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From Flashcardlet > Clinical Lab Med 4 > Flashcards

Clinical Lab Med 4 Flashcards

1
Q

What is the shorthand of the CBC?

A

WBC on left
Hg on top
Hct on bottom
pH on right

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2
Q

What is the short hand for the basic metabolic panel?

A 
Na on top left
K on bottom left
Cl on top middle
HCO3 or CO2 on bottom middle
BUN top line
Creatinine middle line
Glucose bottom line
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3
Q

What are two other names for the basic metabolic panel?

A

Chem 7, SMA 7

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4
Q

When is the basic metabolic panel ordered?

A

In almost every medical situation, along with the CBC

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5
Q

What does the basic metabolic panel measure?

A

Electrolyte levels

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6
Q

What precautions must be taken when drawing for a BMO?

A

Avoid contamination if patients are receiving IV fluids

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7
Q

What are the normal ratios of sodium and potassium, intra and extracellularly?

A

Na should be higher in the extracellular space and lower in the intracellular space
K should be lower in the extracellular space and higher in the intracellular space

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8
Q

What is the normal serum value of K in the ECF?

A

1.5-2%

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9
Q

What is the Na/K ratio maintained by?

A

Na-K pump

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10
Q

What does the ratio of extracellular to intracellular K establish?

A

Resting membrane potential of cells

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11
Q

What is the ratio of K essential for the function of?

A

Excitable tissues

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12
Q

What are three excitable tissues?

A

Nerve, skeletal and cardiac muscle

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13
Q

What kind of changes alter the membrane potential?

A

Changes in intra/extracellular K concentration

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14
Q

What does change in the membrane potential alter?

A

Alters the excitability of the tissues

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15
Q

What do the concentrations of K look like with a polarized cell?

A

10 inside the cell and 1 outside - difference in charge between intra/extracellular

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16
Q

What do the concentrations of K look like with a depolarized cell?

A

10 inside the cell and 5 outside - the difference between the charges get smaller

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17
Q

What do the concentrations of K look like with a repolarized cell?

A

10 inside the cell and 1 outside - difference in charges widen again

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18
Q

What organ is responsible for 90% of the total K excreted from the body?

A

Kidney

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19
Q

Where do we get potassium from?

A

Our diets

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20
Q

What is responsible for the excretion of the remaining 10% of K?

A

Stool and sweat

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21
Q

What are the four causes of hypokalemia?

A

Transcellular shifts
Inadequate intake of K
Extra-renal losses
Renal losses

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22
Q

What are three types of transcellular shifts?

A

Alkalemia
Insulin excess/acute glucose loads
Beta 2 agonists

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23
Q

How does alkalemia cause hypokalemia?

A

Alkalemia is an increased pH, therefore there are less H+ ions in the ECF
H+ moves out of the cell to decrease pH in ECF
To balance charges, K+ moves into the cell
This causes decreased K+ concentration in ECF

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24
Q

How does insulin excess or acute glucose loads cause hypokalemia?

A

Insulin picks up glucose in the blood and carries it into the cell - on the way insulin picks up a K+ too

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25
Q

How do beta 2 agonists cause hypokalemia?

A

Beta 2 agonists act in the flight or flight mechanism. They stimulate the uptake of K+ into the cell to increase the polarity of the cell, increasing the excitability of the tissues

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26
Q

What beta agonist is present in the heart?

A

Beta 1

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27
Q

What beta agonist is present in the lungs?

A

Beta 2

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28
Q

What beta agonist is present in the blood vessels?

A

Beta 2

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29
Q

What does a beta 2 agonist do to vessels and branches of the lungs?

A

Dilation - allows more oxygen to flood the cells

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30
Q

What is the normal range of potassium intake per day?

A

50-150 meq/day

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31
Q

What are two examples of extra-renal losses?

A

GI origin

Sweatin

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32
Q

How does a GI origin cause hypokalemia?

A

Vomiting, NG suction, diarrhea, and laxative abuse cause the loss of electrolytes

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33
Q

How does sweating cause hypokalemia?

A

Sweat is responsible for 10% of natural K loss

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34
Q

What are three types of renal losses leading to hypokalemia?

A

Loop or thiazide diuretics
Renal tubular acidosis
Hyperaldosteronism

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35
Q

How do loop or thiazide diuretics cause hypokalemia?

A

Extra excretion in urine

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36
Q

What is an example of a thiazide diuretic?

A

HCTZ - hydrochlorothiazide

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37
Q

What is an example of a loop diuretic?

A

Lasix

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38
Q

What is the relationship between K and aldosterone?

A

Inverse

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39
Q

How does hyperaldosteronism cause hypokalemia?

A

Increase aldosterone means decreased potassium

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40
Q

Why does aldosterone have an inverse relationship with K?

A

Aldosterone causes the body to hold onto Na+, which means we need to rid the body of another positive charge, K+ (decreases K+ concentration)

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41
Q

Where is aldosterone produced?

