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H2O Toxicity: Extracellular Overload

Water is the basis for our very existence, life could not exist without it - heck, its usefulness is reinforced by the fact that nearly 71% of the globe's surface is made up of this inorganic compound were all too familiar with (H2O). Water plays an important part in our daily lives. 60% of our make-up is also derived from water. Water is a valuable commodity, we've made that point clear; however, did you know that in the right circumstance, water can be dangerous and even deadly! I am not talking about flash floods or hurricanes -- this week's topic is the rare event known as: water intoxication. We can have too much of a good thing.

The problem comes from the disruption of our homeostatic environment. Our bodies thrive on balance and a very high intake of water in a short amount of time is messing with our electrolyte balance and forcing a relative hyponatremic (low sodium) or hypotonic event which has some dire consequences. Let's break this down:

Water intoxication occurs when you drink so much water and you drink it so fast that you overwhelm the ability of the kidneys to get rid of excess water. As a result, your blood and body fluids become too dilute. This is called hyponatremia, which refers to the fact the concentration of sodium falls as the blood becomes dilute. In fact, the technical term for water intoxication in the setting of exercise is called “exercise-associated hyponatremia” or EAH, but here for consistency - I will simply use the term water intoxication. The reason this is a problem is because the dilution of the blood affects the movement of water in and out of the cells of the body. Normally, the blood concentration of sodium must be kept between 135 and 145 mmol/L, because at that level, the blood and body fluids are isotonic (balanced) with the cells of the body. The image below is unbalanced which forces the net movement of fluid into the cells, which will cause them to swell/burst. Consider the consequences to the brain during an event like this.

Think about the last sporting event you or even your children attended. We have become as a society, borderline obsessed with hydration. The tumbler business is booming. I'm not saying the fluid replacement shouldn't be encouraged, we just have to be careful and not simply subconsciously drink in the absence of thirst because its readily available and visible. You see how it can almost become mechanical.

Signs and symptoms of water intoxication can vary per individual, but could include: altered mental status, poor motor coordination, signs of increased ICP, hyperventilation, and most notably seizures. Picking up on neurological issues early is paramount.

Water Toxicity Prevention Tips + Facts:

  • Even during periods of heavy exercise, limit fluid intake to 4-5 cups per hour

  • Use your God-given thirst mechanism -- it's a reliable resource

  • Baseline renal function and "ability to clear" water is also an important factor

  • Lightheadedness and dizziness could be a symptom of OVER or UNDER hydration

  • Event can occur with some mental disorders ex. (psychogenic polydipsia)

  • Treatments will be focused on diuretics, hypertonic saline or vasopressin receptor antagonists*

  • The drugs above get us back to an isotonic environment by: water release and increasing solute (Na) concentrations

  • Could also be seen in colleges (as part of hazing)

Continue to be mindful and deploy a commonsense approach to fluid replacement as the summer heat continues to bear down on us.

July 31, 2023

Author: Joshua Ishmael, MBA, MLS(ASCP)CM, NRP

Pass with PASS, LLC.

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