Disturbances of fluid and electrolyte balance

1. Disturbances of fluid and electrolyte balance Csaba Hermann MD Dept. of Anesthesiology and Intensive Care Semmelweis University

2. Homeostasis The maintenance of normal volume and normal composition of the extracellular fluid is vital to life. Homeostasis: the various physiologic arrangements which serve to restore the normal state, once it has been disturbed Fluid balance Electrolyte balance Osmotic balance Acid-base balance

3. General principles Diffusion: movement of the particles in a solution from the area of high concentration to the area of lower concentration Electrolyte: inorganic substance that dissociates into ions Osmosis: diffusion of solvent molecules (water) into region in which there is a higher concentration of a solute (electrolyte) to which the membrane is impermeable Osmotic pressure: the pressure necessary to prevent solvent migration Osmol: concentration of osmotic active particles

4. General principles Osmolarity : number of osmoles per liter of solution Osmolality: number of osmoles per kilogram of solvent Measurement: depression of freezing point Calculation (plasma): 2x(Na+K)+glucose+BUN (mmol/l) Tonicity: effective osmolality of a solution relative to plasma Colloids: high molecular weight particles (> 20000 D) Oncotic pressure (colloid osmotic pressure): the pressure necessery to prevent diffusion of solvent molecules (water) into region in which there is a higher concentration of a colloid to which the membrane is impermeable