Real Lessons in Diffusion and Osmosis

Real Lessons in Diffusion and Osmosis

Water toxicity: Hyponatraemic encephalopathy - Hyponatremia

In September 1999, a 19-year-old Air Force recruit collapsed during a 5.8-mile walk, with a body temperature of 108 degrees Fahrenheit. Doctors concluded he had died of both heat stroke and low blood sodium levels as a result of overhydration.

During January 2000, a 20-year-old trainee in the Army drank around 12 quarts of water during a 2- to 4-hour period while trying to produce a urine specimen for a drug test. She then experienced fecal incontinence, lost consciousness and became confused, then died from swelling in the brain and lungs as a result of low blood sodium.

How did they die?

The simplest answer is that lost sweat (salt and water) is replaced by ingested water (no salt). This dilutes the sodium in the bloodstream, and hyponatremia results.During exercise in the heat, more salt is lost in sweat per hour than is usually replaced by food and fluids, including sports drinks. Your body can tolerate a degree of imbalance for a short period of time, but it may decompensate if this continues for too long.

What are the symptoms of hyponatremia?

The spectrum of symptoms can range from mild to severe and can include nausea, muscle cramps, disorientation, slurred speech, confusion, and inappropriate behavior. As it progresses, victims may experience seizures or coma, and death can occur. Severe hyponatremia is a true medical emergency. These neurological symptoms are thought to result from the movement of water into brain cells, causing them to swell and disrupt their functioning

What is the treatment?

Minor symptoms, such as nausea and mild muscle cramps, can be treated by eating salty foods and hydrating with a sodium containing sports drink. More severe symptoms require treatment by qualified medical personnel. If you think you are suffering from hyponatremia or are unsure, seek medical attention immediately.

In an interview with Reuters Health, Gardner explained that drinking too much water is dangerous because the body cannot excrete that much fluid. Excess water then goes to the bowel, which pulls salt into it from the body, diluting the concentration of salt in the tissues.

• Changing the concentration of salt, in turn, causes a shifting of fluids within the body, which can then induce a swelling in the brain. The swollen organ will then press against the bones of the skull, and become damaged.
• Since it can dilute your blood, and diluted blood causes tissue cells to swell. The brain cannot swell inside the skull and the pressure can build up to a dangerous level. There should be no problem if you drink plenty of water and urinate pale urine. Danger signs to look out for, are compulsive drinking, not being able to urinate, or dark urine in spite of drinking lots of water.

The body continually regulates its handling of sodium. When dietary sodium is too high or low, the intestines and kidneys respond to adjust concentrations to normal. During the course of a day, the intestines absorb dietary sodium while the kidneys excrete a nearly equal amount of sodium into the urine. If a low sodium diet is consumed, the intestines increase their efficiency of sodium absorption, and the kidneys reduce its release into urine.

The concentration of sodium in the blood plasma depends on two things: the total amount of sodium and water in arteries, veins, and capillaries (the circulatory system). The body uses separate mechanisms to regulate sodium and water, but they work together to correct blood pressure when it is too high or too low. Too low a concentration of sodium, or hyponatremia, can be corrected either by increasing sodium or by decreasing body water..

How much water is safe to drink?

In 1998, the Army released fluid replacement guidelines, which recommend a certain intake of water but limit it to 1 to 1-1/2 quarts per hour and 12 quarts per day.

Excessive drinking of beer, which is mainly water and low in sodium, can also produce hyponatremia when combined with a poor diet.

Marathon running, under certain conditions, leads to hyponatremia. Races of 25-50 miles can result in the loss of great quantities (8 to 10 liters) of sweat, which contains both sodium and water. Studies show that about 30% of marathon runners experience mild hyponatremia during a race. But runners who consume only pure water during a race can develop severe hyponatremia because the drinking water dilutes the sodium in the bloodstream. Such runners may experience neurological disorders as a result of the severe hyponatremia and require emergency treatment.

Sports drinks

Electrolytes are commonly found in sports drinks. In oral rehydration therapy, electrolyte drinks containing sodium and potassium salts replenish the body's water and electrolyte levels after dehydration caused by exercise, diaphoresis, diarrhea, vomiting, intoxication or starvation.

"It is unnecessary to replace losses of sodium, potassium and other electrolytes during exercise since it is unlikely that a significant depletion of the body's stores of these minerals will occur during normal training. However, in extreme exercising conditions over 5 or 6 hours (an Ironman or ultramarathon, for example) the consumption of a complex sports drink with electrolytes is recommended."(-Elizabeth Quinn, trainer and health professional) [1] Athletes who do not consume electrolytes under these conditions risk overhydration (or hyponatremia).