Emergency cesarean section under general anesthesia using remimazolam in a pregnant woman with Fontan circulation

A 32-year-old woman (weight 53 kg, height 164.7 cm, para 1) with a gestational age of 32 weeks and 3 days was admitted to the emergency department due to premature rupture of membranes. She was diagnosed with congenital heart disease (CHD), a double-outlet right ventricle, complete atrioventricular septum defect, pulmonary atresia and patent ductus arteriosus. Her surgical history included fenestrated Fontan operation at 2 years of age and fenestration closure at 3 years of age. Since then she was under periodic observation without any symptom aggravation at the center where she had undergone heart surgery. During pregnancy she had been taking 100 mg aspirin, which was planned to be discontinued after 36 weeks. Regarding her pregnancy-related care, she was followed-up at a women’s hospital near her home but was transferred to our center due to bed availability in the neonatal intensive care unit (NICU).

Preoperative electrocardiogram showed sinus rhythm (heart rate 73 bpm), incomplete right bundle branch block, left anterior fascicular block and right ventricular hypertrophy. Echocardiography showed a single ventricle with preserved contractility (ejection fraction 56.1%), mild to moderate mitral valve regurgitation and trivial aortic valve regurgitation. Laboratory findings were within normal ranges except mild anemia (hemoglobin 10.4 g/dl) and mild thrombocytopenia (platelet count 111,000/μl). Arterial blood gas analysis (ABGA) showed pO₂ 78.3 mm Hg and paCO₂ 25.8 mm Hg in room air. The fetus was in a breech presentation and estimated fetal weight was 1567 g.

The patient was treated with atosiban (a competitive antagonist of oxytocin) infusion for tocolysis and two doses of betamethasone (12 mg, intramuscular, 24 h apart) for fetal lung maturation were administered. With uterine contractions not subsiding and a non-stress test showing intermittent minimal fetal heart rate variability, emergency cesarean section was decided at gestational age of 32 weeks and 5 days. After deciding on the surgery, preoperative consultations were made with a cardiologist, cardiovascular surgeon, and pediatrician to prepare for intraoperative events and postoperative care.

Considering the risk of epidural hematoma following catheterization or needling owing to continued aspirin use and thrombocytopenia and rapid decrease in systemic vascular resistance (SVR) that could cause hemodynamic instability, general anesthesia was chosen over regional anesthesia. The patient was intraoperatively monitored using pulse oximetry, electrocardiography, noninvasive blood pressure measurement and bispectral index (BIS, A‑2000 XP; Aspect Medical System, Newton, MA, USA). For continuous blood pressure monitoring, the radial artery was catheterized. With a pediatrician on standby, after applying a surgical drape to the patient, remimazolam was infused at 6 mg/kg/h and remifentanil at 3 ng/mL using target-controlled infusion (Minto model; Orchestra®; Fresenius-Vial, Brezins, France). Upon confirming that the BIS value dropped below 60, rocuronium (50 mg) was administered, manual ventilation was initiated and surgery was begun immediately after endotracheal intubation. Anesthesia was maintained with remimazolam at 1–2 mg/kg/h and remifentanil at 1–2 ng/ml with target-controlled infusion. During surgery a tidal volume of 325–375 ml without positive end-expiratory pressure (PEEP) was administered, which resulted in a mean airway pressure of 4–5 cmH₂O, and the normal range of end tidal CO₂ (EtCO₂) was achieved with a respiratory rate of 7–10 breaths/min. The baby was delivered 2 min after surgery initiation and cried immediately (1-min APGAR score of 7, activity: 1, pulse: 2, grimace: 2, appearance: 1, respiration: 1). After standard neonatal care including tactile stimulation, drying and warming and clearing the airway, approximately 30 s of positive pressure ventilation was performed. At 5 min after delivery the baby’s respiratory status improved and the APGAR score was 9 (activity: 1, pulse: 2, grimace: 2, appearance: 2, respiration: 2). The newborn, weighing 1746 g, was subsequently transferred to the neonatal intensive care unit (NICU). After placental delivery carbetocin (0.1 mg) mixed with 0.9% NaCl (100 ml) was administered. The surgery was completed after confirming adequate hemostasis and uterine contraction. For recovery after general anesthesia sugammadex (200 mg) was administered with a train-of-four count of 1 (NMT Mechanosensor; GE Healthcare, Berlin, Germany). In addition, flumazenil (0.2 mg) was administered to ensure rapid reversal of the effects of remimazolam and to help prevent possible hypoventilation. The endotracheal tube was removed after confirming that the patient’s BIS value was > 90 and the train-of-four ratio was > 98%. The patient was hemodynamically stable and no inotropics or vasopressors were required. Total surgical time was 23 min and anesthesia time was 45 min. Intraoperatively, 600 ml of crystalloid was administered, estimated blood loss was 400 ml and urine output was 150 ml. The patient was transferred to the intensive care unit with 5 l/min of oxygen applied via a facial mask.

During the immediate postoperative period, a cardiologist provided patient care. Postoperative ABGA showed pO₂ 197.1 mm Hg and paCO₂ 26.1 mm Hg with 4 l/min of oxygen applied via a facial mask, and oxygen supplementation was slowly tapered with target SpO₂ of ≥ 95%. Postoperatively, the patient’s hemoglobin level dropped to 7.8 g/dL; hence, two packs of red blood cells were transfused and 15 ml ferric hydroxide (300 mg iron) was administered. On postoperative day 1 the patient was transferred to a general ward with hemoglobin 10.4 g/dl and stable vital signs without oxygen supplementation. The patient’s chest X‑ray, electrocardiogram, and cardiac enzymes were checked daily and showed no abnormalities. The patient was transferred to the obstetrics department on the 3rd postoperative day and discharged on the 7th postoperative day without complications.

The baby maintained SpO₂ above 95% on room air in the NICU and ventilator care was unnecessary. An echocardiogram performed on the 5th day after birth showed normal results and a brain ultrasound performed on the 7th day after birth showed a heterogeneous periventricular white matter echo and no germinal matrix or intraventricular hemorrhage. Additionally, a screening test for congenital metabolic abnormalities in newborns performed on the 7th day after birth showed normal results. The baby received NICU care for phototherapy owing to neonatal jaundice and was discharged on the 30th day after birth.

To our knowledge, this is the first case report of cesarean section under general anesthesia using remimazolam in a patient with Fontan circulation. Herein, general anesthesia was performed using remimazolam, remifentanil, and rocuronium and the mother remained hemodynamically stable during surgery. She recovered appropriately after administration of flumazenil and sugammadex. The newborn was also stable without complications.

Remimazolam can be considered as a reasonable choice when performing a cesarean section with the patient under general anesthesia in women with Fontan circulation. Further studies on its impact on mothers and newborns are warranted.