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Fluid and Electrolytes
Terms in this set (62)
What is intracellular fluid?
(ICF) Fluid contained within the cells. It accounts for approximately 40% of the body weight and is essential for cell function and metabolism.
What is extracellular fluid?
(ECF) Fluid found outside the cells. ECF carries water, electrolytes, nutrients, and oxygen to the cells and removes the waste products of cellular metabolism. It accounts for 20% of body weight and exists in three main locations in the body
What are the three ECFs?
Interstitial fluid, Intravascular fluid, and trans-cellular fluid.
What is interstitial fluid?
Fluid BETWEEN the cells or in the tissues
What is intravascular fluid?
It is the plasma in the blood.
What is transcellular fluid?
The fluid in
- GI tract, pleural spaces, synovial capsules, digestive juices.
What is an excess of interstitial fluid called?
What is the main function of intravacular fluid?
To transport blood cells.
What is third spacing?
When fluid accumulates in a portion of the body from which it is not easily exchanged with the rest of the ECF (e.g., burns, blisters, ascites).
What are electrolytes?
Substances that develop an electrical charge when dissolved in water (e.g., sodium, potassium)
What are nonelectrolytes?
Substances that will not conduct electricity (e.g. glucose, urea).
What are some important functions of body fluids?
Maintain blood volume, regulate body temperature, transport material to and from cells, serve as a medium for cellular metabolism, assist with digestion of food, and serve as a medium for excreting waste.
What is osmosis?
Movement of water (or other pure solute) across a membrane from an area of a less concentrated solution to an area of more concentrated solution.
What are crystalloids?
Solutes that readily dissolve (e.g., electrolytes).
What are colloids?
Larger molecules that do not readily dissolve (e.g., proteins).
What is osmolarity?
Also known as tonicity, refers to the concentration of solutes providing pressure in body fluid.
What are osmols?
The number of particles of solute per per kilogram of water and is expressed as milliosmoles per kilogram (mOsm/kg). Sodium is the greatest determinant of serum osmolality; potassium is the greatest determinant of intracellular osmolality. Glucose and urea also contribute to osmolality in the ICF and ECF.
What is an isotonic solution?
Isotonics have the same osmolality as blood; thus, no osmosis will occur. Isotonic fluids are often given by intravenous (IV) infusion if blood volume is low because the fluid will remain in the vascular space.
What is a hypotonic solution?
A solution with lower osmolality than blood. When a hypotonic solution is infused, water moves by osmosis from the vascular system into the cells.
What is a hypertonic solution?
A solution that contains a higher concentration of solutes than does blood. When a hypertonic solution is infused, water moves by osmosis from the cells into the ECF.
What is diffusion?
A passive process by which molecules of a solute move through a cell membrane from an area of higher concentration to an area of lower concentration. Movement occurs until the concentrations are equivalent on both sides of the membrane.
What are some examples that alter diffusion?
Small molecules more more rapidly than larger molecules, large differences in concentration requires a longer period of time to reach equilibration, and higher temperatures cause molecules to move faster, so that diffusion occurs more rapidly.
What is filtration?
The movement of both water and smaller particles from an area of high pressure to low pressure.
What is hydrostatic pressure?
It is the force created by fluid within a closed system and is responsible for normal circulation of blood. Blood flows from the high-pressure arterial system to the lower pressure capillaries and veins. As fluid (plasma) moves through the capillary membrane, only solutes of a certain size can flow with it.
What is osmotic pressure?
It is the power of a solution to draw water. A highly concentrated solution (many molecules in solution) has a high osmotic pressure and draws water. The plasma proteins in the blood exert osmotic (colloidal) pressure to help maintain fluid in the vascular space. When hydrostatic pressure exceeds osmotic pressure, fluid leaves the vessels.
What is filtration pressure?
It is the net pressure created when hydrostatic pressure exceeds osmotic pressure. This pressure difference is the force that moves fluid and solutes.
When does active transport occur?
It occurs when molecules (e.g., electrolytes) move accross cell membranes against a concentration gradient (from an area of a low concentration to an area of high concentration). Active transport requires energy expenditure.
What is the fluid intake recommended by The Institute of Medicine?
A total fluid intake of 2,700 mL per day for women and 3,700 mL per day for men. Further, the IOM states that we should obtain 80% of this intake from drinking fluids and the remaining 20% from food and cellular metabolism of foods.
What daily intake will maintain hydration in older adults?
1,500 mL to 2,000 mL of non-caffeinated fluids.
What are some situation that increase plasma osmolality?
Excessive fluid loss, excessive sodium intake, and decreased fluid intake.
What are some situations that inhibit the thirst mechanism?
A high intake of fluids, fluid retention, excessive IV infusion of hypotonic solutions, and low sodium intake.
What is sensible fluid loss?
It is measurable and/or perceived (e.g., urine, diarrhea, ostomy, and gastric drainage).
How much fluid is lost with urination?
1,500 mL/day. Urine accounts for the greatest amount of fluid loss. Urine output varies according to intake and activity, but should remain at least 30 to 50 mL/hour. The volume of urine increases as intake increases, and it decreases to compensate for other fluid losses (e.g., vomiting and excessive perspiration).
