Dehydration

Dehydration is described as an extreme loss of body water and/or a low intake of water (Lacey et al, 2019). An individual who is experiencing dehydration has a total body water volume that is below their 'euvolaemic state' (normal volume of fluids in the body) (Hooper et al, 2015).

Dehydration causes water to move from intracellular spaces to extracellular spaces, which has an impact on metabolic functions as well as the osmolality of fluids within bodily fluid compartments (Shaw et al, 2021). These issues give rise to the symptoms experienced by people with dehydration and inform the approaches to management.

Dehydration can differ from volume depletion, in that dehydration occurs when the whole body is deficient in water, often accompanied by a rise in blood sodium (hypernatraemia), while volume depletion is a term used to indicate a loss of fluids and salts specifically in extracellular spaces (Marquez et al, 2023).

The signs and symptoms of dehydration will vary according to its severity. Symptoms must be carefully considered, as they may overlap with the signs and symptoms of other conditions. Common symptoms of dehydration include:

• excessive thirst
• dry mucosa and eyes
• postural dizziness and/or hypotension
• fatigue
• confusion
• cramps
• chest and/or abdominal pain
• tachycardia with weak pulse strength on palpation
• tachypnoea
• oliguria or anuria
• reduced central venous pressure
• delayed capillary refill time (>3 seconds) (Shaw et al, 2021; Marquez et al, 2023)

Early signs of dehydration are less severe than later ones and may include headache and excessive thirst, although these early symptoms may not be as perceptible in older people (Picetti et al, 2017).

There are multiple reasons that an individual may become dehydrated, including:

• a history of diarrhoea and/or vomiting
• poor fluid intake (common in older people)
• overuse of diuretics
• excessive fluid loss as a result of sweating (from heat, exercise, sepsis) or severe skin disease
• certain conditions (eg Addison’s disease)
• hyperglycaemic diuresis
• burns (Miller, 2015; Picetti et al, 2017)

There are often multiple pathological causes of dehydration that need to be taken into account when considering the causes and management of dehydration.

A diagnosis of dehydration may be determined by the history of the patient's presentation for medical care as well as clinical signs and symptoms (Armstrong et al, 2016). Some visual clues may reinforce suspected diagnosis before the nurse undertakes any diagnostic testing. These include:

• sunken eyes
• chapped and cracked lips
• rapid breathing

Vital sign monitoring may also indicate dehydration, including:

• low blood pressure and/or postural hypotension
• narrow pulse pressure
• rapid pulse
• rapid breathing
• oliguria or anuria
• delayed capillary refill time (Shimizu et al, 2012; Shaw et al, 2021)

Objective tests for dehydration can include:

• urea and electrolytes (raised urea and sodium)
• raised serum osmolality
• raised urine osmolality – with decreased urine output (Shimizu et al, 2012; Shaw et al, 2021)

Understanding the exact cause of the dehydration may involve undertaking other investigations to identify infective organisms (eg in the urine or faeces) or measuring other potential causes, such as high

Dehydration is usually managed by removing or reversing the cause, where this is possible. This requires a structured and thorough assessment of the patient to create an indication of appropriate treatment. Treatment will also depend on the severity of dehydration, as indicated by the patient's assessment results.

The nurse’s role in managing dehydration includes:

• providing curative or management therapy (eg antibiotics or insulin, if appropriate) under the guidance of a prescriber
• providing supportive therapy (eg fluids and electrolytes) under the guidance of a prescriber
• managing the comfort of the patient (eg providing mouth care)
• monitoring for complications and improvement (eg pulse and respiration rates, blood pressure measurement and temperature)
• keeping an accurate record of hydration (eg maintaining fluid balance and weight charts)
• maintaining the patient’s safety (eg using bedrails and/or direct observation)

General management of dehydration requires several considerations, including:

• Understanding the patient’s

Nursing and Midwifery Council: standards of proficiency for registered nurses

Part 1: Procedures for assessing people’s needs for person-centred care

1. Use evidence-based, best practice approaches to take a history, observe, recognise and accurately assess people of all ages

Part 2: Procedures for the planning, provision and management of person-centred nursing care

5.4 record fluid intake and output and identify, respond to and manage dehydration or fluid retention

5.9 manage fluid and nutritional infusion pumps and devices

Armstrong LE, Kavouras SA, Walsh NP, Roberts WO. Diagnosing dehydration? Blend evidence with clinical observations. Curr Opin Clin Nutr Metab Care. 2016;19(6):434-438. https://doi.org/10.1097/MCO.0000000000000320

Casey JD, Brown RM, Semler MW. Resuscitation fluids. Curr Opin Crit Care. 2018;24(6):512-518. https://doi.org/10.1097/MCC.0000000000000551

Hooper L, Abdelhamid A, Attreed NJ et al. Clinical symptoms, signs and tests for identification of impending and current water‐loss dehydration in older people. Cochrane Database Syst Rev. 2015; 4:CD009647. https://doi.org/10.1002/14651858.CD009647.pub2

Lacey J, Corbett J, Forni L et al. A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications. Annals of Medicine. 2019;51(3-4), 232-251. https://doi.org/10.1080/07853890.2019.1628352

Mahon A, Jenkins K, Burnapp L. Oxford Handbook of Renal Nursing.  Oxford: Oxford University Press; 2013

Marquez A, Haque SK, Batlle D. Best practice: volume depletion in adults. 2023. https://bestpractice.bmj.com/topics/en-gb/937 (accessed 26 October 2023)

Miller HJ. Dehydration in the Older Adult. J Gerontol Nurs. 2015;41(9):8-13. https://doi.org/10.3928/00989134-20150814-02

National Institute for Health and Care Excellence (NICE). Intravenous fluid therapy in adults in hospital. 2017.