Dehydration Dangers and Complications
Occasional mild to moderate dehydration rarely causes any dangers in otherwise healthy individuals. On the other hand, chronic or severe dehydration can result in life-threatening complications, especially in elderly and those with underlying chronic diseases.
1. Heat Injury
Heat injury refers to an increase in body temperature due to dehydration (with the inability to sweat and thus lose heat) and exposure to heat. Other symptoms include weakness, nausea, headache and painful cramps [14,16].
The 2 severe phases of heat injury are heat exhaustion and heat stroke.
|Skin||Sweaty, cool, pale ||Dry, hot, flushed [4,14]|
|Body temperature||98.6-104 °F (37-40 °C)||>106-115 °F (41-46 °C)|
First aid in heat injury [14,17]:
- Move a person to a cool place, remove excessive clothes and enable a cool shower or bath.
- Offer a cool beverage, preferably plain water.
- Call a doctor, because a person may need an intravenous fluid infusion.
2. Heart and Circulation Complications
Dehydration can cause orthostatic hypotension — a drop in the systolic (upper) blood pressure for at least 20 mm Hg upon raising . The main symptoms are dizziness or fainting within 3 minutes after raising . You can prevent orthostatic hypotension in the morning by drinking 300-500 mL water 15 minutes before getting up .
In susceptible individuals, long-term dehydration increases the risk of blood clots in the veins (deep vein thrombosis) [11,12].
Severe dehydration may lead to a drop in blood volume (hypovolemia) and consequently inadequate blood perfusion of the tissues (hypovolemic shock). Symptoms and signs include anxiety, lethargy, clammy and pale skin, weak pulse and low blood pressure. If not treated promptly, hypovolemic shock can be deadly.
In an otherwise healthy person, even severe dehydration rarely results in heart attack. In individuals with coronary artery disease or impaired heart valves, dehydration can trigger chest pain (angina pectoris) or irregular heart rhythm (arrhythmia). When dehydration is so severe that it leads to hypovolemic shock, it may result in heart attack .
3. Kidney Complications
In dehydration, mucous membranes in the tubular organs, such as ureters, urinary bladder and urethra, dry up, which may increase the risk of urinary tract infections .
Severe dehydration can result in acute kidney failure — an inability to excrete water and waste materials through the kidneys. Marathon runners with muscle disintegration (rhabdomyolysis) may be at increased risk [8,9].
Chronic dehydration increases the risk of kidney stones .
Severe dehydration can result in elevated blood sodium levels (>145 mmol/L) or hypernatremia.
Hypernatremia can result in the movement of water from the brain cells and thus in brain shrinkage. Symptoms include confusion and seizures .
5. Other Complications
Dehydration can increase the risk of:
- Acute mountain sickness 
- Exercise-induced asthma 
- Hyperglycemia (in diabetes mellitus) 
- Yeast infection in the mouth (oral thrush, candidiasis) 
- Bed sores 
There is a lack of evidence about the association of dehydration with fibromyalgia.
6. Dehydration and Death
An otherwise healthy person who has lost more than 10% of body weight due to dehydration can go into a coma or die. Here you can read how long you can survive without water.
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