Med Surg - Fluid/Electrolyte Imbalances

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Med Surg - Fluid/Electrolyte Imbalances
2013-08-09 09:24:58
Electrolyte Fluid Imbalances Med Surg

Med Surg 2 Concorde Chapter 13
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  1. The three processes important to control normal fluid and electrolyte imbalances:
    • Filtration
    • Diffusion
    • Osmosis

    Note: these all occur in the in the intercellular spaces.
  2. The movement of fluid through a cell or blood vessel membrane because of hydrostatic pressure differences on both sides of the membrane
  3. Give an example of hydrostatic filtering force:
    Blood pressure; it moves whole blood from the heart to capillaries where filtration can occur to exchange water, nutrients and waste products and tissues.
  4. a "water-pushing" pressure; a force that pushes water outward from a confined space through a membrane
    Hydrostatic pressure
  5. How does edema develop in a patient with right-sided heart failure?
    • volume of blood on the right side of the heart increases greatly because the right ventricle is too weak to pump blood efficiently into the pulmonary blood vessels. 
    • blood backs up into venous system
    • venous hydrostatic pressure rises
    • capillary hydrostatic pressure rises until it is higher than the hydrostatic pressure of the interstitial space
    • as a result, excess filtration of fluid from capillaries into the interstitial space occurs, forming visible edema.
  6. The free movement of solutes across a permeable membrane from an area of high concentration to an area of lower concentration; DOWN a concentration gradient
  7. the concentration of molecules per volume of solution; the number of miliosmoles per liter of solution
  8. provides a measure of body fluid concentration and is reflected in the body's hydration status; the number of miliosmoles per kilogram of solution
  9. the movement of water only through a selectively permeable membrane
  10. The normal osmolarity value for plasma and other blody fluids ranges from:
    270 to 300 mOsm/L
  11. The body functions best when the osmolarity of fluids in all body spaces is close to
    300 mOsm/L
  12. Fluids with osmolarities greater than 300 mOsm/L are
  13. Fluids with osmolarities of less than 270 mOsm/L
  14. Fluid outside the cells is called
    • extracellular fluid; ECF
    • contains about 1/3 (15 L) of total body water
  15. The ECF includes:
    • interstitual fluid; also called third space fluid (blood, lymph, bone and connective tissue water
    • transcellular fluids; cerebrospinal fluid, synovial fluid, peritoneal fluid, and pleural fluid
  16. These processes act together at the capillary membrane to maintain both ECF and ICF volumes within their normal ranges:
    Osmosis and Filtration
  17. Electrolytes and their normal values:
    • Sodium (Na)      136-145 mEq/L
    • Potassium (K)    3.5-5.0 mEq/L
    • Calcium (Ca)      9.0-10.5 mg/dL
    • Chloride (Cl)      98-106 mEq/L
    • Magnesium (Mg) 1.3-2.1 mEq/L
    • Phosphorus (P)   3.0-4.5 mg/dL
  18. Reference range and significance of abnormal value for Sodium:
    • 136-145 mEq/L
    • elevated: Hypernatremia; dehydration; kidney disease; hypercortisolism
    • low: Hyponatremia; fluid overload; liver disease; adrenal insufficiency
  19. Reference range and signif. of abnormal value for Potassium:
    • 3.5-5.0 mEq/L
    • elevated: Hyperkalemia; dehydration; kidney disease; acidosis; adrenal insufficiencies; crush injuries
    • low: hypokalemia; fluid overload; diuretic therapy; alkalosis; insulin administration; hyperadoseronism
  20. Reference range, international recommended units and significance of abnormal value for Calcium:
    • 9.0-10.5 mg/dL
    • 2.25-2.75 mmol/L
    • elevated: Hypercalcemia; hyperthyroidism; hyperparathyroidism
