Dehydration (cont.)

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How is dehydration diagnosed?

Dehydration is often a clinical diagnosis. Aside from diagnosing the reason for dehydration, the health care professional's examination of the patient will assess the level of dehydration. Initial evaluations may include:

  • Mental status tests to evaluate whether the patient is awake, alert, and oriented. Infants and children may appear listless and have whiny cries and decreased muscle tone.
  • Vital signs may include postural readings (blood pressure and pulse rate are taken lying down and standing). With dehydration, the pulse rate may increase and the blood pressure may drop because the blood is depleted of fluid. People taking beta blocker medications for high blood pressure, heart disease, or other indications, occasionally lose the ability to increase their heart rate as a compensation mechanism since these medications block the adrenaline receptors in the body.
  • Temperature may be measured to assess fever. While it is common to measure temperature in the ear (tympanic) or by mouth (orally), a rectal thermometer may be used to assess core body temperature if the patient appears warm, but no fever is noted tympanically or orally.
  • Skin may be checked to see if sweat is present and to assess the degree of elasticity (turgor). As dehydration progresses, the skin loses its water content and becomes less elastic. The amount of sweat is often felt in the armpit or groin, two areas that tend to have moisture normally.
  • The mouth can become dry and the health care professional may look at or feel the tongue to see how wet it is.
  • Infants may have additional evaluations performed, including checking for a soft spot on the skull (sunken fontanelle), and assessing the suck mechanism, loss of sweat in the armpits and groin, and muscle tone. All are signs of potential significant dehydration.
  • Pediatric patients are often weighed during routine child visits, thus a body weight measurement may be helpful in assessing how much water has been lost with the acute illness. This is very rough estimate because all scales are not the same, and for infants and children, it is important to know what clothing they were wearing when the original weight was taken.

Laboratory testing

The purpose of blood tests is to assess potential electrolyte abnormalities (including sodium, potassium, chloride, and carbon dioxide levels) associated with the dehydration. Other tests may or may not be ordered depending upon the underlying cause of dehydration, the severity of illness, and the health care professional's assessment of their needs and resources available.

Other blood tests may be helpful in determining the level of dehydration. Hemoglobin and red blood cell counts may be elevated because the blood is more concentrated with water loss from the intravascular space.

Kidney function tests including BUN and creatinine may be elevated, and this is one way of measuring the severity of dehydration.

Urinalysis may be ordered to determine urine concentration, the more concentrated the urine, the more dehydrated the patient.

Medically Reviewed by a Doctor on 5/21/2013

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