What is the concentration of ORS in (mmol/l)?

Answer 1

Oral rehydration salts (ORS)

Composition of ORS. The principles underlying ORT have been applied to the development of a balanced mixture of glucose and electrolytes for use in treating and preventing dehydration, potassium depletion, and base deficit due to diarrhoea. To attain the latter two objectives, salts of potassium and citrate (or bicarbonate) have been included, in addition to sodium chloride. This mixture of salts and glucose is termed oral rehydration salts (ORS); when ORS is dissolved in water, the mixture is called ORS solution. The following guidelines were used in developing the WHO/UNICEF-recommended ORS solution:

the solution should have an osmolarity similar to, or less than that of plasma, i.e., about 300 mOsmol/l or less;
the concentration of sodium should be sufficient to replace efficiently the sodium deficit in children or adults with clinically significant dehydration;
the ratio of glucose to sodium (in mmol/l) should be at least 1:1 to achieve maximum sodium absorption;
the concentration of potassium should be about 20 mmol/l in order adequately to replace potassium losses;
the concentration of base should be 10 mmol/l for citrate or 30 mmol/l for bicarbonate, which is satisfactory for correcting base-deficit acidosis due to diarrhoea. The use of trisodium citrate, dihydrate, is preferred, since this gives ORS packets a longer shelf life.
Sodium concentration: ORS solution has been used to treat millions of diarrhoea cases of different etiologies in all ages, and has proved to be remarkably safe and effective. Nevertheless, because stool electrolyte concentrations vary in different types of diarrhoea and in patients of different ages, doctors are sometimes concerned about using a single ORS solution in all clinical situations. In this regard, Table 2.1 compares the composition of ORS solution with the average electrolyte composition of stool in different kinds of acute watery diarrhoea. The stools of patients with cholera contain relatively large amounts of bicarbonate and potassium. In children with acute non-cholera diarrhoea, the concentrations of sodium, bicarbonate, and chloride in the stool are lower, although they vary considerably.
A child with dehydration due to diarrhoea has deficits of sodium and water. In cases of severe dehydration, the sodium deficit has been estimated to be 70-110 mmol for each 1000 ml of water. The sodium concentration of 90 mmol/l in ORS solution is within this range and hence it is suitable for the treatment of dehydration. During the maintenance phase, however, when ORS is used to replace continuing stool losses, the concentration of sodium excreted in the stool averages 50 mmol/l. Although this could be replaced with a separate solution containing 50 mmol of sodium, the same result can be obtained by giving the standard ORS with water or breast milk. This approach reduces the average concentration of sodium ingested to a range that is both safe and effective, and any modest excess of sodium or water can be excreted in the urine; this is especially important in young infants, in whom renal function is not fully developed. A major advantage of this approach is that it avoids confusing mothers, nurses, and even doctors, who might otherwise have to use different ORS solutions for the rehydration and maintenance phases of treatment.