Which is the most likely cause of fetal bradycardia after reversal of muscle relaxants in a pregnant patient during surgery?

Which is the most likely cause of fetal bradycardia after reversal of muscle relaxants in a pregnant patient during surgery?

• A. Fetal head compression
• B. Maternal hypoxia
• C. Fetal hypoxia
• D. Reversal agents

Answer: (D)

The main idea is that reversal drugs used after neuromuscular blockade can trigger fetal bradycardia because they cross the placenta and enhance cholinergic (parasympathetic) effects on the fetus. When a nondepolarizing blocker is reversed, acetylcholinesterase is inhibited to raise acetylcholine at the neuromuscular junction, and an anticholinergic is given to protect the mother from bradycardia. Some of these drugs reach the fetus and increase vagal stimulation, slowing the fetal heart rate. The timing—bradycardia occurring after reversal—points to the pharmacologic effect of the reversal agents rather than head compression or hypoxia, which would have other patterns or accompanying signs. In practice, if this happens, assess maternal oxygenation and blood pressure and manage the fetus accordingly, recognizing that the reversal agents are the most likely cause in this scenario.

The main idea is that reversal drugs used after neuromuscular blockade can trigger fetal bradycardia because they cross the placenta and enhance cholinergic (parasympathetic) effects on the fetus. When a nondepolarizing blocker is reversed, acetylcholinesterase is inhibited to raise acetylcholine at the neuromuscular junction, and an anticholinergic is given to protect the mother from bradycardia. Some of these drugs reach the fetus and increase vagal stimulation, slowing the fetal heart rate. The timing—bradycardia occurring after reversal—points to the pharmacologic effect of the reversal agents rather than head compression or hypoxia, which would have other patterns or accompanying signs. In practice, if this happens, assess maternal oxygenation and blood pressure and manage the fetus accordingly, recognizing that the reversal agents are the most likely cause in this scenario.