A

Adrenal cortex

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42
Q

What test can be used to determine the etiology of the hypokalemia?

A

24 hour urine measurement for potassium

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43
Q

What electrolyte do we also watch when we do a 24 hour urine collection?

A

Watch K and Na

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44
Q

What does sodium excretion of less than 100 meq/day suggest?

A

Inadequate intake of potassium and sodium

45
Q

What does sodium excretion greater than 100 meq/day and potassium excretion less than 25 meq/day suggest?

A

Extra-renal losses

46
Q

What does potassium excretion greater than 25 meq/day suggest?

A

Renal wasting of potassium

47
Q

How does a mild case of hypokalemia manifest?

A

Malaise
Fatigue
Neuromuscular disturbances - weak/hyporeflexia

48
Q

How does a severe case of hypokalemia manifest?

A

GI disorder
Cardiac arrhythmia
Paralysis

49
Q

What kind of GI disorders result from hypokalemia?

A

Constipation
Ileus
Vomiting

50
Q

What is an ileus?

A

No peristalsis moving an obstruction in the GI tract (No physical obstruction)

51
Q

What heart rate presents with hypokalemia?

A

Tachycardia - more excitable cardiac tissue due to hyperpolarization

52
Q

What are the arrhythmias that present with hypokalemia?

A

Ventricular tachycardia and Ventricular fibrillation

53
Q

What are some oral treatments for hypokalemia?

A

Potassium supplements given as potassium chloride (KCl)

54
Q

What form does KCl come in?

A

Liquid or slow release capsules and tablets

55
Q

Are dietary alterations sufficient to offset hypokalemia?

A

Most likely insufficient

56
Q

What is condition is possible with oral potassium supplementation, and what is necessary to screen for?

A

Severe hyperkalemia can result, K levels should always be monitored during therapy

57
Q

If you give a patient 40 of lasix, how much K should you also give them?

A

20 K

58
Q

How much does plasma K transiently rise by after a dose of 40-60 meq of potassium?

A

Can rise up to 1 - 1.5 meq/liter

59
Q

When is oral K supplementation not indicated for a patient with hypokalemia?

A

IV therapy is more appropriate more patients with severe hypokalemia, or patients who are unable to take oral supplements

60
Q

What is the amount of K in a typical potassium run?

A

10 meq/hr, up to 30-40 total

61
Q

Why is non dextrose solution needed to administer potassium IV?

A

Dextrrose may actually decrease plasma K through a response by insulin driving K into the cells

62
Q

What is the maximum amount of K that is able to be given to patients in very rare, life threatening hypokalemia cases?

A

Up to 100 meq/hr

63
Q

Where does a large does of K need to be administered (which port)?

A

Usually femoral vein - cannot be central line because introducing that much potassium close to the heart can stop the heart

64
Q

What symptom do patients complain of with IV K?

A

Burning veins - put a cool pack around the site of infusion

65
Q

What is the golden rule with introducing any substance to the body?

A

Start low, go slow - it is easy to give more, but difficult to correct if too much was given

66
Q

When should aggressive IV K be stopped?

A

Once the emergency situation has subsided - rapid replacement of K is dangerous

67
Q

What are four causes of hyperkalemia?

A

Redistribution of K from ICF to ECF
Potassium loads
Pseudohyperkalemia
Decreased renal excretion

68
Q

What are four ways that redistribution of K from ICF to ECF causes hyperkalemia?

A

Acidosis
Insulin deficiency
Beta 2 receptor blockade
Hyperosmolarity

69
Q

How does acidosis cause hyperkalemia?

A

Acidosis occurs with increased H+ levels ECF
H+ (from HCl) enters the cell to increase pH
K+ has to exit cell to balance charges

70
Q

Why doesn’t Cl from HCl enter the cell along with the H+ during redistribution in acidosis?

A

Cellular permeability to anions of mineral acids is low, so H+ moves relatively unaccompanied into the cell

71
Q

How does insulin deficiency cause hyperkalemia?

A

Usually insulin would come by and grab K along with glucose to enter the cell. Without enough insulin, the normal K+ molecules are left in the ECF

72
Q

How do beta 2 receptor blockers cause hyperkalemia?

A

A physical blocker impedes the epi/norepi/etc from reaching the beta 2 receptor, so the beta 2 receptor can’t stimulate the K+ uptake into the cell (which would cause increased excitability due to hyper polarization)

73
Q

What happens to the heart rate and force of contraction with beta blockers?

A

Slowed heart rate and decreased force of contraction

74
Q

How does hyperosmolarity cause hyperkalemia?

A

Hypertonic ECF results in water movement out of the cell, resulting in a relatively increased K concentration inside of the cell (because ECF is more diluted), creating an outward gradient

75
Q

What are two examples of potassium loads from an exogenous source causing hyperkalemia?

A

IV KCl administration

Blood transfusions

76
Q

How does a blood transfusion cause hyperkalemia?

