Atomic EnergyĬommission, and their subjects were "volunteers" from the San Quentin state prison. Hilariously, when Prentice et al (1952) were researching the use of this dangerous radioactive isotope on human subjects, their work was sponsored by the Life Insurance Medical Research Fund and the U. Total body water measurement with radiolabelled tritium Most commonly used markers fail at least one of these ideal requirements, but this has not stopped anybody. Not prone to changing the distribution of fluid between compartments.Uniformly distributed in that compartment.Confined to the compartment of interest.That sounds easy in principle, but in reality it relies on the good behaviour of the marker substance, which would have to be: The key is to pick a marker substance that is distributed into the compartment of interest, administer a known amount of it, and then measure its volume of distribution. The broad term to describe most of the techniques used for the measurement of body fluid compartments would be "indicator dilution technique". The principle of measuring a fluid compartment There are few peer-reviewed articles to cover this material broadly as an overview all you end up finding are very specialised and specific articles describing an individual technique. Non-peer reviewed resources which must be mentioned include, and by extension the Kerry Brandis Anaesthetic Viva book (everyone should have one). Plasma volume: albumin tagged with Evans Blue, provided you adjust for a constant slow leak of albumin into the interstitial spaceĪs always with these fundamental concepts in physiology, the only place you ever find detailed explanations are the chapters of textbooks, and they don't always feel the need to expand on anything with detailed references.Extracellular fluid: bromine-82 or mannitol however 82Br also distributes into cells, and mannitol increases the extracellular fluid volume.Total body water: radioactive tritium or deuterium, which distributes into total body water.Several indicators for measuring body fluid compartments are noted in popular textbooks:.An ideal indicator is safe, not metabolized or rapidly excreted, confined to the compartment of interest and not prone to changing the distribution of fluid between compartments.Volume of the compartment = (dose of marker) / (concentration of marker)
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