How much fluid is lost with defecation?
100 to 200 mL/day. Soft stools contain more water than hard stools. As stool frequency increases, water loss also increases.
How much fluid is lost through the skin?
About 600 mL/day. Fever, exercise, and some disease processes increase metabolic activity and heat production, leading to increased fluid loss.
What is a sensible loss of fluid through the skin?
Perspiration. Perspiration varies based on temperature, skeletal muscle activity, and metabolic activity.
What is an insensible loss of fluid through the skin?
What is an insensible loss of fluid through the lungs?
About 300 mL/day of insensible loss occurs through the lungs as water is exhaled with each breath. An increase in respiratory rate increases the amount of fluid lost.
What organ is the principal regulator of fluid and electrolyte balance?
Where are the pressure sensors located to stimulate or inhibit the release of antidiuretic hormone?
The vascular system stimulates or inhibits the release of ADH from the pituitary gland.
What does antidiuretic hormone (ADH) do?
ADH causes the kidneys to retain fluid. If fluid volume within the vascular system is low, fluid pressures within the system decrease, and more ADH is released. If fluid volume (and therefore pressure) increases, less ADH is released, and the kidneys eliminate more fluid.
What is the renin-angiotensin system?
When extracellular (i.e., intravascular) fluid volume is decreased, receptors in the glomeruli respond to the decreased perfusion of the kidneys by releasing renin. Renin is an enzyme responsible for the chain of reactions that converts angiotensinogen to angiotensin II. Angiotensin II acts on the nephrons to retain sodium and water and directs the adrenal cortex to release aldosterone.
What does aldosterone do?
When aldosterone is released, it stimulates the distal tubules of the kidneys to reabsorb sodium and excrete potassium. Sodium reabsorption results in passive reabsorption of water, thereby increasing plasma volume and improving kidney perfusion. When fluid excess is present, renin is not released, and this process stops.
How does the thyroid affect fluid volume?
Thyroid hormone affects fluid volume by influencing cardiac output. An increase in thyroid hormone causes an increase in cardiac output, thereby increasing glomerular filtration rate and urine output. A decrease has the opposite effect.
How does atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) affect fluid maintenance?
These peptides are important in renal and cardiovascular regulation of fluid maintenance. Natriuresis (natriuretic) is the discharge of sodium through urine. All three of these peptides are produced by heart cells; in addition, BNP is also released from the brain. In clinical practice, BNP can be measured in the serum to help determine presence of heart failure with fluid excess and to distinguish heart failure from pulmonary edema. The test can be performed at the bedside.
What is the primary function of sodium?
Sodium (Na+) is the major cation in the ECF. Its primary function is to regulate fluid volume. When sodium is reabsorbed in the kidney, water and potassium are also reabsorbed, thereby maintaining ECF volume.
What is the daily limit that adults should consume of sodium?
Adults should limit the intake of salt to 2,300 mg/day. People who are especially sensitive to the blood pressure-raising effects of salt are advised to limit salt intake to 1,500 mg/day. This includes people (including children) with a chronic disease (e.g., hypertension, diabetes, chronic kidney disease), African Americans, and those older than age 51. This limitation applies to nearly half of the U.S. population.
How much potassium is found in ECF?
Only 2% of body potassium.
What does potassium do in the body?
Potassium (K+) is the major cation of the ICF and is the key electrolyte in cellular metabolism.
How much K+ should an adult consume daily?
It is recommended to consume at least 4,700/day.
What are some side effects of hypokalemia?
Moderate potassium deficiency is associated with increases in blood pressure, salt sensitivity, risk of kidney stones, and risk of bone turnover. Low intake of dietary potassium is associated with increased risk of stroke.
What is calcium responsible for?
Ca2+ is responsible for bone health and neuromuscular and cardiac function and is an essential factor in blood clotting.
Where is the calcium located in the body?
About 99% of body calcium is located in the bones and teeth. The remaining 1% circulates in the blood and affects system functions.
Where is the magnesium located in the body?
Mg2+ is a mineral used in more than 300 biochemical reactions in the body. Like calcium, only about 1% of magnesium is found in the blood. The remaining 99% is divided between the ICF and bone (in combination with calcium and phosphorus).
How much chloride (Cl-) should a healthy adult consume per day?
A healthy adult between the ages of 19 and 50 should consume 2.3 grams of chloride each day along with 1.5 grams of sodium to replace daily losses and maintain serum blood levels.
Where is Cl- most abundant?
o Chloride (Cl-) is the most abundant anion in the extracellular fluid.
What does phosphorus combine with in the body?
Most phosphorus in the body is combined with oxygen, forming phosphate-mostly bound with calcium in the teeth and bones as calcium phosphate.
Major cation in the ECF
most abundant anion in the extracellular fluid.
the major cation of the ICF and a key electrolyte in cellular metabolism.
Responsible for bone health and neuromuscular and cardiac function and is an essential factor in blood clotting.
a mineral used in more than 300 biochemical reactions in the body.
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