A

Blood transfusions are full of packed red blood cells. As they enter through lines some cells break and release their intracellular K+ contents

77
Q

What are six examples of potassium loads from an endogenous source causing hyperkalemia?

A 
Rhabdomyolysis
Hemolysis
Tumor lysis
Burns
Major surgery
GI bleeding
78
Q

How does rhabdomyolysis cause hyperkalemia?

A

A crush injury resulting in the break down of muscle cells causes the release of K+ from the cell

79
Q

How does hemolysis or tumor lysis cause hyperkalemia?

A

K+ contents spill from lysed cells

80
Q

How do burns cause hyperkalemia?

A

Tissue destruction causes the break down of cells, therefore the release of K+ contents

81
Q

What is pseudohyperkalemia?

A

False report of hyperkalemia - levels appear high due to error

82
Q

What is an example of how pseudohyperkalemia can result?

A

RBC hemolysis - if the lab tech shook the collection tube too much and RBCs broke apart, causing the release of their intracellular K+ contents

83
Q

What are five examples of how decreased renal excretion causes hyperkalemia?

A 
Acute or chronic oliguric renal failure
Decreased distal nephron sodium delivery
Impairment of renin
Decreased aldosterone production
Impaired response to aldosterone
84
Q

How does acute or chronic oliguric renal failure cause hyperkalemia?

A

Not enough urine is produced, so the body is not excreting K

85
Q

When is decreased distal nephron sodium delivery seen?

A

Volume depletion

86
Q

How does the impairment of the renin angiotensin aldosterone system cause hyperkalemia?

A

The system results in the production of aldosterone, which causes the retention of Na in the cell, which causes K to be pumped out of the cell

87
Q

Describe the renin angiotensin aldosterone system

A

Kidney releases renin due to decreased BP
Liver releases angiotensinogin at all times
Renin and angiotensinogin combine to form angiotensin I
ACE turns angiotensin I to angiotensin II
Angiotensin II vasoconstricts - Increases BP
Angiotensin II also causes the release of aldosterone
Aldosterone causes the holding of Na and water, increasing volume and increasing BP

88
Q

What are two ways that the RAA system can be impaired?

A

Hyporeninemic and hypoaldosteronism

89
Q

What are two drugs that cause hypoaldosteronism?

A

ACE inhibitors - Angiotensin never turns from I to II

Angiotensin receptor blockers - II is made but doesn’t stimulate production of aldosterone

90
Q

What is an example of an impaired response to aldosterone causing hyperkalemia?

A

Use of K sparing diuretics like aldactone

91
Q

What is aldactone?

A

K+ sparing diuretic that prevents the build up of fluid by preventing the body from holding onto Na and therefore water. The body holds onto K+

92
Q

What drug combination might we give a heart patient so that their K concentrations are not disrupted?

A

Lasix (would decrease K)
Aldactone (would increase K)
The two cancel out the K concentration effects and help CHF patients keep fluid off

93
Q

What kind of neuromuscular manifestations present with hyperkalemia?

A

Weakness, paresthesias, areflexia

94
Q

What kind of cardiac arrhythmia manifestations present with hyperkalemia?

A

Bradycardia with a risk of V fib or cardiac arrest

95
Q

Why does hyperkalemia cause bradycardia?

A

ECF potassium concentration increases so the cell membrane is depolarized, and tissue excitability decreases

96
Q

What kind of ECG changes present with hyperkalemia?

A

Peaked T waves

Wide QRS complex

97
Q

What are some modalities for correcting hyperkalemia?

A

Shifting K from ECF to ICF

Reducing total potassium

98
Q

What does calcium administration do for a hyperkalemic patient?

A

Does not lower K concentrations, but temporarily antagonizes the cardiac and neuromuscular effects, stabilizing the heart and buying time

99
Q

How long do the effects of calcium administration last?

A

Effect occurs in minutes and lasts about one hour

100
Q

How can we treat hyperkalemia with a shift from ECF to ICF?

A

Administration of glucose/insulin

101
Q

What is a cation exchange resin?

A

Binds K in excahnge for another cation (Na) in the intestinal tract to remove K from the body

102
Q

What symptom presents with cation exchange resin?

A

Diarrhea

103
Q

What effect does a cation exchange resin have on Na concentrations?

A

Holds onto Na - need to be careful with patients who cannot tolerate Na loads

104
Q

When do we use cation exchange resins?

A

If hyperkalemia results from decreased K excretion or from increased K load

105
Q

What is an example of a cation exchange resin?

A

Kayexalate

106
Q

What is a procedure that can be used to treat hyperkalemia in excessive and extreme cases?

A

Hemodialysis - very effective, but only used in situations where more conservative methods have failed or are inappropriate

107
Q

What are some treatments for chronic hyperkalemia?

A

Dietary restriction

Loop diuretics or kayexalate

108
Q

What is the GFR of patients with renal failure that receive treatment for chronic hyperkalemia?

A

GFR of less than 10ml/min

109
Q

What is the dietary restriction for potassium?

A

40-60 meq/day

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