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Liz's Clinical Chemistry Module 3 > Water and Electrolyte Balance > Flashcards

Flashcards in Water and Electrolyte Balance Deck (138)
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1
Q

4 factors which must be controlled in the human body to maintain homeostasis

A
  • Water balance b/w fluid compartments
  • Electrolyte balance
  • pH: 7.40
  • Temperature: 37°C
2
Q

All water w/in cell membranes; the medium through which CHEMICAL RXNS OF CELLULAR METABOLISM OCCUR

A

Intracellular fluid

3
Q

Major ions/constituents in intracellular fluid

A
  • Cations: K+ and Mg2+
  • Anions: protein, organic phosphates, sulfates
  • Low concentrations of: Na+, Cl-, HCO3-
4
Q

All water outside of cell membranes; the medium through which all METABOLIC CHANGES occur

A

Extracellular fluid

5
Q

Major ions/constituents in extracellular fluid

A

Interstitial fluid and plasma

6
Q

The directly measureable plasma is known as what?

A

Intravascular fluid (plasma)

7
Q

Major ions/constituents in intravascular fluid

A
  • Large amount of protein
  • High concentrations: Na+, Cl-
  • Moderate concentrations: HCO3-
  • Low concentrations: Ca2+, Mg2+, phosphate, sulfate, K+, organic acids
8
Q

Fluid that directly bathes the cells of body includes pericardial, pleural, peritoneal, and synovial body fluids; cannot be sampled for direct measurement

A

Interstitial fluid

9
Q

Major ions/constituents in interstitial fluid

A
  • High: Na+, Cl-
  • Medium: HCO3-
  • Low: NO proteins
10
Q

The force that tends to move water from dilute solutions to concentrated solutions

A

Osmotic pressure

11
Q

How do osmotic pressure differences maintain the composition of extracellular and intracellular fluids?

A

Predominance of K+ in the intracellular fluid and Na+ in the extracellular fluid PLUS plasma proteins that are the major contributors to the osmotic pressure b/w these compartments

12
Q

What maintains electroneutrality b/w compartments?

A

Gibbs-Donnan Equilibrium

13
Q

How does the Gibbs-Donnan equilibrium maintain the composition of extracellular and intracellular fluids

A

It maintains the electroneutrality b/w compartments by keeping the anion total equaling the total cations (the use of non-diffusable anions is important)

14
Q

3 chemical constituents that contribute to osmotic pressure differences b/w EXTRACELLULAR and INTRACELLULAR fluid compartments

A
  • K+
  • Na+
  • Plasma proteins
15
Q

3 means by which water balance is maintained b/w INTERSTITIAL and INTRACELLULAR fluid compartments

A
  • Membrane characteristics
  • Colloid osmotic pressure (COP)
  • NaK- ATPase pump
16
Q

How do passive transport differences maintain an equilibrium b/w intravascular and interstitial fluids, including importance of maintaining normal plasma protein concentrations in homeostasis?

A

?????

17
Q

How do colloid osmotic pressure differences maintain an equilibrium between intravascular and interstitial fluids, including importance of maintaining normal plasma protein concentrations in homeostasis?

A

Protein in the plasma causes water to move into the plasma from the interstitial fluid b/c there is no protein in the ISF. This movement is from colloid osmotic pressure

18
Q

How do hydrostatic pressure differences maintain an equilibrium between intravascular and interstitial fluids, including importance of maintaining normal plasma protein concentrations in homeostasis

A

Hydrostatic pressure from the heart causes fluid to move from the plasma into the interstitial fluid

19
Q

How do colloid osmotic pressure differences maintain an equilibrium between interstitial and intracellular fluids

A

Because there is protein in the cells and not in the interstitial fluid, water flows from the interstitial fluid to the cells due to osmotic pressure

20
Q

How do membrane characteristics (lipid solubility, size of solute, water permeability, and charge) maintain an equilibrium between interstitial and intracellular fluids

A

Permeability is directly related to lipid solubility and size and inversely related to the water solubility of the solute

21
Q

How does the NA-K-ATPase pump maintain an equilibrium between interstitial and intracellular fluids

A

The pump actively pumps sodium out of cells and pumps in K+ maintaining equilibrium

22
Q

Why is the NaK-ATPase pump necessary for water balance?

A

Keeps the water balanced b/w the interstitial and intercellular fluids

23
Q

NaK-ATPase pump movement of substances IN and OUT of the cell

  • Water?
  • Na+?
  • K+?
A
  • Water: out (follows Na+)
  • Na+: out
  • K+: in
24
Q

How does the hypothalamus regulate water balance?

