Key Point:

• Lower respiratory tract infections are often accompanied by an increase in the body’s secretion of antidiuretic hormone, making extra fluid intake potentially hazardous.

QUEENSLAND, AUSTRALIA—It has long been conventional wisdom to recommend drinking “plenty of fluids” for someone with a respiratory infection. However, a recent analysis of available literature has indicated that in patients with lower respiratory tract infections extra fluids could result in fluid overload and hyponatremia.[1]

Researchers from Queensland, Australia, conducted a systematic review using the following three questions:
• Does recommending increased fluid intake for acute respiratory infections improve the duration and severity of symptoms?
• Are there any adverse effects from this recommendation?
• Are any benefits or harm related to site (ie, upper or lower respiratory tract) or severity of illness?

After examining four databases of published clinical trials, the researchers identified three studies for analysis. Two of these were prospective prevalence studies of children with moderate to severe pneumonia; one study contained 100 subjects and the other 73 subjects. The third was a case series of four infants.

In the two prospective studies, hyponatremia occurred in 31% to 45% of the children. At the time of fluid administration, none of the children had signs of dehydration. In one study, four children having serum sodium levels below 125 mmol/L died following fluid administration.

The case series included three infants with bronchiolitis and one with pneumonia. According to the report three of these infants developed hyponatremia following fluid administration but were successfully treated with fluid restriction. However, one infant did suffer seizures.

Historically, the reasons for giving extra fluids to patients with respiratory infections included replacement of fluids lost due to fever and respiratory tract evaporation, reduction in the viscosity of mucus, and correction of dehydration due to the patient drinking less.

CHALLENGING CONVENTIONAL WISDOM

How could fluids be harmful? According to the researchers, an increase in antidiuretic hormone secretion has been observed in adults and children with lower respiratory tract infections, such as bronchitis, bronchiolitis, and pneumonia. Thus, the administration of extra fluids in the presence of increased antidiuretic hormone levels could potentially lead to fluid overload. In pneumonia, antidiuretic hormone secretion increases with the degree of lung parenchymal involvement.

The authors stressed the need for randomized controlled trials to confirm existing evidence. Until then, the researchers advised caution when telling patients—especially those with lower respiratory tract infections—to drink plenty of fluids.

—Gale Jurasek

Reference
1. Guppy MPB, Mickan SM, Del Mar CB. “Drink plenty of fluids”: a systematic review of evidence for this recommendation in acute respiratory infections. BMJ. 2004;328:499-500.

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