    • low: hypocalcemia; vitamin D deficiency; hypothyroidism; kidney disease; excessive intake of phosphorus-containing foods and drinks
  21. Reference range and signif. of abnormal values for Chloride:
    • 98-106 mEq/L
    • elevated: Hyperchloremia; metabolic acidosis; respiratory alkalosis; hypercortisolism
    • low: Hypochloremia; fluid overload; excessive vomiting or diarrhea; adrenal insufficiency; diuretic therapy
  22. Reference range, international recommended units and significance of abnormal value for Magnesium:
    • 1.3-2.1 mEq/L
    • 0.65-1.05 mmol/L
    • elevated: hypermagnesemia; kidney disease; hypothyroidism; adrenal insufficiency
    • low: hypomagnesemia; malnutrition; alcoholism; ketoacidosis
  23. Reference range, international recommended units and significance of abnormal value for  Phosphorus:
    • 3.0-4.5 mg/dL
    • 0.97-1.45 mmol/L
    • elevated: Hyperphosphatemia; kidney disease; hypoparathyroidism; acidosis; hypocalcemia
    • low: Hypophosphatemia; chronic atacid use; hyperparathyroidism; hypercalcemia; vitamin D deficiency; alcoholism; malnutrition
  24. Normal Plasma Electrolyte Values for People Older Than 60 Years
    Reference Ranges

    •                60-90 years              >90 years
    • Ca          9.0-10.5 mg/dL       8.2-9.6 mg/dL
    • Cl           98-106 mEq/L         98-111 mEq/L
    • Mg           1.3-2.1 mEq/L        1.3-2.1 mEq/L
    • P            3.0-4.5 mg/dL        3.0-4.5 mg/dL 
    • Na         136-145 mEq/L        132-146 mEq/L
  25. Impact of Age related changes on Fluid Balance - Skin
    • loss of elasticity
    • decreased turgor
    • decreased oil production
    • result: skin becomes an unreliable indicator of fluid status, especially the back of the hand; dry, easily damaged skin
  26. Impact of age related changes on Fluid Balance - Kidney
    • decreased glomerular filtration
    • decreased concentrating capacity
    • result: poor excretion of waste products; increased water loss, increasing the risk for dehydration
  27. impact of age related changes on Fluid Balance - Muscular
    • decreased muscle mass
    • result: decreased total body water; greater risk for dehydration
  28. Impact of age related changes of Fluid Balance - Neurologic
    • diminished thirst reflex
    • result: decreased fluid intake, increasing the risk for dehydration
  29. Impact of age related changes of Fluid Balance - Endocrine
    • Adrenal atrophy
    • result: poor regulation of sodium and potassium, predisposing the patient to hyponatremia and hyperkalemia
  30. What trigger the sensation of thirst?
    a rising blood osmolarity or a decreasing blood volume
  31. Obligatory Urine Output: The minimum amount of urine per day needed to excrete toxic waste products:
    400 to 600 mL
  32. Water loss from skin, lungs and stool:
    insensible water loss
  33. Insensible water loss in a healthy adult is:
    • 500 to 1000 mL/day
    • this loss increases greatly during thyroid crisis, trauma, burns, states of extreme stress, and fever.
  34. Hormones that help control fluid and electrolye imbalance:
    • Aldosterone
    • Antidiuretic Hormone
    • Natriuretic Peptide
  35. Aldosterone
    • Hormone secreted by the adrenal cortex when sodium levels in the ECF are decreased
    • prevents both water and sodium loss
  36. Aldosterone Action
    • acts on the kidney nephrons; triggering them to reabsorb sodium and water from the urine back into the blood
    • this increases blood osmolarity and volume
    • prevents excessive kidney excretion of sodium
    • helps prevent blood potassium levels from becoming to high
  37. Antidiuretic hormone or vasopressin
    • produced in the brain
    • stored in the posterior pituitary gland
    • release from the posterior pituitary is controlled by the hypothalmus in response to changes in blood osmolarity.
