Pathophys: Electrolyte Disturbance Na And K Flashcards Preview

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Flashcards in Pathophys: Electrolyte Disturbance Na And K Deck (51):
1

60-40-20 Rule

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


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

2

Osmolality

The solute or particle concentration of a fluid

H2O diffuses across most cell membranes to achieve osmotic equilibrium

ECF osmolality = ICF-osmolality

3

Electrolyte solute compositions differ due to differences in....

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

4

Compartment restriction determines the ________

Toxicity or effective osmolality

5

Major ECF solutes include:

Na+
Cl-
HCO3-

6

Major ICF solutes include

K+ and ATP

7

Excreted solute

Organic waste and excess electrolytes

8

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

Urine osmolality

Electrolyte excretion is highly regulated

9

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

Independent

10

ADH secretion is controlled by:

Osmoreceptors
Baroreceptors

11

Osmoreceptors

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

12

Baroreceptors

Located in aortic arch and carotid arteries
Respond to changes in pressure

13

ADH is made in the ________ and stored in the __________

Made in the hypothalamus and stored in the posterior pituitary

14

ADH regulates these 2 things...

Plasma Osmolality
Blood pressure

15

How does ADH regulate plasma osmolality?

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

16

How does ADH regulate blood pressure?

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

17

What is the major cation in ECF?

Na+

18

Normal plasma Na+ values?

135-145 mEq/L

19

What is the normal plasma osmolarity?

285-295 mOsm/kg

20

Primary goal of regulating Na and H2O excretion?

Support the requirements of the cardiovascular system

21

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

H2O

22

Disorders of plasma Na+ concentration are caused by _______

H2O homeostasis

Changes in the relative ratio of Na+ to body water

23

Na+ value of hyponatremia

Na <135

Seizure threshold: 125
Life threatening: 120

24

What happens to the cell in hyponatremia?

Osmotic water shift into the cell
Increase ICF volume
Cellular swelling

25

Clinical features of Hyponatremia?

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

...Neuro symptoms: seizures, coma

Chronic hyponatremia is better tolerated

26

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

Isotonic Hyponatremia (aka pseudohyponatremia)

Hypertonic hyponatremia (aka redistributive hyopnatremia)

27

Isotonic hyponatremia

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

Hypertonic Hyponatremia

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

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

Hypovolemic Hyponatremia
Euvolemic Hyponatremia
Hypervolemic Hyponatremia

30

Hypovolemic Hyponatremia

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

Euvolemic Hyponatremia

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

Hypervolemic Hyponatremia

Proportionally greater increase in total body water

Decrease in Na+ plasma

33

Hypernatremia value

Na+ > 145

34

Hypernatremia

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

Clinical features of Hypernatremia

Dehydration, "doughy" skin, irritability, lethargy, weakness, seizures

Highest risk
Elderly with decreased thirst or impaired thirst mechanism

36

Major cation in ICF

Potassium

37

Normal potassium values

2.5-5.0

Daily requirement: 1-2

Principle regulator: kidneys

38

Potassium is the major determinant of ___________

Resting membrane potential

39

Changes in plasma K have a direct effect on ________________

Cellular excitability and automaticity

40

Hypokalemia value

Plasma K <3.5

41

During hypokalemia, the resting membrane of excitable cells ________

Increases

It becomes more negative and less sensitive to excitation

Cellular hyperpolarization

42

EKG changes in Hypokalemia

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

Causes of hypokalemia

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

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

44

Hyperkalemia value

K > 5

Life threatening when K >7

45

During hyperkalemia, the resting membrane potential becomes less __________

Electronegative

Partial depolarization

46

Clinical features of hyperkalemia

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

Cardiac conduction abnormalities

Parenthesis -> weakness -> paralysis

47

EKG changes in hyperkalemia

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

48

Causes of Hyperkalemia

-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

Pseudohyperkalemia

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

ADH responds to:

Decrease volume
Increase Plasma osmolality
Increase H2O reabsorption

51

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

K + = Cardiovascular system
Na+ = Neurological system