Assessing adults for dehydration

Assess the hydration status of all adults with gastroenteritis so that appropriate rehydration can be given.

No single clinical feature reliably predicts dehydration in adults. Thorough history and assessment of clinical symptoms and signs are required to assess dehydration in adults; laboratory investigations are used to supplement these if indicated (see Assessing clinical and laboratory features of dehydration in adults). To use percentage weight loss as an indicator of dehydration, an accurate recent premorbid weight must be known.

When determining the severity of dehydration in adults with gastroenteritis, consider the risk factors for dehydration or associated electrolyte abnormalities listed in Risk factors for dehydration or associated electrolyte abnormalities in adults with acute gastroenteritis. Consider the need for closer monitoring or early referral in patients with these risk factors. If the patient is in hospital, consider the need for advice from a senior clinician.

In older patients, traditional symptoms and signs of dehydration may be absent, and presentation may be atypical; symptoms and signs can include increased confusion, functional decline, chest pain and falls. Assessment of dehydration may be further confounded by comorbidities such as heart, liver or kidney failure. Features that may be useful in identifying dehydration in older patients include fatigue, increased urine osmolality, decreased axillary moisture and fluid intakeHooper, 2015.

Table 1. Assessing clinical and laboratory features of dehydration in adults
[NB1]
Clinical and laboratory features	Degree of dehydration [NB2]
Clinical and laboratory features	mild	moderate	severe
level of consciousness	alert	slightly lethargic	altered level of consciousness
patient-reported thirst [NB3]	mild	moderate	intense
oral mucous membranes [NB3] [NB4]	slightly dry	dry	parched, with furrowing of tongue
sternal skin turgor [NB3]	normal	obvious loss of skin turgor	marked loss of skin turgor
eyes	normal	normal	sunken
respiratory rate	normal	normal or +	++
pulse rate [NB3] [NB5] [NB6]	normal	+	++
blood pressure	normal	mild hypotension or postural hypotension	severe hypotension with peripheral vasoconstriction
urine output [NB3]	normal or –	– –	– – – or anuric
plasma urea [NB7]	normal	++	+++
plasma creatinine [NB7] [NB8]	normal	+	+++
urea:creatinine ratio [NB7]	normal or +	+++	+++
plasma osmolality	normal	normal	+++
urinary ketones	+	++	+++
Note: + = slightly increased; ++ = moderately increased; +++ = significantly increased; – = slightly decreased; – – = moderately decreased; – – – = significantly decreased NB1: Evidence for the predictive value of the features listed in this table is limited. No single feature reliably predicts dehydration in adults; a thorough history and assessment of clinical symptoms and signs are required. NB2: When determining the severity of dehydration in adults with gastroenteritis, consider the risk factors for dehydration or associated electrolyte abnormalities listed in Risk factors for dehydration or associated electrolyte abnormalities in adults with acute gastroenteritis. Consider the need for closer monitoring or early referral in patients with these risk factors. NB3: Sign typically unreliable in older patients. NB4: Can be confounded by anticholinergic drugs. NB5: Can be confounded by rate-controlling drugs, pacemakers or conduction abnormalities. NB6: Unreliable in patients taking drugs that lower heart rate (eg beta blockers). NB7: Confounding factors may reduce the validity of this measurement. NB8: Assess relative to baseline.

Figure 1. Risk factors for dehydration or associated electrolyte abnormalities in adults with acute gastroenteritis

The risk of dehydration or associated electrolyte abnormalities may be increased in adults with any of the following factors:

chronic disease (eg diabetes, chronic kidney disease)
kidney transplantation
short bowel syndrome or ileostomy
immunocompromise
pre-existing malnutrition or frailty
where there is concern about adherence to treatment or monitoring for dehydration at home
intractable or bilious vomiting
medications that may cause electrolyte abnormalities (eg diuretics)
advanced age.