When Raelene Brooks, PhD RN, was a critical care nurse in the intensive care unit (ICU), the cardiothoracic surgeon would always ask her, “how is my patient’s urine output?” after he performed heart transplants. At first, Brooks was confused as to why the urine output would be so important when a patient had just received a new heart. But one day, he told her, “Well, it’s a good indicator of whether or not that new heart is pumping adequately, because remember, all of your vital organs are anatomically as if they were on a totem pole. Kidneys are the last vital organ down below. So if you’re getting blood flow to the kidneys, that means everything up above got perfused.”
Today, Brooks is a Dean of the College of Nursing at the University of Phoenix. She spoke to MedShadow about the importance of hydration to our day-to-day lives and long term health.
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What Dehydration Does to Your Body
Your blood, which delivers vital nutrients and molecules to your organs, is made primarily of water. Your heart pumps that blood throughout your body so that those crucial components can reach your organs and keep them functioning. To do that, you need adequate blood pressure. Without enough water, your blood pressure drops and your heart can’t pump hard enough for it to reach all of your organs.
How Do You Tell If You’re Dehydrated?
Dehydration can cause a variety of symptoms.
Thirst: One of the first signs of dehydration is that you’re thirsty. Your brain has receptors that help it monitor how much water you have in your body and when the amount drops too low, your hypothalamus—a structure deep in your brain that helps keep your hormones balanced—messages to you that you’re thirsty.
Headaches, fatigue and confusion: Your brain is surrounded by fluid. If you don’t have enough water, “the brain starts to send off signals,” says Brooks, which can cause headaches. Your brain also just might not work as efficiently as usual, making you a little tired and slow.
Higher heart rate and dizziness: When you’re dehydrated, your blood pressure lowers and your heart has to work harder to pump blood throughout your body. The low blood pressure can make you feel dizzy.
Less Urine: One of the first signs that you’re dehydrated is a change in your urine output. When you’re hydrated, your urine is a very light yellow color. If it gets darker yellow or you are urinating much less than usual, you’re probably dehydrated.
Cracked lips and dry skin: When you don’t have enough water, your skin and lips can become dry and chapped.
How Much Water Do You Need in a Day?
How much water you need in a day varies depending on your climate, your level of activity, what exactly you’re drinking (for example the caffeine in coffee can make you urinate more, meaning you may need a little more water to rehydrate), and your overall health. As long as your liver and kidneys are healthy, Brooks says, that drinking about a gallon of water a day is great for most people. If you do have liver or kidney damage, you need to be a little more careful to balance what you drink with the other nutrients you’re consuming, because water can leak out of your blood vessels and cause swelling elsewhere.
How Long Does it Take to Rehydrate?
To rehydrate, you need to consume fluids, which your digestive system processes and your heart pumps through your body. The amount of time it takes to rehydrate varies widely depending on how dehydrated you are, whether you drink plain water or fluids with electrolytes and carbohydrates, and how much food is in your stomach. One very small study found that people could rehydrate within 45 minutes of drinking 600ml of water or sports drink.
How You Get Dehydrated
You can get dehydrated in a variety of ways. Maybe you just went too long without sipping a drink, or you sweat so much during a hard workout that you couldn’t replace all that lost fluid and electrolytes fast enough. If it’s hot out, you’re more likely to end up dehydrated. If you’ve had diarrhea, or you’ve been vomiting, you likely need to hydrate, but drinking water or sports drinks might feel hard on your stomach. Even certain medications can make you more prone to dehydration.
Drugs that Can Cause Dehydration
Diuretics are drugs that make you urinate more. Sometimes, this is the main purpose of the drug. For example, diuretics are often prescribed for people with heart failure to prevent fluid buildup. However, many other drugs can make you head to the restroom more often as a side effect. Some drugs that can cause dehydration as a side effect include:
- Antibiotics
- Alcohol
- Anticholinergic drugs (a type of drug that blocks receptors for a signalling molecule called acetylcholine, either as it’s main action or as a side effect. Many types of drugs are anticholinergic such as antihistamines as well as drugs for Parkinson’s, incontinence and more.)
- Antidepressants
- Antihistamines
- Beta-blockers
- Corticosteroids
- Laxatives
- Lithium
Who Needs to Be Extra Careful About Hydration?
Most of us will be just fine if we notice we’re a little dehydrated and start to drink some water. However, people with certain conditions have to be more careful to avoid drinking too much or too little water.
Diabetes
“Sugar is a very sharp molecule,” explains Brooks. If you have uncontrolled diabetes, the excess sugar may not be fully dissolved in your blood. By the time your blood gets to your kidneys, these sharp sugar molecules can start to injure the kidneys.
Liver Disease
Your liver regulates a protein called albumin which helps you stay hydrated. Without enough albumin, water will start to leak out of your blood vessels and cause swelling elsewhere in your body. When patients have severe liver disease (less than 30% of their liver function) Brooks explains that healthcare providers will usually provide albumin through an IV. When they do this, fluid can rush back into the blood vessels too quickly, so sometimes the provider will also prescribe a diuretic to prevent the blood pressure from getting too high.
Kidney Disease
Chronic dehydration may be a risk factor for developing kidney disease later on. Dehydration prevents your kidneys from filtering out waste and other molecules that can cause problems such as urinary tract infections (UTIs) and kidney stones that can permanently damage your kidneys if not properly treated.
Alcohol Use Disorders
Alcohol is a diuretic, so the more alcohol you drink, the more likely you are to become dehydrated. Dehydration is responsible for at least some of the symptoms of a hangover the night after you have had one too many drinks. If you’re imbibing, consider alternating one glass of water after each alcoholic beverage to help maintain your hydration.
Hydration and Weight Loss
Staying hydrated may help you maintain a healthy body weight, says Brooks. Her research team found that women tended to overeat when they’re dehydrated, she says. So while drinking an extra glass of water now and then probably won’t suddenly lead to dropping pounds, it may help you recognize when you’re full sooner, rather than mistaking your thirst for continued hunger.
“It might not just be that we’re hungry. We’re thirsty, and we need to be hydrated,” she says.
