Study suggests altered vagus nerve activity, creating resistance in the esophagus while swallowing
Infants exposed to opioids while in the womb often show signs of gastroesophageal reflux disease. But a study by neonatologists at Nationwide Children’s found that feeding troubles are more likely due to excessive pressure and a lack of coordinated muscle contractions in the esophagus.
The researchers suggest that the activity of the vagus nerve, which controls swallowing and the gut, is turned up in a way that excitatory responses are heightened while relaxation responses are subdued. And the effect may be long-lasting. The babies in the study were weeks or months from birth and past any medical management of neonatal abstinence syndrome (fetal drug exposure).
“Neuroactive drugs affect the developing neurological system,” says Sudarshan Jadcherla, MD, a principal investigator in the Center for Perinatal Research at Nationwide Children’s and leader of the study, published in The Journal of Maternal-Fetal & Neonatal Medicine. “That’s where the problems occur.”
Jadcherla and his colleagues believe this study is the first to identify the mechanics underlying feeding difficulties in infants with fetal opioid exposure. These babies tend to vomit, arch their backs, cough and choke.
Using a specially constructed pressure-sensing catheter, the research team measured the strength and coordination of the esophagus of six infants with fetal opioid exposure and 12 infants without, while at rest and while swallowing. They found pressure in the lower sphincter in opioid-exposed babies was significantly higher at rest and opened slowly and inadequately. When swallowing, these babies had longer contractions all along the esophagus and the resting, or nadir, pressure in the lower sphincter was higher than in the controls’.
While feeding, “the bolus doesn’t move efficiently, because of resistance,” says Dr. Jadcherla, who is also medical director of the Neonatal and Infant Feeding Disorders Program at Nationwide Children’s and professor of pediatrics at The Ohio State University College of Medicine.
“We now know it’s not reflux so we don’t treat it with acid-suppressive medication,” he says. “Acid is needed for good digestion of milk. If acid’s suppressed, you create a new problem.”
Compared to control babies, the drug-exposed babies were born smaller, spent more time in the ICU and their length of stay was greater by almost a month.
“Drug-exposed babies have four things in common: dysmaturity (their organ systems fail to mature at the rate or to the function expected for gestational age), feeding difficulties, growth problems and a need for parents to understand their problems,” Dr. Jadcherla says.
“We can use information from this study to better care for these babies and better educate and support the moms,” he continues. “When you advocate for the baby, you advocate for the mother and baby.”
Dr. Jadcherla is now seeking a grant for a longitudinal study, tracking opioid-exposed babies over time to determine when feeding difficulties occur, how they change over time and when subsequent problems occur.
Citation: Hart BJ, Viswanathan S, Jadcherla SR. Persistent feeding difficulties among infants with fetal opioid exposure: mechanisms and clinical reasoning. Journal of Maternal-Fetal & Neonatal Medicine. 2018 Sep 9:1-7 [Epub ahead of print]