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Lecture Notes

Fluid and Electrolytes 


  1. Body fluids
    1. water
      1. the most important nutrient of life
      2. humans can only survive for a few days without water
    2. primary function of water in the body
      1. provides a medium for transporting nutrients to cells and waste from cells and for transporting substances such as hormones, enzymes, blood platelets, and red and white blood cells
      2. facilitates cellular metabolism and proper cellular chemical functioning
      3. acts as a solvent for electrolytes and nonelectrolytes
      4. helps maintain normal body temperature
      5. facilitates digestion and promotes elimination
      6. acts as a tissue lubricant
  2. Body fluid compartments
    1. intracellular fluid (ICF) compartment
      1. contains fluid within the cells
      2. constitutes about
        1. 40% of an adult's body weight
        2. 70% of an adult's total-body water
    2. extracellular fluid (ECF) compartment
      1. contains fluid outside the cells
      2. constitutes about:
        1. 20% of an adult's body weight
        2. 30% of an adult's total-body water
      3. includes:
        1. intravascular fluid
          1. fluid found within the vascular system
            1. e.g., plasma
        2. interstitial fluid
          1. fluid that surrounds tissue cells
    3. total-body water
      1. refers to the total amount of water in the body expressed as a percentage of body weight
      2. in the normal adult, total-body water:
        1. represents 50% - 60% of the body weight of a normal adult
        2. total-body water is divided as follows:
          1. cell fluids = 35% - 45%
          2. ECF = 15% - 20%
          3. plasma = 5%
          4. interstitial fluid = 10% - 15%
  3. Variations in fluid content
    1. total-body water varies according to:
      1. a person's age
        1. infants
          1. total-body water = 77%
        2. adults
          1. total-body water = 50% - 60%
        3. elderly
          1. total-body water = 45%
        4. risk factors:
          1. since infants have considerably more body fluid and ECF than adults, they are more at risk for problems with fluid balance compared to adults
      2. lean body mass
        1. fat cells
          1. contain little water
        2. lean tissue
          1. is rich in water
        3. risk factors:
          1. since fat cells contain little water, obese people are more at risk for problems with fluid balance compared to thin people
      3. gender
        1. females
          1. tend to have proportionally more body fat than males
        2. males
          1. tend to have proportionally less body fat than females
        3. risk factors:
          1. since women have more body fat than males, women are more at risk for problems with fluid balance compared to males
  4. Electrolytes
    1. electrolytes
      1. definition
        1. substances capable of breaking down into electrically charged ions when dissolved in solution
    2. ion
      1. definition
        1. atom or molecule carrying an electrical charge
      2. types of ions
        1. cations
          1. carry a positive charge
        2. anions
          1. carry a negative charge
    3. nonelectrolytes
      1. definition
        1. substances incapable of breaking down into electrically charged ions when dissolved in solution and, consequently, remain intact
      2. types of nonelectrolytes
        1. urea
        2. glucose
    4. measurement of electrolytes
      1. how measured
        1. measured in terms of their chemical combining power, or chemical activity
      2. unit of measurement of electrolytes
        1. the milliequivalent (mEq)
          1. describes the chemical activity of electrolytes
          2. 1 mEq of either a cation or anion is chemically equivalent to the activity of 1 mg of hydrogen
          3. 1 mEq of any cation is equivalent to1 mEq of any anion
          4. mEqs for each electrolyte in the body vary within a relatively narrow range
          5. total cations in the body are normally equal to the total anions in the body in homeostasis
    5. regulation of electrolytes
      1. sodium (Na+)
        1. chief electrolyte in the ECF
        2. functions:
          1. regulating ECF volume and distribution
          2. maintaining blood volume
          3. transmitting nerve impulses and contracting muscles
        3. average daily requirement:
          1. average daily requirement
            1. not known
          2. intake of 500 mg or 0.5 g maintains balance
        4. sodium-rich foods:
          1. bacon
          2. ham
          3. sausage
          4. catsup
          5. mustard
          6. relish
          7. processed cheese
          8. canned vegetables
          9. bread
          10. cereal
          11. salted snack foods
          12. table salt (about 46% sodium)
        5. losses:
          1. eliminated primarily by the kidneys
          2. small amounts are lost in the feces and perspiration
        6. regulation:
          1. renal absorption or excretion
          2. aldosterone increases Na+ reabsorption in the collecting ducts of the tubules
        7. normal range for serum sodium:
          1. 35 - 145 mEq (mmol/L)
      2. potassium (K+)
        1. chief electrolyte in the ICF
        2. functions:
          1. maintaining ICF osmolality
          2. transmitting nerve and other chemical impulses
