Hyponatremia-Part 2
Torn Between Two Ideals
Our bodies have many built in survival mechanisms that function without our conscious awareness or direction. Two important functions related to successful completion of races in the heat and humidity are maintenance of both hydration and normonatremia (normal blood sodium levels). Unfortunately, these functions are often in competition with each other.
Dehydration is not uncommon in the heat, and can cause a drop in our blood pressure. When dehydrated, pressure sensitive receptors located in our carotid arteries, called baroreceptors, sense a drop in our blood pressure. This in turn sets off a variety of counter measures, one of which is the release of Antidiuretic Hormone (ADH) from the pituitary gland in our brains, which tells the kidneys to conserve water, making our urine more concentrated, and reducing urination. Some triathletes experience “shutdown” in their ability to urinate during Ironman races, and this mechanism likely plays a major role in this phenomenon. The net effect is an increase in hydration and blood pressure. Unfortunately, this extra water reabsorbed by the kidneys also contributes to hyponatremia.
Hyponatremia, on the other hand, has the opposite effect in that this condition leads to reductions in the release of ADH, thus allowing the kidneys to excrete more water, making our urine more dilute, and increasing urination. Urinating more water will result in an increase in sodium concentration in the blood. Unfortunately, the loss of this water leads to further reductions in blood pressure. Some triathletes experience increases in urination of especially dilute urine after a Ironman, which is the body’s way of correcting a hyponatremia that evolved during the race.
In truth, the regulation of water and sodium is much more complex then what I have presented here. However, for the purposes of this discussion, two competing physiological processes are trying to maintain an optimum internal environment-one corrective process improves dehydration, but potentially makes hyponatremia worse, while the opposite occurs when trying to improve hyponatremia. So, which process wins when both are competing?
This is a complex question, and one that still has no firm answer. Research is ongoing, however. Suffice it to say, it is probable that dehydration plays a more significant role in stimulating protective responses, which may have a role in perpetuating hyponatremia.
To be continued...see below for Part 3.
Our bodies have many built in survival mechanisms that function without our conscious awareness or direction. Two important functions related to successful completion of races in the heat and humidity are maintenance of both hydration and normonatremia (normal blood sodium levels). Unfortunately, these functions are often in competition with each other.
Dehydration is not uncommon in the heat, and can cause a drop in our blood pressure. When dehydrated, pressure sensitive receptors located in our carotid arteries, called baroreceptors, sense a drop in our blood pressure. This in turn sets off a variety of counter measures, one of which is the release of Antidiuretic Hormone (ADH) from the pituitary gland in our brains, which tells the kidneys to conserve water, making our urine more concentrated, and reducing urination. Some triathletes experience “shutdown” in their ability to urinate during Ironman races, and this mechanism likely plays a major role in this phenomenon. The net effect is an increase in hydration and blood pressure. Unfortunately, this extra water reabsorbed by the kidneys also contributes to hyponatremia.
Hyponatremia, on the other hand, has the opposite effect in that this condition leads to reductions in the release of ADH, thus allowing the kidneys to excrete more water, making our urine more dilute, and increasing urination. Urinating more water will result in an increase in sodium concentration in the blood. Unfortunately, the loss of this water leads to further reductions in blood pressure. Some triathletes experience increases in urination of especially dilute urine after a Ironman, which is the body’s way of correcting a hyponatremia that evolved during the race.
In truth, the regulation of water and sodium is much more complex then what I have presented here. However, for the purposes of this discussion, two competing physiological processes are trying to maintain an optimum internal environment-one corrective process improves dehydration, but potentially makes hyponatremia worse, while the opposite occurs when trying to improve hyponatremia. So, which process wins when both are competing?
This is a complex question, and one that still has no firm answer. Research is ongoing, however. Suffice it to say, it is probable that dehydration plays a more significant role in stimulating protective responses, which may have a role in perpetuating hyponatremia.
To be continued...see below for Part 3.
posted by MedionMan at 7:35 PM
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