Pathophys: Electrolyte Disturbance Na And K

Question 1

60-40-20 Rule

Answer 1

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

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

Question 2

Osmolality

Answer 2

The solute or particle concentration of a fluid

H2O diffuses across most cell membranes to achieve osmotic equilibrium

ECF osmolality = ICF-osmolality

Question 3

Electrolyte solute compositions differ due to differences in….

Answer 3

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

Question 4

Compartment restriction determines the ________

Answer 4

Toxicity or effective osmolality

Question 5

Major ECF solutes include:

Answer 5

Na+
Cl-
HCO3-

Question 6

Major ICF solutes include

Answer 6

K+ and ATP

Question 7

Excreted solute

Answer 7

Organic waste and excess electrolytes

Question 8

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

Answer 8

Urine osmolality

Electrolyte excretion is highly regulated

Question 9

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

Answer 9

Independent

Question 10

ADH secretion is controlled by:

Answer 10

Osmoreceptors

Baroreceptors

Question 11

Osmoreceptors

Answer 11

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

Question 12

Baroreceptors

Answer 12

Located in aortic arch and carotid arteries

Respond to changes in pressure

Question 13

ADH is made in the ________ and stored in the __________

Answer 13

Made in the hypothalamus and stored in the posterior pituitary

Question 14

ADH regulates these 2 things…

Answer 14

Plasma Osmolality

Blood pressure

Question 15

How does ADH regulate plasma osmolality?

Answer 15

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

Question 16

How does ADH regulate blood pressure?

Answer 16

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

Question 17

What is the major cation in ECF?

Answer 17

Na+

Question 18

Normal plasma Na+ values?

Answer 18

135-145 mEq/L

Question 19

What is the normal plasma osmolarity?

Answer 19

285-295 mOsm/kg

Question 20

Primary goal of regulating Na and H2O excretion?

Answer 20

Support the requirements of the cardiovascular system

Question 21

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

Answer 21

H2O

Question 22

Disorders of plasma Na+ concentration are caused by _______

Answer 22

H2O homeostasis

Changes in the relative ratio of Na+ to body water

Question 23

Na+ value of hyponatremia

Answer 23

Na <135

Seizure threshold: 125
Life threatening: 120

Question 24

What happens to the cell in hyponatremia?

Answer 24

Osmotic water shift into the cell
Increase ICF volume
Cellular swelling

Question 25

Clinical features of Hyponatremia?

Answer 25

Nausea, eyes is, headache, malaise, lethargy, irritability, muscle twitching, weakness, hyperactive DTR ...Neuro symptoms: seizures, coma Chronic hyponatremia is better tolerated

Question 26

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

Answer 26

Isotonic Hyponatremia (aka pseudohyponatremia) Hypertonic hyponatremia (aka redistributive hyopnatremia)

Question 27

Isotonic hyponatremia

Answer 27

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

Question 28

Hypertonic Hyponatremia

Answer 28

Increased plasma osmolality Caused by HYPERGLYCEMIA or presence of osmotically active compound (mannitol, glycine, sorbitol) H2O movement from ICF to ECF Decrease Plasma sodium

Question 29

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

Answer 29

Hypovolemic Hyponatremia Euvolemic Hyponatremia Hypervolemic Hyponatremia

Question 30

Hypovolemic Hyponatremia

Answer 30

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)

Question 31

Euvolemic Hyponatremia

Answer 31

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

Question 32

Hypervolemic Hyponatremia

Answer 32

Proportionally greater increase in total body water Decrease in Na+ plasma

Question 33

Hypernatremia value

Answer 33

Na+ > 145

Question 34

Hypernatremia

Answer 34

Can develop as a result gain of Na, loss of H20 or a combination of the two Cellular SHRINKAGE Effluent of H20 from ICF

Question 35

Clinical features of Hypernatremia

Answer 35

Dehydration, "doughy" skin, irritability, lethargy, weakness, seizures Highest risk Elderly with decreased thirst or impaired thirst mechanism

Question 36

Major cation in ICF

Answer 36

Potassium

Question 37

Normal potassium values

Answer 37

2.5-5.0 Daily requirement: 1-2 Principle regulator: kidneys

Question 38

Potassium is the major determinant of ___________

Answer 38

Resting membrane potential

Question 39

Changes in plasma K have a direct effect on ________________

Answer 39

Cellular excitability and automaticity

Question 40

Hypokalemia value

Answer 40

Plasma K <3.5

Question 41

During hypokalemia, the resting membrane of excitable cells ________

Answer 41

Increases It becomes more negative and less sensitive to excitation Cellular hyperpolarization

Question 42

EKG changes in Hypokalemia

Answer 42

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

Question 43

Causes of hypokalemia

Answer 43

Alkalosis (H+ moves out of cell to buffer pH) Insulin B2-adrenergic agonist (albuterol) GI losses (vomiting diarrhea) Renal losses (diuretics, renal disease)

Question 44

Hyperkalemia value

Answer 44

K > 5 Life threatening when K >7

Question 45

During hyperkalemia, the resting membrane potential becomes less __________

Answer 45

Electronegative Partial depolarization

Question 46

Clinical features of hyperkalemia

Answer 46

Impaired NM transmission Faster depolarization, delayed depolarization, decreased conduction velocity Cardiac conduction abnormalities Parenthesis -> weakness -> paralysis

Question 47

EKG changes in hyperkalemia

Answer 47

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

Question 48

Causes of Hyperkalemia

Answer 48

- 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)

Question 49

Pseudohyperkalemia

Answer 49

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

Question 50

ADH responds to:

Answer 50

Decrease volume Increase Plasma osmolality Increase H2O reabsorption

Question 51

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

Answer 51

K + = Cardiovascular system | Na+ = Neurological system