          3. regulating cardiac impulse transmission and muscle contraction
          4. skeletal and smooth muscle function
          5. regulating acid-base balance
        3. average daily requirement:
          1. average daily requirement
            1. not known
          2. intake of 50 - 100 mEq maintains K+ balance
        4. potassium rich foods:
          1. bananas
          2. peaches
          3. kiwi
          4. figs
          5. dates
          6. apricots
          7. oranges
          8. prunes
          9. melons
          10. raisins
          11. broccoli
          12. potatoes
        5. losses:
          1. excreted primarily by the kidneys
            1. kidneys have no effective means of conserving potassium
            2. potassium deficits develop rapidly if it is excreted in excess without being replaced simultaneously
          2. gastrointestinal excretions
          3. some perspiration and saliva
        6. regulation:
          1. renal excretion and conservation
          2. aldosterone increases K+ excretion
          3. movement into and out of cells
          4. insulin helps K+ move into cells
          5. tissue damage and acidosis shifts K+ out of cells into the ECF
        7. normal range for serum potassium:
          1. 3.5 - 5 mEg/L (mmol/L)
      3. calcium (Ca++)
        1. most abundant electrolyte in the human body
          1. 99% is in the bones
          2. 1% is in the ECF
        2. functions:
          1. forming bones and teeth
          2. transmitting nerve impulses
          3. regulating muscle contractions
          4. maintaining cardiac pacemaker (automaticity)
          5. blood clotting
          6. activating enzymes such as pancreatic lipase and phospholipase
        3. average daily requirement:
          1. average daily requirement
            1. 1 g for adults
            2. higher amounts are required for:
              1. children
              2. pregnant and lactating women
              3. post-menopausal women not taking estrogen
              4. people over 65
        4. calcium rich foods:
          1. milk
          2. cheese
          3. dried beans
          4. green vegetables
            1. e.g., broccoli, kale, turnip greens shrimp
          5. canned salmon or sardines
          6. black strap molasses
          7. calcium-fortified tofu
          8. almonds
        5. losses:
          1. urine
          2. feces
          3. bile
          4. digestive secretions
          5. perspiration
        6. regulation:
          1. redistribution between the bones and ECF
          2. parathyroid hormone (PTH) and calcitriol (Vitamin D) increase serum Ca++ levels
          3. calcitonin decreases serum Ca++ levels
        7. normal range for serum calcium:
          1. 4.5 - 5.5 mEg/L (mmol/L)
      4. magnesium
        1. second most important cation in the ICF
          1. primarily found in the ICF
          2. also present in the heart, bone, nerve, and muscle tissues
        2. functions:
          1. intracellular metabolism
          2. operating the sodium-potassium pump
          3. relaxing muscle contractions
          4. transmitting nerve impulses
          5. regulating cardiac function
        3. average daily requirement:
          1. average daily requirement
            1. 18 - 30 mEq for adults
            2. higher amounts are required for:
              1. children
        4. magnesium rich foods:
          1. vegetables
          2. nuts
          3. fish
          4. whole grains
          5. peas
          6. beans
        5. losses:
          1. excreted by the kidneys
        6. regulation:
          1. conservation and excretion by the kidneys
          2. intestinal absorption increased by vitamin D and parathyroid hormone
        7. normal range for serum magnesium:
          1. 1.3 - 2.1 mEg/L (mmol/L) with 1/3 of that bound to plasma proteins
      5. chloride (CL-)
        1. chief electrolyte in the ECF
          1. present in the blood, interstitial fluid, lymph, and in minute amounts in the ICF
        2. functions:
          1. hydrochloric acid (HCL) production
          2. regulating ECF balance and vascular volume
          3. regulating acid-base balance
          4. buffer in oxygen-carbon dioxide exchange in red blood cells (RBCs)
        3. average daily requirement:
          1. average daily requirement
            1. not known
        4. chloride rich foods:
          1. foods high is sodium
          2. dairy products
          3. meat
        5. losses:
          1. excreted by the kidneys
        6. regulation:
          1. normally paired and excreted and reabsorbed along with sodium in the kidneys
          2. aldosterone increases chloride reabsorption with sodium
        7. normal range for serum chloride:
          1. 95 - 105 mEg/L (mmol/L)
      6. bicarbonate (HC03-)
        1. chief chemical base buffer within the body
          1. present in both the ECF and ICF
        2. functions:
          1. chief chemical base buffer involved in acid-base balance
          2. essential component of the carbonic acid-bicarbonate buffering system
        3. average daily requirement:
          1. average daily requirement
            1. not known
        4. bicarbonate rich foods:
          1. unlike other electrolytes that must be consumed in the diet, adequate amounts of bicarbonate are produced through metabolic processes to meet the body's needs
        5. losses:
          1. excreted by the kidneys
