Electrolyte Problems in Kidney Disease: When Your Sodium Is Off

Here is why a high or low sodium level is a big deal.

Athlete crouched with a sport drink
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Our body's electrolytes are certain elements that are vital to life. They affect us in profound ways. Everything from generation of a brain cell's energy to a nerve cell's electricity, from our body's water content to our heart's rhythm, and more, is dependent on electrolytes like sodium, potassium, calcium, magnesium, and others being in a certain range (and you thought that an electrolyte is something you take to relieve a cramp!).

In fact, life as we know it, would not exist without these elements which are an intricate part of our physiology.

Let's delve into even deeper territory to understand why our existence would not have been possible without these electrolytes. These seemingly simple elements are in fact the bridge that connects us to the very birth of our universe. Confused? Well, here is a simple explanation. What we call electrolytes are essentially elements (like sodium, potassium, or magnesium) that came into existence during the dawn of the universe.

For instance, magnesium was produced by nuclear fusion of carbon on stars. Eventually, once the star exploded into a giant super nova, magnesium spread across the Universe and into our physiology. Yes, there is a bit of stardust in all of us! When the 13th century Persian poet, Rumi famously wrote, "we come spinning out of nothingness, scattering stars like dust", he was partly true.

Electrolytes and the Kidney

Let's examine electrolytes and their disorders from a much more mundane perspective. Electrolyte abnormalities are very common in kidney disease states for one simple reason—it is the kidney that typically has a central role in maintaining normal levels of most electrolytes.

Therefore, these abnormalities are a consequence of abnormal kidney function, rather than a cause.

Both low and high levels of electrolytes can be seen when the kidneys malfunction, but can have a multitude of other indirect causes. The finer details of every possible cause and its respective treatment is beyond the scope of this article. However, here is a brief overview of issues related to abnormal sodium levels.

Hyponatremia: A State of Low Sodium Level

Typically, a sodium level in blood of less than 135 meq/L is considered abnormal, and called hyponatremia. Two major determinants of the sodium level in the blood are, (a) the amount of sodium in the blood, and (b) the amount of water in the blood. In many disease states, a low sodium level is not a problem of lack of sodium, but in fact an excess of water for the amount of sodium (which ends up effectively diluting the sodium content).

Remember, when we measure sodium level in the blood, it is not the absolute amount of sodium, but in fact its concentration that we look at. Which means the water content of the blood will impact sodium concentration as well. Understanding this concept is essential to realizing why sodium falls in certain disease states, and why the treatment is not always to "eat more salt/sodium."

Some of the common causes of low sodium levels are as follows (this is not an exhaustive list):

  • Actual loss of sodium from the blood: This could happen from diarrhea, vomiting, excessive sweating, etc. This is commonly seen in long distance runners when loss of sodium in the sweat is further worsened by oral intake of just water without any salt, further amplifying the drop in sodium. This can in extreme cases lead to life-threatening consequences including seizures.
  • States of water excess: These would include congestive heart failure, cirrhosis, and advanced kidney failure.
  • SIADH: This stands for syndrome of inappropriate antidiuretic hormone production. ADH, or AntiDiuretic Hormone is a hormone produced by the hypothalamus in the brain, and regulates the amount of water retained by the kidney. When excessively high amount of ADH is produced, it will cause sodium level in the blood to drop.
  • Hormonal causes: low thyroid levels, or hypothyroidism, adrenal insufficiency
  • States where excess fluid intake might be an issue: This can be caused by primary polydipsia, where excessive water intake will dilute the sodium in the blood, essentially causing water intoxication. A similar state can also be created with consumption of copious amounts of beer, referred to as "beer potomania".

Treatment of Hyponatremia

Once low sodium level has been confirmed on blood testing, treatment will depend on what is the cause of low sodium, and even how quickly it has developed. For instance, in states of excess water in the body (like congestive heart failure or SIADH), water restriction or strategies geared towards promoting water excretion from the body are instituted. On the other hand, in states where there is actual deficit of salt/sodium in the body, replacing the sodium in the form of salt tablets or as part of IV fluids is recommended. Rapid correction could be dangerous, especially when hyponatremia has persisted for a while.

Hypernatremia: A Case of Too High Sodium Level

A blood level of sodium higher than 145 meq/L is referred to as "hypernatremia". The most common cause of hypernatremia is an elevation in sodium created because of a deficit of water. Hence, disease states associated with dehydration, or increase water loss from the body (like diabetes insipidus, use of diuretics, diarrhea etc.) can cause hypernatremia. The average person typically starts to get a strong sensation of thirst when sodium levels begin to go up in the blood. As long as they have access to water, the sodium level should come down. The problem however arises if people do not have access to water, or if they lose too much water from the kidneys or the gut, or if they cannot sense thirst (as can happen in elderly patients). Since most hypernatremia states involve dehydration, treatment strategies include administration of water rich IV fluids, or oral intake of water.

Here as some of the common causes of high sodium level in the blood:

  • Excessive loss of water from the skin, as could occur from excessive sweating or burns
  • Loss of water from the gut/diarrhea
  • Diabetes insipidus, a state where excess water is lost in the urine
  • Inability to sense thirst because of problems with a certain part of the brain which regulates thirst (called the hypothalamus)
  • Sodium overload or salt poisoning: This can happen from accidental administration of too much concentrated saline to patients where concentrated "hypertonic" saline is given (for instance, in cases of traumatic head injury). Massive amounts of salt intake can theoretically lead to this as well. In fact, salt can be absorbed through the skin in babies, a phenomena seen as a complication of a custom of "salting" practiced in parts of Turkey.

What Effect Does High or Low Sodium Have on You?

Symptoms of abnormal sodium levels depend on the severity of the abnormality, and the rapidity of its development. They can range from mild symptoms like headache, to more severe ones like gait abnormalities, cramps, heart rhythm changes, etc. One dreaded complication of excessively low sodium level is the risk of seizures. Hence, timely treatment is necessary.

Sources:

Halawa I, Andersson T, Tomson T., Hyponatremia and risk of seizures: a retrospective cross-sectional study. Epilepsia. 2011 Feb;52(2):410-3. doi: 10.1111/j.1528-1167.2010.02939.x. Epub 2011 Jan 26.

Sanghvi SR, Kellerman PS, Nanovic L, Beer Potomania: An Unusual Cause of Hyponatremia at High Risk of Complications From Rapid Correction, AJKDOctober 2007Volume 50, Issue 4, Pages 673–680.

Syndrome of inappropriate antidiuretic hormone secretion, medlineplus.gov, Updated October 2015.

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