Fluid and Electrolyte Balance Human Biochemistry Fluid and Electrolyte Balance

Fluid and Electrolyte Balance Body Fluids Water makes up between 50-60% of your total body weight Water is found in 3 main locations known as fluid compartments. Fluid Compartments – the areas in the body where fluid is located

Fluid and electrolyte balance Intracellular Fluid – fluid found inside cells Makes up  33% of total body weight There are Two types of Extracellular Fluid: Interstitial Fluid (IF) – fluid found in the microscopic spaces between cells (makes up  10% of total body weight) Plasma – fluid found in blood vessels (makes up  4% of total body weight) Intracellular Fluid (ICF) Extracellular Fluid (ECF)

Fluid and electrolyte balance Fluid levels vary by mass and type of tissue: fat has little to no water in it so people with extra body fat have a lower percentage of water/pound (total body weight=tbw) NEWBORN INFANTS: 75-80% tbw ADULT MALES: 55-60% tbw ADULT FEMALES: 50-55% tbw

Fluid and electrolyte balance Mechanisms that Maintain Fluid Balance The body maintains fluid balance by adjusting the fluid output to match fluid intake. Fluid intake occurs by taking in liquids or from the foods we eat or from tissue catabolism Fluid output occurs by excreting water from our lungs, *kidneys, large intestine, and sweat (skin) When fluid intake and output are equal then the total amount of water in the body does not change.

Fluid and electrolyte balance The amount of fluid output is determined by the kidneys because the body maintains fluid balance by changing the amount of urine excreted to match fluid intake. ADH controls urine output (AntiDiuretic Hormone)by stimulating the kidneys to reabsorb water so that it remains in the body. ANH controls urine output (AntiNaturetic Hormone) by stimulating the kidneys to filter out more sodium (and thus more water). Aldosterone causes the kidneys to reabsorb sodium salts keeping water in the body.

Fluid and electrolyte balance The regulation of fluid intake isn’t quite known. It is believed that when fluid loss exceeds fluid intake, saliva production DECREASES (making you “thirsty”) so you drink water and thereby reduce the need for fluids As long as there is “life” in your body you will always lose water (through breathing) so you will always need to have fluid intake

Fluid and electrolyte balance The Importance of Electrolytes There are two types of compounds that are in water: nonelectrolytes and electrolytes Nonelectrolytes – compounds that do not dissociate in water Electrolytes – substances that ionize in solutions rendering the solutions capable of conducting an electric current Important positively charged electrolytes are: Na+, K+, Ca2+, and Mg2+ Important negatively charged electrolytes are: Cl-, HCO3-, proteins, HPO4-, and many others

Fluid and electrolyte balance Some important functions of electrolytes include: nerve conduction Muscle contraction Influence the movement of water between fluid compartments Due to osmosis: “Where sodium goes, water will soon follow” because: the sodium will lower the concentration of water in the fluid compartment. Water will then diffuse from an area of high concentration (where the sodium isn’t) to low concentration (where the sodium is)

Fluid and electrolyte balance Na+ H2O H2O H2O K+ Na+ K+ H2O H2O H2O H2O K+ H2O Na+ H2O Na+ H2O H2O K+ Na+ H2O H2O K+ Na+ H2O H2O H2O K+ H2O H2O K+ H2O H2O H2O K+ Na+ Na+ H2O H2O H2O K+ H2O H2O H2O Na+ H2O H2O

Fluid and electrolyte balance The reabsorption and secretion of sodium into the urine determines how much water is then secreted into the urine (as with water, Na+ secretion is usually equal to Na+ intake) Capillary Blood Pressure and Blood Proteins Blood releases water out of the capillaries due to capillary blood pressure. Capillary Blood Pressure – the blood pressure found in the capillary vessels (it is a “water-pushing” force)

Fluid and electrolyte balance Plasma volume usually maintains a stable volume with short-lived, infrequent fluctuations. Plasma proteins work to “pull” water into the blood vessels from interstitial fluid When there is a dietary insufficiency (resulting in low plasma proteins) there will be a decrease in plasma volume.  plasma proteins means water will diffuse into the interstitial fluid out of the blood vessels

Fluid and electrolyte balance H2O K+ K+ H2O K+ H2O H2O H2O K+ H2O H2O Plasma Proteins H2O K+ H2O H2O H2O H2O K+ H2O Plasma Proteins Plasma Proteins K+ H2O K+ H2O H2O H2O H2O H2O H2O Plasma Proteins H2O K+ H2O H2O H2O Plasma Proteins K+ H2O K+ H2O H2O H2O H2O H2O K+ H2O K+ Capillary Interstitial Fluid

Fluid and electrolyte balance Fluid Imbalances Edema is the term used to describe the condition commonly referred to as “swelling”. Edema – accumulation of fluid in a tissue, as in inflammation; swelling

Fluid and electrolyte balance EDEMA CAN BE CAUSED BY: Retention of Electrolytes: kidney disease/failure or an in a secretion of aldosterone Increase in capillary blood pressure: can be caused by venous congestion (slow blood flow through narrowed veins) due to heart failure Decrease in the concentration of plasma proteins: plasma proteins may leak into interstitial fluid due to infections, injuries, or severe burns

Fluid and electrolyte balance Dehydration is the most common type of fluid imbalance. Dehydration – clinical term that refers to an abnormal loss of fluid from the body’s internal environment Dehydration can be caused by: Too small fluid intake Too much fluid output (strenuous activity) At the onset of dehydration: IF volume decreases first but then plasma volume can decrease which will cause circulation problems

Fluid and Electrolyte Balance Overhydration isn’t very common. Overhydration – too large fluid input that can put a burden on the heart Usually over hydration is caused by giving intravenous fluids too fast. **MYTH: overhydration can dilute urine so that a drug test can be passed