Hyponatremia-Part 1
Hyponatremia, or reduced blood sodium concentrations, has been recognized as one of the most concerning potential health hazards of ultra endurance events. Hyponatremia has been reported in up to 20% of Ironman participants. When it occurs in triathletes, it usually happens during long course races performed in hotter temperatures, and especially so when combined with the one-two punch of heat and humidity. However, this problem may occur even in short course events in susceptible individuals, especially if these events are associated with relatively high heat and high humidity.
Sodium vs. Salt
Sodium is one component of salt (table salt). Salt, or sodium chloride, contains 1 part sodium to 1.5 parts chlorine. Your sweat on average contains anywhere from about 1.75 grams of salt (700 mg sodium plus 1050 mg chlorine) to 3 grams of salt (1200 mg of sodium plus 1800 mg chlorine) per liter. If you sweat an average of one liter per hour, you lose anywhere from 1.75-3 grams of salt per hour. Multiply this by a 12 hour Ironman (yes we do sweat in the water, albeit less than on land) , and you have 21-36 grams of salt lost (or 8.4-14.4 grams of sodium lost). Since a teaspoon of salt contains about 6 grams, this equals about 4-6 teaspoons of salt lost. Some might not think this seems like a whole lot, but if you consider that a 140 lb person only has about 40 grams (almost 7 teaspoons) of salt in his/her blood to begin with, you start to get a feel for how significant these losses can be!
According to one of the most respected textbooks in medicine, and a definite authority on the topic, relative to sweat, “these losses are almost entirely replaced by...solutions (including Gatorade) that have a much lower salt concentration. The net effect is water retention and, in some cases, symptomatic hyponatremia, with a fall in plasma sodium concentration...”
Quoted from Clinical Physiology of Acid-Base and Electrolyte Disorders-4th Edition, 1994. Chapter 23, pp 656. Edited by Burton David Rose.
It is important to understand the difference between amount and concentration of sodium. Amount refers to weight, and can be measured in milligrams (1/1000 gram) or grams. Concentration refers to weight in a given volume of water, and is measured in milligrams/litre or grams/litre. When speaking of ingesting a sports drink, concentration of sodium in the drink is the important issue when comparing different brands.
Definition
Hyponatremia is defined as a blood sodium concentration of < 135 mEq/liter (< 3.10 g/liter), with normal ranges usually falling between 138-142 mEq/liter (3.17-3.27 g/liter). In the most severe cases, blood sodium concentration may fall to below 120 mEq/liter (2.76 g/liter), a true medical emergency! As can be seen with these numbers, there is not much difference between normal and an emergency situation (about .50 g of sodium/liter, or 1/12 teaspoon/liter!). Symptoms of hyponatremia include nausea, muscular cramping, stomach upset, vomiting, dizziness, seizures and delirium. Coma and even death may result, and has been reported in several cases.
To be continued...see below for Part 2.
Sodium vs. Salt
Sodium is one component of salt (table salt). Salt, or sodium chloride, contains 1 part sodium to 1.5 parts chlorine. Your sweat on average contains anywhere from about 1.75 grams of salt (700 mg sodium plus 1050 mg chlorine) to 3 grams of salt (1200 mg of sodium plus 1800 mg chlorine) per liter. If you sweat an average of one liter per hour, you lose anywhere from 1.75-3 grams of salt per hour. Multiply this by a 12 hour Ironman (yes we do sweat in the water, albeit less than on land) , and you have 21-36 grams of salt lost (or 8.4-14.4 grams of sodium lost). Since a teaspoon of salt contains about 6 grams, this equals about 4-6 teaspoons of salt lost. Some might not think this seems like a whole lot, but if you consider that a 140 lb person only has about 40 grams (almost 7 teaspoons) of salt in his/her blood to begin with, you start to get a feel for how significant these losses can be!
According to one of the most respected textbooks in medicine, and a definite authority on the topic, relative to sweat, “these losses are almost entirely replaced by...solutions (including Gatorade) that have a much lower salt concentration. The net effect is water retention and, in some cases, symptomatic hyponatremia, with a fall in plasma sodium concentration...”
Quoted from Clinical Physiology of Acid-Base and Electrolyte Disorders-4th Edition, 1994. Chapter 23, pp 656. Edited by Burton David Rose.
It is important to understand the difference between amount and concentration of sodium. Amount refers to weight, and can be measured in milligrams (1/1000 gram) or grams. Concentration refers to weight in a given volume of water, and is measured in milligrams/litre or grams/litre. When speaking of ingesting a sports drink, concentration of sodium in the drink is the important issue when comparing different brands.
Definition
Hyponatremia is defined as a blood sodium concentration of < 135 mEq/liter (< 3.10 g/liter), with normal ranges usually falling between 138-142 mEq/liter (3.17-3.27 g/liter). In the most severe cases, blood sodium concentration may fall to below 120 mEq/liter (2.76 g/liter), a true medical emergency! As can be seen with these numbers, there is not much difference between normal and an emergency situation (about .50 g of sodium/liter, or 1/12 teaspoon/liter!). Symptoms of hyponatremia include nausea, muscular cramping, stomach upset, vomiting, dizziness, seizures and delirium. Coma and even death may result, and has been reported in several cases.
To be continued...see below for Part 2.
posted by MedionMan at 7:36 PM
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