The phenomenon of involuntary dehydration, the delay in full restoration of a body water deficit by drinking, has been described extensively but relatively little is known about its physiological mechanism. It occurs primarily in humans when they are exposed to various stresses including exercise, environmental heat and cold, altitude, water immersion, dehydration, and perhaps microgravity, singly and in [...]
Levels of thirst and ad libitum drinking decrease with advancing age, making older people vulnerable to dehydration. This study investigated age-related changes in brain responses to thirst and drinking in healthy men. Thirst was induced with hypertonic infusions (3.1 ml/kg 0.51M NaCl) in young (Y) and older (O) subjects. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET). Thirst activations were identified by correlating rCBF with thirst ratings. Average rCBF was measured from regions [...]
To determine if athletes' muscle mass affects the usefulness of urine specific gravity (U(sg)) as a hydration index. Nine rugby players and nine endurance runners differing in the amount of muscle mass (42 +/- 6 vs. 32 +/- 3 kg, respectively; P = 0.0002) were recruited. At waking during six consecutive days, urine was collected [...]
Water is considered an essential nutrient because the body cannot produce enough water itself, by metabolism of food, to fulfil its need. When the quantity or quality of water is inadequate, health problems result, most notably dehydration and diarrhoea. As a result of contaminated water and poor hygiene, related infections are still a serious problem. Indeed, in theSouth African setting water availability and sanitation are critical issues because [...]
It is well known that fluid and electrolyte balance are critical to optimal exercise performance and, moreover, health maintenance. Most research conducted on extreme sporting endeavour (>3 hours) is based on case studies and studies involving small numbers of individuals. Ultra-endurance sportsmen and women typically do not meet their fluid needs during exercise. However, successful [...]
A complete urinalysis includes physical, chemical, and microscopic examinations. Midstream clean collection is acceptable in most situations, but the specimen should be examined within two hours of collection. Cloudy urine often is a result of precipitated phosphate crystals in alkaline urine, but pyuria also can be the cause. A strong odor may be the result [...]
In order to test the hypothesis that urine colour can be used as an index of hydration in critically ill patients, we selected 40 intensive care and high-dependency patients and correlated urine colour (scored on an eight-point scale) with various indices of hydration: urine:plasma sodium, osmolality and urea ratios, urine output and central venous pressure. In addition, we compared the colour-chart score with scores made by intensive care nurses (without the benefit of a colour chart) in [...]
These experiments examined relationships between initial osmolality and carbohydrate (CHO) composition of an infused solution and osmolality and water and CHO absorption in a test segment. A triple-lumen tube with a 10-cm mixing segment and a 40-cm test segment was passed into the duodenojejunum. The infusion port was approximately 10 cm beyond the pyloric sphincter. [...]
PURPOSE: This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat. METHODS: Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a [...]
Dehydration is the most common fluid and electrolyte problem among the elderly. The usual causes of water loss are frequently absent in dehydrated elderly patients. Age-related changes in total body water, thirst perception, renal concentrating ability, and vasopressin effectiveness probably predispose to dehydration. Dehydration related to infection, high-protein tube feedings, cerebral vascular accidents, and medication-related hypodypsia are particularly relevant for elderlypatients. Appropriate treatment [...]