A

Neurons shrink and hypothalamus signals need for water

25
Q

Four stimuli for both the water-intake and water-output areas of the hypothalamus

A
  • ↑ extracellular water osmolarity
  • Angiotensin II
  • ↓ in intravascular volume (leading to ↓ distension receptor activity)
26
Q

The effect of stimulation of both the water intake and water output areas of the hypothalamus

A
  • Water input: ↑ thirst

- Water output: ↑ ADH secretion from posterior pituitary

27
Q

The net effect of hypothalamic stimulation on water balance

A
  • Water input: ↑ free water intake

- Water output: ↓ free water output by kidney

28
Q

Primary stimulus for antidiuretic hormone (ADH) release

A

Increase in ECW osmolality

29
Q

Natriuretic peptides

- Two conditions that result in the release and increase in the blood

A

Secreted in response to intravascular volume expansion and defend against salt-induced CHF

30
Q

Natriuretic peptides

- Source and three physiological effects of atrial natriuetic peptide (ANP)

A
  • Source: cardiac atria

- Effects: reduce the increase in venous pressure, increases vascular permeability and promotes natriuresis and diuresis

31
Q

Natriuretic peptides

- Source and three physiological effects of brain natriuetic peptide (BNP)

A
  • Source: produced in cardiac ventricles

- Effects: cardiovascular, natriuretic, and diuretic effects similar to ANPq

32
Q

Natriuretic Peptides

- Three sources and one physiological effect of C-type natriuretic peptide (CNP)

A
  • Source: brain, vascular endothelial cells, renal tubules

- Effect: venous dilator

33
Q

What is the effect ADH has on the renal collecting ducts?

A

Stimulation of water output area of the hypothalamus causes pores of the collecting ducts to become more permeable to water (↑ water reabsorption)

34
Q

Causes of extracellular fluid loss

A
  • Trauma (and other causes of acute blood loss)
  • Burns
  • Pancreatitis, peritonitis
  • Vomiting, diarrhea, diuretics
  • Renal or adrenal disease taht causes salt wasting
35
Q

Causes for hypernatremic dehydration

A
  • Water and food deprivation
  • Diabetes insipidus
  • Excessive sweating
  • Osmotic diuresis association w/ glucosuria
  • Diuretic therapy
36
Q

Causes of extracellular fluid gain

A
  • Heart failure
  • Hepatic cirrhosis
  • Nephrotic syndrome
  • Intravenous fluid overload
37
Q

The most common cause of water intoxication

A

Extracellular fluid gain caused by syndrome of inappropriate ADH secretion (SIADH)

38
Q

Sodium reference range

A

136-145 mEq/L

39
Q

Four functions of sodium

A
  • Maintain normal H2O distribution
  • Maintain normal osmotic pressure
  • Neuromuscular processes
  • Acid-base balance
40
Q

Contrast diabetes and the syndrome of inappropriate ADH (SIADH) secretion according to ADH and sodium levels

A
Diabetes inspidus
- High urinary output
- Low levels ADH
- Hypernatremia
- Dehydrated
- Loss of too much fluid
SIADH
- Low urinary output
- High leevls of ADH
- Hyponatremia
- Overhydrated
- Retains too much fluid
41
Q

Sodium is a major ____ cation

A

Extracellular

42
Q

Three renal processes by which normal levels of sodium are maintained in the body

A
  • Kidneys-filtered in the glomeruli; reabsorption in the PCT, loops of Henle, and DCT
  • Aldosterone controls Na+ in DCT
  • BNP gets rid of Na+
43
Q

Depletional hyponatremia causes ____ hyponatremia

A

Absolute

44
Q

Two general causes of depletional hyponatremia

A
  • Renal loss

- Non-renal loss

45
Q

Two general causes of renal losses in depletional hyponatremia

A
  • Diuretic loss

- Hypoaldosteronism

46
Q

Two general causes of non-renal losses in depletional hyponatremia

A
  • GI loss

- Skin loss

47
Q

3 general causes of hyponatremia

A
  • Depletional
  • Dilutional
  • Pseudohyponatremia
48
Q

Dilutional hyponatremia is a ____ hyponatremia

A

Relative

49
Q

Two general causes of dilutional hyponatremia

A
  • SIADH

- Hyperglycemia

50
Q

Why does SIADH and hyperglycemia lead to increased water volume in dilutional hyponatremia?

A
  • ADH is secreted all the time, which causes use to retain H2O diluting Na+
  • Increased glucose in urine causes it to be diluted w/ H2O
51
Q

Two general causes of pseudohyponatremia

A
  • Hyperlipidemia

- Hyperproteinemia

52
Q

Why does hyperlipidemia and hyperproteinemia cause low sodium results in pseudohyponatremia?