        6. regulation:
          1. excretion and reabsorption by the kidneys
          2. regeneration by the kidneys
        7. normal range for serum bicarbonate:
          1. 25 - 29 mEg/L (mmol/L)
      7. phosphate (PO4-)
        1. chief anion in the ICF
          1. present also in the ECF, bone, skeletal muscle, and nerve tissue
        2. functions:
          1. forming bones and teeth
          2. metabolizing carbohydrate, protein, and fat
          3. cellular metabolism; producing ATP and DNA
          4. muscle, nerve, and RBC function
          5. buffer in the oxygen - carbon dioxide exchange in RBCs
        3. average daily requirement:
          1. 1 g for adults
          2. higher amounts are required for:
            1. children
            2. pregnant and lactating women
            3. post-menopausal women not taking estrogen
            4. people over 65
        4. phosphate rich foods:
          1. beef
          2. pork
          3. dried peas and beans
        5. losses:
          1. excreted by the kidneys
        6. regulation:
          1. excretion and reabsorption by the kidneys
          2. parathyroid hormone decreases serum levels increasing renal excretion
          3. reciprocal relationship with calcium
            1. increasing serum calcium levels decreases phosphate levels
            2. decreasing serum calcium levels increases phosphate levels
        7. normal range for serum phosphate:
          1. 2.5 - 4.5 mEg/L (mmol/L)
  5. Fluid and electrolyte movement
    1. osmosis
      1. movement of a solvent across a selectively permeable cell membrane from an area of higher concentration of solutes to an area of lower concentration of solutes until equilibrium is established
        1. solvents
          1. liquids that hold a substance in solution
            1. e.g., when sugar is added to coffee, the coffee is the solvent
          2. the primary solvent in the human body is water
        2. solutes
          1. substances that are dissolved in a liquid
            1. e.g., when sugar is added to coffee, the sugar is the solute
          2. solutes may be crystalloids or colloids
            1. crystalloids
              1. salts that dissolve readily into true solutions
                1. e.g., sodium
            1. colloids
              1. substances that do not readily dissolve into true solutions
                1. e.g., large protein molecules
        1. osmolality
          1. the concentration of solutes in body fluids
            1. osmolality is:
              1. determined by the total solute concentration within a fluid compartment
              2. measured as parts of solute per kilogram of water
              3. reported as milliosmols per kilogram (mOsm/L)
                1. osmolality of plasma is 275 - 295 mOsm/L
            1. the greatest determinant of osmolality within a fluid compartment is sodium concentration
        1. tonicity
          1. may be used ro refer to the osmolality of a solution
          2. isotonic solutions
            1. have the same osmolality as body fluids
              1. e.g., between 275 - 295 mOsm/L
              2. e.g., 0.9% normal saline
            2. with isotonic solutions:
              1. water remains in the intravascular compartment without any net flow across selectively permeable cell membranes
          3. hypertonic solutions
            1. have a higher osmolality than body fluids
              1. e.g., greater than 295 mOsm/L
              2. e.g., 3 % normal saline
            1. with a hypertonic solution in the intravascular compartment:
              1. water moves out of the intracelluar compartment (inside the cells) and into the intravascular compartment that is hypertonic causing cells to shrink
          1. hypotonic solutions
            1. have a lower osmolality than body fluids
              1. e.g., less than 275 mOsm/L
              2. e.g., 0.45 % normal saline
            1. with hypotonic solutions:
              1. water moves out of the intravascular compartment and into the intracellular compartment (inside the cells) that is hypertonic causing the cells to burst
    2. diffusion
      1. movement of solutes across a selectively permeable cell membrane from an area of higher concentration of solutes to an area of lower concentration of solutes until equilibrium is established
        1. "coasting downhill"
      2. diffusion is affected by:
        1. the size of the solutes
          1. larger solutes move less quickly and, consequently, have a lower rate of diffusion
          2. smaller solutes move more quickly and, consequently, have a higher rate of diffusion
        2. the concentration of the solutes
          1. solutes move from an area of higher concentration of solutes to an area of lower concentration of solutes
        3. the temperature of the solutes
          1. increases in temperature increase the rate of motion of solutes and, consequently, leads to a higher rate of diffusion
          2. decreases in temperature decrease the rate of motion of solutes and, consequently, leads to a lower rate of diffusion
    3. active transport
      1. movement of solutes across a selectively permeable cell membrane, usually against a pressure gradient and with the expenditure of metabolic energy, from an area of higher concentration of solutes to an area of lower concentration of solutes until equilibrium is established
        1. "pumping uphill"
      2. in active transport:
