Acute Gastroenteritis

Abstract

In managing acute diarrhea in children, clinicians need to be aware that management based on “bowel rest” is outdated, and instead reinstitution of an appropriate diet has been associated with decreased stool volume and duration of diarrhea. In general, drug therapy is not indicated in managing diarrhea in children, although zinc supplementation and probiotic use show promise.After reading this article, readers should be able to:Acute gastroenteritis is an extremely common illness among infants and children worldwide. According to the Centers for Disease Control and Prevention (CDC), acute diarrhea among children in the United States accounts for more than 1.5 million outpatient visits, 200,000 hospitalizations, and approximately 300 deaths per year. In developing countries, diarrhea is a common cause of mortality among children younger than age 5 years, with an estimated 2 million deaths each year. American children younger than 5 years have an average of two episodes of gastroenteritis per year, leading to 2 million to 3 million office visits and 10% of all pediatric hospital admissions. Furthermore, approximately one third of all hospitalizations for diarrhea in children younger than 5 years are due to rotavirus, with an associated direct cost of $250 million annually. (1)(2)Diarrhea is defined as the passage of three or more loose or watery stools per day (or more frequent passage of stool than is normal for the individual). Stool patterns may vary among children; thus, it is important to note that diarrhea should represent a change from the norm. Frequent passage of formed stools is not diarrhea, nor is the passing of “pasty” stools by breastfed young infants. (2)(3)There are three clinical classifications of diarrheal conditions:The clinical manifestations of acute gastroenteritis can include diarrhea, vomiting, fever, anorexia, and abdominal cramps. Vomiting followed by diarrhea may be the initial presentation in children, or vice versa. However, when emesis is the only presenting sign, the clinician must contemplate other diagnostic possibilities, such as diabetes, metabolic disorders, urinary tract infections, meningitis, gastrointestinal obstruction, and ingestion. The characteristics of the emesis, such as color, intensity, and frequency, as well as relationship to feedings, often lead to the most likely diagnoses. (1)(2)(4)A complete history and physical examination always must be performed. The clinician should inquire about the duration of illness; the number of episodes of vomiting and diarrhea per day; urine output; the presence of blood in the stool; accompanying symptoms such as fever, abdominal pain, and urinary complaints; and recent fluid and food intake. Recent medications and the child’s immunization history also should be reviewed. The physical examination should focus on identifying signs of dehydration such as level of alertness, presence of sunken eyes, dry mucous membranes, and skin turgor. (1)(3)Viruses are the cause of the majority of cases of acute gastroenteritis in children worldwide. Viral infections usually are characterized by low-grade fever and watery diarrhea without blood. Bacterial infections may result in infiltration of the mucosal lining of the small and large intestines, which in turn causes inflammation. Children thus are more likely to present with high fever and the presence of blood and white blood cells in the stool. Table 1 lists the common causal pathogens of acute gastroenteritis in children. (2)Dehydration related to acute gastroenteritis is a major concern in pediatric patients. Therefore, clinicians in primary care offices, emergency departments, and hospital settings must assess the circulatory volume status as part of the initial evaluation of children presenting with acute gastroenteritis. This assessment is essential in guiding the decision making regarding therapy and patient disposition.In 1996, the CDC published recommendations on the assessment of dehydration, which were subsequently endorsed by the American Academy of Pediatrics (AAP). These guidelines classified patients into three groups based on their estimated fluid deficit: mild dehydration (3%–5% fluid deficit), moderate dehydration (6%–9% fluid deficit), and severe dehydration (>10% fluid deficit or shock). These classifications are similar to those delineated by the World Health Organization (WHO) in 1995, which also divided patients into three groups: no signs of dehydration (<3%–5%), some signs of dehydration (5%–10%), and severe dehydration (>10%).The authors of studies have evaluated the correlation of clinical signs of dehydration with posttreatment weight gain and have demonstrated that the first signs of dehydration might not be evident until 3% to 4% dehydration. Furthermore, more obvious clinical signs of dehydration become apparent at 5% dehydration, and indications of severe dehydration become evident when the fluid loss reaches 9% to 10%. As a result, the CDC revised its recommendations in 2003 and combined the mild and moderate dehydration categories, acknowledging that the signs of dehydration might be apparent over a relatively