The use of antiemetic medications is controversial. These drugs should not be prescribed until the etiology of the vomitingis known, and then only for severe symptoms. Phenothiazines, such as prochlorperazine, may be useful for reducing symptoms in food poisoning and motion sickness. Their side-effectprofile must be considered carefully, however, and the doseprescribed should be conservative. Anticholinergics (e.g., scopolamine) and antihistamines (e.g., dimenhydrinate) are usefulfor the prophylaxis and treatment of motion sickness. Drugsthat block serotonin 5-HT3 receptors, such as ondansetron andgranisetron, are frequently used for viral gastroenteritis and canimprove tolerance of oral rehydration therapy. They are helpful for chemotherapy-induced vomiting, often combined withdexamethasone. No antiemetic should be used in patients withsurgical emergencies or when a specific treatment of the underlying condition is possible. Correction of dehydration, ketosis,and acidosis is helpful to reduce vomiting in most patients withviral gastroenteritis.
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Diarrhea is a major cause of childhood morbidity and mortality worldwide. Deaths from diarrhea are rare in industrializedcountries, but are common elsewhere. Acute diarrhea is a majorproblem when it occurs with malnutrition or in the absence ofbasic medical care (see Chapter 30). In North America, mostacute diarrhea is viral and is self-limited, requiring no diagnostic testing or specific intervention. Bacterial agents tend to causemuch more severe illness and typically are seen in food-associated outbreaks or in regions with poor public sanitation. Bacterial enteritis should be suspected when there is dysentery(bloody diarrhea with fever) and whenever severe symptoms arepresent. These infections can be diagnosed by stool culture orother assays for specific pathogens. Chronic diarrhea lasts more than 2 weeks and has a wide range of possible causes, includingserious and benign conditions that are more difficult to diagnose.
Parents use the word diarrhea to describe loose or watery stools, excessively frequent stools, or stools that are large in volume. Constipation with overflow incontinence can be mislabeled as diarrhea. A more exact definition of diarrhea is excessive daily stool liquid volume (>10 mL stool/kg body weight/day). Stool texture, volume, and frequency help to characterize the episode of diarrhea.
Diarrhea may be classified by etiology or by physiologic mechanisms (secretory or osmotic). Etiologic agents include viruses,bacteria or their toxins, chemicals, parasites, malabsorbed substances, and inflammation. Table 126-9 lists common causes of diarrhea in childhood. Secretory diarrhea occurs when the intestinal mucosa directly secretes fluid and electrolytes intothe stool and is the result of inflammation (e.g., inflammatorybowel disease, chemical stimulus). Secretion also is stimulatedby mediators of inflammation and by various hormones, suchas vasoactive intestinal peptide secreted by a neuroendocrinetumor. Cholera is a secretory diarrhea stimulated by the enterotoxin of Vibrio cholerae, which causes increased levels of cAMP within enterocytes and leads to secretion into the small-bowellumen.