A child suffering from acute diarrhoea is brought to the casualty and is diagnosed as having severe dehydration with pH of 7.23. Serum Na-125, Serum K-3, HCO3- 16. The best I.V. fluid of choice is-

Hyponatremia causes severe dehydration Clinical features Patients with hypernatraemia generally have reduced cerebral function, either as a primary problem or as a consequence of the hypernatraemia itself, which results in dehydration of neurons and brain shrinkage. In the presence of an intact thirst mechanism and preserved capacity to obtain and ingest water hypernatraemia may not progress very far. If adequate water is not obtained, dizziness, delirium, weakness and, ultimately, coma and death can result. Management Treatment of hypernatraemia depends on both the rate of development and the underlying cause. If there is reason to think that the condition has developed rapidly, neuronal shrinkage may be acute and relatively rapid correction may be attempted. This can be achieved by infusing an appropriate volume of intravenous fluid (isotonic 5% dextrose or hypotonic 0.45% saline) at an initial rate of 50-70 mL/hr. In older, institutionalised patients, however, it is more likely that the disorder has developed slowly, and extreme caution should be exercised in lowering plasma sodium to avoid the risk of cerebral oedema. Ref Davidson 23rd edition pg 360