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NRS 250: Exam 1 > Module 3: Fluids and Electrolytes > Flashcards

Module 3: Fluids and Electrolytes Flashcards

1
Q

Total Body Water

A
  • ICF = 2/3, ECF = 1/3
  • ECF: Interstitial Fluid = 3/4, plasma 1/4
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2
Q

Total Body Water Percentages average male

A
  • 70 kg male
  • Total Body Water = 60%
  • ICF= 40%
  • ECF = 20%
  • Interstitial fluid = 15%
  • Plasma = 5%
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3
Q

weight conversion lbs to kg

A

1lb = 0.45kg

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4
Q

Total Body Water Estimates for average female

A
  • Total Body Water = 50% body weight
  • ICF = 33%
  • ECF = 17%
  • Interstitial Fluid = 12.75%
  • Plasma = 4.25%
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5
Q

Body Water Across the Ages

A
  • newborn infants: risk due to low body fat, high metabolism, increased SA for evaporation
  • All infants: risk due to low body weight, immature renal conservation of fluids
  • Older adults: risk due to declining renal function, increased water loss through skin, decreased thirst
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6
Q

Osmolality of the blood

A

~300mOsm/kg

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7
Q

Isotonic

A

0.9%NaCl

no change in cells

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8
Q

Aquaporins

A

allow water to move freely between ECF and ICF

  • increase in number in distal convoluted tubule due to ADH
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9
Q

What will happen to NET filtration if capillary permability increases?

A
  • decreased venous reabsorption and increased arterial filtration
  • loss of proteins from the blood will decrease capillary oncotic pressure and reduce reabsorption of fluid to the capillary
  • it will also increase oncotic pressure of the interstitium and increase filtration
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10
Q

Reabsorption

A

fluid re-enters blood/lymph in interstitium

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11
Q

Net Filtration Equation

A
  • Net filtration = [OUT] - [IN]
  • Net = [HPc + OPi] - [OPc + HPi]
    • there is always a net 1% left behind that gets reabsorbed into the lympatic system
  • Positive number? Filtration, more fluid entering the interstitium
  • Negative Number? Reabsorption into capillaries
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12
Q

Filtration

A
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13
Q

Hydrostatic vs Oncotic Pressure

A
  • Hydrostatic pressure: fluid pushed away from the source
  • Oncotic Pressure: pressure of proteins and solutes that draw fluid toward them
  • **these forces are also called Starling Forces**
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14
Q

Dependent Edema

A

fluid accumulaties in gravity dependent areas

  • standing = feet and legs
  • supine = sacrum, buttock
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15
Q

Swelling and fluid accumulation can:

A
  • limit nutrients, oxygen, and waste diffusion
  • limit blood flow = ischemia
  • cause pain due to increased pressure on nerves
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16
Q

**Most Common Mechanisms of Edema**

A
  1. increased capillary hydrostatic pressure
  2. increased capillary membrane permeability
  3. decreased capillary oncotic pressure
  4. lymphatic obstruction
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17
Q

Increased capillary hydrostatic pressure

A

Common mechanism of edema

  • venous obstruction, salt and water retention, heart failure
  • causes: fluid movement into the tissues
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18
Q

Increasesd capillary membrane permeability

A

Common mechanism of edema

  • burns, inflammation
  • causes: loss of plasma proteins to interstitial space
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19
Q

Decreased capillary oncotic pressure

A

common mechanism of edema

  • decreased syntehsis of plasma proteins (cirrhosis, malnutrition)
  • increased loss of plasma proteins (nephrotic syndrome)
  • increased plasma Na+ and H2O retention (dilution of plasma proteins)
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20
Q

Polydypsia

A

excessive thirst

  • common in diabetes mellitus
  • certain brain pathologies but psychogenic mechanism is unclear
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21
Q

Thirst is triggered by:

A
  1. high serum osmolality
    1. sensed by peripheral and central osmoreceptors
  2. Low blood pressure
    1. sensed by peripheral baroreceptors
  3. hormone and medication effects
    1. i.e. Angiotensin II
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22
Q

Natriuretic Peptides

A

Natriuretic = urine excretion of sodium

  • secreted by myocardial cells in atrai and ventricles
    • ex. during volume overload and heart failure
  • ANP and BNP
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23
Q

ANP and BNP

A

Natriuretic Peptides

  • secreted by the myocardial cells in atria and ventricles
  • Actions within the kidney:
    • inhibit secretion of renin, angiotensin II, aldosterone, and ADH
    • increases GFR by vasodilating the afferent arterioles
  • Result:
    • increased urine formation
    • decreased blood volume
    • decreased blood pressure
24
Q

Normal Function of Sodium

A
  • 90% of cations in ECF are Na+
    • determines osmolality of ECF
  • osmotic balance
  • electrical graidents
  • acid/base role
  • cellular reactions
  • transport mechanisms
25
Q

Normal Range of Sodium

A

135-145 mEq/L

26
Q

Causes of Hyponatremia

A
  • Low Sodium
  • water intoxication/dilution
  • sodium loss
  • inadequate intake
27
Q

What happens to the fluid compartments of hyponatremia

A
  • gain intracellular fluid , cells swell
  • water leaves the ECF, hypovolemia
28
Q

Causes of Hypernatremia

A
  • loss of water
  • gain of sodium
29
Q

What happens to the fluid compartments during hypernatremia?

