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Week 2 > Pathophys: Electrolyte Disturbance Na And K > Flashcards

Pathophys: Electrolyte Disturbance Na And K Flashcards

1
Q

60-40-20 Rule

A

Total body water = 60%
Of that… 40% Intracellular
20% extracellular

Of the extracellular
75% = Interstitial fluid
25% = plasma

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2
Q

Osmolality

A

The solute or particle concentration of a fluid

H2O diffuses across most cell membranes to achieve osmotic equilibrium

ECF osmolality = ICF-osmolality

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3
Q

Electrolyte solute compositions differ due to differences in….

A

Membrane permeability, activity of transporters, channels, and ATP driven pumps

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4
Q

Compartment restriction determines the ________

A

Toxicity or effective osmolality

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5
Q

Major ECF solutes include:

A

Na+
Cl-
HCO3-

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6
Q

Major ICF solutes include

A

K+ and ATP

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7
Q

Excreted solute

A

Organic waste and excess electrolytes

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8
Q

Main way the body controls water excretion in normal circumstances is to control__________

A

Urine osmolality

Electrolyte excretion is highly regulated

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9
Q

Regulation of water excretion (and urine osmolality) is _________ is solute excretion

A

Independent

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10
Q

ADH secretion is controlled by:

A

Osmoreceptors

Baroreceptors

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11
Q

Osmoreceptors

A

Neurons responsive to change in osmolality
Located in tissues surrounding the cerebral third ventricle
Shrink and swell in response to changes in local osmolality

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12
Q

Baroreceptors

A

Located in aortic arch and carotid arteries

Respond to changes in pressure

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13
Q

ADH is made in the ________ and stored in the __________

A

Made in the hypothalamus and stored in the posterior pituitary

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14
Q

ADH regulates these 2 things…

A

Plasma Osmolality

Blood pressure

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15
Q

How does ADH regulate plasma osmolality?

A 
Osmoreceptors detect changes in plasma osmolality
ADH release
V2 receptors in principle cells
Regulation of AQP2 H20 channels via Gs
H2O reabsorption/secretion
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16
Q

How does ADH regulate blood pressure?

A

Baroreceptors detect changes in volume
V1 receptors in VSM
Regulation of vascular tone
Changes in total peripheral resistance

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17
Q

What is the major cation in ECF?

A

Na+

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18
Q

Normal plasma Na+ values?

A

135-145 mEq/L

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19
Q

What is the normal plasma osmolarity?

A

285-295 mOsm/kg

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20
Q

Primary goal of regulating Na and H2O excretion?

A

Support the requirements of the cardiovascular system

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21
Q

Na disturbances are caused by changes in total body ________, not changes in Plamsa Na

A

H2O

22
Q

Disorders of plasma Na+ concentration are caused by _______

A

H2O homeostasis

Changes in the relative ratio of Na+ to body water

23
Q

Na+ value of hyponatremia

A

Na <135

Seizure threshold: 125
Life threatening: 120

24
Q

What happens to the cell in hyponatremia?

A

Osmotic water shift into the cell
Increase ICF volume
Cellular swelling

25
Q

Clinical features of Hyponatremia?

A

Nausea, eyes is, headache, malaise, lethargy, irritability, muscle twitching, weakness, hyperactive DTR

…Neuro symptoms: seizures, coma

Chronic hyponatremia is better tolerated

26
Q

What are the 2 types of hyponatremia based on Plasma osmolality?

A

Isotonic Hyponatremia (aka pseudohyponatremia)

Hypertonic hyponatremia (aka redistributive hyopnatremia)

27
Q

Isotonic hyponatremia

A

Normal plasma osmolality
Caused by condition that leads to high serum lipid or protein levels

Increase in plasma solids
Decrease plasma osmolality due to proportion is plasma volume that is caused by excess lipids or proteins

28
Q

Hypertonic Hyponatremia

A

Increased plasma osmolality
Caused by HYPERGLYCEMIA or presence of osmotically active compound (mannitol, glycine, sorbitol)

H2O movement from ICF to ECF
Decrease Plasma sodium

29
Q

What are the three types of hyponatremia based on volume status?

