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Recognising and preventing dehydration among patients


This article discusses how to recognise signs of dehydration and ensure patients receive adequate oral hydration. More information is available as a learning resource in our learning unit on dehydration

Citation: Cambell N (2014) Recognising and preventing dehydration among patients. Nursing Times; 110: 46, 20-21. 

Author: Naomi Campbell is hydration lead nurse, Peninsula Community Health, Cornwall.


Water is our primary and most important nutrient. It makes up approximately two-thirds of our body. We need to maintain a healthy level of body water content by regularly drinking enough to replace the natural water loss filtered by the kidneys, in the form of essential healthy urine production to remove waste products. Insufficient water leads to dehydration, which is the underlying cause of many common conditions including: constipation; falls; urinary tract infections; pressure ulcers; malnutrition; incontinence; and confusion. Dehydration can also lead to life-threatening conditions, such as acute kidney injury, cardiac disease and venous thromboembolism.

Understanding thirst

The sensation of thirst is the body’s way of prompting us to drink to replace fluid loss to maintain adequate hydration levels. This “thirst response” is a complex negative hormonal feedback system controlled by osmoreceptors in the brain that monitor sodium levels, along with baroreceptors in the great blood vessels that detect changes in blood volume and pressure.

When the body loses more water than it consumes, the sensation of thirst is triggered and an antidiuretic hormone is released instructing the kidneys to reduce urine output. When hydration is restored, sensation of thirst disappears and the kidneys are instructed to release more water (Begum and Johnson, 2010).

The natural ageing process reduces the effectiveness of the “thirst response”. This explains why older people often do not feel thirsty, sometimes forgetting to have a routine drink, those with dementia being particularly vulnerable. Therefore anyone over 65 years should be considered at increased risk of dehydration (Mentes, 2013).

On average, healthy kidneys produce 1,500ml of urine a day to remove waste products, so adults are recommended to drink at least this amount in the form of pure water or hot and cold drinks (British Dietetic Association, 2012).

However, many people may need to drink as much as 2.5-3L, depending on the environmental temperature, level of exertion, sweating, body size or other types of fluid loss from wounds, drains, stomas, diarrhoea and vomiting, or blood loss. In more specific terms, water intake is sometimes calculated in relation to body weight, at 30-35ml/kg; this same calculation is used to reflect a healthy hourly urine output.

There is evidence that some people can remain adequately hydrated on less than 1,500ml, but this is dependent on a good food intake and a sedentary lifestyle (Lecko and Best, 2013; Begum and Johnson, 2010).

Detecting dehydration

Early signs of dehydration include:

  • Thirst sensation;
  • Dry mouth;
  • Headaches;
  • Reduced concentration;
  • Darker, more concentrated urine.

If fluid intake is not increased the symptoms will worsen and moderate dehydration will develop.

Signs of moderate dehydration

  • Reduced urine output, increasingly darker colour and stronger odour (Mentes, 2006);
  • Increasingly dry mouth, cracked lips;
  • Dry eyes due to reduction in tears;
  • Lethargy and increased sleepiness;
  • Mild or increased confusion;
  • Irritability and agitation;
  • Worsening constipation;
  • Dizziness due to postural hypotension (drop of systolic BP by 20mmHg), often resulting in falls;
  • Sunken eyes;
  • Unexpected reduction in wound exudate;
  • Reduced skin elasticity/turgor.

If not recognised and corrected through increased oral fluid intake, the circulating volume will become so low that the patient will eventually develop hypovolaemic shock caused by acute dehydration.

Signs of acute dehydration

  • Low systolic blood pressure (100mmHg or less);
  • Rapid, thready pulse;
  • Increased respiration rate;
  • Cold extremities;
  • Reduced capillary refill time due to peripheral shut down;
  • Hyper or hypo delirium (agitation and severe confusion or conversely increased sleepiness and reduced responsiveness);
  • Reduced conscious level;
  • Greatly reduced urine output (oliguria).

Acute dehydration is a medical emergency requiring intravenous fluid replacement and close monitoring of blood chemistry. It greatly increases the risk of acute kidney injury (AKI) due to inadequate perfusion of the kidney cells or drug toxicity, resulting in irreversible harm or mortality (National Institute for Health and Care Excellence, 2013; Lecko and Best, 2013). Incidence of AKI due to preventable dehydration is increasing in hospitals and the community (National Confidential Enquiry into Patient Outcome and Death, 2009):

  • Approximately 20% of acute admissions to hospital are associated with AKI, highlighting that the majority of cases begin in the community;
  • AKI can also develop in hospital and is increasingly found across general medical and surgical wards;
  • AKI accounts for 100,000 deaths in secondary care - it is believed that one-third of these could be avoided with better prevention, detection and management (NCEPOD, 2009).

