Allied Chapter 20 Fluid And Electrolyte Balance

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Fluid

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* Fluid comprises approximately 55 percent of the adult body weight
* We maintain this weight through water ingested, tissue catabolism, beverages, and food
* Fluid is eliminated through the kidneys, skin, lungs, and gastrointestinal tract.
* An excess amount of fluid in the body can cause edema, or swelling, which if left untreated can cause stress on the heart and lungs
* A lack of fluid can create a state of dehydration, which can be critical to the body as well, if ignored.
* total body water in infants constitutes approximately 75 to 80 percent of their body weight, grown males 60%, females 50%
* men have less water weight per pound of body weight than women - says the book I think this is wrong
* body fluid percentages continue to decrease in infants until about age 10 where they stabilize
* elderly body fluid decreases because of loss of muscle mass (65% water) and an increase in fat (20% water)
* 2400 ml is the approximate fluid output in a 24 hour period
* kidneys are the chief regulators of sodium in body fluids, and produce approximately 1400 mL of urine a day
* typically ingest 700 mL of water in the foods we eat, 1500 mL of daily fluid intake, 200 mL by catabolism, and lose 100 mL of water through perspiration
* fluid output that changes the most is from the kidneys.
* adipose (fat) tissue contains the least amount of water of any body tissue; more fat in the body the less total water content per kilogram of body weight.

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ions

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* dissociated particles of an electrolyte

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nonelectrolytes

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* substances that do not dissociate or break up in water
* ie. glucose

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edema

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* tissue swelling caused by excess Interstitial fluid (IF)
* can occur in any organ or tissue of the body.
* lungs, brain, and dependent body areas such as the legs and lower back are affected most often
* most common is the subcutaneous tissues of the ankle and foot

possible causes:
1. retention of electrolytes (especially Na) in the extracellular fluid
2. an increase in capillary blood pressure
3. a decrease in the concentration of plasma proteins

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intracellular

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* describes fluid found inside the cells

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overhydration

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* describes fluid found outside the cells

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extracellular

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* total volume of body fluids larger than normal

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diuretic

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* "causing urine"
* stimulates urine output

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Body Fluid Compartments

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* a place where fluids or the body are thought to be contained.
* each compartment is actually a group of separated spaces in the body that in many ways function as if they are all in one compartment

body fluids are distributed into two main compartments:
1. Intracellular fluid (ICF) - fluid within the cells - about 25L
2. Extracellular fluid (ECF) - fluid located outside of the cells
a. Interstitial fluid (IF) - fluid in the spaces between the cells (the larges volume of water about 12 L)
b. Plasma - the liquid fraction of whole blood - about 3 L

In addition to the two primary extracellular locations, other extracellular fluids include:
1. Lymph
2. Cerebrospinal fluid
3. Specialized joint fluids
4. Humors of the eye

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Intracellular fluid (ICF)

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* fluid within the cells
* Intracellular fluid constitutes approximately two-thirds of the body fluid; the largest volume of body fluid
* water has many functions inside the cell but mainly serves as a solvent in which important chemical reactions of the cell can occur.

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Extracellular fluid (ECF)

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* fluid located outside of the cells
* compose approximately one-third of body fluid
* consists mainly of the liquid part of whole blood; the plasma found in the blood vessels and the interstitial fluid (IF) that surround the cells
ie. lymph, cerebrospinal fluid, humors of the eye, and the synovial joint fluid.

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Interstitial fluid (IF)

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* fluid in the spaces between the cells
* the largest volume of water
* of the three main body fluids IF volume varies the most

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Plasma

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* the liquid fraction of whole blood
* NaCl is the most abundant electrolyte in blood plasma

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Cerebrospinal fluid

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* an extracellular fluid
* The cerebrospinal fluid, humors of the eye, and specialized joint fluids are sometimes referred to as transcellular fluid

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Specialized joint fluids

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* an extracellular fluid
* The cerebrospinal fluid, humors of the eye, and specialized joint fluids are sometimes referred to as transcellular fluid.

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Humors of the eye

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* an extracellular fluid
* The cerebrospinal fluid, humors of the eye, and specialized joint fluids are sometimes referred to as transcellular fluid.

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Mechanisms That Maintain Fluid Balance

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* that the volumes of intracellular fluid, interstitial fluid, plasma, and the total volume of water in the body remain relatively constant
* most important is the body's chief mechanism for adjusting fluid output. it mustequal fluid intake.
* In order for this constant state to be maintained, fluid intake needs to equal fluid output
* variables such as sex, weight, and age may alter the amount of fluid in the body, the principle of water balance being dependent on intake equaling output remains the same
* The average adult has an intake of 2400 mL and an output of 2400 mL in a 24-hour period
* When extracellular fluid falls below normal, the hormone aldosterone can return the volume to within normal levels.

