Hyperhydration

One of the clinical forms of impaired water metabolism is an excess volume of water in the body - hyperhydration or hyperhydria.

The essence of this condition is that the amount of fluid in the body is much higher than the physiological norm and the possibility of its renal excretion.

Epidemiology

It is known that at least 75% of the body weight in infants is water, in the elderly - up to 55%; due to the greater volume of tissues in the body of women, their percentage of water is lower than that of men.

However, there is no statistics of increased hydration at the population level, since there are no adequate biological markers to determine the state of the body's water balance, and there are no objective data on the volume of its consumption.

Causes overhydration

With the consumption of too much fluid (over two liters per day), overhydration is associated if polydipsia occurs - not physiological, but pathological  constant thirst . It can be psychogenic (for example, in patients with schizophrenia), but, in most cases, it is caused by a violation of hormonal regulation of the most complex processes of water metabolism and maintenance of the body's salt balance.

For example, with the development of Conn's syndrome -  primary hyperaldosteronism associated with hyperplasia or neoplasms of the adrenal cortex, the level of the hormone aldosterone synthesized by its glomerular cells increases, which participates in water metabolism, stimulating the absorption of  sodium by the  kidneys. Also, an increase in aldosterone occurs when the sympathetic-adrenomedullary system is activated in cases of psychological stress. And in case of abnormalities or lesions of the hypothalamus (traumatic, tumor or neurotoxic origin), excess fluid is due to increased secretion of vasopressin, which regulates water retention by the kidneys, - antidiuretic hormone (ADH), which doctors call the syndrome of its inadequate production, hyperhydropexy syndrome or Parkhon's syndrome.[1]

However, most often the reasons for the accumulation of water in the body lie in problems with its excretion - in case of functional failures of the systems intended for this. This refers to nephrological diseases that negatively affect the  endocrine apparatus of the kidneys , which play a key role in regulating fluid balance. These are nephritis, all  forms of glomerulonephritis , nephrolithiasis,  chronic renal failure , in which glomerular filtration is impaired and the kidneys' ability to adequately compensate by increasing the rate of urine formation decreases.

Risk factors

Experts associate risk factors for the development of overhydration with diseases that can lead to fluid retention in the body, in particular, cardiological and vascular chronic pathologies (with arterial hypertension), hypothyroidism, uncontrolled diabetes and diabetes insipidus, liver cirrhosis, trauma and inflammation of certain brain structures, bacterial pneumonia and pulmonary tuberculosis. In the case of malignant tumors of various localization and their metastasis, the hyperhydration syndrome is part of the paraneoplastic syndrome.

In addition, pathologically increased hydration can be iatrogenic and observed with intravenous  infusion therapy  (in almost 2% of hospital patients), with peritoneal hemodialysis, as well as as a side effect of lithium preparations, long-term treatment with neuroleptics (antidepressants) or prolonged use of corticosteroids, blockers calcium channels, non-steroidal anti-inflammatory drugs.

Among healthy people, athletes (participants in marathons and other long-term sporting events) and people working in high-temperature environments are at greatest risk of overhydration - due to excessive drinking and sweating with loss of electrolytes. [2]

The risk of developing this condition is also increased in infants, the elderly, in people with low body weight and chronic alcoholics.

Pathogenesis

The pathogenesis or mechanism of overhydration is due to disturbances in the process of homeostatic regulation of water and mineral balance, which is provided by the corresponding hormones.

Excessive water intake, as well as excessive or low sodium intake, can initiate a number of hormonal reactions, largely mediated by antidiuretic hormone. An increase in the release of vasopressin leads to a decrease in the tone of the renal arterioles with an increase in the reabsorption (resorption) of water from the urine, which reduces its volume and excretion (diuresis), that is, retains water in the body, mainly due to an increase in the volume of extracellular fluid.[3]

Aldosterone, acting on the corresponding receptors in the tubules and collecting ducts of the nephron, with increased secretion retains more Na + and water (osmotically free).

At high osmolarity of body fluids (concentration of ions and other dissolved particles in them), excess water remains in the extracellular space, at low osmolarity, it passes from the extracellular space into cells, causing them to swell, that is, an increase in volume. As a result, the metabolism and functions of cells change.

Symptoms overhydration

If overhydration develops rapidly, then its first signs include vomiting and imbalance and coordination.

Clinical symptoms with elevated ADH levels depend on the degree of decrease in serum Na + levels. At the initial stage, they are manifested by headache, decreased or lack of appetite, nausea and vomiting. With a rapid decrease in the sodium content in the blood, convulsions appear, general anxiety increases, and the development of cerebral edema leads to  stupor and coma .

