Exam 3 (Electrolytes) Flashcards

1
Q

Cations vs Anions

A

Cations: positively charged particles
Anions: negatively charged particles

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2
Q

What are electrolytes?

A

Soluble substances (ions or minerals that have a charge) found in liquid serum or plasma

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3
Q

What are the general overall functions of electrolytes?

A

Coagulation, Energy production, cell metabolism, skeletal/cardiac muscle function, volume and fluid gradients between cells/blood/tissues

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4
Q

Humans are predominantly ______, making up ______% of body weight.

A

Water; 50-75%

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5
Q

Water % ______ with age.

A

Declines

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6
Q

Do women or men have less % water?

A

Women

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7
Q

Do obese people have less or more water than non-obese people?

A

Less

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8
Q

Intracellular fluid and % of total water

A

Fluid found inside of all cells - appx 66% of total water weight

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9
Q

Extracellular fluid + 2 groups; % of total water?

A

Fluid found outside of cells that can be broken into 2 groups:
Intravascular: found in vasculature; plasma portion of whole blood
Interstitial: fluid surrounding the cells

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10
Q

Active transport

A

Moves substances against concentration gradient and requires ATP

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11
Q

Passive transport

A

AKA diffusion; moves substances with the concentration gradient and requires no ATP

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12
Q

What is the major extracellular cation?

A

Sodium

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13
Q

What is largely responsible for the osmolality of plasma?

A

Sodium

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14
Q

What is the reference range for serum sodium?

A

135-145 mmol/L

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15
Q

How many Na ions are pumped out of the cell for every 2 K ions in the cell?

A

3 Na per 2 K

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16
Q

What is plasma sodium heavily regulated by?

A

water intake and loss of water through sweat and renal functions

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17
Q

If plasma sodium osmolality is high, what occurs?

A

Hypothalamic thirst centers in the brain drive increased water consumption and ADH is released to increase water reabsorption from urine

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18
Q

What is hyponatremia usually due to?

A

Increased sodium loss (decreased aldosterone, K deficiency)
Increased water retention (renal failure, nephrotic syndrome)
Water imbalance (excessive water intake, increased ADH)

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19
Q

What is a critical sodium level?

A

Hyponatremic <120 mmol/L

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20
Q

How are sodium levels regulated?

A

Water intake and water loss (aldosterone increases sodium reabsorption and ADH increases water reabsorption)

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21
Q

Signs and symptoms of Hyponatremia

A

GI distress, neurological symptoms (weak, headache, seizure, ataxia)

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22
Q

What is Hypernatremia caused by?

A

excessive water loss (diabetes insipidus, diarrhea, profuse sweating)
increased sodium retention (increased aldosterone)
Decreased water intake

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23
Q

Is Hypo or Hypernatremia more critical?

A

Hyponatremia

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24
Q

How can we detect sodium levels in the lab?

A

Serum/plasma (lithium heparin tube, green top) using Ion Selective Electrodes (ISE)

Can also test urine

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25
Q

Does hemolysis impact sodium levels? Why?

A

Not really because sodium is located outside of cells

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26
Q

Direct vs Indirect ISE

A

Direct ISE uses undiluted sample using whole blood
Indirect ISE uses diluted sample using plasma or serum

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27
Q

What is the major intracellular cation?

A

Potassium

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28
Q

Functions of potassium in the body

A

Regulation of neurons for action potentials, heart contractions, ICF volume, Hydrogen ion regulation, skeletal muscle contractions

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29
Q

How are potassium levels related to Sodium and Hydrogen ions?

A

If K ions decrease, ICF increases Na and H levels which decreases ECF levels of Na and H (leads to hyponatremia and alkalosis of blood pH)

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30
Q

What is the normal reference range for serum K?

A

3.5-5.1 mmol/L

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31
Q

What is potassium regulated by?

A

The renal system with tubular secretion and absorption (Nearly all K is reabsorbed in the PCT)

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32
Q

What are the 3 influences of potassium distribution between the ICF, ECF, and urine?

A

Na/K pumps, Insulin, and Catecholamines

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33
Q

How does exercise affect potassium levels?

A

Potassium is released from skeletal muscles during exercise due to firing multiple action potentials which could raise potassium levels greatly

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34
Q

Does hemolysis affect potassium levels?

A

Yes

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35
Q

What can hypokalemia lead to?

A

Decreased muscle contractions leading to paralysis and decreased HR

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36
Q

What can cause hypokalemia?

A

Renal dysfunction, cellular loss due to alkalosis or insulin overdose, decreased intake of fluid, gastrointestinal loss

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37
Q

What can hyperkalemia lead to?

A

Increased action potentials (cells are easier to excite) leads to muscle fatigue, paralysis, arrhythmia, death because muscle cells cannot repolarize properly

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38
Q

What are the causes of hyperkalemia?

A

Decreased renal excretion (renal failure)
Cellular shift (blood acidosis, hemolysis)
Increased intake
Collection error

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39
Q

How does improper collection affect potassium levels?

