Body fluids and electrolytes
Ian Peate, Helen Dutton in Acute Nursing Care, 2014
The extracellular fluid (ECF) consists of fluid outside the cells, decreases with advancing age and is more readily lost from the body than intracellular fluid. This fluid is commonly subdivided into smaller compartments; the intravascular and the interstitial compartments or spaces. The intravascular compartment consists of fluid within the blood vessels (i.e. the plasma volume). The average adult blood volume is approximately 5 – 6 litres, of which about 3 litres is plasma (Edwards 2001, Marieb and Hoehn 2010). The interstitial fluid is water in the ‘gaps’ between the cells and outside the blood vessels and also includes lymph fluid (sometimes called the ‘third space’). Transcellular fluid is contained within specialised cavities of the body, e.g. pleural, synovial, pericardial fluids and digestive secretions which are separated from the interstitial compartment by a layer of epithelium. This fluid is similar to interstitial fluid and is often considered as part of interstitial volume (Edwards 2001). At any given time transcellular fluid is approximately 1 litre (Heitz and Horne 2004). Figure 4.1 shows how the fluids are dis tributed in the body.
Gastrointestinal Tract as a Major Route of Pharmaceutical Administration
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
Body water is distributed primarily into the following major body compartments while the total body water as a percentage of body weight varies from 50% to 70% in women and men, respectively. Extracellular fluid comprises the blood plasma and contains approximately 4.5% of the body weight, while interstitial fluid is ∼16% while lymph ∼1.2%. Interstitial fluid (30%–40%) is the sum of the fluid contents of all cells in the body. Transcellular fluid (∼2.5) includes cerebrospinal, intraocular, peritoneal, pleural, and synovial fluids as well as digestive secretions. Fat is ∼20% (Rang et al., 2016). Within each of the aqueous compartments, substances usually exist both in free solution and in bound form. Substances are transported via the circulatory system partially unbound and partly bound as noted previously. Proteins such as albumin chemically “lock” a substance which renders it pharmacologically inactive while the unbound portion of the substance is considered to be the free fraction and is the pharmacologically active portion of the substance. Plasma protein binding significantly influences both the distribution and the relationship between the pharmacological activity and the substance concentration in the plasma (Waterhouse and Farmery, 2012). As the number of available binding sites approaches saturation at higher substance concentration levels, other substances may be displaced. This displacement activity is a critical function in chemical interactions.
Circulatory controls
Burt B. Hamrell in Cardiovascular Physiology, 2018
If, for instance, fluid intake is reduced, extracellular fluid volume decreases. Blood pressure falls and renal arterial perfusion is reduced. There is then less stretch of the kidney afferent arterioles and the juxtaglomerular cells (Figure 12.4a). Also, there is more sympathetic stimulation of the juxtaglomerular cells due to the response of the neural baroreceptor reflex. Renin release is increased (Figure 12.4b). Angiotensinogen, constantly produced and released into the bloodstream by the liver, is enzymatically cleaved by circulating renin to produce angiotensin I, a mostly inactive precursor of angiotensin II (Figure 12.5). Vascular endothelial cells produce angiotensin converting enzyme (ACE). ACE converts angiotensin I into angiotensin II (Figure 12.5).
Antibiotic exposure at the site of infection: principles and assessment of tissue penetration
Published in Expert Review of Clinical Pharmacology, 2019
Nynke G. L. Jager, Reinier M. van Hest, Jeffrey Lipman, Jason A. Roberts, Menino O. Cotta
Interstitial fluid surrounds the tissue cells and is the main component of extracellular fluid in the human body [7]. Antibiotic concentrations within the interstitial fluid of a tissue can be measured using microdialysis. This technique consists of the insertion of a microdialysis probe into the tissue or organ of interest. The probe is continuously flushed with a tissue-compatible perfusion fluid and has a semipermeable membrane that allows substance uptake by passive diffusion. Since only low-molecular-weight substances are diffusible through the membrane, this technique only allows the sampling of unbound concentrations of small molecules present in the interstitial fluid [33]. The major advantages of microdialysis over tissue biopsies are (i) its capacity for continuous sampling within a time period, such as an antibiotic dosing interval, in the same individual and the same area with minimal tissue perturbation, allowing it to be potentially utilized in almost every human tissue and (ii) in the case of extracellular infections, which account for the majority of bacterial infections, the measurement of antibiotic concentrations at the site of interest.
Non-thermal membrane effects of electromagnetic fields and therapeutic applications in oncology
Published in International Journal of Hyperthermia, 2021
Peter Wust, Ulrike Stein, Pirus Ghadjar
In summary, the membrane stiffness Y of aggressive tumor cells ranges from 200 to 800 Pa, leading to resonant frequencies between 10 Hz and 10 kHz (see above), while normal cells do not resonate or have less resonance in this frequency window. Furthermore, because of the typical microenvironment, tumor cells are isolated and surrounded by extracellular fluid. Such single cells are more susceptible to an incident AM-RF and show the theoretically predicted resonance behavior. In comparison, normal cells are connected to one another in a tissue and show a different—presumably significantly lower resonance behavior—at higher frequencies. The different mechanical properties of tumor cells and tissues can increase the therapeutic ratio of AM-RF if an appropriate modulation frequency spectrum is selected; data suggest that lower frequencies <1 kHz are more effective.
Simulated biological fluids – a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres
Published in Critical Reviews in Toxicology, 2021
Emma Innes, Humphrey H. P. Yiu, Polly McLean, William Brown, Matthew Boyles
A 2017 ISO technical report (TR) for the assessment of nanomaterial biodurability identified a number of standardised test methods using SBFs for sweat, sebum, and digestive fluid replication, however, again no common or recognised methodology for inhalation investigations with SLFs. The TR only goes as far as providing suggested fluid compositions, various examples are provided for lung extracellular fluid, and one for lysosomal fluid (this example is termed, phagolysosomal simulant fluid (PSF) and is discussed later in comparison to other lysosomal simulant fluids). Given the range of fluids used as SLFs in the literature, the aim of this review was to highlight those fluids, or specific fluid constituents, that have been shown to suitably replicate the actual biological environment of the lung, either by composition or the observed effect. This review provides an overview of biofluids that are used in relation to exposure by inhalation through examination of the current peer-reviewed literature. Focus is given to fluids that are used to simulate specific extracellular and intracellular compartments found in the lung, namely lung lining fluid and lysosomal fluid. Both historic and progressive use of these fluids have been appraised and, where possible, certain components that play pivotal roles in dissolution mechanisms have been identified.
Related Knowledge Centers
- Body Fluid
- Body Water
- Cell Biology
- Lymph
- Multicellular Organism
- Circulatory System
- Blood
- Cell
- Fluid Compartments
- Blood Plasma