NICE (2013) has highlighted that reliance on a carer for access to oral fluids is a key risk factor for AKI. This emphasises the importance of assessing:

  • Patients’ ability to hold and lift a cup safely to their mouth;
  • The level of encouragement and prompting needed to drink.

It also highlights the need for adequate staffing levels to ensure all patients receive adequate support to drink in order to reduce avoidable harm caused by lack of essential nursing hydration care.

Preventing dehydration

Nurses should be familiar with the recommendations outlined in the Francis report (2013), which highlights the need for proper records to be kept of the food and drink supplied and consumed by older patients. A fluid balance chart should be started for all patients who are acutely unwell or considered at risk of dehydration.

Accurate documentation of oral intake and urine output provides essential evidence to support appropriate interventions and further review by the multidisciplinary team. Nurses must decide how best to monitor urine output for patients who are not catheterised, supported by clear guidelines and protocols to reflect clinical needs.

Early Warning Scores (EWS) should always include review of urine output, as well as highlighting changes to vital signs; this will better support nursing and clinical staff to exclude or identify dehydration as the underlying cause. Nurses should lead by example, taking every reasonable opportunity to encourage hydration and acknowledging and valuing best practice within their team. The following measures ensure optimal fluid intake and management:

  • Include in every staff handover a review of patients’ hydration status and the level of support needed to eat and drink;
  • Ensure patients’ preferred choice of drinks and food are available at all times, and offer appropriate assistance and encouragement, drinking equipment and social interactions;
  • Offer timely continence support;
  • Raise awareness among the care team, patients and their families about the importance of hydration, providing enhanced education.

Nurses must ensure all staff, including healthcare assistants and cleaners responsible for clearing dirty cups or unfinished drinks, are made aware of the importance of accurate documentation and provide them with information about the volume of all drinks containers.

Boost your CPD and work towards your next revalidation with our learning unit on dehydration

Nursing Times subscribers have free access to a range of learning units, including one on Preventing Dehydration. This unit explains the biological functions of water and its importance to health. It covers the different causes of dehydration and the physical and emotional harm dehydration can cause.

Once you have been through the learning unit, you will be able to:

  • Explain the biological function of water and its importance to health
  • Describe different causes of dehydration
  • Describe the physical and emotional harm caused by dehydration
  • List the signs and symptoms that inform a diagnosis of dehydration
  • Identify those persons at risk of developing dehydration
  • Describe strategies to prevent dehydration

Readers' comments (6)

  • All education is valuable and it is good to see that Nursing Times is addressing this issue.

    But what on earth are nurses being taught in their training? You can't get much more basic than this! How on earth can it be that a nurse can get out into the real world without being aware of the need for adequate hydration and how to prevent dehydration?

    At the risk of sounding like a dinosaur, this kind of thing was something we learnt about right from the start. If people are brought into hospital suffering from dehydration, that is one thing; for them to develop it whilst on a ward is quite another. Perhaps we can accept that on a busy ward, the early signs can me missed - no excuse, but let's be realistic - but surely it would be better if proper hydration were included in the care plan right from the start? Whether (it is perceived as) needed or not?

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  • if guests visit your house don't you ensure their comfort and see to it they have enough refreshments - all basic civility and common sense.

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  • Many elderly people arrive in A&E departments suffering moderate/severe dehydration which has developed in the community.

    Evidence of AKI is easily demonstrated in many of these old folk and rectifying their dehydrated is no easy task.

    It must also be remembered that "dehydration" can affect babies and young children !

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  • If this article was posted to educate registered Nurses, then I am frightened.
    I remember being taught this on my first day of clinical practice. It has been applied and expanded upon since.
    Is the Nursing Times trying to infer that many qualified Nurses cannot recognise dehydration? At least it confirms NT's opinion of Registered Nurses.

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  • As an experienced nurse I agree.

    However, as the daughter of someone with severe dementia who until recently lived alone in her own home, you can't physically force someone who does not actually feel thirsty to take a drink................she would see that as bullying.

    In her care home they encourage and continually remind her to drink but if she leaves it it's still her decision......

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