Most people are often dehydrated

Common and dangerous in old patients

Desiccosis and dehydration are common problems in geriatric patients. Age-physiological changes in the hormonal balance and kidney function in combination with external influences increase the associated risk with sometimes life-threatening consequences. Targeted diagnostics and rapid therapy are necessary in view of the vulnerability of multimorbid elderly patients. The prevention of dehydration in the elderly is of particular importance.

The average life expectancy, which increases annually by approx. 3.5 months with a constantly low birth rate (1.4 births / woman), leads to an aging of our society (Fig. 1).

In 2004 life expectancy in Germany was 81.6 years for women and 76 years for men. The so-called old-age quotient (number of people over 65 per 100 people aged 15-65) will double in Europe by 2050 (see Fig. 2).

Demographic developments and medical progress are leading to far-reaching changes in the health care system: the spectrum of diseases is shifting more and more from acute to chronic diseases, and medical activity is shifting from curative intervention to the management of resulting functional deficits with a focus on maintaining quality of life and autonomy. The detection and treatment of typical geriatric syndromes (cf. Overview 1) is, in view of the tendency to "underreporting" in many older patients, e.g. Sometimes of greater relevance than the individual organ diagnoses.

Physiological age changes

Various physiological changes make old people much more susceptible to disorders of water and electrolyte homeostasis compared to young adults:

  • The body composition changes significantly from the age of 30 to 80: The water content decreases from 60% to 45%, in particular the FCV is reduced. The proportion of body fat, on the other hand, increases from 17% to 30%, at the same time the (muscle) protein proportion decreases - with considerable consequences, among other things. for pharmacotherapy.
  • Renal function deteriorates with increasing age: from the age of 40, the renal plasma flow decreases by 1% / year, the GFR decreases by 10 ml / min per decade. The absolute value of the serum creatinine in geriatric patients alone is unreliable; the decisive factor is the glomerular filtration rate, which is dependent on age, weight and gender. Various formulas, e.g. B. those according to Cockcroft & Gault (1973), are helpful in assessing the kidney function of older patients (see Fig. 3). In addition, the kidneys' ability to concentrate decreases, which leads to dehydration.
  • The feeling of thirst decreases with increasing age, even with a lack of fluids with a corresponding increase in serum osmolarity, too little fluid is consumed.
  • Age-related changes in endocrine function such as lower renin and aldosterone levels as well as reduced response of the kidneys to ADH and higher basal ANP levels promote dehydration and reduced Na reabsorption.

Meet the above Age-physiological changes combined with exogenous disruptive factors or acute intercurrent illnesses result in some vitally threatening changes in the state of hydration, which mostly present themselves as combined disorders of the water and electrolyte balance.

Causes of dehydration and desiccosis in geriatric patients

Disorders of the fluid and electrolyte homeostasis are based on reduced water supply and / or increased losses (see Table 1).

In particular, the feeling of thirst, which decreases with increasing age, even with higher serum osmolarity, is a risk factor for desiccosis. After a 24-hour thirst experiment, older men drank significantly less water than younger ones and were able to normalize their serum Na concentration more slowly and inadequately (Philipps et al., 1991 ). Swallowing disorders of various origins can be considered as the somatic cause of a desiccosis. It is not uncommon for patients with urinary incontinence to restrict their fluid intake in order to reduce the symptoms of their dysfunction. If there is a lack of social contact or care deficits, the lack of fluids is often compensated for too late or not at all. One of the most common causes of increased fluid loss in old age is diuretic therapy, which can also lead to electrolyte disorders.

Consequences of desiccosis

Desiccosis leads to multiple complications and even life-threatening risks. The dry skin of desiccated elderly patients is vulnerable and the risk of pressure ulcers is increased. The lack of fluids also favors constipation, which is often complained about anyway. Significant volume depletion can lead to orthostatic dysregulation and falls. Especially with multimedia and possibly other exogenous disruptive factors, desiccosis is a favorable factor for the development of delirium. Pronounced dehydration can cause acute kidney failure in geriatric patients; rhabdomyolysis is a further threatening complication. The worsening rheology in desiccosis can result in acute myocardial infarction or apoplectic insult.

