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Hydration – a lesson learned

I would like to share the following story of my first experience of running an ultra-marathon. I think it's an interesting story but more importantly for me I'm writing it as a warning – as the run quite nearly killed me.

On Saturday 12th July Lou and I took part in the the Osmotherley Phoenix, a 33 mile race in the North York Moors. The race was extremely well organised with six manned check points each with a good supply of water, cake and cheerful marshals, plus an extra unmanned checkpoint that also had a good water supply. It's a good job there was so much water as it was a lovely summer's day with temperatures around 25C and not much wind.

On the run both Lou and I were carrying two 500ml bottles each and at most checkpoints we filled both with water or squash and then drank that before the next checkpoint. So, I probably consumed about five or six litres of water in the almost nine hours it took us to complete the run (the heat and hills slowed us considerably!) For around the last hour I started to feel pretty awful and a bit wobbly on my legs. By the time we finished the run I felt really bad and just sat in the village in for about an hour, wandering over to sit with an on-site ambulance crew as I didn't feel any better. The ambulance crew thought I was dehydrated or suffering from the heat and encouraged me to drink more water – so I drank almost another litre while sitting in the ambulance. After a while the ambulance gave us a lift back to our camp-site as I was in no state to walk the half mile or so myself.

Almost as soon as we arrived back at our tent after being dropped off I vomited and that is the last thing I remember of Saturday. Soon after vomiting my muscles began cramping. Then I collapsed and started to have a fit or seizure with my breathing becoming erratic. We got fantastic first aid and support from the camp-site manager and the people around us, but it took an hour for the ambulance to arrive – possibly the longest hour of Lou's life. Once on site they gave me oxygen and got me hooked up to a drip. The assumption was that I was suffering from dehydration or heat stroke. l was taken to A&E at Friarage Hospital in Northallerton where I was given an CT scan but it was a blood test that finally revealed the correct diagnosis – I was suffering from Hyponatraemia or Water Intoxication with my blood sodium level at 113 mEq/L. To put this in context, 135 is considered normal and anything lower than 125 is severe.

I've given some links below to more information on Hyponatraemia, but essentially it is a result of drinking too much water, which dilutes the sodium levels in your blood and in turn causes cells to swell up via a process of osmosis. When this happens in the brain you have a seizure.

It was Sunday evening before I regained consciousness though it was Monday morning before I had much understanding where I was – the Intensive Care Unit. The doctors were allowing my sodium levels to increase gradually, and by Monday lunchtime they had recovered to 125. I was moved to a regular ward for a final 24 hours to continue recovering, finally being discharged on Tuesday afternoon.

There have been a few well publicised deaths from Hyponatraemia – including Leah Betts (ecstasy related) and an American lady who drank a large volume of water as part of a radio competition. Crucially there have also been several deaths related to marathons and other endurance sports, in which salt loss from heavy sweating combined with drinking excess water leads to significant reduction in sodium levels. That is to say that if I had drunk the same amount of water but had spent the day sitting around then it's quite likely I would have been fine. Indeed my t-shirt and running pack were covered in salt marks. Normally on such a run I would have used salt tablets and that may have prevented the problems (though this isn't certain), but I didn't do so on this run because the water supplies were so good. It's also worth pointing out that Lou drank a comparable amount to me and she suffered no ill effects. I'm not sure if that's because Lou doesn't sweat as much as me or just because her body is different, not retaining the water in the way I did.

I know that when I say I drank five or six litres of water many people will think that that's a crazy amount to drink and I must have been forcing it down. However, it really didn't feel that way at the time and in fact the US army guidelines are to drink 1.5 litres per hour in temperatures above 30 degrees C. It was a hot day, we were out for a long time and I don't think I had a wee during the entire run – which I took to mean I needed to drink more. So, I would just urge people to be careful out there – drinking too much is actually far more dangerous than not drinking enough.

Luckily, despite such a close shave, I should suffer no longer term consequences. We are hugely grateful to everyone at the Friarage Hospital for everything they did for us. I'm back at work now after a week off but am operating well below my best – it will be several more weeks before my brain fully recovers from the seizure.

Wikipedia – Hyponatremia
Wikipedia – Water Intoxication
Published article
Runners World
American Medical Athletics Institute

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