        1. a solute combines with a carrier on the outside surface of a cell membrane
        2. the solute and carrier move to the inside surface of the cell membrane
        3. once on the inside surface of the cell membrane, the solute and carrier separate and the solute is released to the inside of the cell
      3. the sodium-potassium pump
        1. important active transport mechanism:
          1. under normal conditions:
            1. sodium concentrations are higher in the ECF
            2. potassium concentrations are higher in the ICF
          2. to maintain these conditions, the sodium-potassium pump continually:
            1. pumps sodium out of the cells into the ECF
            2. pumps potassium into the cells into the ICF
    4. filtration
      1. movement of solutes and solvent across a permeable cell membrane from an area of higher concentration of solutes to an area of lower concentration of solutes until equilibrium is established
      2. influenced by two pressures
        1. colloid osmotic, or oncotic, pressure
          1. the pressure exerted by solutes in water
          2. "water-pulling pressure"
            1. major source in keeping water from moving out from a confined space through a permeable cell membrane
            2. plasma proteins in the blood exert a colloid osmotic, or oncotic, pressure that prevents water from moving out from the intravascular to extravascular compartments to maintain vascular volume
        1. hydrostatic pressure
          1. the pressure exerted by water within a closed system on the wall of a container in which it is contained
          2. "water-pushing pressure"
            1. major source in moving water outward from a confined space through a permeable cell membrane
            2. plasma and blood cells exert hydrostatic pressure that moves water outward from the intravascular to extravascular compartments
        1. filtration pressure
          1. the difference between the colloid osmotic, or oncotic, pressure and hydrostatic pressure
          2. important concept at the capillary bed
            1. on the arteriole side of the capillary bed hydrostatic pressure is greater than colloid osmotic, or oncotic, pressure
              1. helps force or filter water and dissolved substances into the interstitial space
            1. on the venule side of the capillary bed, colloid osmotic, or oncotic, pressure is greated than hydrostatic pressure
              1. helps force or filter water and dissolved substances into the capillary
  6. Fluid balance
    1. a person's fluid intake should normally be approximately balanced by fluid loss
      1. fluid intake sources
        1. ingested liquids
          1. 1300 mL/24 hours
        1. water in ingested food
          1. 100 mL/24 hours
        1. metabolic oxidation
          1. 300 mL/24 hours
        1. total
          1. 2600 mL/24 hours
      1. fluid losses
        1. kidneys
          1. 1500 mL/24 hours
        1. skin
          1. insensible loss
            1. imperceptible losses
              1. e.g., from evaporation and respiration
            1. 200 - 400 mL/24 hours
          1. sensible loss
            1. 300 - 500 mL/24 hours
        1. lungs
          1. 400 mL/24 hours
        1. gastrointestinal
          1. 100 mL/24 hours
        1. total
          1. 2500 - 2900 mL/24 hours
  7. Acid-base balance
    1. body fluids must maintain an acid-base balance to sustain health and life
    2. acidity or alkalinity of a solution is determined by its concentration of hydrogen ions
      1. an acid
        1. a substance containing hydrogen ions that can be liberated or released, e.g.:
          1. carbonic acid (H2CO3) releases a hydrogen ion to form a bicarbonate base (HCO3-)
        2. strong versus weak acid
          1. a strong acid is an acid that dissociates (separates) completely in solution and releases all of its hydrogen ions
          2. a weak acid is an acid that dissociates (separates) incompletely in solution and releases only a small number of its hydrogen ions
      2. an alkali, or base
        1. a substance that can accept or trap hydrogen ions, e.g.:
          1. bicarbonate base (HCO3-) traps a hydrogen ion to form carbonic acid (H2CO3)
        2. strong versus weak base
          1. a strong base is a base that binds or accepts hydrogen ions easily
          2. a weak base is a base that binds or accepts hydrogen ions less easily
    3. unit of measure of acid-base balance is pH
      1. the pH scale ranges from 1 - 14
        1. neutral solution
          1. has a pH of 7
        1. acid solution
          1. has a pH of 1 - 6.9
          2. as hydrogen ions increase and a solution becomes more acidic, the pH becomes less than 7
        1. alkaline solution
          1. has a pH of 7.1 - 14
          2. as hydrogen ions decrease and a solution becomes more basic, the pH becomes more than 7
      2. the pH of blood
        1. the normal pH of blood
          1. 7.35 - 7.45
        2. acidosis
          1. a condition characterized by an excess of hydrogen ions in the ECF and a pH less than 7.35
        3. alkalosis
          1. a condition characterized by a deficit of hydrogen ions in the ECF and a pH more than 7.45
      1. narrow range of the pH of blood is achieved through three major homeostatic regulators of hydrogen ions
        1. carbonic acid (H2CO3) - sodium bicarbonate (HCO3-) buffer system
          1. when too much acid is in the blood:
