Consider the following:
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The World Health Organization solution is 90 mEq/L Na+, 20 mEq/L K+, 80 mEq/L Cl-, 20 g/L glucose; osmolarity is 310; CHO:Na = 1.2:1; administer 250 mL (approximately 8 oz) every 15 minutes until fluid balance is clinically restored, then 1.5 L of oral fluid per liter of stool.
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Other oral rehydration products include Naturalyte, Cera Lyte, Rehydralyte, and Pedialyte.
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Oral rehydration may not decrease the duration or volume of diarrhea.
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Small amounts of oral fluids may be given repeatedly while the patient is still vomiting.
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Oral rehydration has been largely responsible for the tremendous decrease in the death rate in underdeveloped countries from infectious diarrhea, including cholera.
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The glucose/sodium transport mechanism remains intact despite enterotoxigenic illness. Coupled transport is one of several mechanisms of sodium and water absorption in the bowel. It is the direct entry of sodium and water across the cell at the intestinal brush border membrane via the linking (coupling) of 1 organic molecule, such as glucose, to 1 sodium molecule. This is the principle upon which ORT is based. Optimally, therefore, the ratio of carbohydrate to sodium should approach 1:1. Glucose is necessary to stimulate the absorption of water and electrolytes by the small intestines.
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The solution must be iso-osmolar or hypo-osmolar to avoid an increased osmotic load in the small intestines contributing to an osmotic diarrheal effect, pulling fluid into the lumen.
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Studies have shown oral and IV rehydration to be equivalent therapies in patients who can tolerate the oral fluid.
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Although standard glucose-electrolyte solutions achieve and maintain rehydration, they may not reduce stool volume or duration of diarrheal illness, affecting compliance.
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Newer solutions with complex carbohydrates and short chain polypeptides of cereals and legumes are now available to provide additional organic cotransport molecules with no increase in osmolarity. These appear to offer the advantage of decreased stool volumes and shortened duration of illness.
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Hektoen enteric agar with Escherichia coli colonies. Different growth media are necessary for identifying different enteric pathogens, suppressing the growth of nonpathogens, and allowing for chemical reactions to assist in identification. The appearance results from the organism's ability to ferment lactose placed in the medium. This results in the production of acid, which lowers the pH and causes a change in the pH indicator placed in the medium. Salmonella and Shigella organisms do not ferment lactose.
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Example of Salmonella on Hektoen enteric agar. The medium also contains ferric ammonium citrate, which indicates the production of hydrogen sulfide by the appearance of a black precipitate.
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The MacConkey medium is commonly used and differentiates lactose fermenters, which produce acid, decrease the pH, and cause the neutral red indicator to give the colonies a pink-to-red color.
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The Christensen method is used to determine if an organism produces the enzyme urease (Yersinia) or not (Salmonella, Shigella, Vibrio). Hydrolysis of urea produces ammonia and carbon dioxide, alkalinizing the medium and turning the phenol red from light orange to magenta (pink).
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Often, a combination of methods may be used for identification. The tube on the left is triple sugar iron (TSI) agar. The alkaline slant and acid butt (K/A) indicates an organism that ferments glucose only (not lactose or sucrose). The middle tube is indole positive, as indicated by the pink ring, and indicates the organism's ability to split tryptophan to form indole. The tube on the right is urease negative. Taken together, these tests indicate the organism is likely Shigella.
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Gram stain may be helpful in identifying an etiologic agent. This stain shows gram-negative bacilli, which could be Salmonella or Shigella with 2 polymorphonucleocyte cells (PMNs).
