Friday, July 10, 2015

Too Much of a Good Thing

& is used with permission.
While interviewing Kelly "Ambulance Driver" Grayson for this week's BCP segment of the Gun Blog Variety Cast, he mentioned water intoxication, which is something I'd briefly heard of via murder shows like NCIS  and CSI. Since this has turned out to be an unofficial "water week" on the blog, it seems only proper that I discuss what happens when you over-hydrate. 

Before I begin, I need to explain some terminology. In toxicology, there's a metric known as Median Lethal Dose, and abbreviated as LD50. The definition for LD50 is a bit complicated for some people, so I'm going to break it down as a process:
  1. Scientists decide to test the lethality of a substance. 
  2. They administer carefully calibrated doses of it to an animal population. 
  3. They stop when these doses have killed 50% of the animals. This is LD50, aka "lethal dose, 50%."
  4. The dosage is then measured against the body weight of the animals. 
  5. This allows the scientists to extrapolate a formula for how lethal this substance is to humans, again based on body weight. 
    • Example: Aspirin has an LD50 rating of 200mg per kg of weight in lab rats. Therefore it is generally assumed (because lethality testing on humans is illegal) that 15,000 milligrams (or 15 grams, or about half an ounce) will kill a 165 pound (75 kg) human 50% of the time. 
  6. Of course, as Evelyn likes to point out, humans are not widgets. We all have different diets and biochemistries, so none of this is exact; it's just a rough guideline for how bad things are for you if you ingest enough of a substance.
With all of that said, it's very hard to achieve a lethal dose of water; part of that has to do with water being very benign, and part has to with the fact that our stomachs can only hold so much of it. According to the American Chemical Society, the LD50 for water is 6 liters, or 1.5 gallons, for a 75kg (165 lb) person. 

Water Intoxication/Hyponatremia
What is important about this dosage is that you have to drink all of this water at the same time. The human body is very, very good at processing water, as anyone who has gone out for a night of drinking will attest, so simply drinking this much water over the course of day, or even a few hours, is fine. The problem occurs when it happens all at once, and it's not because the water itself is poisonous; it's because that much water dilutes the salt concentration of your blood and results in a condition known as hyponatremia -- in other words, you have flushed out vital nutrients and chemicals with all that water. 

However, just because it's hard to take a lethal does doesn't mean that you can drink 1.45 gallons and expect to be fine. Past a certain point, too much water can make you essentially drunk (hence the term water intoxication), which can render you helpless or a danger to yourself and others, especially if you get behind the wheel of a car while so afflicted. 

It's also very easy for babies up to 9 months to become hyponatremic. Because of their small bodies and low sodium reserves, they can easily take in too large of a dose if drinking water from a bottle. In a bug-out situation where milk or formula is not readily available, it may be tempting to give your baby water -- be very careful doing so. According to Grayson, "Hyponatremia has happened to infants whose parents were mixing too dilute a formula. I saw it once with an indigent mother who was trying to stretch her powdered formula as much as she could."

It is recommended that babies 4-6 months old should have no more than 2 ounces of water per day. For more information, please read this PDF.

Symptoms of water intoxication are similar to those of heath exhaustion or heat stroke: feeling hot, nausea, headache, vomiting, diarrhea, and feeling unwell. This can cause problems because the first thing people do when they thing their friend has a heat injury is to offer them water to drink, so the first question you need to ask a potential sufferer is "Have you been drinking enough water?"

In addition, the patient may be confused, irritable, drowsy, or have significant changes in personality or behavior. This is due to the brain swelling from increased water pressure. Left untreated, this can result in seizures, coma, and death. 

The recommended treatment for water intoxication is slow, regulated injection of saline into the patient by medical professionals to restore sodium balance to the blood. This is not something a typical prepper can perform, however, 

According to Grayson, if this happens post-STHF, the victim will "either live through it, or won't, on his own."  Now, I'm not the type to just sit back and do nothing, especially when it comes to a loved one -- but I'm not going to give you bad medical advice, either. If you want to find a way to increase their salt content or decrease their water content, that's up to you.

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