Gastrointestinal System
Gastrointestinal function in pregnancy and during labor is a topic
that continues to be controversial. However, there is no doubt that the gastrointestinal
trace undergoes significant anatomic and physiologic changes that increase the risk
of aspiration associated with anesthesia. Progesterone relaxes smooth muscle; consequently,
it impairs esophageal and intestinal motility during pregnancy. Although it was
always accepted that gastric emptying was delayed during pregnancy, it has recently
been suggested that gastric emptying is not always delayed in pregnant women. Recent
work by Wong and coworkers suggests that the ingestion of 300 mL of water may actually
enhance gastric emptying in healthy, term, nonobese, nonlaboring parturients.[20]
However, the risk of aspiration remains real in parturients, especially when undergoing
general anesthesia. Even if gastrointestinal motility has not been affected during
pregnancy, established labor and
the administration of parenteral opioids have been found to delay gastric emptying.
[21]
[22]
Epidural analgesia using local anesthetics without opioids does
not affect gastric emptying, and the use of small doses of epidural fentanyl has
similarly been shown to have no effect on gastric function.[23]
[24]
[25]
The pain of labor, however, may delay gastric emptying and promote
emesis. These changes may be caused by the effects of placentally derived gastrin.
[26]
Because of the gastrointestinal alterations
associated with pregnancy, the use of endotracheal intubation is warranted to reduce
the risk of aspiration if general anesthesia is required.