  38. ADH action
    • acts directly on kidney tubules and collecting ducts, making them more permeable to water
    • more water is reabsorbed by the tubules and returned to the blood decreasing blood osmolarity by making it more dilute
  39. Hormones secreted by special cells that line the atria and ventricles of the heart
    Natriuretic Peptide
  40. Peptide secreted by the heart ventricular cells is called:
    BNP: brain natriuretic peptide
  41. Action of NP (Natriuretic Peptides)
    • secreted in response to increased blood volume and pressure
    • NP binds to receptors in the nephrons creating effects opposite of aldosterone
    • Kidney reabsorption of sodium is inhibited while glomerular filtration is increased; causing increased urine output
  42. What functions do the kidneys monitor:
    • blood pressure
    • blood volume
    • blood oxygen levels
    • blood osmolarity (related to Na concentration)
  43. Enzyme that converts angiotensinogen to angiotensin I
  44. Renin is secreted by the _____________:
    Kidneys; special cells in the kidney tubule in an area of the nephron known as the juxtaglomerular complex
  45. What is the triggering event that causes Renin to be secreted?
    • any change in the blood that indicates to the kidney that tissue and organ perfusion are at risk. ie.
    • Low blood pressure
    • Low blood volume
    • Low blood oxygen
    • Low blood Na level
  46. Renin-Angiotensin II Pathway
    Renin activates-------> Angiotensinogen: when activated is Angiotensin I----->Agiotensin I is acted on by ACE (angiotensin-converting enzyme)----> ACE converts Angiotensin I into Angiotensin II: most active form of Angiotensin I
  47. RAA pathway (renin-angiotensin-aldosterone)
  48. Angiotensin II starts several different activities that all work to increase blood volume and pressure. What are they?
    • 1. Causes constriction of arteries and veins throughout the body
    •   result: increased peripheral resistance & reduced size of vascular bed; raises blood pressure without adding blood volume
    • 2. Constrict the size of the arterioles that feed the kidney nephrons
    •   result: lower glomerular filtration rate & reduced urine ouput preventing further water loss which helps raise blood pressure
    • 3. Cause adrenal glands to secrete aldosterone
    •   result: kidneys reabsorb water and Na, preventing them from being excreted which allows more water and sodium to be returned to the blood increasing blood pressure and volume.
  49. What is the ultimate objective of the Renin-Aldosterone pathway?
    Maintenance of adequate tissue perfusion by increasing blood pressure and volume.
  50. Why is urine output used as an indicator of perfusion adequacy after surgery or invasive procedures?
    because the RAA pathway is greatly stimulated when a patient is in shock or stressed as in surgery.
  51. Three drug classes used to manage hypertension:
    • Diuretic drugs
    • ACE inhibitors
    • ARBs
  52. What are diuretic drugs used for?
    • hypertension management
    • they increase the excretion of Na so that less is present in blood, resulting in lower blood volume
  53. What are ACE Inhibitors used for?
    • hypertension management
    • disrupt the renin-angiotensin II pathway by reducing the amount of angtiotensin-converting enzyme (ACE) made so that less angtiotensin II is present.
    • with less angiotensin II present there is less vasoconstriction and peripheral resistence, less aldosterone production, and greater excretion of water. All leading to decreased blood volume and blood pressure.
  54. What are ARBs?
    • a class of drugs to manage hypertension
    • Angiotensin receptor blockers
    • they disrupt the renin-angiotensin II pathway by blocking the receptors that bind with angiotensin II so that the tissues cannot respond to it and blood pressure is lowered.