            1. the excess acid combines with the sodium bicarbonate (HCO3-) part ot this system
            2. the above returns the pH of the blood to its normal range of 7.35 - 7.45
          1. when too much base is in the blood:
            1. the excess base combines with the carbonic acid (H2CO3) part of this system
            2. the above returns the pH of the blood to its normal range of 7.35 - 7.45
          1. ratio of carbonic acid (H2CO3) and sodium bicarbonate (HCO3-) in the blood:
            1. the amount of carbonic acid (H2CO3) and sodium bicarbonate (HCO3-) in the blood varies
            2. a ratio of 20 parts of sodium bicarbonate (HCO3-) to 1 part of carbonic acid (H2CO3) is typically maintained
            3. the ratio of 20 parts of sodium bicarbonate (HCO3-) to 1 part of carbonic acid (H2CO3) maintains the pH of blood within its normal range of 7.35 - 7.45
          2. quickness of response of the carbonic acid (H2CO3) - sodium bicarbonate (HCO3-) buffer system in restoring acid-base balance
            1. almost immediate
            2. almost instantaneously a normal blood pH is restored by the carbonic acid (H2CO3) - sodium bicarbonate (HCO3-) buffer system
        2. respiratory mechanisms
          1. carbon dioxide (CO2) is constantly produced by cellular metabolism
            1. carbon dioxide (CO2) can combine with water to form carbonic acid (H2CO3), e.g.:
              1. carbon dioxide (CO2) + water (H20) makes carbonic acid (H2CO3)
            2. carbonic acid (H2CO3) can dissociate from water to form carbon dioxide (CO2) (to be exhaled) and water, e.g.:
              1. carbonic acid (H2CO3) breaks down into carbon dioxide (CO2) and water (H20)
          2. the lungs help to regulate acid-base balance by eliminating or retaining carbon dioxide (CO2) and, thus, controlling the amount of carbonic acid (H2CO3) available in the blood
          3. when the pH of the blood is too acidic:
            1. the respiratory center is stimulated
            2. rate and depth of respiration is increased
            3. carbon dioxide (CO2) is excreted
            4. carbonic acid (H2CO3) levels fall
            5. pH of the blood returns to its normal range of 7.35 - 7.45
          4. when the pH of the blood is too alkaline:
            1. the respiratory center is depressed
            2. rate and depth of respiration is decreased
            3. carbon dioxide (CO2) is retained
            4. carbonic acid (H2CO3) levels rise
            5. pH of the blood returns to its normal range of 7.35 - 7.45
          5. quickness of response of respiratory mechanisms in restoring acid-base balance
            1. not immediate
            2. takes minutes for a normal blood pH to be restored by respiratory mechanisms
        3. renal mechanisms
          1. the kidneys help to regulate acid-base balance by excreting or retaining hydrogen ions and forming or excreting sodium bicarbonate ions
          2. when the pH of the blood is too acidic:
            1. the kidneys excrete hydrogen ions
            2. the kidneys form sodium bicarbonate ions
            3. pH of the blood returns to its normal range of 7.35 - 7.45
          3. when the pH of the blood is too basic:
            1. the kidneys retain hydrogen ions
            2. the kidneys excrete sodium bicarbonate ions
            3. pH of the blood returns to its normal range of 7.35 - 7.45
          4. quickness of response of renal mechanisms in restoring acid-base balance
            1. response is not immediate
            2. takes hours to days for a normal blood pH to be restored by renal mechanisms
  8. Fluid imbalances
    1. fluid volume deficit (FVD)
      1. deficiency in both the amount of water and electrolytes in the ECF where water and electrolyte proportions remain near normal
        1. commonly known as hypovolemia
      2. occurs as a result of:
        1. abnormal losses through the skin, gastrointestinal tract, or kidney
        2. decreased intake of fluid
        3. bleeding
        4. a shift of fluid into a third space
          1. the shift of fluid from the intravascular space into an area where it is not readily accessible as ECF, e.g.:
            1. sequestered in the bowel
            2. in the interstitial spaces as edema
            3. in inflamed tissue
            4. in potential spaces such as the peritoneal or pleural cavities
          2. the patient with a shift of fluid into a third space may not manifest signs/symptoms of fluid volume deficit
    2. fluid volume excess (FVE)
      1. excessive retention of water and sodium in similar proportions to normal ECF
        1. commonly known as hypervolemia
      2. occurs as a result of:
        1. excessive intake of sodium chloride
        2. administering sodium-containing infusions too rapidly, particularly to patients with impaired regulatory mechanisms
        3. disease processes that alter regulatory mechanisms, such as congestive heart failure, renal failure, cirrhosis of the liver, and Cushing's syndrome
      3. in FVE, both the intravascular and interstitial spaces have an increased water and sodium chloride content
        1. excess interstitial fluid is known as edema
        2. edema can be found around the:
          1. eyes
          2. fingers
          3. ankles
          4. sacrum
        3. edema may result in a weight gain in excess of 5%
      4. system for grading edema
        1. 1+ pitting edema
          1. slight indentation (2 mm)
