Special Consideration of Drug Disposition
Gary M. Matoren in The Clinical Research Process in the Pharmaceutical Industry, 2020
In the very young human (less than 4 months old), body water is 70% of the body weight, whereas it ranges from 42 to 53% in adult females and from 54 to 58% in adult males. Therefore, in a newborn infant, the higher level of water content will increase the AVD and this, in turn, will result in decreased blood concentration of drug. In such infants, renal blood flow–as related to the total body water content–is also less than that of adults. These factors combine to reduce the glomerular filtration process and, in so doing, slow any renal clearance of drugs whose primary route of elimination is through the kidney. Insulin clearance in the newborn takes about three times longer than it does in the adult. Lastly, the drug-metabolizing enzyme systems do not fully develop until the infant is several months of age. The oxidative pathways and the conjugative mechanisms are particularly affected. Any multiple-dosing regimen involving the newborn should consider the possibility that accumulation of drug can occur and hence wider spacing of doses than is used with adults may be advisable. Since biotransformation may be occurring only slowly and elimination of the drug is not as rapid, it is likely that no loss of therapeutic effectiveness will be seen.
Hydrometry, Hydration Status, and Performance
Henry C. Lukaski in Body Composition, 2017
Except in the very obese, water is the single largest component of the body, representing about 50%–70% of total body mass, and is present in variable amounts in all cells, tissues, and organs (Bender and Bender 1997). The total body water (TBW) content can be expressed in absolute terms (as a volume in mL or a mass in kg), or as a proportion of total body mass (TBW/body mass × 100%). Depending on how it is expressed, the body water content may change when TBW or body mass changes. Body water content is determined by the balance between the rates at which water is added to the body and the rate of water losses. It is tightly regulated to maintain a rather constant volume of water in the body and a constant tissue osmolality. Both the quantity of water in the body and hydration status are important in many different contexts, but unfortunately the two are often confused. The body’s water content is quantified as a volume or mass of water, whereas hydration status takes account of tissue osmolality as well as water content. Body water content, and its measurement, is important for several reasons. As the fractional water content of tissues is relatively constant and the water content of lean tissue is much higher than that of adipose tissue, measurement of body water content can be used to estimate lean tissue mass and therefore body fat content. Body water content and hydration status affect all physiological functions, and if disturbances are sufficiently severe, both physical and cognitive functions are impaired. In extreme situations, death may result from both insufficient and excessive intake of water.
Nutrition in Lifestyle Medicine
James M. Rippe in Manual of Lifestyle Medicine, 2021
While discussion on nutrition simply focus on solid foods, it is important to also include hydration. Water is essential for life, and the body water content is normally tightly regulated, thus remaining relatively constant throughout the day. Water losses of less than 2% of total body water can result in significant declines in both mental and physical performance. Water losses are increased as ambient temperature rises as well as humidity and also by increased levels of physical activity. A variety of foods and beverages normally contribute to the total body water intake. Thus, when individuals are engaged in weight loss strategies, it is important that they consume extra water to make up for the water that they are no longer taking by decreasing the amount of solid foods in their diet.
Relationship between locomotive syndrome and body composition among community-dwelling middle-age and elderly individuals in Japan: The Yakumo study
Published in Modern Rheumatology, 2019
Satoshi Tanaka, Kei Ando, Kazuyoshi Kobayashi, Tetsuro Hida, Taisuke Seki, Koji Suzuki, Kenyu Ito, Mikito Tsushima, Masayoshi Morozumi, Masaaki Machino, Kyotaro Ota, Naoki Ishiguro, Yukiharu Hasegawa, Shiro Imagama
The Inbody 770 BIA unit (Inbody Co., Ltd, Seoul, Korea) was used, which differentiates tissues (such as fat, muscle and bone) based on their electrical impedance [15]. Individuals grasped the handles of the analyzer, in which electrodes are embedded, and stood on the platform, with the sole of the feet in contact with electrodes (two electrodes for each foot and hand). The following variables were calculated for analysis: body mass index (BMI); percent body fat (PBF); proportion of protein and minerals; body fat mass (BFM); soft lean mass (SLM); fat-free mass (FFM); skeletal muscle mass (SMM); total body water volume (TBW); intracellular water volume (ICW); extracellular water volume (ECW); and the extracellular water/total body water (ECW/TBW) ratio, which was used as an indicator of the balance of water within the body water. In this study, each individual performed BIA measurements on an empty stomach so as not to be affected by diet.
Kidney physiology and pathophysiology during heat stress and the modification by exercise, dehydration, heat acclimation and aging
Published in Temperature, 2021
Christopher L. Chapman, Blair D. Johnson, Mark D. Parker, David Hostler, Riana R. Pryor, Zachary Schlader
In humans, water accounts for ~73% of fat free body mass [85]. Under normal conditions, elimination of water from the body is primarily routed through the kidneys with a lesser amount of water loss occurring through sweat loss, evaporation from the skin, respiration, and the gastrointestinal tract (e.g., in feces). The kidneys have a direct role in maintaining euhydration, which is defined as a state of optimal body water content [86]. This is highlighted by the fact that euhydration is maintained with total water intakes ranging from 1.3 to 7.9 L/24 h to maintain plasma osmolality within a normal range (285-295 mOsm/kg) among individuals, in varying environments and circumstances [87]. The process of losing body water is termed dehydration, whereas the state of deficient body water caused by acute or chronic dehydration is known as hypohydration [86].
A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications
Published in Annals of Medicine, 2019
Jonathan Lacey, Jo Corbett, Lui Forni, Lee Hooper, Fintan Hughes, Gary Minto, Charlotte Moss, Susanna Price, Greg Whyte, Tom Woodcock, Michael Mythen, Hugh Montgomery
“Dehydration” is a term which, in clinical use, refers to a deficiency in total body water. Whilst no standard means of defining its presence or severity exists (see below), it appears to be both prevalent and costly within the healthcare setting. In 2015, 37% of patients aged over 65 years old admitted to a large UK hospital were dehydrated [1]. Of 370,758 patients in the 2004 US National Hospital Discharge Survey, there were 518,000 hospitalizations primarily due to dehydration, incurring healthcare costs in excess of 5 billion dollars [2]. The problem is not restricted to hospitalized patients, a recent UK study found one in every five older people living in long-term care to be dehydrated (serum osmolality >300 mOsm/kg) and half to be either dehydrated or at risk of becoming so (≥295–300 mOsm/kg) [3]. Furthermore, it has been repeatedly shown that dehydration is associated with increased mortality and morbidity [3–8].
Related Knowledge Centers
- Body Composition
- Body Fluid
- Extracellular Fluid
- Physiology
- Homeostasis
- Blood Plasma
- Compartment
- Body
- Fluid Balance
- Fluid Compartments