Body Fluid Distribution and Composition (Lecture Notes) - King Salman University

Field of medicine Medicine Program Lecture : (body fluid distribution and ionic composition) Dr : (Dr. Mohamed Talal ) Date : 4 / 10 /2022 oduction ( Patient suffering from Renal Failure = no urine 1 2...

Field of medicine Medicine Program Lecture : (body fluid distribution and ionic composition) Dr : (Dr. Mohamed Talal ) Date : 4 / 10 /2022 oduction ( Patient suffering from Renal Failure = no urine 1 2 3 Normal weight 4 43,5 kg Total body water Accounts for 50 – 70 % of body weight. Example: A 70 kg man, calculate his body weight (= 42 liters). Correlates inversely with body fat. Because females have a higher percentage of fat than males, they tend to have less body water  Body fluid compartments: Intracellular fluid (fluid inside the cells) = 2/3 (40 %) Extracellular fluid (fluid outside the cells) = 1/3 (20 %) Plasma (fluid circulating in the blood position of extracellular and intracellular fl Substance Extracellular Intracellular ( mEq/L ) fluid fluid Na+ 140 14 K+ 4 120 Cl- 105 10 HCO3 - 24 10 Intracellular fluid: Major K+ cations Major Proteins and organic phosphate anions Extracellular fluid Major Na+ cations Major Cl- and HCO3 - anions easuring volumes of body fluid compartmen By dilution method Equations easuring volumes of body fluid compartmen Steps Identification of an appropriate marker substance. Markers for total D2O  Distrusted wherever water is body water found Markers for ECF Mannitol  Large molecular weight volume  Can not cross cell membranes Markers for plasma Radioactive  Too large volume albumin  cannot cross capillary walls ICF and interstitial fluid are determined indirectly easuring volumes of body fluid compartmen Clinical case A man is participating in a research study for which it is necessary to know the volumes of his body fluid compartments. To measure these volumes, the man is injected with 100 mCi of D2O and 500 mg mannitol. During a 2-hour equilibrium period, he excretes 10 % of the D2O and 10% of the mannitol in his urine. following equilibration, the concentration of D2O in plasma is 2.13 mCi/ L and the concentration of mannitol is 32 mg/L. what are his total body water, his ECF volume, and his ICF volume. easuring volumes of body fluid compartmen Clinical case ( the answer ) Measuring the total body water : = 42,2 L easuring volumes of body fluid compartmen Clinical case ( the answer ) Measuring the extracellular fluid : = 14,1 L easuring volumes of body fluid compartmen Clinical case ( the answer ) Measuring the intracellular fluid : Total body fluid volume – extra cellar fluid volume 42. 2−14. 1=28, 1 𝐿 Measuring the total body water : In Body test is a non-invasive body composition analysis that provides a detailed breakdown of your weight in terms of muscle, fat, and water Measuring the total body water : In Body test Preparation for in-body analysis : 1. Do not eat for 3-4 hours before testing 2. Do not exercise for 6-12 hours before testing 3. Ensure access to both feet with removable footwear and socks 4. Avoid putting lotion on hands and feet before testing Measuring the total body water : In Body test analysis 1 = 45% 2 Measuring the total body water : In Body test analysis = 47,4% 1 2