Chapter 27: Fluid, Electrolytes And Acid Base Homeostasis Flashcards
Body Fluid
Substance, usually a liquid that is produced by the body.
Consists of water and dissolved substances.
2/3 is intracellular fluid
Extracellular Fluid
Fluid found outside the cells.
Most abundant cation: Na - accounts for nearly half of osmolarity
Most abundant anion: Cl
80% of ECF is interstitial fluid: occupies space between tissues cells
20% of ECF is blood plasma: liquid portion of blood.
Includes:
Lymph
Blood Plasma
CSF
Synovial Fluids
2 General Barriers Separate Fluid, Interstitial Fluid and blood Plasma
- Plasma Membrane: separates intracellular fluid from the surrounding interstitial fluid.
- Blood Vessel Walls: divide the interstitial fluid from blood plasma.
Fluid Blance
The body is balanced when the required amount of water and solute are present and are correctly proportioned among the various compartments.
Water
Largest single component of the body
45-75% of total body mass, depends on age, gender and amount and adipose tissue
Electrolytes
Inorganic compounds that dissolve into ions.
Sodium, potassium, chloride
Functions:
1. Controlling osmosis
2. Maintaining acid base balance
3. Carry electrical currents
4. Serve as cofactors
Metabolic Water
The bodies other source of water.
Is produced in the body mainly when electrons are accepted by O2 during aerobic respiration and to a smaller extent during dehydration synthesis reactions.
Thirst Center
Area in the hypothalamus.
Governs the urge to drink
Dehydration
When water loss is greater than water gain.
Is a decrease in volume and an increase in osmolarity of body fluid occurs.
Urinary Salt (NaCl) Loss
Main factor that determines bodies fluid volume.
Reason: water follows solutes in osmosis.
2 main solutes in ECF are Na and Cl.
Antidiuretic Hormone (ADH) in Water loss
Or vasopressin. Regulates water balance.
Promotes insertion of water channel proteins into apical membranes of princely cells in collecting ducts of kidneys by insertion of aquaporin-2 into cells.
As a result water permeability of these cells increases and more water is reabsorbed causing reduces loss of water.
Aldosterone in Water Loss
Controls Na levels in blood
By promoting urinary reabsorption of Na increases water reabsorption via osmosis.
Causes reduced loss of water in urine.
Atrial Natriuretic Peptide (ANP) in Water Loss
Promotes natriuretic elevated urinary excretion of Na, accompanied by water.
Increase loss of water in urine.
Water Intoxication
When a person consumes water faster than the kidneys can excrete or when renal function is poor.
Dilute body fluids
Decrease in the osmolarity of interstitial fluids
Is a state in which excessive body water causes cells too swell dangerously.
Causes: mental confusion, seizures, coma and possible death.
4 General Function in the Body when Electrolytes Dissolve and Dissociate
- They are largely confined to particular fluid compartments and are more numerous than non electrolytes. Certain ions control the osmosis of water between fluid compartments.
- Ions help maintain the acid base balance required for normal cellular activities
- Ion carry electrical current, which allows production of action potentials and graded potentials.
- Several ions serve as cofactors needed for optimal activity enzymes.
Contractions of Electrolytes in Body Fluids
Typically expressed in units of milliequivalent per liter (mEq/liter).
These units give the concentration of cation and anion in a given volume of solution.
Sodium
136-148 mEq/liter
Most abundant ion in ECF.
Accounts for 90% of extracellular cations.
Hyponatremia
Caused by a decrease sodium intake.
Due to sodium loss through vomiting, diarrhea, aldosterone deficiency or consuming certain diuretics and excessive water intake.
S & S: muscular weakness, dizziness, headache, hypotension, tachycardia, shock, mental confusion, stupor and coma.
Hypernatremia
May occur with dehydration, water deprivation or excessive sodium in diet or receiving too much IV fluid.
S & S: intense thirst, hypertension, edema, agitation and convulsion.
Chloride
Cl-
Normal blood plasma concentration is 95-105 mEq/liter.
Most prevalent anions in ECF.
Moves easily between the extracellular and intracellular compartments because most plasma membranes contain many Cl leakage channels and antiporters.
Hypochloremia
Due to excessive vomiting, over hydration, aldosterone deficiency, congestive heart failure and receiving certain diuretics such as Lasix.
S & S: muscle spasms, metabolic alkalosis, shallow resps, hypotension and tetany.
Hyperchloremia
Results from hydration due to water loss or water deprivation, excessive chloride intake, severe renal failure, hyperaldosteronism, certain types of acidosis and some drugs.