A

Hypovolemic Hyponatremia
Euvolemic Hyponatremia
Hypervolemic Hyponatremia

30
Q

Hypovolemic Hyponatremia

A

Decrease ECF leads to Increase ADH
This leads to Na+ reabsorption in PCT

Increase ADH increases H2O reabsorption

Nonrenal: Can be caused by vomiting, diarrhea, sweating, burns (urine Na<20)

Renal: caused by inappropriate loss of Na and Cl in urine. Results in high ADH (urine Na>20)

31
Q

Euvolemic Hyponatremia

A

Abnormally high levels of serum ADH
Increased Na+ loss relative to H2O
Decreased ALDO results in increased Na+ excretion in urine which NORMALIZES ECF

32
Q

Hypervolemic Hyponatremia

A

Proportionally greater increase in total body water

Decrease in Na+ plasma

33
Q

Hypernatremia value

A

Na+ > 145

34
Q

Hypernatremia

A

Can develop as a result gain of Na, loss of H20 or a combination of the two

Cellular SHRINKAGE

Effluent of H20 from ICF

35
Q

Clinical features of Hypernatremia

A

Dehydration, “doughy” skin, irritability, lethargy, weakness, seizures

Highest risk
Elderly with decreased thirst or impaired thirst mechanism

36
Q

Major cation in ICF

A

Potassium

37
Q

Normal potassium values

A

2.5-5.0

Daily requirement: 1-2

Principle regulator: kidneys

38
Q

Potassium is the major determinant of ___________

A

Resting membrane potential

39
Q

Changes in plasma K have a direct effect on ________________

A

Cellular excitability and automaticity

40
Q

Hypokalemia value

A

Plasma K <3.5

41
Q

During hypokalemia, the resting membrane of excitable cells ________

A

Increases

It becomes more negative and less sensitive to excitation

Cellular hyperpolarization

42
Q

EKG changes in Hypokalemia

A 
Flattened or inverted T wave
U wave: prolonged polarization or purkinje fibers
Depressed ST Segment
Widened PR interval
Most marked when K <2.7
43
Q

Causes of hypokalemia

A

Alkalosis (H+ moves out of cell to buffer pH)

Insulin
B2-adrenergic agonist (albuterol)
GI losses (vomiting diarrhea)
Renal losses (diuretics, renal disease)

44
Q

Hyperkalemia value

A

K > 5

Life threatening when K >7

45
Q

During hyperkalemia, the resting membrane potential becomes less __________

A

Electronegative

Partial depolarization

46
Q

Clinical features of hyperkalemia

A

Impaired NM transmission
Faster depolarization, delayed depolarization, decreased conduction velocity

Cardiac conduction abnormalities

Parenthesis -> weakness -> paralysis

47
Q

EKG changes in hyperkalemia

A

Peaked T wave
Disappearance of P wave
QRS widening
Sine wave pattern

48
Q

Causes of Hyperkalemia

A
  • Acidosis (H+moves into cell, K+ efflux)
  • Increases in total body K_ (renal failure, addison’s)
  • Transcellular shift in ECF
  • Iatrogenic (K+ in IV fluids, NSAIDs, ACE inhibitors)
49
Q

Pseudohyperkalemia

A

Lab findings of falsely elevated serum K+
Due to K+ efflux before or after blood draw
Suspect in asymptomatic patient with no apparent cause for hyperkalemia

50
Q

ADH responds to:

A

Decrease volume
Increase Plasma osmolality
Increase H2O reabsorption

51
Q

Disturbances in K+ primarily effect the ________ system and Na+ effects the __________ system

A

K + = Cardiovascular system

Na+ = Neurological system

Week 2 (9 decks)

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