Got a Fever? Drink Lots of Fluids (?)

Summarized by Robert W. Griffith, MD
March 26, 2004

When you've got a feverish cold, flu, or bronchitis, you've probably been told (by your doctor?) "drink plenty of fluids". The idea is that you replace all the fluid you've lost by sweating, and/or loosen the mucus in your throat and airways. But just how good is this advice?

Australian researchers have conducted a review of the available evidence, asking themselves 3 questions:

1. Does increasing fluid intake decrease the duration and severity of the symptoms?
2. Are there ill-effects from such a recommendation?
3. Do the answers to the first two questions vary according to the site of the infection - i.e. the upper respiratory tract (nose, throat, sinuses) or the lower respiratory tract (windpipe/trachea, bronchial airways, lungs)?

Their findings are published in the British Medical Journal.

What the researchers found

The scientists searched the published medical literature for all relevant reports about fluid intake and respiratory tract infections. They found, however, that there were no randomized controlled clinical trials, which are the 'gold standard' for proving the effectiveness of a particular treatment.

There were, on the other hand, two uncontrolled studies of children with moderate to severe pneumonia and no evidence of dehydration. In the first, 31 out of 100 children aged 1 month to 12 years had hyponatremia - a low level of sodium in the blood; four of these children died. In the second study 33 babies out of 73 developed hyponatremia.

The scientists also found several case reports of children who had bronchitis or pneumonia, and had quite severe hyponatremia.

What wasn't found is important

This extensive search failed to turn up any evidence that taking extra fluids when you have a respiratory tract infection does any good. The studies just don't exist.

Instead, it seems that in young children there may be a risk of low sodium levels in such infections, because of increased secretion of a hormone (the anti-diuretic hormone); this hormone stimulates water reabsorption by the kidneys to try to prevent dehydration. Giving a lot more fluids when there is no dehydration may increase the risk of hyponatremia and fluid overload.

The bottom line?

There are no well-conducted trials of the benefits and risks of increased fluid intake in respiratory infections; until they are available, one should be cautious about recommending drinking more fluids in such cases, because of the possible risk of bringing on hyponatremia, a potentially dangerous condition. So, don't push the fluids too much! And switching to drinking a salt-solution or Gatorade® won't necessarily help.

Source

• "Drink plenty of fluids": a systematic review of evidence for this recommendation in acute respiratory infection. MPB. Guppy, SM. Mickan, CB. Del Mar, BMJ, 2004, vol. 328, pp. 499--500

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