          2. normal contours
          3. associated with interstitial fluid volume 30% above normal
        2. 2+ pitting edema
          1. deeper pit after pressing (4 mm)
          2. lasts longer than 1+
          3. fairly normal contour
        3. 3+ pitting edema
          1. deep pit (6 mm)
          2. remains several seconds after pressing
          3. skin swelling obvious by general inspection
        4. 4+ pitting edema
          1. deep pit (8 mm)
          2. remains for a prolonged time after pressing, possibly minutes
          3. frank swelling
        5. brawny edema
          1. fluid can no longer be displaced secondary to excessive interstitial fluid accumulation
          2. no pitting
          3. tissue palpates as firm or hard
          4. skin surface shiny, warm, moist
    3. dehydration
      1. deficiency in the amount of water in the ECF without a deficiency in electrolytes
      2. because water is lost while electrolytes, particularly sodium, are retained:
        1. serum osmolality increases
        2. serum sodium levels increase
    4. overhydration
      1. an excess in the amount of water in the ECF without an excess in electrolytes
      2. because water is lost while electrolytes, particularly sodium, are retained:
        1. serum osmolality decreases
        2. serum sodium levels decrease
  9. Electrolyte imbalances
    1. hyponatremia
      1. sodium deficit in the ECF, or serum sodium level less than 135 mEg/L
      2. risk factors
        1. loss of sodium, e.g.,
          1. loss os GI fluids
          2. use of diuretics
          3. adrenal insufficiency
        2. gains of water, e.g.:
          1. excessive administration of IV fluids
        3. disease states associated with SIADH
        4. pharmacologic agents than may impair water excretion
      3. signs/symptoms
        1. anorexia
        2. nausea and vomiting
        3. lethargy
        4. confusion
        5. muscle cramps
        6. muscular twitching
        7. seizures
        8. coma
    2. hypernatremia
      1. sodium excess in the ECF, or serum sodium level greater than 145 mEg/L
      2. risk factors
        1. water deprivation
        2. increased sensible and insensible water loss
        3. ingestion of a large amount of salt
        4. excessive parenteral administration of sodium-containing solutions
        5. profuse sweating
        6. diabetes insipidus
      3. signs/symptoms
        1. thirst
        2. elevated body temperature
        3. tongue dry and swollen
        4. sticky mucus membranes
        5. in severe hypernatremia:
          1. disorientation
          2. hallucinations
          3. lethargy when undisturbed
          4. irritable and hyperactive
          5. focal or grand mal seizures
    3. hypokalemia
      1. potassium deficit in the ECF, or serum potassium level less than 3.5 mEg/L
      2. risk factors
        1. diarrhea
        2. vomiting or gastric suction
        3. potassium-wasting diuretics
        4. steriod administration and certain antibiotics
        5. poor intake as in anorexia nervosa, alcoholism, potassium-free parenteral fluids
        6. polyruia
      3. signs/symptoms
        1. fatigue
        2. anorexia, nausea, and vomiting
        3. muscle weakness
        4. decreased bowel motility
        5. cardiac arrythmias
        6. increased sensitivity to digitalis
        7. polyuria, nocturia, dilute urine
        8. postural hypotension
        9. ECG changes
        10. paresthesias or tender muscles
    4. hyperkalemia
      1. potassium excess in the ECF, or serum potassium level greater than 5.0 mEg/L
      2. risk factors
        1. decreased potassium excretion, e.g.:
          1. oliguric renal failure
          2. potassium-sparing diuretics
          3. hypoaldosteronism
        2. high potassium intake, especially in the presence of renal insufficiency
        3. shift of potassium out of cells, e.g.
          1. acidosis, tissue trauma, malignant cell lysis
      3. signs/symptoms
        1. vague muscle weakness
        2. cardiac arrythmias
        3. paresthesias of the face, tongue, feet, and hands
        4. flaccid muscle paralysis
        5. GI symptoms such as nausea, intermittent intestinal colic, or diarrhea may occur
    5. hypocalcemia
      1. calcium deficit in the ECF, or serum calcium level less than 8.5 mEg/L
      2. risk factors
        1. surgical hypoparathyroidism
        2. malabsorption
        3. vitamin D deficiency
        4. acute pancreatitis
        5. excessive administration of citrated blood
        6. alkalotic states
      3. signs/symptoms
        1. Trousseau's and Chvostek's signs
        2. numbness and tingling of the fingers and toes
        3. mental changes
        4. convulsions
        5. spasm of larygneal muscles
        6. ECG changes
        7. cramps in the muscles of the extremities
    6. hypercalcemia
      1. calcium excess in the ECF, or serum calcium level greater than 10.5 mEg/L
      2. risk factors
        1. hyperparathryroidism
        2. malignant neoplastic disease
        3. prolonged immobilization
        4. large doses of Vitamin D
        5. overuse of calcium supplements
        6. thiazide diuretics
      3. signs/symptoms
        1. muscular weakness
        2. tiredness, lethargy
        3. constipation
        4. anorexia, nausea, vomiting
        5. decreased memory and attention span
        6. polyuria and polydipsia
        7. renal stones
