Drink more water? Beware of water poisoning!

"If you want good skin, you need to drink more water" "Have you caught a cold? Drink more hot water, dear" "If you have to stay up late, remember to drink more water"...

In daily life, water seems to be omnipotent - a cup of hot water can cure all diseases. In some medical scenarios, such as urinary stones, gout, or after undergoing certain ultrasound examinations or contrast examinations, doctors will also recommend drinking more water. But how much is considered too much?

There was a news report that an Australian woman died of water poisoning after participating in a "water drinking contest". Is there a boundary between drinking plenty of water in a healthy way and water poisoning? How much water can cause the risk of poisoning?

Water poisoning, is it real?

In medicine, water intoxication is a type of water-sodium metabolism disorder, which means that the total amount of water taken in by the body greatly exceeds the amount of water excreted, resulting in water retention in the body (that is, the abnormal accumulation and retention of liquid and gas in the body), causing a decrease in plasma osmotic pressure and an increase in circulating blood volume.

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Water intoxication is not common in healthy people. So, in what cases can water intoxication occur?

The reasons for water retention involve both input and output. First, let's look at intake. Normally, our kidneys will dynamically regulate urine excretion. Water intoxication will only occur when we take in a large amount of water and exceed the upper limit of our kidney load.

The reasonable amount of water we drink a day is 2000-2500mL, which is about 8 glasses of water. For some special cases such as stones and gout patients, it can be increased appropriately. Drinking more water (such as the legendary 4 liters of water a day) will not bring obvious benefits to the body.

However, in some cases, such as "holding urine" before ultrasound, or other reasons such as mental stress, as well as the "water drinking competition" mentioned above, water poisoning may occur if drinking water is too "excessive" or "too fast".

Another situation is to replenish a lot of water after strenuous exercise or high temperature environment. At this time, because of the heavy sweating in the early stage, the body's electrolyte loss is obvious. If you drink a lot of water, it is relatively easy to get water poisoning. So you can add some salt to the water after exercise or drink sports drinks containing electrolytes in moderation.

In addition, some iatrogenic factors can also cause water intoxication, such as large amounts of intravenous infusion of electrolyte-free solutions (such as glucose), lavage during some surgeries such as hysteroscopy and transurethral resection of the cyst, and others such as oxytocin or vasopressin, etc.

Infants, pregnant women, and the elderly need to pay special attention to avoid drinking large amounts of water.

Infants and young children have incomplete kidney function and can also get water from breast milk and other liquid foods. The total amount of water intake should be strictly calculated according to different ages, weights, etc. If they drink too much water, they are prone to water poisoning.

The heart and kidneys of pregnant women are burdened, so they should drink water slowly and in moderation.

For the elderly, especially those suffering from heart disease, hypertension, and kidney disease, excessive water intake due to drinking large amounts of water or other situations (such as infusion) will not only lead to water intoxication, but the sudden increase in circulating volume may also induce heart failure, blood pressure fluctuations and other adverse consequences.

Water intoxication, how does it happen?

In most cases, water intoxication occurs due to problems with "water excretion". There is an important "signal light" in the water and sodium balance system called antidiuretic hormone, which acts as its name suggests, with the function of "countering diuresis and urination".

Excessive secretion of antidiuretic hormone is common in situations of tension, blood loss, and shock. In addition, stress stimuli such as acute infection and surgery can lead to increased secretion of antidiuretic hormone.

Antidiuretic hormone will also increase 12 to 36 hours after surgery or even longer. During this period, if you drink a lot of water and do not actively replenish electrolytes, it is easy to cause water intoxication. In addition, endocrine system diseases such as hypothyroidism and adrenal cortex insufficiency may affect the release of antidiuretic hormone.

Of course, if there is a problem with the kidneys that are responsible for our "water and sodium excretion", it will lead to various water and sodium metabolism disorders, such as the oliguria and anuria phase of acute renal failure, or any other reason that causes insufficient renal blood flow or a severe reduction in glomerular blood perfusion. At this time, water "only goes in but not out" and "more in and less out" can easily cause water intoxication.

Therefore, when we suspect "water poisoning", we should be more alert to the functional health level of our body itself.

How to identify water poisoning?

In terms of clinical manifestations, water intoxication can be divided into acute water intoxication and chronic water intoxication. Acute water intoxication is caused by a sharp increase in both extracellular and extracellular fluids, and brain cell edema resulting in increased intracranial pressure. Its manifestations include headache, dizziness, drowsiness or irritability, nausea and vomiting after drinking a lot of water, and even incoherent speech and inability to distinguish the surrounding environment and time. In severe cases, coma may occur.

If the above situation occurs, you must see a doctor immediately. The further development of cerebral edema will lead to irreversible nerve damage, and may even cause brain herniation, and may also cause respiratory and cardiac arrest. In other organs and systems of the body, it will cause acute heart failure, pulmonary edema, dyspnea, congestive hepatomegaly, and edema of the lumbar sacral region or extremities.

Patients with chronic water intoxication may experience symptoms such as fatigue, dizziness, headache, nausea and vomiting, drowsiness, and weight gain.

These symptoms lack specificity, and because chronic water intoxication is often accompanied by primary diseases of the kidney or endocrine system, the symptoms of water intoxication may be ignored or masked, and need to be taken seriously. Biological tests such as blood sodium concentration can determine whether water intoxication has occurred.

Mild water intoxication is relatively easy to correct by limiting water intake, using diuretics, replenishing electrolytes, etc. However, severe water intoxication, especially when accompanied by underlying diseases, requires active treatment under close monitoring by professional medical personnel, and the risks it poses are very high.

Therefore, the scientific drinking plan is to consume water in an appropriate amount and at a uniform speed according to different body conditions and actively and promptly detect the body's "signals".

Source: Chongqing Science and Technology Museum

Author: Liu Yixuan, attending physician of Chongqing Traditional Chinese Medicine Hospital, graduated from Army Medical University.

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