A

Displaces some H2O, picks up more lipids or protein than plasma H2O

53
Q

Three general causes of hypernatremia due to water loss

A
  • GI losses
  • Excessive sweating
  • Diabetes insipidus
54
Q

Three general causes of hypernatremia due to sodium gain

A
  • Ingestion or infusion of Na+
  • Primary hyperaldosteronism (tumor)
  • Secondary hyperaldosteronism
55
Q

Two general causes of hypernatremia

A
  • Water loss

- Sodium gain

56
Q

Reference range of potassium

A

3.5-5.0 mEq/L

57
Q

Two functions of potassium

A
  • Regulation of many cellular processes

- Neuromuscular excitation (heart)

58
Q

Three general causes of hypokalemia

A
  • Increased cellular uptake
  • Increased renal loss
  • Excessive GI loss
59
Q

Why does excess insulin cause hypokalemia?

A

Too much glucose and potassium

60
Q

Why does alkalosis compensation cause hypokalemia?

A

Need more acid in bloodstream so RBCs push H+ ions into blood and take up more K+

61
Q

Four general causes of hypokalemia due to renal loss

A
  • Hyperaldosteronism
  • Diuretic theory
  • Licorice ingestion
  • Renal tubular acdiosis
62
Q

Three general causes of hypokalemia due to excessive gastrointestinal loss

A
  • Vomiting
  • Diarrhea
  • Laxative abuse
63
Q

Five general causes of hyperkalemia

A
  • Increased intake
  • Increased cell lysis
  • Altered cellular uptake
  • Impaired renal excretion
  • Pseudohyperkalemia
64
Q

Three causes of hyperkalemia due to increased intake

A
  • Txn of aged blood
  • Supplements
  • Bananas
65
Q

Three general causes of hyperkalemia due to increased in vivo cell lysis

A
  • Cellular trauma
  • Cellular injury
  • In vivo hemolysis
66
Q

Two general causes of hyperkalemia due to altered cellular uptake

A
  • Compensation for acidosis (H+ taken into cell, K+ pushed out = electroneutrality)
  • Insulin deficiency
67
Q

Two general causes of hyperkalemia due to impaired renal excretion

A
  • Renal insufficiency or failure

- Hypoaldosteronism

68
Q

Reference range of chloride

A

99-109 mEq/L

69
Q

Chloride is a major ____ anion

A

Extracellular

70
Q

Three functions of chloride

A
  • Maintains H2O balance
  • Maintains osmotic pressure
  • Acid-base balance w/ “chloride shift”
71
Q

Three general causes of hypochloremia and associated conditions

A
  • GI losses → prolonged vomiting, nasogastric suctioning
  • Burns → tissue trauma
  • Renal losses → diuretic therapy, compensation for metabolic acidosis
72
Q

Two general causes of hyperchloremia and associated conditions

A
  • Dehydration
  • Renal tubular acidosis → Na+ gain
  • Compensation for metabolic alkalosis
73
Q

REMEMBER: Cl- levels altered in same direction as Na+ = ____ ____

A

Water imbalance

74
Q

REMEMBER: Cl- levels not proportional to Na+ = ____ ____ ____

A

Acid-base imbalance

75
Q

Clinical usefulness of sweat chloride measurements

A

Sweat induced by pilocarpine iontophoresis; cystic fibrosis detected if >60 mEq/L and normal if <40 mEq/L

76
Q

Reference range of bicarbonate

A

22-28 mEq/L

77
Q

Function of bicarbonate

A
  • Levels regulated by the kidney
  • Decrease in metabolic acidosis
  • Increase in metabolic alkalosis
78
Q

Bicarbonate is the 2nd most important ____ anion

A

Extracellular

79
Q

Not all ions measured when electrolytes are performed so a gap exists because of contribution of unmeasured anions: protein, sulfate, phosphate, and organic acids

A

Anion gap

80
Q

Why is the anion gap an expected occurrence?

