric otorhinolaryngologist .
the excised mass was confirmed to be a 5  5  5 cm benign teratoma ( fig .
the aim of the exit procedure is to manage life - threatening neonatal emergencies and thereby increase the survival rate at delivery .
the exit procedure therefore requires a multidisciplinary team approach , including at least two anesthesiologists for both the mother and the fetus , a pediatric otorhinolaryngologist , an obstetric surgeon , a neonatologist , and a team of nurses . during the exit procedure
, anesthesiologists have to maintain the uteroplacental circulation during cesarean section to increase the time available to secure a potentially obstructed fetal airway . in conventional cesarean section ,
the major goals are to minimize the time from anesthetic induction to umbilical cord clamping , thereby minimizing fetal exposure to inhalational anesthetics .
in fact , during the exit procedure , even intramuscular administration of drug cocktails and/or inhalational anesthetics ( 1 - 1.5 mac ) are recommended to ensure a motionless , well - anesthetized fetus .
furthermore , there is no need to limit the time of anesthesia 
 induction or the skin incision to delivery time .
the anesthetic goals and principles for an exit procedure differ markedly from those for a conventional cesarean section with respect to maintaining the uteroplacental circulation until the time of secured delivery .
first , deep inhalational anesthetics ( 1.5 - 3 mac ) are often used to relax the uterine muscles and to maintain the uteroplacental circulation .
inhalational anesthetic concentrations of at least 2 mac are usually recommended for proper relaxation of the uterine muscles and to prevent early placenta detachment . for rapid onset and offset of tocolytic action during the exit procedure , sevoflurane or desflurane are recommended .
these drugs include nitroglycerine and magnesium sulfate . however , nitroglycerin is a better choice than magnesium sulfate because nitroglycerin is easily titratable and short acting .
the onset of uterine relaxation using nitroglycerin is 30 - 60 s , and a loading bolus of 100 g with continuous dosing of 0.5 - 1 g / kg / min is recommended , as needed , to maintain effective uterine relaxation .
lastly , dopamine ( 5 g / kg / min ) , phenylephrine ( 0.05 - 0.1 g / kg / min ) , and ephedrine bolus ( 5 - 10 mg ) can be utilized to maintain the maternal hemodynamics .
many of the suggested anesthetic maneuvers used during the exit procedure to enhance uterine relaxation , such as the use of higher mac inhalational anesthetics combined with short acting tocolytics , potentially decrease maternal blood pressure and uteroplacental perfusion before delivery , and may lead to uterine atony and continued hemorrhage post - delivery .
meticulous on- and off - techniques are critical to achieve full relaxation of the uterus before delivery and to ensure proper contraction to prevent uterine atony and massive hemorrhage post - delivery .
sevoflurane ( 1 - 1.5 mac ) and remifentanil ( 0.1 - 0.5 g / kg / min ) were used to maintain anesthesia . the et concentration of sevoflurane was less than 2 mac before the uterine incision , even though the concentration was set from the beginning of anesthetic induction .
therefore , an additional bolus of nitroglycerine ( 30 g ) was given and infused continuously at 0.5 - 1 g / kg / min .
the uteroplacental circulation was maintained for 7 min ( from uterine incision to cord clamping ) without maternal or fetal accident until the fetus was intubated and the endotracheal tube was confirmed to be in the correct position .
usually , during the exit procedure , the dose of nitroglycerine used in the combined spinal epidural anesthesia is more than 100 g in a bolus , and the et concentration of inhalational anesthetics used in general anesthesia is above 2 mac . in our case , we performed general anesthesia using a lower bolus dose ( two consecutive doses of 30 g ) of nitroglycerine and a lower et concentration of inhalational anesthetics ( 1 - 1.5 mac ) to maintain maternal hemodynamic stability and ensure fetal airway safety .
the exit procedure is a relatively new procedure and holds promise for newborns with airway obstruction .
anesthesia for the exit procedure can be performed in various ways , as long as uterine relaxation and uteroplacental circulation are maintained until the fetal airway is secured .
preoperative planning and communication with regard to anesthesia are the most important factors for success .
 the ex utero intrapartum treatment ( exit ) procedure is a very rare technique performed in cases of fetal congenital malformations . 
 the exit procedure increases the rate of survival at delivery by maintaining the uteroplacental circulation until the airway of the fetus is secured . to maintain the uteroplacental circulation , 
 a higher dose of inhalational anesthetics and/or intravenous nitroglycerin can be used as compared to conventional cesarean section . 
 the aim of this report is to share our anesthetic experience during the exit procedure with members of the korean society of anesthesiology for the first time , and to highlight the maternal implications of the use of inhalational anesthetics and nitroglycerin during cesarean section for the exit procedure . 