Overhydration can be chronic - with a decrease in the volume of excreted urine and edema (including subcutaneous tissue).

Symptoms of a severe form of increased hydration of the body also include: a decrease in temperature; muscle weakness and tremors; convulsions; strengthening or weakening of reflexes; blurred vision; sleep disorders; increased blood pressure; respiratory distress and lack of oxygen with cyanosis (a condition in which the blood and body tissues contain abnormally high levels of acid), anemia, cyanosis (a condition that occurs when the oxygen level in the blood drops sharply), bleeding and shock.

Forms

Depending on the ratio of water levels and the concentration of electrolytes in it, isoosmolar, hypoosmolar and hyperosmolar hyperhydration are isolated.

With an excess of water and its insufficient excretion - subject to normal osmolarity of the extracellular fluid - normoosmotic, isoosmolar hyperhydration or general hyperhydration with an increase in the volume of interstitial fluid is determined.

Hypoosmolar hyperhydration (with serum osmolality below 280 mosmol / kg water, but with significantly increased urine osmolarity) or intracellular hyperhydration is characterized by an increased amount of intracellular fluid due to the transmembrane transition of extracellular fluid into the cells.

If the content of salt and water in the extracellular space is increased (with plasma osmolality above 300 mosmol / kg water), then hyperosmolar hyperhydration is diagnosed, the synonyms of which are: hypertonic hyperhydration, hyperosmotic, extracellular or extracellular hyperhydration. That is, this state is in everything the opposite of intracellular hyperhydria and is characterized by decreased hydration and a decrease in cell volume.

Complications and consequences

Overhydration leads to an  imbalance in water and electrolyte balance  and, if electrolytes are significantly depleted, can cause potentially fatal water poisoning. In particular, hyponatremia develops   - sodium deficiency (in adults, <130-135 mmol / l).

Also, the consequences and complications are manifested by  edematous syndrome  - edema of internal organs and the brain and  metabolic acidosis .

Due to hypoosmolar hyperhydration, intravascular destruction of blood erythrocytes and excretion of the hemoglobin oxidation product in the urine occurs - with the development of anemia.

In chronic renal failure, increased hydration is fraught with serious consequences such as pulmonary edema, structural changes (remodeling) of the heart, and heart failure.

Diagnostics overhydration

Diagnosis of overhydration is usually based on an  examination of the kidneys .

To determine the true cause of overhydration, tests are also needed: general and biochemical blood test; for aldosterone and  antidiuretic hormone in the blood ; to  determine the osmolarity of blood serum ; on serum levels of glucose, creatinine, urea, sodium and potassium, free T4 (thyroxine). Mandatory urine tests include: general, Zimnitsky test (for dilution and concentration of urine), for osmolarity, for GFR (glomerular filtration rate), for Na-uretic factor.[4]

Read more -  Additional methods of kidney examination

Instrumental diagnostics uses bioimpedance measurement; x-ray of the kidneys ; Ultrasound, scintigraphy, CT or MRI of the kidneys; x-ray of the adrenal glands ; MRI of the hypothalamus and adenohypophysis.

Differential diagnosis

Differential diagnosis is carried out with an increase in the volume of circulating blood - hypervolemia.

Treatment overhydration

Treatment of mild overhydration is by limiting fluid intake. In a more severe condition, the diuretics Spironolactone,  Indapamide  (Indapen), Furosemide are used. According to the indications, sodium chloride or sodium bicarbonate (solutions) is administered parenterally.

But if overhydration occurs when sodium levels are elevated due to heart, liver, or kidney disease, then sodium intake is limited to a salt-free diet.

With increased production of vasopressin, new drugs from the group of antagonists of antidiuretic hormone receptors are now being used - vaptans (Conivaptan or Tolvaptan).

At the same time, the treatment of diseases that have caused increased hydration is carried out. [5]

Prevention

In many cases, overhydration can be prevented as long as a person's water intake does not exceed their water loss. Healthy kidneys are able to excrete approximately 800 ml per liter of water (approximately 1-1.2 ml urine per minute).

The need for water varies from person to person and depends on diet, environmental conditions, activity level, and other factors. Experts from the EFSA (European Food Safety Agency) have determined that a sufficient amount of water consumed per day (including drinking water, all types of drinks and liquid from food) is 2.5 liters for everyone over 14 years old.

Forecast

With a mild form of overhydration, doctors give a favorable prognosis. But it should be borne in mind that with cerebral edema due to increased intracranial pressure and blockage of cerebral circulation, a fatal violation of its functions, coma or death is possible.