Dehydration, symptoms and causes

Dehydration, symptoms and causes

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Dehydration, symptoms and types (isotonic, hypertonic or hypotonic). Which water to choose and how much water to drink to hydrate the body.

Dehydration, symptoms

Theredehydrationis linked to a reduced presence ofwaterin body composition. Theredehydrationis characterized by an alteration of the concentrations ofplasma sodium, osmolality and an increase in plasma urea values. Sixsymptomsjust listed are detectable only with laboratory analysis, there are otherssymptomsmore evident to identify in daily life. ThesesymptomsI'm:

  • Thirst (often absent in the elderly and in problem patients)
  • Dryness of the mucous membranes
  • Dry skin
  • Reduction of skin turgor
  • Dry tongue with presence of longitudinal furrows
  • Muscle weakness
  • Reduction in body weight (by 3 - 5%)
  • Poor salivation and dry mouth
  • Oliguria (poor urination)

There are several types ofdehydration: hypertonic, hypotonic and isotonic. Thetreatment of dehydration in the elderlyit's not as easy as you can imagine: drinking is not enough! It is important to restore the correct body water balance but it is equally essential to control hydro-electrolytic alterations and administer the right concentrations of salt based on the type of dehydration highlighted.

Isotonic dehydration

Isotonic dehydration is characterized by a scarcity of fluids having a composition comparable to that of plasma. Plasma osmolality is between 270 and 300 mOsm / l and the concentration of ionic sodium (Na +) is between 130 and 150 mmol / l.


  • Secretory diarrhea
  • Dynamic and paralytic ileus

Hypertonic dehydration

It occurs when water loss involves hypotonic (solute-free) fluids. Generally thisdehydrationit is linked to a reduction in water intake and / or in the presence of an increase in fluid losses. In this case, plasma osmolality is greater than 310 mOsm / l and the sodium concentration (sodium) is greater than 150 mmol / l.


  • He retched
  • Nasogastric tube
  • Gastroenteritis
  • Osmotic diuretics
  • Hyperthermia
  • Hyperthyroidism
  • Burns
  • Peritonitis
  • Nephrogenic diabetes insipidus
  • Losses

Hypotonic dehydration

It is linked to a loss of fluids in the presence of an excess of sodium compared to water. It can also occur with losses of isotonic liquids and with partial replenishment of water or hypotonic liquids. Plasma osmolality + lower than 270 mOsm / l with sodium <130 mmol / l.


  • Diuretics
  • Sweat with a high concentration of sodium
  • Cystic fibrosis
  • Cerebral salt loss syndrome

Dehydration, causes

Thecauses of dehydrationvary according to the type. There isotonic dehydration, for example, it is caused by secretory diarrhea (as in the case of contamination by E.coli, by the vibrio of cholera or by the massive use of laxatives).

Thecausesof thehypertonic dehydration are different: in this case the dehydration is triggered by frequent vomiting, by the elimination of secretions through the nasogastric tube or by diarrhea (gastroenteritis). Hypertonic dehydration is related to disorders such as peritonitis, hyperthyroidism, burns, hyperthermia or massive use of diuretics and osmotics.

Still different is thecauseof thehypotonic dehydration. This dehydration is generally linked to the excessive use of diuretics (especially thiazides). It occurs frequently in the elderly and also in athletes. In particular, in sportsmen and athletes, this dehydration is linked to the loss of sodium through sweating; this condition manifests itself during endurance competitions such as a long marathon or triathlon, especially when athletes are poorly acclimatized and poorly trained. It is also common in patients with cystic fibrosis.

Body water concentration

How much water does our body contain? The percentage varies during the stages of growth. The highest concentrations occur in the early stages of life. In adults, total body water (ATC) amounts to about 50% of weight in women and about 60% of weight in men. Normally the plasma osmolality is between 285-295 mOsm / kg / H2O3.

What happens if I drink little

What happens if I drink too little water? This is a very common question. This question is asked above all by those who lead a very sedentary life. Those who do little physical activity perceive less thirst and thus risk drinking very little.

Therelack of water intakeis one of thecauses of dehydrationmore frequent, especially in the elderly and in those who lead a particularly sedentary life. When there is a low water supply, hypertonic dehydration occurs.

For more information on the topic hydration of the body:

  • What water to drink
  • How much water to drink

Video: Effects of Dehydration (June 2022).