We have had a reprieve from the heat with lower temperatures and a lower heat index this week. Of course, the high temperatures will return soon enough. With those temps come increased dehydration. Consider that 0.08% blood alcohol creates a 17% slowing in reaction time while 4% dehydration creates a 23% slowing in reaction time. We lose 2.5% body water through normal processes such as sweating and respiration every day. Not drinking enough water, for any reason, can quickly cause problems for us and our patients. Many of us have been depriving ourselves for years to “get the job done” including the need to make seat time in a rig or aircraft more convenient because you don’t have to run to the restroom. (Hard to do mid-call, even harder to do mid-flight.) And we have all heard the story of the dedicated surgeon that had nursing start an IV and pass a foley in him during a particularly long surgery. May sound outlandish but it allowed the guy to maintain mental and physical acuity. Might be a little easier if we just drank a little more water throughout the day.
Thirst can kick in with as little as 1% dehydration, so pay attention. By the time you are experiencing more thirst, decreased production of saliva, difficulty swallowing, it is time to do something about it. When we hit the 4% level we are two quarts (roughly 1900 ml) of water below par. At that point we have no business driving, flying or treating anything or anyone!
At 8% (4L or 4.25 qt.) loss we are in renal failure. We experience a substantial loss of plasma volume, blood viscosity is elevated, we have excess BUN and a falling blood pressure.
So, how do we prevent this? Remember that 2.5% (5 cups, 1200 ml) we lose every day? That figure is based on an average sized, at rest human. With work and a heat index that will be back in triple digits soon, that will not maintain any of us. The National Academy of Medicine suggest that we let our thirst be the guide but that an average adult male should consume about 3.7L (15 cups) of water a day, and a female should drink about 2.7L (11 cups) per day. This includes all water, included in food, other drinks, etc. (Probably shouldn’t be all Diet Coke…huh.)
Best practice is to remember to grab a bottle of water often. Drink it slowly. To maximize the absorption, drink a bottle (500 ml) of water during about an hour. If I grab a soft drink or a coffee, I grab a water also. Check and balance: look at your urine. How dark is it and are you putting out at least 30 ml/hr. Where have I heard that before? Many people carry around a little treasure trove of medical values, cheat notes etc., clipped behind their ID. If you are not sure, add a visual urine chart. Remember that some sports electrolyte replacement drinks are osmotic diuretics. Powerade® is near human values, but if you drink Gatorade®, especially in a dehydrated state, drink two bottles of water with each bottle of product.