Electrolyte imbalances

Water and electrolyte imbalances are often combined in geriatric patients. Depending on the relationship between the loss of water and electrolytes, a distinction can be made between isotonic, hypotonic or hypertonic dehydration. Sodium is the most important osmotically effective substance in the extracellular space. A common cause of hypertonic dehydration (Serum Na> 150 mmol / l) is fever with water loss through breathing and sweating. The clinical symptoms can range from lethargy to seizures to coma, with a serum Na concentration> 160 mmol / l the mortality is over 50%. The electrolyte normalization should be done slowly and not exclusively with glucose 5% (free water) because of the risk of brain edema.

The incidence of a Hyponatremia for nursing home residents is up to 50% and can have various causes (see Fig. 4). Except for z. B. elevated serum glucose or protein values ​​as the cause of hyperosmolar or isoosmolar hyponatremia, hyponatremia is usually associated with serum hypoosmolarity. A distinction can be made between dehydration (e.g. due to diuretic therapy), euvolemia (e.g. in the context of a syndrome of inadequate ADH secretion = SIADH) or hypervolaemia (e.g. in cardiac or renal insufficiency). SIADH is an important cause of hyponatremia with normal FCV in old age. In addition to tumors, pulmonary or cerebral diseases, drugs such as neuroleptics, antidepressants or anticonvulsants are often prescribed, especially in old age. The urine sodium concentration is used to further differentiate hypoosmolar hyponatremia (urine Na <20 mmol / l: extrarenal Na loss,> 20 mmol / l: renal loss). Compensation for hyponatremia must also be slow because of the risk of pontine myelinolysis.

Symptoms of desiccosis

As stated earlier, thirst is not a sure sign of dehydration in the elderly. Clinical symptoms of desiccosis in the elderly include: B. dry mucous membranes, reduced skin turgor with standing skin folds, reduced sweat production (dry axilla) and reduced jugular vein filling. Depending on the severity and dynamics of the desiccosis, the spectrum of clinical manifestations can range from weakness, dizziness, apathy to seizures and acute delirium, from hypotension with a tendency to collapse and fall to volume deficiency shock and acute kidney failure.

Laboratory tests usually show an increase in serum hematocrit and in creatinine and urea (with an increased serum urea / serum creatinine quotient, usually> 20: 1).

Therapy and prevention of desiccosis in old age

In addition to eliminating the cause, the central therapeutic measure for any dehydration in old age is adequate fluid substitution. Depending on how pronounced the fluid deficit is and how quickly the dehydration developed, the options range from oral administration to subcutaneous infusion to intravenous fluid administration.

Drinking is the most physiological option, but for the reasons outlined above, it requires continuous stimulation, monitoring and guidance and thus a high expenditure of time for the nursing staff. The creation - and control - of individual drinking plans is an important prevention of potentially dangerous dehydration conditions for elderly people with a reduced feeling of thirst. The advantage of subcutaneous hydration for mild to moderate desiccosis is above all the low technical and personnel expenditure. This so-called hypodermoclysis can also be carried out easily and effectively at home or in the nursing home. Isotonic solutions such as Ringer's solution, NaCl 0.9% or glucose 5% are suitable for subcutaneous infusion, and the application site is the abdomen, thighs or back. More pronounced volume losses usually require intravenous fluid or electrolyte replacement, which, however, requires medical supervision and is usually carried out as part of inpatient care.

In patients with chronic dehydration and simultaneous malnutrition that cannot be remedied otherwise, the installation of a PEG (percutaneous endoscopic gastrostomy) should also be considered, taking into account the indication, prognosis and the declared will of the patient and his relatives (see Table 2).


1. Pfisterer M., P. Oster, chap. 4.4 Desiccosis in: Hansen… “Medicine of Aging and the Old Man”, Schattauer Verlag….
2. V. Renteln-Kruse, W. (Ed.) "Medicine of Aging and Old People", 2nd edition, Steinkopff Verlag 2009
3. Wedding U., L. Pientka, K. Höffken, B. Strauss (eds.) “Basic knowledge of the medicine of aging and the elderly”, 1st edition, Huber Verlag 2007




Center for acute geriatrics and early rehabilitation
Municipal Clinic Munich GmbH