wide range of fluid loss (Table 2). The ultimate goal of this assessment is to identify which patients can be sent home safely, which should remain under observation, and which are candidates for immediate, aggressive therapy. (1)Serum electrolytes are not indicated routinely in patients who have acute gastroenteritis. Authors of several studies have evaluated the utility of laboratory tests in assessing the degree of dehydration, and the evidence reveals that such studies are imprecise and may distract clinicians from focusing on signs and symptoms that have proven diagnostic utility. Commonly obtained laboratory tests, such as blood urea nitrogen and bicarbonate concentrations, generally are helpful only when the results are markedly abnormal. Thus, these laboratory tests should not be considered definitive predictors of dehydration. (1)(5)(6)(7) Additionally, current evidence demonstrates that urinary indices, including specific gravity and the presence of ketones, also are not useful diagnostic tests for identifying the presence of dehydration. (8)(9) Therefore, measurement of electrolytes should be reserved for patients afflicted with severe dehydration who require intravenous (IV) fluid therapy upon initial clinical assessment and for those in whom hypernatremic dehydration is suspected (ie, ingestion of hypertonic solutions). (1)Stool studies should be considered during outbreaks, especially in child care settings, schools, and hospitals, where there is a public health concern that mandates the identification of a pathogen and the identification of the source of disease. Other special circumstances that warrant the collection of stool samples for identification of enteric pathogens include the evaluation of children who have dysentery, a history of recent foreign travel, and managing young or immunocompromised children who present with high fever. (2)The introduction of oral rehydration solutions (ORSs) has decreased significantly the morbidity and mortality associated with acute gastroenteritis worldwide. (1) ORS is the cornerstone of therapy in managing uncomplicated cases of diarrhea.ORSs began to evolve in the 1940s, as an initiative of Daniel Darrow at Yale and Harold Harrison at Baltimore City Hospital. Darrow performed studies in children who had acute diarrhea and identified the need for appropriate replacement of sodium (Na+), potassium (K+), and alkali to correct the metabolic acidosis. Subsequently, Harrison added glucose to a balanced electrolyte solution and established that such a solution could be used successfully for rehydration. In 1953, Chatterjee first demonstrated that ORSs could rehydrate patients who have cholera and avoid the need for IV fluids.Studies evaluating the mechanism of intestinal solute transport have revealed that the absorption of water in the gastrointestinal tract is a passive process that depends on the osmotic gradient created by the transcellular transport of electrolytes and nutrients. Although there are alternate mechanisms that contribute to the absorption of Na+ in the enterocyte, it is the coupled transport of Na+ and glucose at the intestinal brush border that is responsible for the success of ORSs.Sodium-solute-coupled cotransport is an energy-dependent process. The Na+ gradient within the cell is maintained by the Na+–K+ adenosine triphosphatase pump on the basolateral membrane of the enterocyte. Subsequent research has revealed that other solutes, such as amino acids, also were absorbed by active transport mechanisms involving Na+ ion coupling.Clinical studies of ORSs in patients who have cholera in the Philippines and India have confirmed that oral replacement of water and electrolytes produced a sufficient osmotic gradient to rehydrate patients successfully, even in severe diarrheal disease. Solutions of lower osmolarity that maintain the 1:1 glucose to Na+ ratio function optimally as oral solutions for diarrhea management. Subsequent clinical studies have confirmed the dramatic effect that ORSs had on decreasing mortality in acute diarrheal disease; consequently, the WHO and the AAP have endorsed the implementation ORSs worldwide. (4)Most cases of acute gastroenteritis in children are self-limiting and do not require the use of medications. An initial critical step in the management of acute gastroenteritis usually begins at home with early fluid replacement. Families should be instructed to begin feeding a commercially available ORS product as soon as the diarrhea develops. Although producing a homemade solution with appropriate concentrations of glucose and Na+ is possible, serious errors can result in attempting to use a homemade solution. Thus, standard commercial oral rehydration preparations should be recommended where they are readily available. (4)ORS is recommended by the WHO and the AAP as “the preferred treatment of fluid and electrolyte losses caused by diarrhea in children with mild to moderate dehydration.” The basis of this endorsement is meta-analysis comparing ORSs with traditional IV rehydration. The evidence supports low overall treatment failures with ORSs (3.6%), defined as the need to revert to IV therapy, without