A

loss of intracellular fluid, cells shrink

  • water moves into the ECF –> hypervolemia
30
Q

Normal Function of Potassium

A

K+ is the major intracellular electrolyte (high in cells, low in body)

  • intracellular osmolality
  • cells resting electrical potential
  • H+ and Na+ levels
  • Metabolic functions
  • Glycogen deposition in the liver and skeletal muscle
31
Q

Causes of hypokalemia

A
  • insulin related K+ cellular uptake
  • indaquate intake (rare but can happen in poor diet, alcoholism, anorexia nervosa)
  • redistribution of K+ due to acid/base imbalance (H/K shift)
  • GI and renal loss due to increased fluid flow
32
Q

Hypokalemia and cell excitability

A
  • low K+ in the ECF = more K+ gradient
  • resting membrane potential is hyperpolarized and less excitable
33
Q

Normal Levels of Potassium

A

3.5 -5.0 mEq/L

34
Q

Causes of Hyperkalemia

A

High levels of potassium

  • excessive intake (rare: ingestion of salt substitutes)
  • redistribution of K+ due to acid base
  • decreased renal excretion, renal failure
  • cellular trauma, expecially trauma to the muscles that releases potassium from inside the cell
  • insulin deficit especially when coupled with high intake of K+
    • insulin usually helps to bring K+ into the cells
35
Q

Hyperkalemia and cell excitability

A

high ECF K+ = less gradient

  • hyperexcitability followed by lack of depolarization
    • loss of “reset” membrane potential
36
Q

Why do we see fatigue with both high and low K+?

A
  • Low K+ = difficult to generate action potentials
  • High K+ = difficult to reset to get new action potentials
37
Q

Regulation of Potassium

A
  1. Cellular uptake of K+ (into ICF out of ECF)
    1. insulin
    2. aldosterone
    3. beta-adrenergic stimulation
    4. alkalosis (high blood pH, blood is too basic)
  2. Cellular release of K+ (from ICF to ECF)
    1. alpha-adrenergic stimulation
    2. acidosis
  3. Excretion:
    1. urine
    2. stool
    3. sweat
38
Q

Functions of Calcium

A
  • bone and tooth structure
  • co-factor for enzymes
  • cellular signaling pathway
  • plasma membrane stability
  • neurotransmitter release
  • muscle contraction
39
Q

Mechanisms of Hypocalcemia

A
  • inadequate dietary intake
  • removal of parathyroid gland, low PTH
  • vitamind D deficiency
  • bone metastasis (increased Ca2+ deposition)
  • pancreatitis (free fatty acids bind calcium)
  • high pH, alkalosis (less free Ca2+)
  • low albumin –> hypoalbuminemia
  • end-stage renal disease
40
Q

Mechanisms of Hypercalcemia

A
  • high PTH, PTH secreting tumor
  • bone metastases from breast, prostate, blood, cervical cancers
  • excess vitamin D
  • prolonged immobilzation (bone breakdown)
  • low pH, acidosis (more free Ca2+)
41
Q

Hypercalcemia and cell excitability

A
  • Calcium has a stabilizing effect on membrane voltage
  • higher threshold, decreased excitability
42
Q

Hypocalcemia and cell excitability

A
  • Calcium is a membrane voltage stabilizer
  • decreases the threshold, increases excitability
43
Q

Parathyroid hormone: Ca2+ and HPO42-

A

increases calcium, decreases phosphate

44
Q

Vitamin D: calcium and phosphate

A

increases calcium, increases phosphate

45
Q

Calcitonin and Calcium

A

decreases calcium

46
Q

Hormonal mechanisms of calcium and phosphate regulation

A
  • PTH: increases calcium, decreases phosphate
  • Vitamin D: increases calcium, decreases phosphate
  • Calcitonin: decreases calcium
47
Q

pH and Calcium Regulation

A
  • low pH (aciditic) increases ionization of calcium
    • more free Ca2+
  • high pH (basic) decreases ionization of calcium
    • less free Ca2+
48
Q

Phosphate as it relates to Calcium regulation

A
  • high levels of phosphate bind calcium (less free Ca2+)
  • excretion of phopshate increases free Ca2+
49
Q

Hyperphosphatemia is caused by:

A
  • low GFR/ renal function
  • breakdown of metastatic tumors
  • laxative abuse
  • low PTH
  • **Results in low serum calcium**
50
Q

Hypophosphatemia is caused by:

A
  • vitamin D deficiency
  • high antacid use
  • alcohol abuse
  • malabsorption syndromes
  • respiratory alkalosis
51
Q

Function and Location of Magnesium

A
  • intracellularly along with K+
  • cofactor in many enzymatic reactions
  • interacts with calcium and potassium channels
52
Q

Location and Function of Phosphate

A
  • 85% in the bone
  • intracellularly as inorganic phosphate
  • part of phospholipids and ATP
  • highly related to Calcium
53
Q

Normal Levels of Calcium in the body

A

9.0-10.5 mg/dL, ionized 5.5-5.6mg/dL

54
Q

Normal Levels of Magnesium

A

1.5-2.5mg/dL

55
Q

Normal Levels of Phosphate (HPO24-)

A

2.5-4.5

NRS 250: Exam 1 (11 decks)

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