        8. neurotic behavior
        9. cardiac arrest
    7. hypomagnesemia
      1. magnesium deficit in the ECF, or serum magnesium level less than 1.3 mEg/L
      2. risk factors
        1. chronic alcoholism
        2. intestinal malabsorption
        3. diarrhea
        4. nasogastric suction
        5. drugs, e.g.:
          1. thiazide diuretics
          2. aminoglycoside antibiotics
          3. excessive doses of vitamin D
          4. citrate preservative in blood
      3. signs/symptoms
        1. neuromuscular irritability
          1. increased reflexes
          2. coarse tremors
          3. convulsions
        2. cardiac manifestations
          1. tachyarrythmias
          2. increases susceptibility for digitalis toxicity
        3. mental changes
          1. disorientation
          2. mood changes
    8. hypermagnesemia
      1. magnesium excess in the ECF, or serum magnesium level greater than 3.0 mEg/L
      2. risk factors
        1. renal failure
        2. adrenal insufficiency
        3. excessive administration during treatment of eclampsia
        4. hemodialysis with hard water or dialysate high in magnesium content
      3. signs/symptoms
        1. flushing a sense of skin warmth
        2. hypotension
        3. depressed respirations
        4. drowsiness, hypoactive reflexes, and muscular weakness
        5. cardiac abnormalities
    9. hypophosphatemia
      1. phosphate deficit in the ECF, or serum phosphate level less than 2.5 mEg/L
      2. risk factors
        1. glucose administration
        2. refeeding after starvation
        3. hyperalimentation
        4. alcohol withdrawal
        5. diabetic ketoacidosis
        6. respiratory alkalosis
      3. signs/symptoms
        1. cardiomyopathy
        2. acute respiratory failure
        3. seizures
        4. decreased tissue oxygenation
        5. joint stiffness
    10. hyperphosphatemia
      1. phosphate excess in the ECF, or serum phosphate level greater than 4.5 mEg/L
      2. risk factors
        1. renal failure
        2. chemotherapy
        3. large intake of milk
        4. excessive intake of phophate-containing laxatives, e.g.:
          1. fleets phosphosoda
        5. large vitamin D intake
        6. hyperthyroidism
      3. signs/symptoms
        1. short term consequences:
        2. symptoms of tetany, e.g.:
          1. tingling of the fingertips and around the mouth
          2. numbness
          3. muscle spasms
        3. long-term consequences:
          1. precipitation of calcium phosphate in nonosseus tissue sites, e.g.:
            1. kidneys
            2. joints
            3. arteries
            4. skin
            5. cornea
  10. Acid-base imbalances
    1. respiratory acidosis
      1. a primary excess of carbonic acid in the ECF
      2. cause of respiratory acidosis:
        1. decreased alveolar ventilation, e.g.:
          1. lung disease such as COPD
          2. central nervous system depression due to anesthesia or narcotic overdose
        2. consequent increase in carbon dioxide
      3. lab findings in respiratory acidosis:
        1. pH less than 7.35
        2. PaCO2 greater than 45 mm Hg
        3. HCO3-
          1. normal or slightly elevated in acute cases
          2. above 26 mEg in chronic cases
      4. to compensate for a respiratory acidosis:
        1. the lungs:
          1. unable to participate in compensation since they are the source of the problem
        2. the kidneys:
          1. retain more bicarbonate
          2. excrete more hydrogen ions
    2. respiratory alkalosis
      1. primary deficit of carbonic acid in the ECF
      2. cause of respiratory alkalosis:
        1. increased alveolar ventilation, e.g.:
          1. pyschogenic or anxiety-related hyperventilation
          2. fever
        2. consequent decrease in carbon dioxide
      3. lab findings in uncompensated respiratory alkalosis:
        1. arterial pH greater than 7.45
        2. PaCO2 less than 35 mm Hg
      4. to compensate for a respiratory alkalosis:
        1. the lungs
          1. unable to participate in compensation since they are the source of the problem
        2. the kidneys
          1. excrete more bicarbonate
          2. retain more hydrogen ions
    3. metabolic acidosis
      1. primary deficit of bicarbonate ions in the ECF
      2. cause of metabolic acidosis:
        1. increase in hydrogen ions and/or excessive loss of bicarbonate ions, e.g.:
          1. renal failure
          2. diabetic ketoacidosis or starvation when fat tissue is used for energy (forms acid ketone bodies as a by-product)
      3. lab findings in metabolic acidosis:
        1. pH less than 7.35
        2. PaCO2 greater than 38 mm Hg with respiratory compensation
        3. HCO3- less than 22 mmEg/L
      4. to compensate for a metabolic acidosis:
        1. the lungs
          1. increase the rate and depth of respiration to increase the excretion of carbon dioxide
        2. the kidneys
          1. retain more bicarbonate
          2. excrete more hydrogen ions
    4. metabolic alkalosis
      1. primary excess of bicarbonate ions in the ECF
      2. cause of metabolic alkalosis:
        1. excessive loss of hydrogen ions and/or increase in bicarbonate ions, e.g.:
          1. ingestion of bicarbonate of soda as an antacid
          2. prolonged vomiting with loss of HCL from the stomach
      3. lab findings in metabolic alkalosis:
        1. pH greater than 7.35
