Various signs, including postural vital signs, capillary refill time, skin turgor and moistness of the axillae, tongue and mucous membranes, may be used in the assessment of patients with suspected hypovolemia. McGee and colleagues conducted a literature review to identify which, if any, signs and symptoms were reliable in the clinical evaluation of volume depletion and dehydration.
A MEDLINE search was used to retrieve articles on the bedside diagnosis of hypovolemia. Some studies were of patients with known amounts of blood loss, while others were of patients who presented to emergency departments and were suspected of having hypovolemia as a result of symptoms such as vomiting, diarrhea and decreased oral intake.
As far as the reliability of postural vital signs in the diagnosis of hypovolemia is concerned, a review of 25 studies of postural vital signs in more than 3,500 normovolemic persons revealed that a postural pulse increase of 30 per minute or more (the common threshold used in clinical studies) had a specificity of 96 percent. In normovolemic adults, a postural pulse increment of more than 30 beats per minute affects only about 2 to 4 percent of persons. Studies suggest that postural hypotension occurs in up to 10 percent of normovolemic adults younger than 65 years and in 11 to 30 percent of adults older than 65 years. The authors found that the most helpful physical findings in the evaluation of patients with suspected blood loss were severe postural dizziness (preventing measurement of vital signs with the patient upright) and a postural pulse increase of 30 beats per minute or more. Mild postural dizziness had no value in the diagnosis of hypovolemia.
Normal capillary refill time ranges from two seconds in children and adult men to three seconds in adult women and four seconds in the elderly. One study revealed that a prolonged refill time does not accurately predict 450 mL of blood loss. This sign was found to have a 6 percent sensitivity and a 93 percent specificity.
While the literature indicates that the finding of a dry axilla increases the probability of hypovolemia, studies suggest that this is an insensitive physical sign, with only a 50 percent sensitivity. Signs that point away from hypovolemia are moist mucous membranes, lack of sunken eyes and lack of furrows on the tongue.
The authors conclude that a large increase (more than 30 beats per minute) in the postural pulse or severe postural dizziness (precluding upright vital signs) is required to diagnose hypovolemia related to blood loss, although these findings are often absent in the setting of moderate blood loss. The literature review indicated that few findings have proven reliability in the diagnosis of hypovolemia related to diarrhea, vomiting and decreased oral intake. Decreased capillary refill time and poor skin turgor have been shown not to be of diagnostic value. Thus, the authors state that physicians should not hesitate to order serum electrolyte, blood urea nitrogen and creatinine determinations if hypovolemia is suspected.