S & S: lethargy, weakness, metabolic acidosis and rapid deep breathing.
Potassium
Most abundant cations in intracellular fluid.
3.5-5.0 mEq/liter
Plays a key role in establishing the resting membrane potential and in repolarization phase of action potentials in neurons and muscle fibers.
Hypokalemia
Results from excessive loss due to vomiting or diarrhea, decreases potassium intake, hyperaldosteronism, kidney disease and therapy with some diuretics.
S&S: muscle fatigue, flaccid paralysis, mental confusion, increased urine output, shallow resp and changes in ECG (flatten T wave).
Hyperkalemia
Due to excessive potassium intake, renal failure, aldosterone deficiency, crushing injuries to body tissues or transfusion of hemolyzed blood.
S&S: irritability, nausea, vomiting, diarrhea, muscular weakness. Can cause death by ventricular fibrillation.
Bicarbonate
Second most prevalent ion in extracellular anions.
Normal blood plasma concentration: 22-26 mEq/liter
HCO3 concentration increases as blood flows through systemic capillaries because the CO2 released by metabolically active cells combines with water to form carbonic acid. The carbonic acid then dissociated in H and HCO3.
Calcium
Most abundant mineral in the body as a large amount of calcium is sorted in the bone
98% is in the skeleton and teeth
Regulated by: PTH, calcitriol and calcitonin
Total: 9.0-10.5 mg/dL
Ionized: 4.5-5.5 mEq/liter
Hypocalcemia
May be due to increased calcium loss, reduced calcium intake, elevated phosphate levels or hypoparathyroidism.
S&S: numbness and tingling of fingers, hyperactive reflexes, muscle cramps, tatany and convulsion, bone fractures, spasm of laryngeal muscles that can cause death.
Hypercalcemia
May result from hyperparathyroidism, some cancers, excessive intake of vitamin D and Paget’s disease of the bone.
S&S: lethargy, weakness, anorexia, nausea, vomiting, polyuria, itching, bone pain, depression, confusion, parenthesis, stupor and coma.
Phosphate
Present as calcium phosphate salts which are structural components of bone and teeth.
About 85% of the phosphate in adults.
Important intracellular anions, at normal pH of body fluids, HPO42 is the most prevalent form.
1.7-2.6 mEq/liter
Hypophosphatemia
May occur through increased urinary losses, decreased intestinal absorption or increased utilization.
S&S: confusion, seizures, coma, chest and muscle pain, numbness and tingling of fingers, decreased coordination, memory loss and lethargy.
Hyperphosphatemia
Occurs when kidneys fail to excrete excess phosphate as in renal failure.
Can also result from increased intake of phosphate or destruction of body cells when releases phosphates into blood.
S&S: anorexia, nausea, vomiting, muscular weakness, hyperactive reflexes, tetany and tachycardia.
Magnesium
In adults about 54% of total body magnesium is part of bone matrix as magnesium salts.
Is the second most common intracellular cation.
Mg2 is a cofactors for certain enzymes needed for the metabolism of carbohydrates and proteins and for the sodium potassium pump.
1.3-2.1 mEq/liter
.
Hypermagnesemia
Occurs in renal failure or due to increased intake of Mg2 such as antacids.
Also occurs in aldosterone deficiency and hypothyroidism.
S&S; hypotension, muscular weakness or paralysis, nausea, vomiting and altered mental functioning.
Acid Base Balance
This balance is critical importance to normal cellular function to keeping the H+ concentration (pH) of body fluids at an appropriate level.
Mechanism that Help Maintain the pH
The removal of H from the body fluids and its subsequent elimate on from the body depends on the following 3 major mechanism:
1. Buffer systems: buffers act quickly to temporarily bind H, removeing the highly reactive, excess H from solution. Buffers thus raise pH of body fluids but do not remove H from the body.
2. Exhalation of CO2: be increasing the rate and depth of breathing, more CO2 can be exhaled. Within mins this reduces the level of carbonic acid in blood which raises the blood pH.
3. Kidney excretion of H: the slowest mechanism but the only way to eliminate acids other than carbonic acid is through their excretion in urine.
Actions of Buffer Systems
Body consist of a weak acid and the salt of that acid which functions as a weak base.
Buffers prevent rapid, drastic changed in the pH of body fluids by converting strong acids and bases into weak acids and weak bases within fractions of a second.
Buffer System
Most abundant buffer in intracellular fluid and blood plasma.