  55. Adaptive Actions to preserve perfusion during dehydration
  56. A weight change of 1 lb, corresponds to a fluid volume change of about _____ mL.
    500 mL
  57. Dehydration with water and electrolyte loss is called:
    • Isotonic Dehydration
    • most common type of fluid loss problem
  58. Decreased circulating blood volume is known as:
    • Hypovolemia
    • leads to inadequate tissue perfusion
  59. Physical Assessment for Dehydration - Cardiovascular changes
    • heart rate increases
    • weak peripheral pulses
    • decreased pulse pressure
    • decreased blood pressure
    • orthostatic or postural hypotension
    • light-headed or dizziness
    • neck vein distension in the supine position
    • neck veins flat when sitting
    • neck and hand veins are flat even when they aren't raised above heart level
  60. Physical Assessment for Dehydration - Respiratory Changes
    increased rate due to decreased blood volume reduces perfusion and oxygenation
  61. Physical Assessment for dehydration - Integumentary changes
    • assess for color, moisture and turgor
    • in older person check turgor over the sternum or on the forehead
    • check for tenting
    • oral mucous membranes will not be moist; may be covered with a thick sticky pastelike coating and may have cracks or fissures.
  62. Physical assessment for dehydration - Neurologic changes
    • confusion
    • low grade fever; temp over 102 for more than 6 hrs is especially at risk
    • for every degree Celsius increase above normal in body temp a minimum additional 500 mL is lost.
  63. Physical assessment for dehydration - Kidney changes
    • monitor urine output comparing total output with total fluid intake and daily weights
    • urine may be concentrated, with a spec. grav. of 1.030
    • urine color is dark amber with strong odor
    • output below 500 mL/day for any patient without kidney disease is cause for concern
    • Weigh patient same time each day; same scale
  64. The focus of management for the patient with dehydration is
    • to prevent injury
    • prevent further fluid losses
    • increase fluid compartment volumes to normal ranges
  65. Nursing priorities for patients with dehydration include:
    patient safety: monitor vitals, esp. heart rate and blood pressure. Pt. at risk for falls due to orthostatic hypotension, dysrhythmia, muscle weakness and possible confusion. Assess muscle strength, gait stability and alertness. Fall precautions.

    fluid replacement: mild to mod. dehydration is corrected with oral fluid replacement. Urge fluid intake and measure. Divide total amount needed by nurses shifts to avoid overload. Oral rehydration therapy.

    drug therapy: severe or life threatening dehydration requires  IV. Antidiahrreals, antiemetics, antipyretics, and antimicrobials may be used if caused diahrrea, vomiting, or fever.
  66. Causes of Fluid Overload:
    • Excessive fluid replacement
    • kidney failure
    • heart failure
    • long term corticorsteroid therapy
    • SIADH
    • water intoxicatioin
    • psychiatric disorders with polydipsia
  67. Expected Lab Values with Fluid Overload
    • normal serum electrolyte
    • decreased hemoglobin, hematocrit and serum protein levels.
  68. Expected Lab Values with Dehydration
    elevated levels of hemoglobin, hematocrit, serum osmolarity, glucose, protein, blood urea nitrogen and various electrolytes because more water is lost and other substances remain, increasing the osmolarity or concentration of blood (hemoconcentration)
  69. Indicators of fluid overload:
    • bounding pulse
    • increasing neck vein distention
    • presence of crackles in lungs
    • increasing peripheral edema
    • reduced urine output