        2. PaCO2 greater than 45 mm Hg with respiratory compensation
        3. HCO3- greater than 26 mEg
      4. to compensate for a metabolic alkalosis:
        1. the lungs
          1. decrease the rate and depth of respiration to decrease the excretion of carbon dioxide
        2. the kidneys
          1. excrete more bicarbonate
          2. retain more hydrogen ions
  11. Assessing fluid and electrolyte imblances
    1. measure fluid intake and output
    2. daily weights
    3. monitor laboratory studies
      1. complete blood count
        1. increased hematocrit values
          1. dehydration
        1. decreased hematocrit values
          1. acute, massive blood loss
        1. increased hemoglobin values
          1. hemoconcentration of the blood
        1. decreased hemoglobin values
          1. anemia, severe hemorrhage
      1. serum electrolytes
      2. urine pH and specific gravity
      3. arterial blood gasses
        1. steps in reading arterial blood gasses
          1. determine whether the pH is alkalotic or acidotic
          2. determine the cause of the change of pH
            1. in respiratory acid-base imbalances, the pH and PaCO2 values are inversely abnormal (move in opposite directions)
              1. in respiratory acidosis:
                1. the pH is less than 7.35
                2. the PaCO2 is increased
                3. the HCO3- is normal
              1. in respiratory alkalosis:
                1. the pH is greater than 7.45
                2. the PaCO2 is decreased
                3. the HCO3- is normal
            1. in metabolic acid-base imbalances, the pH and HCO3- are both high or both low
              1. in metabolic acidosis:
                1. the pH is less than 7.35
                2. the HCO3- is decreased
                3. the PaCO2 is normal
              1. in metabolic alkalosis:
                1. the pH is greater than 7.45
                2. the HCO3- is increased
                3. the PaCO2 is normal
          1. determine if there is a compensatory attempt to return the pH to normal
            1. in respiratory acidosis:
              1. if the pH is less than 7.35
              2. if the PaCO2 is increased
              3. but the HCO3- is increased
                1. the kidneys are attempting to retain HCO3- to compensate
            1. in respiratory alkalosis
              1. the pH is greater than 7.45
              2. the PaCO2 is decreased
              3. the HCO3- is decreased
                1. the kidneys are attempting to excrete HCO3- to compensate
            1. in metabolic acidosis
              1. the pH is less than 7.35
              2. the HCO3- is decreased
              3. the PaCO2 is decreased
                1. the lungs are attempting to compensate by excreting CO2
            1. in metabolic alkalosis
              1. he pH is greater than 7.45
              2. the HCO3- is increased
              3. the PaCO2 is increased
                1. the lungs are attempting to compensate by retaining CO2
          1. determine if compensation has occurred
            1. compensation is absent if:
              1. the pH is abnormal
              2. one component is abnormal
              3. a second component within normal range
            1. compensation is partial if:
              1. the pH is abnormal
              2. one component is abnormal
              3. a second component is beginning to change
            1. compensation is complete if:
              1. the pH is within normal range
              2. one component is abnormal
              3. a second component is changed to move the pH within normal range
  12. Diagnosing
    1. fluid volume excess
    2. fluid volume deficit
    3. risk for fluid volume deficit
    4. risk for fluid volume excess
  13. Planning
    1. patient goals/expected outcomes:
      1. the patient will demonstrate fluid volume, electrolyte, and acid-base balance, as evidence by:
        1. maintaining an approximate balance between fluid intake and output
        2. maintaining serum electrolytes within normal range
        3. maintaining pH within normal range
        4. maintaining arterial blood gases within normal range
        5. maintaining a urine specific gravity within normal range
        6. maintaining body weight +/- 5 pounds of typical body weight
        7. reporting relief of symptoms of fluid, electrolyte, and acid-base disturbances (specify) after implementation of appropriate treatment
  14. Implementing
    1. developing a dietary plan
    2. modifying fluid intake
      1. increasing fluids
      2. restricting fluids
    3. administering medications
      1. mineral-electrolyte preparations
      2. diuretics
    4. admnistering intravenous therapy
  15. Evaluating
    1. evaluation strategies:
      1. did the patient maintain an approximate balance between fluid intake and output?
      2. did the patient maintain serum electrolytes within normal range?
      3. did the patient maintain pH within normal range?
      4. did the patient maintain arterial blood gases within normal range?
      5. did the patient maintain a urine specific gravity within normal range?
      6. did the patient maintain body weight +/- 5 pounds of typical body weight?
      7. did the patient report relief of symptoms of fluid, electrolyte, and acid-base? disturbances (specify) after implementation of appropriate treatment?

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This page was last modified on 1/1/03