Several other factors act as mechanisms for regulating extracellular and intracellular volumes. Three of the main factors are:
1. Concentration of electrolytes in the extracellular fluid (ECF)
2. Capillary blood pressure
3. Concentration of proteins in blood

four organs control fluid output:
1. kidneys - 1400 ml
2. lungs - 350 ml
3. skin - 450 ml
4. intestines - 200 ml = 2400 ml

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Electrolytes

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* compounds that have molecular bonds that dissociate when dissolved in water into separate particles called ions.
* required for many cellular activities such as nerve conduction and muscle contraction
* influence the movement of water amount the three fluid compartments of the body
* The concentration of electrolytes in the extracellular fluid is important because electrolytes influence the movement of water among the fluid compartments of the body
* if the concentration of sodium in interstitial fluid spaces rises above normal, the volume of fluid also increases, creating edema and tissue swelling
* in 24 hours, more than 8 liters of fluid containing 1000 - 1300 mEg of sodium are poured into the digestive system

* A compound such as table salt (NaCl) has a molecular bond that permits it to break up. This dissociation in water solution causes salt to separate into charged particles of Na+ and Cl-.

The dissociated particles of an electrolyte are ions and they carry an electrical charge:
* Cations are positively charged (Na+).
* Anions are negatively charged (Cl-).

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Aldosterone Regulation Mechanism

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* controls sodium reabsorption in the kidney
* Aldosterone is a hormone secreted by the adrenal cortex that increases Na+ and water reabsorption by the kidney tubules and the excretion of potassium (K+)
* when the blood level of aldosterone increases sodium is moved from the kidney tubules to the blood
* Water reabsorption causes an increase in extracellular fluid volume, which increases blood volume and blood pressure.
* It is important to remember that the antidiuretic hormone (ADH) secreted by the posterior lobe of the pituitary gland also contributes to the regulation of the amount of water reabsorbed by the kidney tubule
* ANH or atrial natriuretic hormone is released from the heart's atrial wall and increases urine volume
* urine volume is also regulated by ADH - the antidiuretic hormone, this is the type of fluid output that changes the most
* renal tubule regulation of salt and water is the most important factor in determining urine volume
* where salt goes, water soon follows

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thirst

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* is associate with any condition that decreases total volume of body water
* when fluid loss from the body exceeds fluid intake, salivary secretion decreases, producing a "dry-mouth feeling" and the sensation of thirst

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capillary blood pressure

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* the force that pushes fluid out of the capillary and plasma and into the interstitial fluid
* water-pushing force in blood
* If capillary blood pressure increases, more fluid is forced out (filtered or pushed out) of the blood plasma into the interstitial fluid. this fluid shift, changes blood and IF volumes. it decrease blood volume by increasing IF volume.

**out of cap blood to IF - depends on capillary blood pressure
**into blood from IF - depends on the concentration of proteins in blood plasma, from osmotic pressure create a water-pulling or water-holding force

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fluid shift

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* the transfer of fluid from the blood to the interstitial fluid
* this results in a decrease in blood volume and an increase in interstitial fluid (they move interstitial fluid into the plasma)

* If capillary blood pressure decreases, less fluid would filter out of the blood into the interstitial fluid, Blood volume would increase and the interstitial fluid would decrease.

This reverse situation occurs only slightly and briefly. It depends a great deal on the concentration of proteins in the blood:
* Plasma proteins in the blood hold water and draw it into the blood from the interstitial fluid.
* If the concentration of blood proteins decreases, less water moves into the blood from the interstitial fluid.
* Blood volume decreases and interstitial fluid volume increases.

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fluid imbalances

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* involve either abnormally low or abnormally high volumes of body fluids
* The fluid imbalance seen most often is a condition that refers to an abnormal loss of fluid known as dehydration
* Much less common than dehydration is a condition that refers to an abnormal increase in fluid input in the body known as overhydration
* Another imbalance that is critical to homeostasis and related to the "intake and output" of electrolytes is electrolyte imbalance.

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Dehydration

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* A deficiency in body water or fluid
* a common condition and occurs when water output exceeds water intake
* fluid imbalance seen most often or most common
* IF volume decreases first, then eventually ICF and plasma volume decrease below normal if no treatment is given.
* can be caused by too fluid intake or too few of fluid output

Several factors can contribute to a state of dehydration such as:
* Profuse sweating
* Vomiting
* Diarrhea
* Use of medications that provide a diuretic effect

* Loss of skin elasticity is a sign of dehydration. Skin that does not return quickly to its normal shape after being pinched indicates interstitial water loss.
* even if you don't drink for days, fluid output will continue though dramatically decreased (not just urine output)

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overhydration

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* An excess in body water or fluid is called overhydration, which is less common than dehydration
* Fluid buildup results in edema which increases blood volume and places additional stress on vital organs—such as the heart and lungs—to accommodate the increased volume.
* can be caused by giving IV fluids too rapidly or in too large of an amount. this puts too heavy a burden on the heart by increasing the volume of blood to be pumped.