    Note: check every two hours at least for these manifestations
  70. Hematocrit values:
    • Children 1-10 y/o: 31%-41%
    • Adult women: 38%-47%
    • Adult men: 40%-54%
    • Critical values: <15% or >60%
  71. Hemoglobin Values:
    • Adult men: 14-18 g/dL
    • Adult women: 12-16 g/dL
    • Critical Values: <5g/dL
  72. Blood Urea Nitrogen Values (BUN)
    • Adult: 5-20 mg/dL
    • Elderly: 8-21 mg/dL
    • Critical Values: >100 mg/dL
  73. Serum creatnine values:
    • Adult Male: 0.2-0.6 mg/dL
    • Adult Female: 0.6-1 mg/dL
    • Critical Values: 4 mg/dL
  74. Normal plasma ___________ level ranges from 3.5 to 5.0 mEq/L.
  75. A serum potassium level below 3.5 mEq/L.
  76. Common Causes of Hypokalemia
    • Drugs: diuretics, corticosteroids, digitalis
    • increased aldosterone secretion
    • cushing's syndrome
    • diarrhea and vomiting
    • wound drainage
    • prolonged nasogastric suction
    • heat-induced excessive diaphoresis
    • kidney disease impairing reabsorption of potassium
    • nothing by mouth
    • Alkalosis
    • hyperinsulinism
    • hyperalimentation
    • total parenteral nutrition
    • water intoxication
  77. A serum potassium level higher than 5.0 mEq/L.
  78. Common Causes of Hyperkalemia
    • over-ingestion of potassium containing foods or meds
    • transfusion of whole blood or packed cells
    • adrenal insufficiency (addison's disease, adrenalectomy)
    • Kidney failure
    • potassium sparing diuretics
    • ACE inhibitors
    • Tissue damage
    • acidosis
    • hyperuricemia
    • uncontrolled uricemia
  79. Assessment findings of hypokalemia:
    • Thready, weak irregular pulse
    • weak peripheral pulses
    • orthostatic hypotension
    • shall, ineffective respirations
    • diminished breath sounds
    • anxiety, lethargy, confusion, coma
    • skeletal muscle weakness, eventual flaccid paralysis
    • loss of tactile discrimination
    • paraesthesis
    • deep tendon hyporeflexia
    • decreased motility, hypoactive bowel sounds
    • nausea, vomiting, constipation, abdominal distention
    • paralytic ileus
  80. Assessment findings for Hyperkalemia
    • slow weak irregular heart rate
    • decreased blood pressure
    • skeletal weakness leading to respiratory failure
    • early: muscle twitches, cramps, paresthesias, and burning numbness in hands, feet and around mouth
    • late: profound weakness, ascending flaccid paralysis in the arms and legs (trunk, head and respiratory muscles become affected when the serum potassium level reaches a lethal level.
    • increased motility, hyperactive bowel sounds
    • diarrhea
  81. Common potassium food sources
    • avocado
    • bananas
    • cantaloupe
    • carrots
    • fish
    • mushroom
    • oranges
    • potatoes
    • pork, beef, veal
    • raisins
    • spinach
    • strawberries
    • tomatoes
  82. A mineral; major cation in the ECF; levels are 136 to 145 mEq/L
  83. Serum sodium level below 136 mEq/L
  84. Common causes of hyponatremia
    • excessive diaphoresis
    • diuretics (high-ceiling)
    • wound drainage
    • ↓ secretion of aldosterone
    • hyperlipidemia
    • kidney disease
    • low salt diet
    • nothing by mouth
    • cerebral salt wasting syndrome
    • hyperglycemia
    • nephrotic syndrome
    • heart failure
    • excessive ingestion of hypotonic fluids
    • psychogenic polydipsia
  85. A serum sodium level over 145 mEq/L
  86. Causes of hypernatremia
    • hyperaldosteronism
    • kidney failure
    • corticosteroids
    • cushings syndrom
    • excess oral sodium ingestion
    • nothing by mouth
    • increased metabolic rate
    • fever
    • hyperventilation
    • infection
    • excessive diaphoresis
    • watery diarrhea
    • dehydration
  87. Assessment findings for hyponatremia and hypernatremia
    see pg 89 in Saunders NCLEX book
  88. Common food sources of Sodium
    • Bacon
    • Butter
    • canned food
    • cheese
    • frankfurters
    • ketchup
    • lunch meat
    • milk
    • mustard
    • processed food
    • snack food
    • soy sauce
    • table salt
    • white and whole wheat bread
  89. The body functions best when blood _____ levels are maintained between 9.0 and 10.5 mg/dL.
  90. A total serum calcium level below 9.0 mg/dL