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Dehydration and heatstroke

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 6 minutes read

Dehydration is a condition characterised by an inadequate amount of fluid in the body, resulting from either insufficient fluid intake or excessive fluid loss. This imbalance disrupts the body's normal functions and can lead to a range of symptoms and health complications. Dehydration occurs when the body loses more fluids than it takes in, causing a decrease in the volume of water and electrolytes (such as sodium, potassium, and chloride) circulating in the body. This can happen due to various factors, including excessive sweating, vomiting, diarrhoea, fever, prolonged exposure to heat, or insufficient fluid intake. Dehydration can manifest with symptoms such as thirst, dry mouth, dark urine, fatigue, dizziness, headache, confusion, and, in severe cases, rapid heartbeat, low blood pressure, and loss of consciousness. Prompt recognition and treatment of dehydration are essential to restore fluid balance, prevent complications, and promote overall well-being.

Ensuring adequate hydration to ensure our bodies remain healthy can be a tough ask, especially in hot conditions, and during strenuous activities or exercise. Hot temperatures and increased water and salt losses can lead to dehydration. Mild dehydration may be felt as thirst, headache, mild dizziness, reduced need to urinate and dry skin. In its more severe form, dehydration can result in reduced alertness, fatigue, muscle cramps, loss of consciousness and long-term damage to your kidneys.

Doctor’s advice

What are the signs of dehydration

Inadequate intake of fluids is a leading cause of dehydration with many people not ensuring that they have the recommended 2 - 2.5 litres of water a day. Mild dehydration during the summer months is very common however if combined with a high amount of sun exposure it can result in heat exhaustion or heatstroke.

Common signs and symptoms of dehydration include:

  • Thirst. Thirst is often the first sign of dehydration. When the body is lacking fluids, it sends signals to the brain indicating the need for water.
  • Dry mouth and lips. Decreased saliva production can lead to a dry mouth and parched lips, contributing to feelings of thirst and discomfort.
  • Dark urine. Dehydration can cause urine to become darker in colour, ranging from amber to deep yellow. This occurs because the kidneys conserve water by producing concentrated urine.
  • Infrequent urination. In dehydration, the body conserves water by reducing urine output, leading to infrequent urination or decreased urine volume.
  • Fatigue and weakness. Dehydration can result in fatigue, weakness, and decreased energy levels as the body's cells and organs lack adequate hydration to function optimally.
  • Dizziness or lightheadedness: Dehydration can cause a drop in blood pressure and reduced blood flow to the brain, leading to dizziness, lightheadedness, or fainting.
  • Headache. Dehydration may trigger headaches or migraines due to changes in blood flow and electrolyte imbalances in the brain.
  • Dry skin. Insufficient hydration can lead to dry, flaky skin and exacerbate skin conditions such as eczema or psoriasis.
  • Muscle cramps. Dehydration can disrupt electrolyte balance, leading to muscle cramps, spasms, or twitching, particularly during physical activity.
  • Rapid heartbeat. In severe dehydration, the heart may beat faster to compensate for decreased blood volume and maintain adequate circulation, resulting in palpitations or an irregular heartbeat.
  • Sunken eyes. Dehydration can cause the eyes to appear sunken or hollowed out due to reduced fluid levels in the body.
  • Confusion or irritability. Severe dehydration can impair cognitive function and mood, leading to confusion, irritability, or difficulty concentrating.
  • Decreased skin elasticity. Dehydration may decrease skin turgor or elasticity, causing the skin to lose its ability to bounce back when pinched or pulled gently.
  • Weak pulse. In extreme cases of dehydration, the pulse may become weak or difficult to detect due to reduced blood volume and circulation.

What are the symptoms of heatstroke?

It is a medical emergency that requires immediate treatment to prevent serious complications and death. Symptoms of heatstroke can vary in severity but may include:

  1. High body temperature. Heatstroke is marked by a core body temperature of 40°C (104°F) or higher. This elevated temperature is a hallmark feature of heatstroke and distinguishes it from less severe heat-related illnesses like heat exhaustion.

  2. Altered mental state. Heatstroke can cause confusion, agitation, delirium, hallucinations, disorientation, or even loss of consciousness. Changes in mental status may indicate central nervous system dysfunction due to the effects of extreme heat on the brain.

