Intrauterine fetal bradycardia after accidental administration of the anesthetic agent in the subdural space during epidural labor analgesia -A case report-
A 38-year-old G1P0 primigravida was admitted to our hospital at 40+6 weeks gestation for a normal vaginal delivery. She had no history of medical illness or trauma. The initial fetal heart rate (HR) was 120-150 beats/min and showed good reactivity and variability. When the diameter of the cervical opening was approximately 4 cm, lumbar epidural analgesia was planned, and an intravenous (IV) infusion of lactated Ringer's solution (1,000 ml) was administered. An 18-gauge Tuohy needle (Portex® Regional Anaesthesia Tray, Smiths Medical, UK) was blindly inserted into the lumbar epidural space at the L3-4 level in the left decubitus position. A Tuohy needle was advanced to 5 cm, at which point the epidural space was identified on the first attempt using the loss of resistance (LOR) technique. After ensuring that there was no cerebrospinal fluid (CSF) or blood leak, we slowly injected a test dose, i.e., 4 ml of 1% lidocaine with 15 µg of epinephrine. An epidural catheter (Portex® Regional Anaesthesia Tray, Smiths Medical, UK) was inserted without any resistance. The catheter tip was threaded 4 cm in the cephalad direction beyond the Tuohy needle, after catheter placement. We confirmed that there was no CSF and blood by aspirating the catheter. Then, we mixed 20 ml of 0.75% ropivacaine and 100 µg of fentanyl with normal saline (total volume, 100 ml), and subsequently injected 12 ml of the mixture, The rest of the mixture was injected into the epidural space with a patient controlled epidural analgesia (PCEA) pump (Pain Management Provider®, Abbott, USA) with a basal flow rate of 5 ml/h plus a 5 ml bolus with a 5 min lockout. At 5 minutes after the initial dose administration, her blood pressure (BP), HR, and respiratory rate (RR) were 120/70 mmHg, 72 beats/min, and 20 breaths/min, respectively. We subsequently assessed the extent of bilateral sensory blockade by observing the loss of cold sensation to alcohol sponges and the loss of sensation to pinpricks. At that time, the sensory level was located at the tenth thoracic dermatome, and the motor function was intact. At 15 minutes after the initial dose administration, the patient complained of a pulling sensation and tightness at the back of her neck. At 20 minutes after the initial dose administration, the patient showed drowsiness and a depressed mental status; therefore, we encouraged her to take deep breaths and stopped the PCEA pump. The total injected volume of the drug mixture was 1.5 ml. At that time, her vital signs were as follows: BP, 90/60 mmHg; HR, 60 beats/min; and RR, 8 breaths/min. The sensory level was at the eighth thoracic dermatome; however, no change in motor function was observed. Because of the reduced RR and depressed mental status, the patient was placed in the Trendelenburg position and was administered 100% O2 via a facial mask at a flow rate of 5 L/min. At 3 min after position change, her vital signs were as follows: BP, 76/49 mmHg; HR, 55 beats/min; RR, 8 breaths/min; and SpO2, 95%. The sensory level was the third thoracic dermatome, but her motor functions were not affected. After the patient was injected with 10 mg of ephedrine, an obstetrician examined the fetal status via ultrasonography. The fetus showed severe bradycardia, (HR, 70 beats/min); despite being in the normal range (HR, 100-150 beats/min) before this event. Therefore, we decided to perform an emergency cesarean section, which was planned to occur within 30 min, followed by prompt intrauterine fetal resuscitation. At that time, the patient's vital signs were as follows: BP, 80/51 mmHg; HR, 52 beats/min; RR, 8 breaths/min; and SpO2, 92%. We moved the patient to the left lateral recumbent position, injected 0.5 mg of atropine via the maternal IV line, started rapid fluid replacement, and continuously monitored the fetal HR. At 5 min after intrauterine fetal resuscitation, the fetal HR was 100 beats/min, but the patient still showed a depressed mental status and complained of dyspnea. Artificial respiration was performed immediately by using AMBU bag because the patient's SpO2 decreased to 82%. Consequently, her SpO2 recovered to 95%, while the fetal HR increased to 120 beats/min and showed good variability. The fetal HR had decreased for approximately 10 minutes. Fifteen minutes after recovery of the SpO2 level, the patient was transferred to the operating room on artificial ventilation. The arterial blood gas analysis performed immediately before the operation revealed the following: pH, 7.086; PaCO2, 66.6 mmHg; PaO2, 218.6 mmHg; HCO3, 19.6 mEq/L; base excess, -10.8; and SaO2, 99.0%. The patient's preoperative vital signs were as follows: BP, 94/62 mmHg; HR, 90 beats/min; and RR, 8 breaths/min. Anesthesia was induced by the administration of 4 mg/kg of IV thiopental, while tracheal intubation was facilitated by the administration of 1 mg/kg of IV succinylcholine. After tracheal intubation, anesthesia was maintained with O2, air, and 1.5-2.0 vol% sevoflurane. For the muscular block, 4 mg of vecuronium was administered. A live infant, weighing 3.06 kg, was delivered. The incision to delivery time was 3 min. The Apgar score was 8/9. After 40 minutes, the patient was transferred to a recovery room after extubation, because she showed complete recovery during the emergence period. After that point, her vital signs were stable, tidal volume > 400 ml, RR was 12 breaths/min, and SpO2 was 99% in room air. A neurological examination performed in the recovery room, showed that the patient had an alert mental status, and that her orientation-related mental functions were normal. The sensory and motor functions of the patient recovered completely, but she complained of mild numbness in her thighs and calves. Arterial blood gas analysis performed in the recovery room revealed the following: pH, 7.350; PaCO2, 30.7 mmHg; PaO2, 156.3 mmHg; HCO3, 16.6 mEq/L; base excess, -7.8; and O2 saturation, 98.9%. After 1 hour in the recovery room, the patient was transferred to the general ward. After 2 days, no post-dural puncture headache or other neurological complications were observed, therefore, she was discharged along with the infant, who did not show complications, or neurological abnormalities.