Oral Rehydration Therapy: Sipping a Simple Solution Saves Lives Diarrhea-inducing microorganisms such as Vibrio cholera, which causes cholera, are the leading cause of death in children younger than...


Oral Rehydration Therapy: Sipping a Simple Solution Saves Lives


Diarrhea-inducing microorganisms such as Vibrio cholera, which causes cholera, are the leading cause of death in children younger than age 5 worldwide. The problem is especially pronounced in developing countries, refugee camps, and elsewhere where poor sanitary conditions encourage the spread of the microorganisms, and medical supplies and health-care personnel are scarce. Fortunately, a low-cost, easily obtainable, uncomplicated remedy—oral rehydration therapy (ORT)—has been developed to combat potentially fatal diarrhea. This treatment exploits the symporters located at the luminal border of the villus epithelial cells.


Let us examine the pathophysiology of life-threatening diarrhea and then see how simple ORT can save lives. During digestion of a meal, the crypt cells of the small intestine normally secrete succus entericus, a salt and mucus solution, into the lumen. These cells actively transport Cl2 into the lumen, promoting the parallel passive transport of Na1 and H2O from the blood into the lumen. The fluid provides the watery environment needed for enzymatic breakdown of ingested nutrients into absorbable units. Glucose and amino acids, the absorbable units of dietary carbohydrates and proteins, respectively, are absorbed by secondary active transport. This absorption mechanism uses the Na1–glucose (or amino acid) cotransport carriers (SGLT) located at the luminal membrane of the villus epithelial cells (see p. 75). In addition, separate active Na1 carriers not linked with nutrient absorption transfer Na1, passively accompanied by Cl2 and H2O, from the lumen into the blood.


The net result of these various carrier activities is absorption of the secreted salt and H2O along with the digested nutrients. Normally, absorption of salt and H2O exceeds their secretion, so not only are the secreted fluids salvaged, but also additional ingested salt and H2O are absorbed.


Cholera and most diarrhea-inducing microbes cause diarrhea by stimulating the secretion of Cl2 or impairing the absorption of Na1. As a result, more fluid is secreted from the blood into the lumen than is subsequently transferred back into the blood. The excess fluid is lost in the feces, producing the watery stool characteristic of diarrhea. More important, the loss of fluids and electrolytes that came from the blood leads to dehydration. The subsequent reduction in effective circulating plasma volume can cause death in a matter of days or even hours, depending on the severity of the fluid loss


In the middle of the past century, physicians learned that replacing the lost fluids and electrolytes intravenously saves the lives of most patients with diarrhea. In many parts of the world, however, adequate facilities, equipment, and personnel are not available to administer intravenous rehydration therapy. Consequently, millions of children still succumbed to diarrhea annually.


In 1966 researchers learned that SGLT is not affected by diarrheacausing microbes. This discovery led to the development of ORT. When both Na1 and glucose are present in the lumen, this symporter transports them both from the lumen into the villus epithelial cells, from which they enter the blood. Because H2O osmotically follows the absorbed Na1, ingestion of a glucose and salt solution promotes the uptake of fluid into the blood from the intestinal tract without the need for intravenous replacement of fluids.


The first proof of ORT’s life-saving ability in the field came in 1971 when several million refugees poured into India from war-ravaged Bangladesh. Of the thousands of refugees who fell victim to cholera and other diarrheal diseases, more than 30% died because of the scarcity of sterile fluids and needles for intravenous therapy. In one refugee camp, however, under the supervision of a group of scientists who had been experimenting with ORT, families were taught to administer ORT to people with diarrhea, most of whom were small children. The scarce intravenous solutions were reserved for those unable to drink. Death from diarrhea was reduced to 3% in this camp, compared with a 10-fold higher mortality among refugees elsewhere.


Based on this evidence, the World Health Organization (WHO) started aggressively promoting ORT. Packets of dry ingredients for ORT are now manufactured locally in more than 60 countries. The WHO estimates that about 30% of the world’s children who contract diarrhea are treated with the prepackaged mixture or home-prepared versions. In the United States, commercially prepared oral solutions are widely available at pharmacies and supermarkets. An estimated 1 million children worldwide are saved annually as a result of ORT
Dec 19, 2021
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