Drinking Fluids During a Cold Not Backed by Medical Evidence

Laurie Barclay, MD

February 26, 2004

Feb. 26, 2004 -- Drinking fluids during a cold is not supported by medical evidence, according to a literature review published in the Feb. 28 issue of the British Medical Journal. There were no randomized trials to determine the benefit or harm of this practice. The investigators therefore advise caution in recommending that patients with lower respiratory tract infections increase fluid intake.

"Doctors often recommend drinking extra fluids to patients with respiratory infections," write Michelle P. B. Guppy, from the University of Queensland in Australia, and colleagues. "However, there are theoretical reasons for increased fluid intake to cause harm."

Theoretical benefits for increasing fluid intake include replacing insensible loss from fever and respiratory tract evaporation, correcting dehydration, and reducing mucus viscosity. However, increased antidiuretic hormone (ADH) secretion has been reported in lower respiratory tract infections such as bronchitis, bronchiolitis, and pneumonia of viral and bacterial etiology. Because ADH conserves fluid by stimulating water reabsorption from the renal collecting ducts, giving extra fluids while ADH secretion is increased could cause hyponatremia and fluid overload. Fluid restriction could therefore be indicated to manage symptoms of hyponatremia, including irritability, confusion, lethargy, coma, and convulsions.

This systematic review of the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, and Current Contents addressed three issues: whether recommending increased fluid intake reduced duration and severity of acute respiratory symptoms, whether there were adverse effects from this practice, and whether there were any benefits or harm related to site (upper or lower respiratory tract) or severity of illness.

Using the Cochrane Acute Respiratory Infections Group search strategy, the investigators found no randomized controlled trials comparing increased and restricted fluid regimens in patients with respiratory infections. In two prospective prevalence studies, children with moderate to severe pneumonia developed hyponatremia at rates of 31% and 45%, and none of these children had clinical signs of dehydration. Four children with a serum sodium level less than 125 mmol/L died during one study. Several case series reported hyponatremia in some patients with respiratory infections. Some of these patients were symptomatic, and all were successfully treated with fluid restriction.

"We found data to suggest that giving increased fluids to patients with respiratory infections may cause harm," the authors write. "To date there are no randomised controlled trials to provide definitive evidence, and these need to be done. Until we have this evidence, we should be cautious about universally recommending increased fluids to patients, especially those with infections of the lower respiratory tract."

The authors report no financial conflicts of interest.

BMJ. 2004;328:499-500

Reviewed by Gary Vogin, MD

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