Main protein buffer in blood plasma: albumin
Proteins are composed of amino acids, organic molecules that contain at least one carbonyl group (-COOH) and at least one amino group (NH2)
These are the functional components of the system.
Carbonic Acid-Bicarbonate Buffer System
Is based on;
Weak base: bicarbonate ion (HCO3)
Weak acid: carbonic acid (H2CO3)
HCO3 is a significant anion in both intracellular and extracellular fluids.
The kidneys also synthesize new HCO3 and reabsorb flittered HCO3, this important buffer is not lost in the urine.
Phosphate Buffer System
Phosphate are major (high concentration) anions in intracellular fluid and minor ones in extracellular fluids.
Allows for buffering of hydrogen ions that are pumped into urine.
This buffer system is an important regulator of pH in the cytosol.
Exhalation of Carbon Dioxide
The simple act of breathing also plays an important role in maintaining the pH of body fluids.
Increase in CO2 increase H and thus lowers the pH.
H2CO3 (carbonic acid) can be eliminated by exhaling CO2 called volatile acid.
Acidosis
Condition in which blood pH is below 7.35.
Increase in H ions.
Major physiological effect: depression (stimulation) of the CNS through depression of synaptic transmission.
Systems: disoriented, then comatose which can lead to death.
Alkalosis
Condition in which blood pH is higher than 7.45.
Major physiological effect: overexcitability in both CNS and PNS.
S&s: nervousness, muscle spasms, convulsion then death.
Compensation
Is a counter response due to a change in blood pH that leads to either acidosis or alkalosis.
A physiological response to an acid-base imbalance that acts to normalize arterial blood pH.
Respiratory Compensation
An altered blood pH due to metabolic causes either hyperventilation or hypoventilation.
This process can help bring blood pH back toward the normal range.
Can occur within minutes and reaches maximum within hours.
Renal Compensation
Occurs if there are changes in blood pH due to respiratory causes.
Changes in secretion of H and reabsorption of HCO3 by the kidney tubules.
.
Respiratory Acidosis
Increased Pco2 (above 45 mmHg) and decrease pH (below 7.35) if no compensation.
Common cause: hypoventilation due to emphysema,
Other causes: pulmonary edema, trauma to respiratory enter, airway obstruction or dysfunction of muscles of respiration
Compensation: Renal - increased excretion of H, increased reabsorption of HCO3. PH will be normal range but Pco2 will be high.
Respiratory Alkalosis
Decreased Pco2 (below 35mmHg) and increased pH (above 7.45) if no compensation.
Causes: hyperventilation due to O2 deficiency, pulmonary disease, cerebrovascular accident or severe anxiety.
Compensation: renal, decreased excretion of H, decreased reabsorption of HCO3. PH will be normal range but Pco2 will be low.
Metabolic Acidosis
Decreased HCO3 (below 22 mEq/liter) and decreased pH (below 7.35) if no compensation.
Causes: loss of bicarbonate ions due to diarrhea, accumulation of acid, renal dysfunction.
Compensation: respiratory, hyperventilation, which increase loss of CO2. Ph will be in normal range but HCO3 will be low.
Metabolic Alkalosis
Increased HCO3 (above 26mEq/Liter) and increase pH (below 7.45) if no compensation.
Most common: loss of acid due to vomiting,
Other causes: gastric suction, or use of certain diuretics, excessive intake of alkaline drugs.
Compensation: respiratory, hypoventilation which slows loss of CO2. PH will be normal range but HCO3 will be high.
Intracellular Fluid
Most abundant cation: K
Most abundant anion: HPO42
Chloride Shift
Occurs between RBC and blood plasma as the blood level of carbon dioxide increase or decreases
Way to control Hydrogen Levels in the Body
- Buffer systems
- Exhaling CO2
- Excretion by kidneys
Metabolic Reactions
Produce nonvolatile acids
Water Composition
As humans grown the water composition decreases
Infants have the greatest: 75%
Toddlers: 60%
Teenagers: 55%
Adults: 45-75% depending on age, gender and mount of adipose tissue.
Hydrogen Ions
1 one is equal to 1 equivalent (mEq)
Hypomagnesium
Due to inadequate intake or excessive loss in urine or feces.
S&S; weakness, irritability, tetany, delirium, convulsion, confusion, anorexia, nausea, vomiting, parathesia and cardiac arrhythmias
Intercalated Cells
Part of the kidney that is most important for regulation of pH o body fluids.
Partial Compartion
Where pH is still below 7.35.
