Fluids and Electrolytes Flashcards

1
Q

What proportion of body weight is water?

A

45-65%

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2
Q

____________ ________ comprises two-thirds of water weight.

A

Intracellular fluid

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3
Q

Extracellular fluid makes up ____-______ of water weight.

A

One-third

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4
Q

_________ is one quarter, and interstitial fluid is three quarters of the extracellular fluid.

A

Plasma

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5
Q

Extracellular fluid loss may be due to acute ______ _____, vomiting, and diarrhoea.

A

Blood loss

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6
Q

State two ways by which extracellular fluid can be gained.

A

IV fluid overload and heart failure

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7
Q

What is the homeostatic response of changes in extracellular fluid?

A

Changes in plasma volume, or osmotic concentrations

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8
Q

The concentration of solutes per kilogram of solvent (mOsm/kg H2O) is ____________.

A

Osmolality

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9
Q

‘Normal’ plasma osmolality is 2__ - 295 mOsm/kg.

A

85

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10
Q

__________ osmolality is from 300 - 900 mOsm/kg.

A

Urine

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11
Q

_________, and its associated anions, account for most of the osmotic activity of plasma.

A

Sodium

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12
Q

___________ is regulated by changes in water balance.

A

Sodium

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13
Q

___________ is regulated by changes in sodium balance.

A

Volume

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14
Q

Measurement of osmolality is done by osmometer, and based on freezing point or ___________ ______________.

A

Vapour depression

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15
Q

State the formula for calculated osmolality.

A

2 x [Na+] + [urea] + [glucose]

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16
Q

__________ _____ are caused by the difference between measured and calculated osmolality.

A

Osmolal gaps

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17
Q

Osmolality - ___________ ___________ = osmolal gap

A

Calculated osmolality

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18
Q

GFR Increases with volume expansion, and decreases with volume ___________.

A

Depletion

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19
Q

What is the role of atrial natriuretic peptide?

A

Promotes sodium excretion by the kidney

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20
Q

True or false: in water excess, ADH secretion and thirst are suppressed.

A

True

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21
Q

Hypernatraemia occurs during _______ ___________.

A

Water depletion

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22
Q

___________ dehydration can be caused by GI losses, inadequate fluid intake, etc..

A

Isotonic

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23
Q

___________ dehydration results from diuretic drugs, osmotic diuresis, etc..

A

Hypertonic

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24
Q

__________ dehydration can be derived from GI losses, and high-sodium sweat (as seen in cystic fibrosis).

A

Hypotonic

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25
Q

Give two causes of high osmolality.

A

Hyperglycaemia and increased urea

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26
Q

______________ are ions that are capable of carrying an electric charge, and may be positive or negative.

A

Electrolytes

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27
Q

List four functions of electrolytes.

A

Volume and osmotic regulation (Na, K, and Cl)

Acid-base balance (HCO3, K, Cl)

Neuromuscular excitability (K, Ca, and Mg)

Myocardial rhythm and contractility (K, Mg, and Ca)

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28
Q

True or false: electrolytes are often measured in conjunction with sodium and urea.

A

True

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29
Q

What is the plasma reference range for sodium?

A

135 - 145 mmol/L

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30
Q

Hyponatraemia is decreased plasma _________.

A

Sodium

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31
Q

Increased sodium loss may be due to _______________, potassium deficiency, diuretic use, ketonuria, prolonged D&V, or salt-losing nephropathy.

A

Hypoadrenalism

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32
Q

__________________ may be due to hyperlipidaemia, or hyperproteinaemia.

A

Pseudohyponatraemia

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33
Q

_______________ hyponatraemia may be attributed to sodium loss and water retention.

A

Hypoosmotic

34
Q

Isosmotic hyponatraemia is due to increased non-__________ cations, and may be observed in pseudohyponatraemia.

A

Sodium

35
Q

______________ hyponatraemia involves increased amounts of other solutes in the plasma.

A

Hyperosmotic

36
Q

_________________ is increased plasma sodium (>146 mmol/L).

A

Hypernatraemia

37
Q

True or false: hypernatraemia is always hyperosmolar.

A

True

38
Q

Increased intake or retention, such as _________________, or sodium bicarbonate excess, is also a factor of hypernatraemia.

A

Hyperaldosteronism

39
Q

<300 mOsm/kg may be observed in ____________ ____________.

A

Diabetes insipidus

40
Q

300 - 700 mOsm/kg indicates a ________ defect in ADH, osmotic diuresis, etc..

A

Partial

41
Q

> 700 mOsm/kg indicates a loss of thirst, insensible loss of water, GI loss of ____________ fluid, and excess intake of sodium.

