A 39-year-old woman, gravida 1 para 0, at 36 weeks gestation is undergoing cesarean delivery for a failed induction of labor for preeclampsia with severe features. The patient has been undergoing an induction of labor under epidural analgesia for the past 24 hours. Despite an increasing oxytocin infusion, she has had minimal cervical dilation, and now, the amniotic fluid has turned meconium stained. In the operating room, a dose of prophylactic antibiotics is administered, and an adequate sensory block is confirmed. Prior to the skin incision, the patient develops acute dyspnea. On repeat vital signs, temperature is 36.7 C (98.1 F), blood pressure is 80/50 mm Hg, pulse is 120/min, and respirations are 16/min. Fetal heart rate monitoring shows recurrent, deep variable decelerations, and tocodynamometry shows increased uterine contractions every 2 minutes. The patient appears flushed and in acute distress. Heart sounds are regular and tachycardic. The lungs have scattered wheezes bilaterally. The abdomen is soft, gravid, and nontender. Which of the following is the most likely cause of this patient's clinical presentation?

Question

A 39-year-old woman, gravida 1 para 0, at 36 weeks gestation is undergoing cesarean delivery for a failed induction of labor for preeclampsia with severe features.  The patient has been undergoing an induction of labor under epidural analgesia for the past 24 hours.  Despite an increasing oxytocin infusion, she has had minimal cervical dilation, and now, the amniotic fluid has turned meconium stained.  In the operating room, a dose of prophylactic antibiotics is administered, and an adequate sensory block is confirmed.  Prior to the skin incision, the patient develops acute dyspnea.  On repeat vital signs, temperature is 36.7 C (98.1 F), blood pressure is 80/50 mm Hg, pulse is 120/min, and respirations are 16/min.  Fetal heart rate monitoring shows recurrent, deep variable decelerations, and tocodynamometry shows increased uterine contractions every 2 minutes.  The patient appears flushed and in acute distress.  Heart sounds are regular and tachycardic.  The lungs have scattered wheezes bilaterally.  The abdomen is soft, gravid, and nontender.  Which of the following is the most likely cause of this patient's clinical presentation?

Quizplus · Accepted Answer

11ec25c8_da0f_865f_bc81_29480089b5a3_MD0003_00 This pregnant patient has acute-onset dyspnea, hypotension, and tachycardia during delivery. The onset of symptoms with concomitant wheezing immediately after administration of prophylactic antibiotics is most consistent with anaphylaxis. Anaphylaxis is a type 1 hypersensitivity reaction mediated by IgE, and a common trigger is antibiotics. Circulating antigens to the antibiotics bind IgE on cells, leading to mast cell and basophil degranulation. The release of inflammatory markers (eg, histamine, leukotriene) leads to vascular permeability, edema, and large fluid shifts with resultant hypotension and tachycardia. In addition, leukotriene and prostaglandins cause bronchoconstriction with resultant dyspnea and wheezes. During pregnancy, the high concentration of mast cells and subsequent prostaglandins in the pelvis cause increased uterine contractions and potential fetal heart rate decelerations (secondary to increased contractions and umbilical cord compression). Treatment involves maternal stabilization with intramuscular epinephrine and left lateral patient placement (aortocaval compression prevention) to maintain a systolic blood pressure that preserves uteroplacental perfusion. Continuous fetal heart rate monitoring is performed to assess fetal response to maternal treatment; further management (eg, immediate delivery, vasopressors) is dependent on maternal and fetal hemodynamic status. (Choices A and D) Patients with preeclampsia and associated proteinuria can develop decreased oncotic pressure and subsequent third spacing, resulting in acute pulmonary or laryngeal edema. In both cases, patients can develop dyspnea; however, those with pulmonary edema have crackles, rather than wheezes, on examination, and neither condition is associated with skin flushing. In addition, preeclampsia is unlikely in this patient with hypotension. (Choice B) Amniotic fluid embolism classically presents with cardiovascular collapse (eg, hypotension) and respiratory compromise (eg, dyspnea) from cardiogenic shock during labor. However, most cases are associated with disseminated intravascular coagulopathy (eg, bleeding), which is not seen in this patient. In addition, patients typically have crackles (ie, pulmonary edema secondary to heart failure), rather than wheezing, on examination. (Choice E) Septic shock is characterized by hypotension and tachycardia due to low systemic vascular resistance in response to proinflammatory mediators generated by an infection. This is unlikely in an afebrile patient with no prior signs of infection. Educational objective: Anaphylaxis is an IgE-mediated hypersensitivity reaction caused by mast cell degranulation with widespread histamine and leukotriene release, resulting in hypotension, tachycardia, bronchoconstriction, and increased uterine contractions in pregnancy.

A 39-Year-Old Woman, Gravida 1 Para 0, at 36 Weeks