A

It can increase them because of increased hemolysis (cells release their contents into the blood stream)

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40
Q

Signs of hyperkalemia

A

Muscle weakness, tingling, numbness, because cells are not contracting appropriately – can lead to cardiac arrest

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41
Q

What is the most abundant extracellular anion?

A

Chloride

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42
Q

What is the function of Chloride?

A

Maintains osmolality, blood volume, electroneutrality between ECF and ICF, plays a role in regulating HCO3 and Na levels

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43
Q

What is the common route of elimination of chloride?

A

Via the kidneys and the skin as sweat

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44
Q

What is the reference range for Chloride levels in serum?

A

98-107 mmol/L

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45
Q

What is the chloride shift?

A

When bicarb leaves the RBC to buffer the blood pH, Cl goes into the RBC to maintain electrical charge

46
Q

What are chloride diseases similar to and why?

A

Sodium level diseases because chloride passively follows sodium

47
Q

What is the second most abundant extracellular anion?

A

Bicarbinate [HCO3]

48
Q

What does HCO3 play a role in ?

A

Regulating and transporting CO2 from tissues and blood to the lungs
Blood pH regulation

49
Q

Normal Serum HCO3 levels? This is identical to which levels?

A

22-29 mmol/L; identical to CO2 levels

50
Q

Blood Alkalosis: HCO3 levels, CO2 levels, leads to what

A

HCO3 levels increased, CO2 levels decreased, leads to the body increasing HCO3 secretion which increases H ions in blood and hypoventilation due to decreased CO2 levels

51
Q

Blood Acidosis: CO2 levels, HCO3 levels, leads to what

A

Increased CO2 levels, decreased HCO3 levels, leads to kidneys increasing HCO3 tubular reabsorption and increased H ion secretion which can cause hyperventilation due to increased CO2

52
Q

What type of conditions are ideal for CO2 samples?

A

Anaerobic because if sample is uncapped, CO2 can evaporate and decrease

53
Q

Two most common ways to measure pCO2 in lab

A

ISE and enzymatic methods

54
Q

Calcium is predominantly stored where? Where is the remainder?

A

Bone; remainder is an extracellular cation in ECF

55
Q

Disease associated with increased HCO3?

A

Blood alkalosis

56
Q

Disease associated with decreased HCO3?

A

Blood acidosis

57
Q

What is the mean ionized Ca level?

A

1.18 mmol/L

58
Q

Calcium levels are vital for?

A

cardiac/skeletal contractions, coagulation cascade function, and neuronal firing

59
Q

Where can calcium be in the blood?

A

Freely circulating as ionized calcium, bound to albumin/proteins, or bound to anions like HCO3

60
Q

How is calcium regulated in the body?

A

PTH increases blood calcium by acting on bone resorption and the kidneys (tubular reabsorption of Ca), Vitamin D increases blood Ca to enhance PTH effect

Calcitonin decreases blood Calcium levels by inhibiting PTH and Vitamin D for bone remodeling. Increases renal excretion of Calcium

61
Q

T/F: Blood ionized calcium levels in neonates are usually higher at birthday and rapidly decline after 1-3 days.

A

True

62
Q

What is hypocalcemia caused by?

A

Hypoparathyroidism, Vitamin D deficiency

63
Q

Signs/Symptoms of hypocalcemia

A

Neurological, muscular, cardiac issues and coagulation issues

64
Q

What is hypercalcemia due to?

A

Hyperparathyroidism, Increased vitamin D

65
Q

How can improper collection of ionized calcium affect results?

A

Increased pH due to decreased CO2 in the tube will decrease ionized calcium as calcium binds to albumin

66
Q

How is total calcium vs ionized calcium measured in the lab?

A

Total calcium measured by CPC
Ionized calcium measured by ISE

67
Q

What is the second most abundant intracellular cation?

A

Magnesium

68
Q

Where is Mg stored?

A

Mostly in bone and muscle, and a trace amount found in RBCs and blood

69
Q

Reference range for serum Magnesium

A

0.66-1.07 mmol/L

70
Q

Function of magnesium

A

Functions as an essential cofactor for many enzymes involved in processes like glycolysis, cell signaling, metabolism

71
Q

How is magnesium regulated?

A

Magnesium is predominantly acquired from dietary sources and regulated by the kidneys where reabsorption occurs in the PCT and loop of Henle

72
Q

What can cause hypomagnesemia?

A

Often seen in hospitalized patients in ICU due to increased excretion (kidney disorders), decreased absorption, decreased intake, and pregnancy

73
Q

Signs of hypomagnesemia

A

Most asymptomatic until Mg levels drop below 0.5 mmol/L

74
Q

What is hypermagnesemia caused by?

A

Very rare condition but most commonly caused by renal failure (GFR less than 15 mL/min)

Can also be caused by decreased excretion, increased intake, bone cancer, dehydration

75
Q

How do we test for magnesium in the lab?

