"Drink plenty of fluids": Authors' reply

We carefully worded our systematic review: there is no direct empirical evidence to support or refute the advice; we ask only that more research is undertaken, and that in the meantime we exercise caution with the age old advice. That the press has run away with a slightly different, sensationalised, slant probably will surprise few, and outrage fewer. But let us look deeper at the indirect evidence. Although an observational study of children with infections of the upper respiratory tract with respiratory syncytial virus showed no increase in secretions of antidiuretic hormone, two case reports describe children with only infections of the upper respiratory tract with hyponatraemia and seizures-one a bottle-fed 10 week old child with a mild cold who was given water and herbal teas over three days; the other a 5 week old with upper respiratory symptoms, conjunctivitis, and poor feeding for two days. In infections of the lower respiratory tract, observational studies show that increased secretion of antidiuretic hormone occurs in bronchiolitis, where it is the norm, not just very ill patients with pneumonia. It is becoming standard management to advise careful monitoring and restriction of fluid intake with bronchiolitis. Would it be responsible to continue to advise the wholesale overhydration of children with acute respiratory infections, even in the absence of empirical data?