A
  • The body exists in a state of electroneutrality, but not all ions are “measured” when electrolytes are performed
  • The “gap” exists b/c of the contribution of unmeasured anions: protein, sulfate, phosphate, and organic acids
81
Q

Clinical purpose of anion gap calculation

A

To estimate unmeasured anions

82
Q

Laboratory purpose of anion gap calculation

A

Instrument error determines acceptability of results

83
Q

Expected range of anion gap using [(Na+K)-(Cl+HCO3)]

A

12-20 mEq/L

84
Q

Expected range of anion gap using [(Na)-(Cl+HCO3)]

A

8-16 mEq/L

85
Q

Three general causes of an increased anion gap and two conditions associated w/ each

A
  • Increased unmeasured anions → Lactic acidosis, ketoacidosis, toxic ingestion
  • Decreased unmeasured cations → decreased Ca2+ and Mg2+
  • Lab error → overestimation of Na+ or underestimation of Cl- or HCO3-
86
Q

Three general causes of a decreased anion gap and one condition associated w/ each

A
  • Decreased unmeasured anions → hypoalbuminemia
  • Increased unmeasured cations → K+, Ca2+, Mg2+, paraproteins
  • Lab error → underestimation of Na+, overestimation of Cl- or HCO3-
87
Q

Reference range of calcium

A

8.5-10.5 mg/dL

88
Q

Four functions of calcium

A
  • Decreases in neuromuscular excitability
  • Blood coagulation
  • Activator in enzymatic reactions
  • Transfer inorganic ions across cell membranes
89
Q

Three forms of Ca2+ in the blood

A
  • Bound
  • Filterable: ionized
  • Filterable: complexed
90
Q

Physiologically active form of Ca2+ in the blood

A

Filterable ionized

91
Q

Five factors that control serum Ca2+ levels

A
  • Absorbed in GI tract; alkali and presence of fat interferes w/ absorption
  • Parathyroid hormone (PTH) (↑ Ca2+)
  • Calcitonin (↓ Ca2+)
  • Vitamin D (↑ Ca2+)
  • Protein (ALB) levels
92
Q

Seven causes of hypocalcemia

A
  • Decreased serum protein (most common)
  • Hypoparathyroidism
  • Steatorrhea
  • Nephrosis
  • Pancreatitis
  • Vitamin D deficiency
  • Heparin during surgery
93
Q

Three causes of hypercalcemia

A
  • Metastatic bone disease (most common)
  • Multiple myeloma
  • Hyperparathyroidism
94
Q

List the most common cause of hypercalcemia

A

Metastatic bone disease (secondary to cancer of breast, lung, and kidney)

95
Q

Two reasons why profoundly decreased ionized Ca2+ levels may be fatal

A
  • Causes tetany, seizures, hypotension, ↓ cardiac function

- Enhances hyperkalemia = fibrillation and cardiac standstill

96
Q

Reference range of Mg2+

A

1.9-2.5 mg/dL

97
Q

Three functions of magnesium

A
  • Activator in enzymatic reactions (transfer/storage)
  • Crucial in cellular physiology
  • CHO, lipid, protein, and nucleic acid metabolism
98
Q

Two general causes of hypomagnesemia and two specific conditions associated w/ each

A
  • Impaired intake → malabsorption, malnutrition, diarrhea, alcoholism
  • Excessive renal loss → diuretics, hyperaldosteronism, and primary hyperparathyroidism
99
Q

Three general causes of hypermagnesemia

A
  • Renal failure
  • Magnesium intoxication
  • Treatment of toxemia of pregnancy (MgSO4 excess)
100
Q

Reference range of phosphorus

A

2.5-4.5 mg/dL

101
Q

Five functions of phosphorus

A
  • Major intracellular anion
  • Metabolism closely related to Ca2+
  • Intermediary metabolism
  • Component of phospholipids, nucleic acids, and ATP
  • Bone mineralization
  • Minor plasma buffer
102
Q

Five general causes of hypophosphatemia

A
  • RIckets
  • Hyperparathyroidism
  • Fanconi’s syndrome
  • Hemolytic anemia
  • Diabetes mellitus
103
Q

Four general causes of hyperphosphatemia

A
  • Glomerular renal failure
  • Hypervitaminosis D
  • Hypoparathyroidism
  • Bone repair
104
Q

of moles of solute particles dissolved/kg H2O (w/w soln)

A

Osmolality

105
Q

Reporting units for osmolality

A

mOsmol/kg H2O (w/w)

106
Q

Reporting units for osmolarity

A

mOsmol/L H2O (w/v)

107
Q

Three substances that have the greatest effect on serum osmolality

A

Na+, glucose, urea

108
Q

Clinical use of serum osmolality measruement

A

Determine the presence of “unmeasured substances” in blood

109
Q

Reference range for serum osmolality

A

280-300 mOsm/kg

110
Q

Seven conditions in which serum osmolality may be increased

A
  • Severe dehydration
  • Renal failure
  • Alcohols
  • Ethylene glycol
  • Ketone bodies
  • Lactic acid
  • Mannitol adminstration
111
Q

