Finally got the results from 1997 Ironman New Zealand Hyponatremia post race volunteer blood test. Now if I just knew what it means and what to do to avoid the condition other than not racing. Someone who is knowledgeable please look at this and offer a solution. It could be of value to me and other rst'ers These are my personal conditions as reported by Dr. Dale Speedy, MBChB, MRNZCGP MSc Sports Medicine.
Supplemental info provided with the report stated that normal serum sodium concentration is 135 - 145 mmol/L. By this I was just below the minimum level after the race. Now for my input on how I felt and the real results. During the last 35 miles of the bike leg I went without fluid intake. Not by choice but I just happened to hit the aid stations when they were dry, no fluid available of any type. I'm told that they did replenish but I just timed it wrong. Very poor logistical support on their part. So that left me rather dehydrated at the beginning of the run. I felt very good on the run till the 14 mile marker though I had gone through my usual cramping stages during the first few miles. By mile 14 I was really feeling the wall but the cramps were gone. Just was unable to muster any speed From the run start I did try to drink as much as possible. I took fluid from every aid station and would have a need to urinate immediately after drinking. I had not experienced this in other IM's. OK, I finally got through the run, won my division and set an IMNZ age group course record, breaking the old one by 35 minutes. The weather conditions were mild though a little on the hot side during the run and very windy on the bike. My effort level was high the entire race. HR mostly at 156 BPM on the bike, which is about my normal race level. I did not have the monitor during the run but did not perceive HR to be high.
At the finish line I felt just fine, was able to walk about without cramping or staggering and got to the med tent for the blood donation. The blood letting took about 15 minutes total, I drank the glass of 7-UP provided and then I met with my Wife. We were talking, (about 25 min post race) I felt tired but otherwise normal considering the race and then I suddenly got nauseated, dizzy and all went black. I hit the deck and next thing I knew was that I was on a cot in the Med tent. My blood pressure was 90 over 60 and two bottles of IV were provided to rehydrate me. After the IV's I felt normal again, considering the race.
OK, so why the black-out? Hyponatremia, dehydration or? What is the solution for prevention of the same thing happing again? More fluid intake? Salt intake, the test indicated I was borderline low? Don't say go slower.
The most common reason for collapse after the finish of a long distance event is due to blood pooling in the legs, and is referred to as postural hypotension (PH). The longer the race, the greater the risk of EAC. There are several factors which contribute to the development of PH and EAC.
During biking and running, the blood vessels in the legs are dilated to enhance blood flow to, and from, the muscles. Similarly, more blood flow goes to the skin to enhance cooling. After exercise stops, these vessels temporarily maintain the dilated state. Also, when exercise ceases, there is loss of the "pumping action" of muscles -- which helps return blood to the heart. These factors result in blood pooling in the lower extremities. Thus, when standing, or in some cases sitting upright, blood collects in the legs, decreasing the amount available to the brain, and syncope -- a.k.a, a "blackout" -- can result. Some athletes will experience warning signs, such as lightheadedness, nausea, and visual disturbance, prior to syncope.
The initial treatment is to lie the athlete down (the "blackout" may have already done this for you), and elevate the legs. The athlete will usually come around in a few seconds. Once awake and alert, the athlete should be encouraged to drink fluids, and stay lying down. Pulse and blood pressure should be measured and medical diagnosis and treatment decisions made by a qualified professional. The athlete should not try to stand back up, because once EAC has occurred it is likely to recur. The conditions which lead to EAC usually persist for a while. An athlete who "pops" back up will likely "pop" right back down again. Athletes who don't respond to the above conservative treatment likely have a more serious underlying medical condition (e.g., hyponatremia) and should have a more in-depth evaluation.
Dehydration can certainly contribute to PH, because the blood volume is less than normal. The greater the dehydration, the greater the risk of PH and, thus, EAC. For a bit of perspective, if an athlete has managed to accumulate 7% or greater body weight loss, they likely will not be able to continue to race and will collapse. A loss of 3% is associated with about a 20 - 25% reduction in exercise capacity, but the athlete can usually finish the race.
A interesting diagnostic point for EAC is whether it occurred before or after the finish line. If it happened before, there usually is an identifiable medical problem which has developed (e.g., hyperthermia, hyponatremia). If EAC occurred after the finish line, it is usually due to PH. *Please note that because of many variables and conditions, any collapse or illness should be appropriately investigated and not assumed to be harmless.*
With respect to the circumstances you report, I cannot comment on the cause of your collapse. A serum sodium concentration of 134 mg/dl, although technically "low", is well within the range of lab error for normal. Regardless, this degree of "hyponatremia" would not usually be expected to cause any symptoms in an otherwise healthy adult. The most appropriate initial step in the future would be to lie down and drink fluids.
Clinical and biochemical characteristics of collapsed ultramarathon runners
Med. Sci Sports/Exercise, 1994 . Noakes, et al.
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