Electrolytes and Eating Disorders
Monday, July 10, 2017
When most people see the term "electrolyte," they think of a sports drink; indeed, Gatorade does contain a few electrolytes. To the cells of your body, however, electrolytes mean everything. Every cell in every body organ performs its job by balancing these infinitely small, electrically-charged particles. Electrolyte problems are inherent to eating disorders - as an ACUTE doctor, I start every day by thinking about electrolytes in my patients. Electrolytes can get complicated, but you don’t need to be a doctor to understand the basics! Here’s a quick overview of some of the electrolyte problems we treat every day at ACUTE.
Hypokalemia, or low blood potassium, is the most common electrolyte problem seen in eating disorders. Patients who purge and/or use laxatives or diuretics are especially prone to this problem. Potassium is the major electrolyte inside nearly all of the cells in the body; we can't measure how much is inside all the cells, but measuring it in the blood gives us a good idea how much potassium is in the body. All the nerves and all the muscles in the body use potassium to do their jobs: nerve cells depend on it to send their signals, and muscle cells depend on it to contract. Patients with low potassium often feel that their muscles are weak - and when this happens to the bowel muscles, they can feel constipated. Most importantly, potassium is essential for the heart - the heart needs a normal potassium level not just to beat strong enough, but to beat with a normal rhythm. When the potassium gets too low (or too high), the heart can go into an abnormal rhythm and even stop working entirely. We can fix low potassium levels through diet, supplements, or medications.
Hypophosphatemia, or low blood phosphate, is another frequent finding - especially during the refeeding process. Phosphate powers every cell in the body - it is the basic "currency" that all cells use to both save up and spend energy, and also helps to deliver oxygen from the lungs to all the cells in the body. Patients with eating disorders typically don’t have enough phosphate in their bank. During refeeding, the body needs lots of phosphate to safely build healthy tissues and get oxygen to all the cells; if there isn’t enough phosphate to go around, the consequences can be devastating. Heart and lung failure are the most dreaded complications - unfortunately, these things sometimes happen when patients go through refeeding without close supervision. This is why we pay such close attention to phosphate levels on ACUTE - we can usually correct the problem by just using a phosphate powder dissolved in some water.
Sodium is the electrolyte that makes salt taste the way it does - and it’s a little more complicated. In some ways, it’s the opposite of potassium. While potassium is mostly inside our cells, sodium is the electrolyte found mostly in the fluid outside of our cells. When we measure sodium in the blood, it doesn’t tell us anything about how much sodium is in the body overall. Instead, measuring sodium tells us how water is balanced in the body. When the sodium level is high (called hypernatremia), this usually means the body is dehydrated - a high sodium level stimulates thirst, and simply drinking water fixes the problem. A low sodium level is called hyponatremia. Hyponatremia occurs when the blood gets too diluted - either there is not enough salt (i.e. sodium) in the body, there is too much water in the body, or both. Low blood sodium may not cause any symptoms, especially when it gradually develops over time (which often happens in eating disorders). But hyponatremia is always, always dangerous - this is because it can cause water to shift into and out of cells very quickly. The cells of the brain are very sensitive to sodium levels; low and rapidly changing sodium levels can cause seizures and brain damage. We therefore take low sodium levels very seriously; when we find this problem, we track it closely and treat it delicately. Fortunately, the treatment is almost always simple - all we need to do is carefully rebalance how much salt and water goes into the body.
Electrolytes can get complicated, but I hope this gives you a good introduction to something I think about every morning. The best part about being an ACUTE doctor is that I get to spend a lot of time with my patients - while I don't bore patients with an electrolyte talk every day, it’s something I’m always happy to discuss!