A

Hypotonic

42
Q

__________ syndrome involves excessive aldosterone.

A

Conn’s

43
Q

Cushing’s syndrome involves __________________.

A

Hypercortisolism

44
Q

True or false: lipaemia interferes with flame emission spectrophotometry.

A

True

45
Q

True or false: heparinised samples are not suitable for use in sodium measurement.

A

False

46
Q

Name a common electrochemical method of measuring electrolytes.

A

Iron selective electrodes (ISE)

47
Q

Outline the principle of iron selective electrodes.

A

Measures activity of electrolytes, in a defined volume of water. Charges are produced by having different ion concentrations on either side of the membrane. Two electrodes, a reference electrode and measuring electrode, are used. The difference in potential between electrodes is a reflection of the difference in ion activity, and is used to calculate a concentration, in mmol/L. Direct ISE uses an undiluted sample; indirect ISE used a diluted sample

48
Q

___________ ISE measurement is more accurate in pseudohyponatraemia, when hyperproteinaemia or hyperlipidaemia displace plasma water.

A

Direct

49
Q

State the principle of flame emission spectrophotometry.

A

When atoms of many metallic elements, especially Na and K, are given sufficient energy, they emit this energy at wavelengths; the energy comes from a flame, which excites the element, and they emit characteristic spectra

50
Q

Potassium is a major intracellular _________ in the body.

A

Cation

51
Q

lThe ___________ reference range of potassium is 3.5-5.0 mmol/L.

A

Serum

52
Q

What is the urine reference range for potassium?

A

30-100 mmol/day

53
Q

Potassium has major effects on contraction of skeletal and cardiac muscles, together with ________ ___________ ____________.

A

Resting membrane potential

54
Q

True or false: H+ concentration is not affected by potassium.

A

False

55
Q

______________ increases K+ excretion.

A

Aldosterone

56
Q

List two features, other than aldosterone, which regulate potassium secretion.

A

Insulin and pH

57
Q

True or false: hyperkalaemia is the most common electrolyte disturbance detected.

A

True

58
Q

List three symptoms of hyperkalaemia.

A

Mental confusion, bradycardia, and weakness

59
Q

Outline the first-used treatment for hyperkaelamia.

A

Infusion of insulin and glucose, to move potassium into cells

60
Q

State three causes of hyperkalaemia.

A

Renal failure, hypoaldosteronism, and use of diuretics.

61
Q

Sample haemolysis or _______________ may cause artifacts to appear in hyperkalaemia investigation.

A

Thrombocytosis

62
Q

Define hypokalaemia.

A

Serum potassium concentration of <3.5 mmol/L

63
Q

Symptoms of _____________ involve muscle weakness, irritability, and paralysis.

A

Hypokalaemia

64
Q

Pseudohypokalaemia may be observed in acute ______________.

A

Leukaemia

65
Q

List two causes of true potassium deficit.

A

Cushing’s disease and acute tubular necrosis

66
Q

What is the treatment for hypokalaemia?

A

Potassium salts, and occasionally IV potassium

67
Q

True or false: serum levels of potassium tend to be lower than those of plasma.

A

False

68
Q

What is the method of choice in measuring potassium?

A

Iron selective electrodes

69
Q

____________ is the most abundant anion in extracellular fluid.

A

Chloride

70
Q

What is the serum (and plasma) reference range for chloride?

A

97-107 mmol/L

71
Q

What is the urine reference range for chloride?

A

110-250 mmol/day

72
Q

Changes in chloride concentration usually follow those of ______________.

A

Sodium

73
Q

If an _______-_______ ______________ is present, chloride can differentially diagnose.

A

Acid-base disturbance

74
Q

What specimen is used in testing the chloride of cystic fibrosis patients?

A

Sweat

75
Q

State a method of chloride quantification, other than iron selective electrodes.

A

Mercurimetric titration

76
Q

What is the chemical formula for bicarbonate?

A

HCO3-

77
Q

Bicarbonate is the second-most common _______ in extracellular fluid.

A

Anion

78
Q

What is the reference range (for serum and plasma) for bicarbonate?

A

24-27 mmol/L

79
Q

True or false: bicarbonate is most accurately quantified when the sample has been incubated at room temperature for one hour.

A

False

80
Q

To measure total CO2 (and thus bicarbonate), if the sample is _____________, CO2 is converted to HCO3-, followed by an enzymatic reaction.

A

Alkalinised

81
Q

CO2
converted to HCO3
-
followed by an enzymatic reaction

A