Urinary and hematologic indexes of hypohydration

Abstract

As part of a large-scale field feeding system test we were able to collect and study hundreds of aliquots of overnight urine samples obtained immediately prior to a fasting blood sample on days 1, 20, and 44 of the field test. The large number of experimental samples (greater than 650) and concomitant collection of blood and urine aliquots along with data on body weights gave us the opportunity to assess and quantitate the sensitivity of commonly used criteria of hypohydration. Urine aliquots for all test days were initially categorized by specific gravity (SG) greater than or equal to 1.03 (n = 124) or less than 1.03 (n = 540). Creatinine levels were elevated (P less than 0.001) in the concentrated urine samples, but a decreased trend in sodium-to-potassium ratios in these samples failed to achieve statistical significance (P greater than 0.05). However, when individuals with high SG urine were subclassified by a criterion of weight loss greater than 3% from original body weight, then creatinine concentrations were elevated (P = 0.05), whereas sodium-to-potassium ratios were decreased (P = 0.05) when subjects also with high SG but weight loss less than 3% were compared. Because of the moderate altitude (2,000 m) of the field site and the time of sojourn (44 days), there occurred a slight, but significant (P less than 0.001), erythropoietic response. Hematocrit and serum osmolality were not significantly different when examined by the criteria of high or low SG urine and weight loss greater than or less than 3% original body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Validity and Reliability of Clinical Signs in the Diagnosis of Dehydration in Children

“…Our results suggest that diminished urination actually occurs early in the process of dehydration, which is in agreement with studies in adult volunteers. 19 Although a high specificity is desirable in a population with a low prevalence of disease, the sensitivity of each of the individual signs was unacceptably low to recommend any one finding as diagnostic of dehydration. One way to boost sensitivity while maintaining a reasonable specificity is to use a parallel testing strategy-in this context, the use of several clinical criteria rather than one.…”

A Galvanic Coupling Method for Assessing Hydration Rates

“…The osmolality of blood increases with dehydration and decreases with increasing hydration. A problem with this method, however, is that it does not track body fluid changes quickly when fluid loss is below 3% of body mass [11,21]. This implies that, for a 70 kg adult, plasma osmolality could only detect changes in body fluid level until the water loss causes up to 2.1 kg decrease in body weight.…”

“…This system requires in vivo access and testing of the blood and is regarded as a later indicator of dehydration rather than a warning system that informs a quick preventative measure [10]. Physical signs such as urine color observation, urine specific gravity test, and body weight changes are some examples of non-intrusive methods for assessing human body hydration [11]. This method gives oversimplified results and poorly sensitive to changes in dehydration [12].…”

A Review on Opportunities To Assess Hydration in Wireless Body Area Networks

“…The volume and concentration fluctuate with daily activities and do not respond quickly to loss of body fluid after exercise or other daily activities. An investigation by Francesconi et al [34] showed that participants who lost up to 3% of body mass through sweating did not show any difference in haematocrit or serum osmolality immediately after. Armstrong et al [22] and Sherrif [14] suggested that the volume of blood plasma does not necessarily change until a certain amount of water had been lost in order to maintain cardiovascular stability.…”