It can occur from:
* An excessive intake of fluids
* The body's inability to excrete water

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electrolyte imbalance

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* related to the intake and output of specific electrolytes.
* critical to homeostasis
* If, for example, the concentration of sodium in interstitial fluid rises above normal, it draws water to the area creating edema. The absorption, distribution, and availability of electrolytes determine the homeostasis of fluid balance.
* Any disruption to the amount of a particular electrolyte can cause electrolyte imbalance, and if not corrected, can cause serious and sometimes fatal consequences

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Common Electrolyte Imbalances

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* Electrolyte imbalances are serious and should be dealt with promptly to return the body to homeostasis
* Some of the common ones in clinical medicine involve sodium, potassium and calcium

Sodium—normal blood level is 136-145mEq/L of blood
* Hypernatremia
* Hyponatremia

Potassium—normal blood level is 3.8-5.1 mEq/L of blood
* Hyperkalemia
* Hypokalemia

Calcium—normal blood level is 8.4-10.5 mg/100ml blood
* Hypercalcemia
* Hypocalcemia

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Hypernatremia

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* excessive amounts of sodium in the body, more than 145 mEq/L
* affects CNS functioning and is characterized by headache, confusion, seizures and in severe cases coma and death
* It is commonly caused by an overuse of salt tablets, dehydration, or prolonged diarrhea
* an electrolyte imbalance

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Hyponatremia

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* inadequate amounts of sodium in the body, less than 136 mEq/L
* affects CNS functioning and is characterized by headache, confusion, seizures and in severe cases coma and death
* It is the result of an excessive production of antidiuretic hormone, a massive infusion of IV fluids not containing sodium, or an excessive salt loss such as with certain diuretics, there is too much water in the extracellular fluid compartment for the amount of sodium present
* an electrolyte imbalance

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Hyperkalemia

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* excessive amounts of potassium in the body, more than 5.1 mEq/L
* normal potassium range in the blood is 3.8 to 5.1 mEq/L
* affects muscle function and results in muscle weakness and paralysis
* It is caused by an increased intake of potassium, the inability to excrete potassium or a shift from the intracellular fluid into the blood that occurs as a result of tissue trauma, burns or kidney failure.
* an electrolyte imbalance

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Hypokalemia

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* inadequate amounts of Potassium in the body, less than 3.8 mEq/L
* affects muscle functioning and results in muscle weakness and cardiac problems
* It also may cause abdominal distention and a diminished rate of passage of intestinal contents
* It is caused by fasting, diets low in potassium, abuse of laxatives and certain diuretics in extreme weight loss programs or by a loss of potassium due to diarrhea, vomiting or gastric suction
* an electrolyte imbalance

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Hypercalcemia

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* excessive amounts of calcium in the body
* normal range of serum calcium is 8.4 to 10.5 mg/dl
* decreases neuromuscular irritability resulting in fatigue, muscle weakness, diminished reflexes and delayed atrioventricular conduction in the heart
* It may be caused by an excessive input or by increased absorption that may occur following an overdose of vitamin D
* It can also result from shifts of calcium from the bone into the extracellular fluid caused by many various pathologies.
* an electrolyte imbalance

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Hypocalcemia

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* inadequate amounts of calcium in the body
* increases neuromuscular irritability, cramping, twitching of muscles, hyperactive reflexes and abnormal cardiac rhythms
* It may be caused from dietary calcium deficiency, decreased absorption or increased calcium excretion.
* an electrolyte imbalance

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hypervolemia

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* excess blood volume

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ions

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* dissociated (broken up) particles of an electrolyte
* the most abundant ions are sodium (positive) and chloride (negative)
* many ions are important "trace" elements in the body ie. iron, for hemoglobin production and iodine for synthesis of thyroid hormones.

ie. positively charged ions: sodium (Na+), calcium (Ca++), potassium (K+) and magnesium (Mg++)
* negative charged ions: chloride (Cl-), bicarbonate (HCO3-), phosphate (HPO4-) and many proteins.

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electrolyte balance

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* refers to homeostasis or relative constancy of normal electrolyte levels in the body fluids.

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pitting edema

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* describes depressions in swollen subcutaneous tissue that do not rapidly refill after an examiner has exerted finger pressure
* often a symptom with congestive heart failure

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milliequivalent (mEq)

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* a unit of measurement related to ion reactivity

ie. the average daily diet contains about 100 milliequivalents of sodium

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water intoxication

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* results from rapidly drinking large volumes of water or giving hypotonic solutions to persons unable to dilute and excrete urine normally.
* can occur with patients with kidney insufficiency or abnormal thirst mechanisms
* causes confusion and lethargy from elevated water content levels, and diluted plasma sodium levels.
* severe cases cause stupor, seizures, and coma