Dehydration

Thirst is not always a sensitive indicator of one’s hydration status, especially in certain populations. In many cases, dehydration can occur without feeling thirsty. Older adults, in particular, may not experience thirst even after fluid loss, placing them at heightened risk.

It is, therefore, important for all individuals, especially during periods of illness, to proactively increase fluid intake in hot weather or when sweating more heavily from physical exertion. Maintaining adequate hydration is critical for homeostasis.

Additionally, the clinical presentation of dehydration can vary depending on age. 

Infant or young child

Signs and symptoms of dehydration in infants and young children:

• Dry mouth and tongue
• No tears when crying
• No wet diapers in over 3 hours
• Sunken eyes and cheeks, giving the face a gaunt appearance
• Sunken soft spot on top of the skull
• Listlessness and decreased activity levels
• Irritability

Adult

The following signs may indicate dehydration in adults:

• Extreme thirst is a classic early symptom as the body attempts to restore fluid balance.
• Less frequent urination suggests the kidneys are concentrating urine to retain water.
• Dark-coloured urine occurs as the urine becomes more concentrated.
• Fatigue, dizziness and confusion are later symptoms that may indicate significant fluid deficit and electrolyte abnormalities affecting physical and cognitive functioning.

Seek prompt medical care if any of the following are observed:

• Prolonged diarrhea can cause significant fluid and electrolyte losses, leading to dehydration over 24 hours or more.
• Changes in mental status, such as irritability, confusion or excessive sleepiness, may indicate dehydration affecting organ function.
• The inability to keep fluids down suggests the severity of dehydration is beyond oral rehydration alone.
• Bloody or black stool may point to more serious underlying conditions requiring medical diagnosis and management.

Calling the family doctor or healthcare provider is advised if concerning signs are present to allow for thorough evaluation and appropriate treatment of potential dehydration.

Dehydration can occur due to inadequate fluid intake from various causes. For example, acute illness may lead to anorexia and reduced oral intake due to nausea/vomiting. Being too busy can also cause neglect of hydration needs. Moreover, limited access to potable water during travel, hiking or strenuous activities also deprives the body of fluid replenishment.

Additional causes involve excessive fluid losses:

• Gastrointestinal losses – Severe acute diarrhea results in massive losses through loose. Exceeding intestinal absorptive capacity leads to watery stool by exceeding intestinal absorptive capacity. Vomiting exacerbates fluid depletion by preventing oral rehydration.
• Increased insensible water loss – Fever triggers hyperthermia-induced diaphoresis. This effect is compounded in cases of concurrent diarrhea/vomiting.
• Sweat gland activation – Vigorous exercise in hot, humid conditions leads to fluid and electrolyte depletion through eccrine gland secretion if intake is not increased to match insensible losses.
• Renal losses – Conditions like undiagnosed diabetes mellitus/insipid overwhelm kidney reabsorption capacity, while loop diuretics induce increased free water clearance prescribed for cardiac/renal diseases.

Prompt oral/IV rehydration therapy and treatment of the underlying precipitant are necessary to prevent further health complications from fluid-electrolyte imbalances due to volume depletion.

Anyone can become dehydrated, but certain people are at greater risk:

• Infants and children. The most likely group to experience severe diarrhea and vomiting, infants and children, are especially vulnerable to dehydration. Having a higher surface area to volume ratio, they also lose a higher proportion of their fluids from a high fever or burns. Young children often can’t tell you that they’re thirsty, nor can they get a drink for themselves.
• Older adults. As you age, your body’s fluid reserve becomes smaller, your ability to conserve water is reduced, and your thirst sense becomes less acute. These problems are compounded by chronic illnesses such as diabetes and dementia and by the use of certain medications. Older adults may also have mobility problems that limit their ability to obtain water.
• People with chronic illnesses. Having uncontrolled or untreated diabetes puts you at high risk of dehydration. Kidney disease also increases your risk, as do medications that increase urination. Even having a cold or sore throat makes you more susceptible to dehydration because you’re less likely to feel like eating or drinking when you’re sick.
• People who work or exercise outside. Your risk of dehydration and heat illness increases when it’s hot and humid. That’s because when the air is humid, sweat can’t evaporate and cool you as quickly as it normally does, and this can lead to an increased body temperature and the need for more fluids.

To maintain proper hydration, drinking water and consuming foods high in water content, such as fruits and vegetables regularly is recommended. For healthy individuals, using thirst as a guide is generally sufficient.

However, increased fluid intake may be needed under certain conditions:

• Gastrointestinal illness – In cases of vomiting or diarrhea, begin oral rehydration with water or electrolyte solution at the first signs of illness to prevent dehydration.
• Strenuous physical activity – Hydration should start a day prior to exercise. Producing pale, diluted urine indicates adequate hydration. Drink fluids at regular intervals during exercise and continue hydrating after to replace sweat loss.
• Hot or cold weather – Both heat and humidity cause increased sweat losses, so drinking additional water is important. Cold weather also results in moisture loss, increasing fluid needs, especially at higher altitudes.
• Illness – Older adults are more prone to dehydration from minor illnesses like influenza, bronchitis or urinary tract infections. Be sure to drink extra fluids when feeling unwell to compensate for losses.

Close monitoring of fluid intake is key for individuals at higher risk of dehydration. Medical care should be sought if signs worsen despite hydration efforts.