Fly Well: You need a drink

Sigmund Freud said, “The mind is like an iceberg, it floats with one-seventh of its bulk above water.” However, without sufficient water the mind may not be doing much of anything. Always staying well hydrated is important to ensure the body is firing on all cylinders; this is even more critical when airborne.

Humans need four to five pints of water daily depending on sex, size, age, and activity, requiring more on hot days at the airport. Under normal circumstances we lose fluid during breathing, sweating, defecation, and, of course, urination. Dehydration (literally “drying out”) occurs from failure to consume enough fluid or increased depletion. Dehydration can be associated with raised or lowered body salt or, most commonly, isotonic dehydration—where salt and water are lost in tandem. Human physiology adjusts for various circumstances, encouraging us to drink more when losses increase and reducing urine output if more fluid leaves from sweating or breathing.

At altitude, “passive” lung losses increase as breathing drier cabin air or aviation oxygen sucks moisture away. Additionally, we breathe faster if not using supplemental oxygen, thereby losing even more moisture. Clever brain signals let us know when we need to consume more fluid, but this diminishes as we climb into our fifth decade and, when focused on piloting, one may neglect to drink enough. With worsening dehydration, thirst actually declines but prior to that point symptoms include reduced sweating, darker urine, increased heart rate, muscle aches, headache, dizziness, confusion, or drowsiness—not good for a pilot. Dehydration, together with hypoxia and time-zone changes contribute to jet lag, because pressurization systems keep cabins in commercial airliners at several thousand feet and the air on board is dry.

Some people are more prone to dehydration’s dangers; asthmatics may be likelier to have an attack and deep vein thrombosis may be more common, especially in those with a prior history or risk factors (“Fly Well: Really Deep, Man” July 2010 AOPA Pilot). Hypertensives taking diuretics know to keep their potassium in check, which can be otherwise disturbed if one is not properly hydrated—and people with kidney, heart, or various intestinal diseases should understand the need for careful drinking habits. Stay focused, people; I am not advocating tequila shots! So after considering yourself, please encourage your passengers to follow a similar regime. Handel’s water music soothed King George I. Let water soothe the monarch of the skies.

So what should you drink before and during flight? Not alcohol, of course, but allow more than “eight hours bottle to throttle” because booze sponges up the water in your body, sucking it dry. Avoid caffeine, found in tea, coffee, cocoa, and sodas; it is a diuretic possibly making you lose more fluid than you consume. On hot, dry days, with increased perspiration, consume liquids containing electrolytes, such as sports drinks, but avoid those containing high-fructose corn syrup; you don’t need the extra sugar and it can actually increase thirst.

For regular hydration, plain old tap water is fine. Make sure you visit the facilities prior to takeoff, but do not just empty the bladder; rather, check the color of your pee—if too dark, rehydrate before you fly. Once aloft, consider taking a good swig every 15 minutes or so—coordinate drinking with a regular cockpit routine to be certain you do this. If after a few hours you do not feel the need to relieve yourself, or have symptoms suggesting impending dehydration, you are not drinking enough and heat stroke or exhaustion may follow. Obviously every airplane should carry that dreaded red bottle—if it has never been used after several long flights…you got it, you are not drinking enough!

Altitude-induced dehydration impacts other body parts and merits attention; bring soothing eye drops along for you and your passengers. Wouldn’t it be nice not to have a nosebleed after a long flight? Dehydration affecting your schnoz can be prevented by using a saline nasal spray. And, while not terribly masculine, lip salve will soothe dried-out lips, but be cautious of petroleum-based products if using oxygen.

Mitch Hedberg, a delightfully wacky comedian, said that his fake plants died because he did not pretend to water them. So don’t pretend to not drink and you will be fine.

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