Clinical use of urine osmolality measurement

A

Assess renal concentrating and diluting ability

112
Q

Reference range of urine osmolality

A

300-1000 mOsm/kg

113
Q

Three specific conditions in which the urine osmolality is decreased

A
  • Diabetes insipidus
  • Polydipsia
  • Renal failure
114
Q

One specific condition in which the urine osmolality is increased

A

Syndrome of Inappropriate ADH Secretion (SIADH)

115
Q

Calculation for serum osmolality

A

(1.86 x Na+) + (BUN/2.8) + (Glucose/18)

116
Q

Calculation for osmolality gap

A

Measured serum osmolality minus calculated serum osmolality

117
Q

Three methods by which Na+ and K+ may be quantitated

A
  • Atomic absorption spectroscopy (reference method)
  • Flame photometry (old method)
  • Ion-selective electrodes (most common)
118
Q

Chloride Method Principle

- Chloride is able to displace thiocyanate from mercuric thiocyanate. The reacts w/ ferric iron to form a red complex

A

Colorimetric (mercuric thiocyanate and ferric nitrate)

119
Q

Chloride Method Principle

- Titration that is the reference method for chloride

A

Coulometric/amperometric

120
Q

Chloride Method Principle

- Most common today; uses a silver/silver chloride reference electrode

A

Ion-selective electrode

121
Q

Chloride Method Principle

- Based on determination of chloride-dependent alpha-amylase activity

A

Enzymatic (chloride method)

122
Q

Chloride Method Principle

- Pilocarpine iontophoresis

A

Sweat chloride (iontophoresis)

123
Q

Chloride Method Principle

- Purpose of reagents in the sweat chloride test

A

????

124
Q

What is the historical calcium precipitation method and two specific dyes used in the spectrophotometric method for measuring calcium

A
  • Historical method: was precipitation with oxalate (Clark and Collip method)
  • Spectrophotometric: o-cresolphthalein or arsenazo III
125
Q

Three reagents used in photometric magnesium methods

A
  • CalMAGite
  • Formazan
  • Methylthymol blue
126
Q

Reagent used in the most common phosphorus method

A

Photometric method
- Reaction of phosphate ions with ammonium molybdate, measured by UV absorption or reduction to the colored compound molybdenum blue

127
Q

Specimen and anticoagulant interferences for sodium method

A
  • Can analyze serum, plasma, whole blood, urine, or other
  • No Na+ in anticoagulant
  • Separate serum/plasma from cells w/in 3 hours
128
Q

Specimen and anticoagulant interferences for potassium method

A
  • Can analyze serum, plasma, whole blood, urine, or other
  • No K+ salt in anticoagulant
  • No hemolysis for K+
  • Separate serum/plasma from cells within 3 hours to prevent K+ leakage
129
Q

Specimen and anticoagulant interferences for chloride method

A
  • Serum or heparinized plasma

- Sweat chloride by pilocarpine iontophoresis

130
Q

Specimen and anticoagulant interferences for bicarbonate/total carbon dioxide method

A
  • Serum, heparinized plasma, or whole blood (usually blood gas specimen)
  • Handled anaerobically b/c loss of CO2
131
Q

Specimen and anticoagulant interferences for magnesium method

A
  • Serum or heparinized plasma

- NO HEMOLYSIS

132
Q

Specimen and anticoagulant interferences for calcium method

A
  • Serum or heparinized plasma
  • Promptly separate from cells to prevent uptake of Ca2+ by RBCs
  • CANNOT use anticoagulants such as EDTA, oxalate, or fluoride that chelates or precipitate calcium
133
Q

Specimen and anticoagulant interferences for phosphorus method

A
  • Serum or heparinized plasma
  • No EDTA or citrate or oxalate anticoagulatns as they interfere w/ formation of phosphomolybdate complex
  • NO HEMOLYSIS
  • Separate from cells promptly
134
Q

Electrolytes for which a hemolyzed specimen is NOT acceptable

A
  • K+
  • Mg2+
  • Phosphorus
135
Q

Intracellular cations/anions

- Rank in order of importance

A
  1. K+
  2. Magnesium
  3. Phosphorus
136
Q

Extracellular cations/anions

- Rank in order of importance

A
  1. Na+
  2. Bicarbonate
  3. Cl-
137
Q

When total body water is increased; serum sodium is decreased

A

ECF gain (overhydration, water intoxication)

138
Q

Symptoms of extracellular fluid gain

A
  • Weight gain
  • Edema
  • Dyspnea
  • Tachycardia
  • Jugular venous distension
  • Portal hypertension
  • Esophageal varices