A 28-year-old primigravid woman at 40 weeks gestation is hospitalized for induction of labor. She has no chronic medical conditions, and her pregnancy has been uncomplicated. Intravaginal misoprostol is administered for cervical ripening followed by intravenous infusion of oxytocin. Progressive uterine contractions are achieved, and the fetal heart rate tracing is reassuring. Patient-controlled bupivacaine via an epidural catheter is started for pain control. Twenty minutes later, the patient experiences perioral numbness, a metallic taste in her mouth, and tinnitus. She also reports feelings of anxiety and palpitations but has no headache or visual disturbances. Blood pressure is 150/86 mm Hg and pulse is 110/min. Physical examination reveals normal deep tendon reflexes and no clonus. While being examined, the patient has a generalized tonic-clonic seizure. Which of the following is the most likely cause of this patient's seizure?

Question

A 28-year-old primigravid woman at 40 weeks gestation is hospitalized for induction of labor.  She has no chronic medical conditions, and her pregnancy has been uncomplicated.  Intravaginal misoprostol is administered for cervical ripening followed by intravenous infusion of oxytocin.  Progressive uterine contractions are achieved, and the fetal heart rate tracing is reassuring.  Patient-controlled bupivacaine via an epidural catheter is started for pain control.  Twenty minutes later, the patient experiences perioral numbness, a metallic taste in her mouth, and tinnitus.  She also reports feelings of anxiety and palpitations but has no headache or visual disturbances.  Blood pressure is 150/86 mm Hg and pulse is 110/min.  Physical examination reveals normal deep tendon reflexes and no clonus.  While being examined, the patient has a generalized tonic-clonic seizure.  Which of the following is the most likely cause of this patient's seizure?

Quizplus · Accepted Answer

During labor, epidural analgesia is the preferred method of pain control because it provides pain relief with minimal maternal and fetal sedation. The epidural catheter is normally inserted into the epidural space to deliver a controlled, low-concentration, slow release of local anesthetic (eg, bupivacaine). However, the epidural catheter can sometimes be inadvertently inserted into the epidural vasculature, resulting in direct delivery of the anesthetic into the maternal circulation and rapid systemic drug absorption. This causes local anesthetic systemic toxicity, which initially blocks inhibitory neural pathways to cause symptoms of CNS overactivity (eg, perioral numbness, metallic taste, tinnitus). This CNS overactivity may develop into a generalized tonic-clonic seizure. Cardiovascular sympathetic activation (eg, tachycardia, hypertension) can follow with a risk of fulminant cardiovascular collapse. Management of local anesthetic systemic toxicity is with drug cessation, benzodiazepines for seizure control, and supportive care. (Choice B) Eclampsia is a common cause of intrapartum seizure and can present with hypertension. In contrast to this patient, those with eclampsia typically have headache, visual disturbances (eg, scotomata), and hyperreflexia with clonus. (Choice C) An inadvertent spinal block can occur if the epidural catheter accidentally punctures the dura and local anesthetic is injected into the intrathecal space. This can cause a "high spinal" or total spinal anesthesia, a life-threatening complication that typically presents with hypotension and respiratory depression due to diaphragmatic paralysis. (Choice D) Misoprostol, a synthetic prostaglandin, is more commonly associated with abdominal pain and diarrhea, which are not seen in this patient. It is not associated with seizures. (Choice E) Oxytocin has a similar structure to antidiuretic hormone and can cause severe hyponatremia, cerebral edema, and seizures if administration is excessive or prolonged (eg, lengthy induction of labor). However, oxytocin toxicity does not typically cause perioral numbness or a metallic taste. Educational objective: Local anesthetic systemic toxicity, a potential complication of epidural analgesia, can cause CNS overactivity (eg, perioral numbness, metallic taste, tinnitus) and generalized tonic-clonic seizures. References: Clinical presentation of local anesthetic systemic toxicity: a review of published cases, 1979 to 2009. (http://www.ncbi.nlm.nih.gov/pubmed/20301824) The third American Society of Regional Anesthesia and Pain Medicine practice advisory on local anesthetic systemic toxicity: executive summary 2017. (http://www.ncbi.nlm.nih.gov/pubmed/29356773)

A 28-Year-Old Primigravid Woman at 40 Weeks Gestation Is Hospitalized