A

Colorimetric methods for total serum Mg using calmagite and formazan dye that form red complex and read at 532 and 660nm. Mg is greatly affected by hemolysis because it is an intracellular ion.

76
Q

What is the predominant intracellular anion?

A

Phosphorous/Phosphate

77
Q

Where is phosphate/phosphorous predominantly found in the body?

A

Bone, soft tissue, and then serum/plasma

78
Q

What is the function of phosphate?

A

Major anion involved in many metabolic processes and genetic material (DNA and RNA’s backbone)

79
Q

Reference range for serum phosphate levels in adults

A

0.81-1.45 mmol/L (lower than children)

80
Q

How is phosphate regulated?

A

The kidneys, vitamin D, and PTH.
(High PTH lowers phosphate levels in exchange for calcium)
(High vitamin D increases phosphate levels and calcium levels)

81
Q

What is hypophosphatemia caused by?

A

Usually a complication of DKA, COPD, cancer, IBS, alcoholism
Hyperparathyroidism
Vitamin D deficiency

82
Q

What is hyperphosphatemia caused by?

A

Renal disease
Hypoparathyroidism
Increased vitamin D

83
Q

How do we test for phosphorous in the lab?

A

Formation of ammonium phosphomolybdate complexes using PO4 from patient that are read at 340 and 600-700 nm

84
Q

Does hemolysis affect phosphorous levels?

A

Yes because it is intracellular.

85
Q

When are lactate levels higher in the body? Why?

A

During strenuous exercise or hypoxic situations. This occurs because in these situations, NADH accumulates faster than NAD+ causing excess H ions in the blood and favor the reaction of pyruvate into lactate and lactic acids

86
Q

How is lactate regulated in the body?

A

There is no formal regulation because it is a byproduct of hypoxic conditions. When oxygen levels are low, lactate levels increase in tissue creating muscle fatigue and weakness.

87
Q

How is lactate removed from the body?

A

The liver removes excess lactate in the blood by converting it back to glucose via gluconeogenesis

88
Q

Type A lactic acidosis

A

Hypoxic conditions that increase lactic acid like MI, CHF, pulmonary edema

89
Q

Type B lactic acidosis

A

metabolic conditions that increase lactic acid like diabetes mellitus, infections, leukemia, liver diseases, and toxins

90
Q

How is lactate measured in the lab?

A

Coupled enzymatic reactions that may be read spectrophotometrically to assess color change intensity

91
Q

What is the anion gap?

A

The difference between unmeasured anions and unmeasured cations

92
Q

The anion gap uses _______ ions to determine increased or decreased ______ ions.

A

measured; unmeasured

93
Q

What is an increased anion gap caused by?

A

Increased unmeasured anions such as PO4, SO4, ketones, methanol, ethanol, ethylene glycol, aspirin, lactic acid

94
Q

What is a decreased AG caused by?

A

Decreased unmeasured anions (hypoalbuminemia) or increased unmeasured cations (hypercalcemia or hypermagnesemia) very rare.

95
Q

What are the measured ions in the anion gap?

A

K, Na, Cl, HCO3

96
Q

What is the formula for anion gap?

A

AG = (cations) - (anions)
so, AG = (Na + K) - (Cl + HCO3)

97
Q

What is reference range for anion gap?

A

10-20 mmol/L

98
Q

Osmolality

A

moles per kg of water

99
Q

How is osmolality measured in the lab (most commonly)?

A

Freezing point depression

100
Q

Osmolarity

A

moles per L of water

101
Q

Excessive water intake will ______ plasma osmolality.

A

Decrease

102
Q

Decreased water consumption will ______ plasma osmolality.

A

Increase

103
Q

Loss of ADH production

A

Neurogenic

104
Q

Loss of ADH response

A

Nephrogenic

105
Q

What does the RAAS system respond to? What does the RAAS system ultimately stimulate?

A

Decreased blood volume. It ultimately stimulates vasoconstriction, release of ADH, and release of aldosterone to increase blood volume and blood pressure.

106
Q

Describe the RAAS system:

A

Renin secreted from kidneys in response to decreased blood volume/pressure (hyponatremia). Renin stimulates angiotensinogen to angiotensin I. Angiotensin I travels to the lungs where ACE converts Angiotensin I into Angiotensin II which causes vasoconstriction, ADH and aldosterone release.

107
Q

What does AVP and ANP do?

A

Work to decrease blood pressure/volume (found in the heart). Opposite system than RAAS

108
Q

What is the formula for osmolality?

A

2 Na + glucose/20 + BUN/3

109
Q

What is the formula for osmolal gap?

A

295 (which is normal osmolality value) - osmolality value calculated

110
Q

What impact would diabetes insipidus have on Na levels and why?

A

Diabetes insipidus patients lose more water in urine due to defective ADH leading to increased sodium levels in the blood.

111
Q

Which cation functions to regulate skeletal and heart muscle contraction?

A

Calcium and potassium

112
Q

What are 3 sources of error with potassium testing?

A

hemolysis, prolonged tourniquet use, and excessive exercise