On dealing with disorders of gastric motility, PHYSIOLOGY explains that vomiting is a reflex action having its start on the endings of certain nerves, such as the pneumogastric, trigeminal, glossopharyngeal, etc.
It may be provoked by exciting the base of the tongue, the soft palate, mucous lining of the stomach, gastric disturbances of a chemical nature of the intestine, of the uterus, of the breast, etc., or it may well be from the brain (psychic influences).
It may also be produced by some substances of the type of ipecacuanha, whose principal reactive is emetine which acts directly on the nervous centers and probably also on the sensitive nerve endings of the mucous membrane of the stomach.
The antiperistaltic contractions of the stomach play only a secondary role in the mechanism of vomiting; the expulsion of matter is the result of the energetic compression of the stomach due to contraction of the abdominal muscles. Magendie demonstrated this with his well known experiment in which he provoked vomiting with an intravenous injection of an emetic in an animal whose stomach had been removed and a bladder used in its place.
These few remarks about the physiopathology of vomiting in general may serve us as an orienting concept when passing upon what has been said about the etiology of vomiting in pregnancy.
Many are the theories that try to explain the etiology of vomiting in pregnancy; but none of them as yet give us a satisfactory explanation upon all the cases of vomiting under the condition we deal with in this paper; even in this pathological problem which has a common denominator it is not possible when dealing with its etiology to overlook the morbid individuality so well expressed in the maxim, “There are diseased, but no diseases and parodying causes, no single cause.”.
From these causes we shall mention only those which are more frequent or at least better known.
C.J. Andrews deals with the etiological problem making a typical classification under three main headings: neurotic, toxaemic and reflex.
In his opinion there is no justification for making another subdivision as the condition is the same all, the only difference being that some features are more prominent in some cases than in others. “A great many clinical facts have given us light upon this matter and have served us as a basis for treatment which otherwise would be entirely empirical,” says the author.
The deficiency o of glycogen in the liver seems to be an accepted fact and according to Titus and Dodds, hypo-glycemia is also demonstrable. Hadden and Guffy find a low sodium chloride content and suggest that this phenomenon is analogous to the vomiting associated with intestinal obstruction.
Franz Arzt, after an extensive study of the gastric contents, concludes that the free hydrochloric acid and total acid of the stomach are lower in pregnancy than in the non- pregnant and that this deficiency is more marked early, at the time nausea and vomiting are most common. This lessening of the free acid in the stomach is probably due to the neutralization caused by the alkaline regurgitations of the duodenal content tot he stomach.
In the opinion of other authors hyperemesis gravidarum is caused by metabolic disorders with perhaps an underlying toxemia of unknown character as the primary disturbing factor. Carbohydrate deficiency is usually evident in its toxic absorption into the blood stream and is response for disturbing the carbohydrate metabolism.
According to E.B. Craigir, vomiting occurring in the early stages of pregnancy may be reflex or neurotic in origin and in the pernicious cases a toxic factor is usually associated with them. Generally speaking, the output of urine diminishes and usually shows the presence of ketone bodies, while both liver and kidneys show pathological changes.
Finally, according to other authors, vomiting is caused by endocrine disorders not being infrequent the finding of exophthalmic goitre coexisting with these cases as also an insufficiency of corpus luteum.
Hyperemesis gravidarum is described as the toxemia of early pregnancy. Cases may be divided into four types:
(1) those in which the vomiting is due to some cause other than the pregnancy, e.g., appendicitis, ulcer, gallstones; (2) those in which irritation of the genitals, such as retroflexed uterus, cervicitis, etc., appears to be mainly responsible: (3) those of nervous origin, such as brain tumor, meningitis, psychosis; (4) those of toxic origin. The latter constitute the largest group.