  3. Flushed skin. The skin may appear flushed, red, hot, and dry to the touch. Profuse sweating, which is common in milder forms of heat-related illness, may cease in cases of severe heatstroke as the body's thermoregulatory mechanisms become overwhelmed.

  4. Rapid heart rate. Heatstroke can lead to an elevated heart rate (tachycardia) as the body attempts to cool itself by increasing blood circulation. However, in severe cases, the pulse may become weak or difficult to detect.

  5. Rapid breathing. Breathing may become rapid (hyperventilation) as the body attempts to expel heat and maintain adequate oxygenation of tissues.

  6. Nausea and vomiting. Heatstroke can cause nausea, vomiting, and gastrointestinal distress, which may contribute to dehydration and electrolyte imbalances.

  7. Headache. Intense headaches or throbbing head pain may occur as a result of dehydration, heat-induced blood vessel dilation, and increased intracranial pressure.

  8. Muscle cramps or weakness. Heatstroke may cause muscle cramps, weakness, or fatigue due to electrolyte imbalances, dehydration, and heat-induced muscle strain.

  9. Seizures. In severe cases of heatstroke, seizures or convulsions may occur as a result of the brain's inability to regulate electrical activity due to extreme heat exposure.

  10. Unconsciousness. Heatstroke can lead to loss of consciousness or coma if not promptly treated. Loss of consciousness is a medical emergency requiring immediate intervention to prevent further complications and preserve life.

How can I avoid dehydration?

To avoid dehydration and maintain proper hydration levels, consider implementing the following top 10 recommended Healthwords strategies:

  1. Drink Plenty of Fluids. Consume an adequate amount of fluids throughout the day, aiming for at least 8-10 glasses per day (approximately 2-2.5 litres). Adjust your fluid intake based on factors such as activity level, environmental conditions, and individual hydration needs.

  2. Monitor urine colour. Pay attention to the colour of your urine as a general indicator of hydration status. Pale yellow or straw-coloured urine typically indicates adequate hydration, while darker urine may suggest dehydration and the need to drink more fluids.

  3. Stay hydrated during exercise. Drink water before, during, and after exercise to replace fluids lost through sweating. Opt for sports drinks containing electrolytes if engaging in prolonged or intense physical activity to replenish sodium, potassium, and other electrolytes lost in sweat.

  4. Limit alcohol and caffeine. Reduce consumption of alcoholic and caffeinated beverages, as they can have diuretic effects and contribute to dehydration. Instead, choose water, herbal teas, or electrolyte-rich drinks as primary sources of hydration.

  5. Eat hydrating foods. Incorporate water-rich foods such as fruits (e.g., watermelon, oranges, strawberries), vegetables (e.g., cucumber, lettuce, tomatoes), and soups into your diet to supplement fluid intake and promote hydration.

  6. Monitor fluid losses. Be mindful of fluid losses through activities such as sweating, vomiting, diarrhoea, or urination, and take steps to replace lost fluids promptly. Increase fluid intake during hot weather, illness, or periods of increased physical exertion to prevent dehydration.

  7. Stay cool in hot environments. Avoid prolonged exposure to high temperatures and take precautions to stay cool during hot weather. Seek shade, wear lightweight, breathable clothing, and use fans or air conditioning to lower body temperature and reduce the risk of dehydration.

  8. Hydrate before bed. Drink water before bedtime to ensure adequate hydration overnight. However, be mindful of excessive fluid intake close to bedtime, as it may disrupt sleep or lead to nighttime awakenings to use the bathroom.

  9. Monitor hydration in special situations. Pay special attention to hydration needs during pregnancy, breastfeeding, illness, or when taking medications that increase fluid loss. Consult healthcare professionals for personalized recommendations and guidance on hydration management in these situations.

  10. Listen to your body. Be attentive to thirst cues and other signs of dehydration, such as dry mouth, fatigue, dizziness, or dark urine. Drink fluids regularly throughout the day, even if you don't feel thirsty, to maintain hydration and support overall well-being.

When should I see my doctor?

If you have been unable to keep down fluids for over 12 hours or have had severe diarrhoea or are feeling weak then it is best to be reviewed by your doctor. If you have any of the symptoms of heatstroke then you should be attending the hospital without delay.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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