an increased incidence of iatrogenic hyponatremia or hypernatremia. (10) Other advantages of ORS include its lower cost, the elimination of the need for intravascular line placement, and the involvement of the parents in providing oral fluid replacement in the home environment when tolerated.Common household beverages such as fruit juices, sports drinks, tea, and soft drinks should be avoided in the management of acute gastroenteritis. Many of these beverages have a high osmolality due to their high sugar content and contain little Na+ and K+; consequently, use of these fluids may worsen the patient’s condition by increasing the stool output and increasing the risk of hyponatremia. Table 3 provides a comparison of the carbohydrate load and electrolyte composition of commercial ORSs with the content of commonly offered household drinks deemed inappropriate for oral rehydration therapy. (4)Treatment of acute gastroenteritis should include two phases of therapy: rehydration and maintenance. In the rehydration phase, fluid should be replaced rapidly in a 3- to 4-hour period. In the maintenance phase, calories, in addition to fluids, are administered.Rapid re-alimentation should follow rapid rehydration, having the goal of returning the patient quickly to an age-appropriate, unrestricted diet. During both phases, persistent fluid losses from vomiting and diarrhea should be replaced continuously. Table 4 summarizes the recommended rehydration and fluid loss replacement therapies based on the degree of dehydration. (1)For more than 15 years, physicians have recognized the importance of early introduction of an age-appropriate diet, compared with the outdated practice of “bowel rest.” Reinstitution of an appropriate diet has been associated with decreased stool volume and duration of diarrhea.Breastfeeding should be continued during both the rehydration and maintenance phases. The diet should be advanced as tolerated to compensate for lost caloric intake during the acute illness. Lactose restriction ordinarily is not indicated, although such restriction might be helpful in cases of diarrhea in malnourished children or among children who have a severe enteropathy. In general, changes to a lactose-free formula should be made only if the stool output significantly increases on a milk-based diet. (1)(3)(4)The ultimate goal for patients who have minimal or no dehydration is to provide adequate fluid intake while continuing an age-appropriate diet. Nutrition should not be restricted. (4) Patients who have diarrhea must have increased fluid intake to compensate for losses and cover maintenance needs; the use of ORSs containing at least 45 mEq Na+/L is preferable to other fluids for preventing and treating dehydration. In principle, 1 mL of fluid should be administered for each gram of stool output. In the hospital setting, soiled diapers can be weighed (without urine), and the estimated dry weight of the diaper can be subtracted. At home, 10 mL of fluid can be administered per kilogram body weight for each watery stool or 2 mL per kilogram for each episode of emesis. As an alternative, children weighing less than 10 kg should be administered 60 to 120 mL (2–4 ounces) of ORS for each episode of vomiting or diarrheal stool, and those weighing more than 10 kg should be fed 120 to 240 mL (4–8 ounces). (1)Children who have mild to moderate dehydration should have their estimated fluid deficit replaced rapidly. Fifty to 100 mL of ORS per kilogram body weight should be administered over a period of 2 to 4 hours to replace the fluid deficit, with additional ORS administered to replace ongoing losses. By using a teaspoon, syringe, or medicine dropper, small volumes of fluid should be offered initially and increased gradually as tolerated. If a child appears to want more than the estimated amount of ORS, more can be offered. Nasogastric (NG) feeding allows continuous administration of ORS at a slow, steady rate for patients who have persistent vomiting or oral ulcerations. Clinical trials support using NG feedings as a well-tolerated, more cost-effective method associated with fewer complications when compared with IV hydration. This method is particularly useful in the emergency department, where hospital admissions can be avoided if oral rehydration efforts are successful. In addition, a meta-analysis of randomized controlled trials comparing ORS versus IV rehydration in dehydrated children demonstrated shorter hospital stays and improved parental satisfaction with oral rehydration. (1)(4)Hydration status should be evaluated on a regular basis in the clinical setting to objectively assess the response to therapy and to evaluate the correction of the dehydration. Upon return to the home setting, caregivers must be provided with and must understand fully the instructions containing specific indications prompting their return for re-evaluation and further medical care. (1)Severe dehydration is characterized by a state of hypovolemic shock requiring rapid treatment. Initial management includes placement of an IV or intraosseous line and rapid administration of 20 mL/kg of an isotonic crystalloid (eg, lactated Ringer