FHR Unaffected by Maternal Temp in MMC Procedures

A study of anesthetic management for fetoscopic myelomeningocele (MMC) repairs finds no correlation between low maternal core temperature and low fetal heart rate (FHR).

Research led by Cincinnati Children’s Fetal Care Center fetal anesthesiologist Rupi Parikh, MD, collected retrospective data from maternal anesthetic records of open and fetoscopic MMC procedures performed at Cincinnati Children’s between 2011 to 2023. An abstract of the findings was presented to the International Fetal Medicine & Surgery Society.

Parikh and her team reviewed FHR trends and specific anesthesia indices. Researchers looked at records of 87 fetoscopic MMC repair patients and 59 open MMC repair patients. They collected data about:

• FHR (preoperative, after laparotomy, end procedure)
• Magnesium levels (fetoscopic)
• Maternal temperature (incision and range for case)
• Surgical time
• Vasopressor use

How Evolving Techniques Improve Anesthetic Management

Fetal anesthesiologists continually work to improve how they deliver anesthesia. "Collaboration and communication with fetal surgeons and other members of the care team are essential, as the health of the mother and fetus are being managed at the same time," Parikh says.

"Advancing and evolving techniques for prenatal MMC repairs help improve anesthetic management," Parikh adds. Before fetoscopic surgical options, MMC repairs were performed through a hysterotomy, requiring high doses of volatile anesthetics to obtain optimal surgical conditions. With the fetoscopic approach, surgeons start magnesium sulfate earlier, at laparotomy. "This approach shows a significant decrease in the concentrations of volatile anesthetic used," Parikh says.

“Any anesthetic technique that leads to an overall decrease in the amount of volatile anesthetic delivered to a developing baby is significant.”

Taking Steps to Prevent or Reduce an FHR Decrease

"In the past year, fetal anesthesiologists at Cincinnati Children’s implemented changes to mitigate an FHR decrease from an anesthetic standpoint," Parikh says. During an MMC repair, the team:

• Prioritizes maternal physiology and hemodynamics
• Maintains maternal blood pressure (this directly correlates with uteroplacental perfusion)
• Optimizes the mother’s core body temperature to keep the fetus warm and avoid changes in homeostasis and hemodynamics

The fetal anesthesia team now also reviews the mother’s labs, paying attention to the hemoglobin/hematocrit.

“Anemia can affect oxygenation and uteroplacental perfusion, so if indicated, we may consider transfusing preoperatively or intraoperatively,” Parikh says.

"While this study did not show a relationship between maternal low core temp and a decrease in FHR, the idea theoretically makes sense," Parikh says. The team will continue to collect data and will proactively keep mothers warm to avoid any potential FHR changes.

In the future, Parikh wants to study the connections between volatile anesthetic delivered to mothers in open and fetoscopic cases, and the magnesium sulfate administered. “I want to learn more about ways to limit exposure to volatile anesthetics to the fetus and developing brain,” she says.

Other areas Parikh wants to research include:

• Incidence of vasopressor administration and its relationship to other variables
• Fetal drug metabolism and the timing of fetal “cocktail” (vecuronium, fentanyl, atropine) dosing