To be a perfect marker a substance must also not be metabolised. Then make proportion calculation.
Blood Flow Blood Pressure And Resistance Anatomy And
Measurement of body fluid volume. Measuring body fluid compartments. Body fluid compartments renal physiology lecture 1 part 1 duration. Humans can survive for 4 to 6 weeks without food but only for a few days without water. Unfortunately some bromine 82 also distributes into the cells. If plasma is x and its volume in body is y then plasmahematocrit100 the volume in body is v. To measure the volume of any fluid compartment within the body you must inject or infuse a marker substance that will equilibrate diffuse freely to a uniform concentration throughout this compartment.
Measuring the extracellular fluid volume with crystalloid tracer. Water is necessary for all life on earth. Extracellular fluid volume measurement. Thus bromine measurements of the ecf volume frequently over estimate the ecf volume. Volume measurement of compartments usmle step 1 dr. If the tracer is metabolised a series of measurements can be made and assuming exponential decline first order kinetics the volume of distribution can be determined by extrapolation back to zero time.
Not interfere with body fluid distribution if the tracer is excreted in the urine then the loss can be determined and corrections made in the calculation. If you measure too soon all you will get is the volume of the functional extracellular fluid. Euvolemia is the state of normal body fluid volume including blood volume interstitial fluid volume and intracellular fluid volume. The plasma volume is calculated by evans blue technique the proportion of plasma and hematocrit is by centrifugation. Hypovolemia and hypervolemia are imbalances.
Gallery of Measurement Of Body Fluid Volume
