Doctors have always advised patients to drink plenty of water if unwell. A new case study reports the risks of drinking too much water and highlights the need for more research to support this traditional advice.
For generations, the predominant medical advice in case of flu or respiratory infections has been to drink plenty of fluids.
Theoretically, this is considered good advice; during a cold, the body secretes more liquids through the nose or may be running a fever, which could lead to more fluid loss.
In the case of infections in general, drinking more water is thought to help with intravascular volume loss, increased vascular permeability, as well as replace the fluids lost in fever and vomiting.
The medical advice to drink plenty of water also rests on the assumption that water consumption is harmless.
A new case report reminds doctors and patients that evidence for the benefits of drinking plenty of water is scarce, and, in fact, drinking too much water can be dangerous.
A new paper, published in BMJ Case Reports, details the case of a 59-year-old woman who drank too much water as a result of her urinary tract infection (UTI).
The woman started to feel the symptoms of a recurring UTI, which had flared up several times in her life previously.
In the case of UTIs, drinking more water than usual has been shown to temporarily reduce the number of bacteria in urine, but the reasons for this remain unclear.
Remembering the doctor’s advice of drinking half a pint of water every half hour, the woman drank several liters of water that day, but her UTI symptoms worsened. As a result, she presented herself to the emergency department at King’s College Hospital in the United Kingdom with symptoms of lower abdominal pain and dysuria.
Urine tests confirmed a UTI, but the patient was otherwise healthy. She had no medical history apart from a recurring UTI, did not smoke or take any medicine or recreational drugs, had no allergies, and was a moderate alcohol drinker.
In the emergency department, the woman was prescribed antibiotics and analgesics for her UTI. However, she soon started displaying new symptoms, such as shakiness and tremor, vomiting, and speech difficulties.
The patient’s Glasgow Coma Scale was 15 – she had an attention deficit, was hesitant in speech, and had difficulty finding her words. Otherwise, the patient was healthy.
Because of her speech impairment, doctors considered the possibility of a stroke. Blood tests and a computed tomography (CT) scan quickly revealed this was not the case. However, blood tests showed signs of hyponatremia.
Hyponatremia is a medical condition caused by abnormally low levels of sodium – lower than 134 millimoles per liter.
Acute hyponatremia, which develops in less than 48 hours, is considered an emergency, as it can have fatal neurological consequences. Critically low levels of sodium can lead to cerebral edema with increased levels of intracranial pressure and brain herniation. This leads to seizures, coma, and death.
The mortality rate for hyponatremia cases is 17.9 percent.
In the case report, the patient’s sodium level was 123 millimoles per liter. The fatality rate for patients with sodium levels lower than 125 millimoles per liter is almost 30 percent.
Water intoxication, which can lead to fatal hyponatremia, has been reported in endurance exercise, in the use of the drug MDMA, and in psychogenic polydipsia – a disorder where the patient drinks large quantities of water compulsively, usually as a result of a psychiatric condition.
After having her water intake restricted to 1 liter per day, the patient’s condition improved significantly in the following 24 hours. Sodium levels were back to normal, and the patient was discharged.
The authors of the case study point out that water intoxication, which can lead to hyponatremia, is a rare occurrence among people with normal physiology. If a patient has normal renal function, it is difficult to drink more water than the body can excrete.
However, if the levels of antidiuretic hormones are elevated, as is the case in some illnesses, this can reduce the excretion of water. In these cases, the authors ask, how sound is the medical advice to drink plenty of liquids?
The case of the 59-year-old woman is similar to a previously reported case, where a healthy young female drank too much water while experiencing gastroenteritis. As a result, she developed acute hyponatremia and died.
In both situations, the patients followed the doctor’s advice, although they overdid the recommended intake of water. As the authors point out:
“Together these two cases highlight the importance of clear history taking, including a collateral, prompt investigation and correction of electrolyte imbalance and, also the need to qualify our advice regarding water consumption in simple infective illness.”
They caution that there is an insufficient amount of research demonstrating the benefits of drinking more fluids during infectious illnesses. In fact, they cite a previous review that found “no randomized controlled trials to provide definitive evidence” of the benefits of such medical advice.
Authors urge doctors not to ignore serum electrolyte levels when presented with a healthy adult who displays severe cerebral symptoms.
“The presentation of a previously, healthy adult with acute cerebral symptoms creates a time-critical clinical challenge,” they note. “However, this must not detract from the need for a comprehensive collateral history to guide diagnostic approach. A history of excessive water intake combined with possible intravascular depletion should prompt speedy analysis of serum electrolyte levels.”