solution, 0.9% sodium chloride). Hypotonic solutions should not be used for acute parenteral rehydration. The patient should be observed closely and monitored on a regular and frequent basis. Serum electrolytes, bicarbonate, urea nitrogen, creatinine, and glucose levels should be obtained, although commencing rehydration therapy without these results is safe. A poor response to the initial, immediate treatment should raise the suspicion of an alternative diagnosis, including septic shock as well as neurologic or metabolic disorders. Therapy may be switched to an oral or NG route as soon as hemodynamic stability is accomplished and the patient’s level of consciousness is restored. (1)(4)The majority of children who experience acute gastroenteritis can be managed on an outpatient basis.The decision to admit patients who have acute gastroenteritis must take into account risk factors predisposing to unfavorable outcomes, such as prematurity, young maternal age, lack of immediate and follow-up access to a health-care facility, and other socio-economic stressors. Clinical indications for the management of acute gastroenteritis in a hospital setting are described in the following scenarios (1):There are several clinical settings in which oral rehydration therapy is contraindicated. These conditions include the care of children who have hemodynamic instability, altered mental status, and shock in which the use of ORSs can increase the risk of aspiration because of the loss of airway protective reflexes. Likewise, ORSs should not be used in cases of abdominal ileus until bowel sounds are present. In cases of suspected intestinal intussusception, which might present with diarrhea or dysentery, the need for radiologic studies and surgical evaluation may be warranted before considering the use of ORSs. (1)(10)If the stool output exceeds 10 mL/kg body weight per hour, the rate of ORS treatment failure is higher. However, ORSs should continue to be offered because the majority of patients will respond well if adequate fluid replacement is administered. (1)For children presenting with persistent emesis, physicians should instruct parents to offer small amounts of ORS; for example, 5 mL with a spoon or syringe every 5 minutes, with a gradual increase in the fluid amount consumed. This technique frequently results in successful fluid replacement and often a decrease in the frequency of vomiting as well. (1)(10)Antibiotics are not indicated in cases of uncomplicated or viral acute gastroenteritis and may actually cause harm. Antimicrobial agents may increase the risk of prolonged carrier stage and relapses in nontyphoid Salmonella infections. Furthermore, treating gastroenteritis due to Shiga toxin producing Escherichia coli with antibiotics may increase the risk of hemolytic-uremic syndrome. The use of antibiotics is reserved for the treatment of acute enteritis complicated by septicemia and in cases of cholera, shigellosis, amebiasis, giardiasis, and enteric fever. (1)(2)(3)Antidiarrheal drugs are not recommended for use because of the risk of their such as are to cause and in children younger than age 3 agents such as have demonstrated in treating acute gastroenteritis in children. an that the intestinal of water and electrolytes without on intestinal has been in children in the setting with the drug is not for use in the United studies of its and are to vomiting from the need to further dehydration and to avoid the need for IV therapy and hospital a has to be an decreasing the rate of admissions in patients with a in the emergency with such as a with and have been to be less in emesis. is by the and only for children than age 2 years and is associated commonly with such as and which may with the rehydration a that is a has been proven to be more than the rate of in with its use is to in children. The use of these medications is not recommended routinely by the AAP or the of these drugs the causes of diarrhea, and the use of may distract the care from the therapy: appropriate fluid and electrolyte replacement and early therapy. is an essential that cells from In cases of acute or diarrhea, there is a loss of zinc due to increased intestinal output. clinical trials in developing in which the of zinc is high have revealed a from zinc therapy in with ORS therapy. The that zinc may the absorption of water and electrolytes, although the mechanism of is not comparing zinc supplementation with have revealed a in stool frequency and of the duration of diarrhea. The addition of zinc to ORSs is recommended by the WHO and the United for the treatment of diarrheal of children. are in that the by a in the intestinal and are the most common probiotic controlled trials have particularly the of in the treatment of acute diarrhea, the duration of the diarrhea by 1 the causes of diarrhea, more in treating gastroenteritis caused by rotavirus, with a in duration of diarrhea of 2 to be more helpful when the therapy is early in the presentation of illness in patients who have viral gastroenteritis. on the other are than that the of intestinal controlled trials have to a in the duration of diarrhea in children; are not recommended