As the elderly are at greater risk of dehydration than younger and healthier people, it is essential that carers know how to identify, prevent and treat it.
It is well-known that Australia is an ageing nation, and that this poses a significant health cost and burden on our society. In 2010, there were more than 160,000 Australians in residential aged care facilities and in 2008-09, about 60 per cent of patients who visited a GP were over 45, compared to less than 50 per cent 10 years earlier.
In light of this ageing population, it is essential that all healthcare providers ensure that treatment measures are targeted and adapted to meet the physiological changes that occur with ageing.
Of late, there has been some public concern about the quality of care in aged care facilities. Evidence has shown that two key indicators of inadequate care in the elderly population need to be watched out for: poor nutrition and inadequate hydration.
In regard to the latter, in July 2012 Professor Michael Woodward, medical director of Aged and Residential Care Services at the Heidelberg Repatriation Hospital, Victoria, published Guidelines to effective hydration in aged care facilities as a practical tool for aged care facility staff, so they can better manage the prevention and treatment of dehydration. This article explores the key concepts of these guidelines, and details ways to integrate simple measures to control dehydration in aged care.
How does dehydration occur?
Dehydration occurs when fluid and electrolyte loss (through vomiting, diarrhoea, sweat and urine) exceeds fluid intake over a period of time. This can be caused by a variety of factors, but is generally due to increased fluid loss (through diarrhoea, vomiting or excessive sweating), decreased fluid intake (when there is poor oral intake due to illness, for example) or a combination of both.
The balance of water and electrolytes in the body at any one time is determined by two regulatory mechanisms: thirst and antidiuretic hormone (ADH or vasopressin). Thirst is an awareness of the desire for fluid and generally controls fluid intake. Thirst is stimulated by cellular dehydration and a decrease in blood volume. Fluid deficiency sends signals to the hypothalamus which triggers the sensation of thirst. Thirst is conversely suppressed when the body has excess water. ADH is regulated by the kidneys and stored in the pituitary gland. If body water is low, the pituitary secretes ADH into the bloodstream, which stimulates the kidneys to conserve water.
Older people have a reduced thirst response and a diminished hormonal response to dehydration (i.e. reduced secretion of ADH). This can be a more pronounced problem for patients with Alzheimer’s disease, which is a common phenomenon in aged care. The elderly are also at increased risk of dehydration due to changes in kidney function and they may also be less able to obtain water due to physical immobility or medical conditions related to cognitive decline. Table one outlines a variety of risk factors for dehydration that can be evident in the elderly. All aged care facility staff should be aware of and attentive to these symptoms, in an attempt to prevent dehydration.
What are the signs and symptoms of dehydration?
There are a variety of signs and symptoms of dehydration, such as dry mucous membranes, dizziness, headache, reduced skin turgor and fatigue. Four specific and clinically significant signs of dehydration in an elderly person have been identified; they include abnormal sub-clavicular and thigh skin turgor, dry oral mucosa and recent changes in consciousness. Notably, axillary sweating has also been shown to be a reliable indicator of dehydration. Aged care staff could test for dehydration by placing some tissue or blotting paper in the axilla for a few minutes; if it is not moistened by sweat, then dehydration is most probably present.
So, what is normal fluid intake for elderly people?
The simple hypothesis is that fluid intake should replace fluid loss. In elderly patients, the recommended minimum amount of fluid is 1500 to 2000 millilitres a day, the equivalent of six to eight 250 ml cups. However, fluid requirements are largely based on weight so, ideally, they should be calculated as follows:
- 100 ml fluid per kg body weight for first 10 kg
- 50 ml fluid per kg body weight for next 10 kg
- 15 ml fluid per kg body weight for each kg after 20 kg
Are there any diagnostic tests for dehydration?
There are various diagnostic tests for dehydration. Serum osmolality is the most accurate – a value above 295 mOsmol usually indicates reduced body water (the reference range for an adult is 280 to 300 mOsmol). The blood urea/creatinine ratio is usually less than 1:10 when dehydration is present and elevated serum sodium (above 145 mmol/L) can indicate hypernatremia, hence dehydration.
What are some strategies to maintain or increase fluid intake for elderly patients?
It is very important that staff at aged care facilities are educated about the importance of hydration and the need to monitor residents’ fluid intake regularly. On a daily basis, staff should be on the lookout for situations where the patient may be at risk of dehydration (such as in cases of gastroenteritis, febrile illness and in those who have swallowing difficulties). Additionally, staff should be well aware of the signs of dehydration, taking particular note of the more useful clinical signs (such as reduced axillary sweating and darker urine than normal).
Studies have been conducted to assess the value of certain strategies in reducing the risk of dehydration. These include the use of a hydration chart, using volunteers to provide a happy hour of fluids and reminding residents to drink.
Fluid intake can be encouraged in the elderly in the following ways.
- Staff can explain the importance of regular fluid consumption.
- Patients can be encouraged to consume a full glass of water or an oral rehydration solution such as Hydralyte (100 to 200 ml) each time they take a dose of medicine.
- Patients can be served wet foods such as jelly and custard as these add to total daily fluid intake.
Oral rehydration solutions – why are they more effective at preventing and treating dehydration?
Because dehydration is caused by a loss of fluid and electrolytes, it is essential that both are replaced to prevent and treat dehydration. Oral rehydration solutions are an effective way to treat mild to moderate dehydration. They contain a set amount of sodium, glucose, potassium, chloride and citrate, as set out by World Health Organisation criteria. The most important features of an oral rehydration solution are:
- They contain the correct balance of sodium and glucose which leads to activation of the sodium-glucose co-transporter in the intestinal lumen – this allows for rapid absorption.
- The solution is hypotonic – this allows for rapid water influx into cells to achieve hydration.
It is important to note that water alone or sugary drinks do not contain the correct balance of sodium and glucose to allow for rapid hydration.
Sarah Curulli is the clinical education pharmacist at the Hydration Pharmaceuticals Trust.Do you have an idea for a story?
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