Electrolytes

Question 1

Plasma [Na+]

Answer 1

Major extracellular fluid (ECF) ion

Actively eliminated from cells via sodium pump

Major influence on osmolality

Question 2

T/F Osmoreceptors that secrete ALDOSTERONE indirectly influence serum Na+ concentration

Answer 2

False: its ADH

Question 3

Renal tubular absorption of Na is regulated via

Answer 3

Aldosterone

Question 4

T/F Na is absorbed through the GI

Answer 4

true: intestinal absorption

Question 5

what 3 things effect plasma volume of Na

Answer 5

Urine, gastrointestinal tract (GIT), sweat (horses)

Question 6

Sodium balance – 2 related & interdependent systems:

Answer 6

osmoregulation & volume regulation

Question 7

osmoreceptors in hypothalamus

Answer 7

sense increased osmolality & secrete ADH

Question 8

stretch receptors

Answer 8

sense volume changes

Question 9

How does ADH regulate Na

Answer 9

Responds to:
- ↑ osmolality
- ↓↓↓ plasma volume
Acts on collecting ducts; maximizes water reabsorption

Question 10

what is the main regulator of Na balance

Answer 10

Renin-angiotensin-aldosterone system (Na resorbed in distal tubule)

Question 11

aldosterone is secreted in response to

Answer 11

• Angiotensin
• Hyperkalemia
• ACTH

Question 12

aldosterone

Answer 12

conserves Na+

Secretes K+

Question 13

causes of hyponatremia

Answer 13

loss of Na+ (GIT, renal, cutaneous)

Shifts (diabetes)

↑ extracellular H2O (CHF)

↓ intake (herbivores)

Question 14

most common cause of hyponatremia

Answer 14

hypovolemia

Question 15

causes of hypovolemia

Answer 15

GIT: vomiting, diarrhea, saliva

Renal loss:

• Hypoadrenocorticism (Addison’s): ↓ aldosterone
• Ketonuria
• Prolonged diuresis

Cutaneous: sweating, burns

3rd space: sequestration of fluid

Question 16

examples of 3rd space syndromes (causing hyponatremia)

Answer 16

Peritonitis

Ascites

Uroabdomen

Chylothorax

GI sequestration

This effectively “dilutes” plasma Na+

Question 17

2 causes of osmotic shifts (causing hyponatrmia)

Answer 17

hyperglycemia

mannitol administration

Question 18

2 causes of increased extracellular water leading to hyponatremia

Answer 18

primary polydipsia (psychogenic water drinking)

excessive administration of Na+ poor IVF

Question 19

consequences of hyponatremia if other osmotically active substances are NOT increased

Answer 19

hypoosmolality

cellular edema (cellular overhydration)

Question 20

what is hypernatremia usually due to

Answer 20

dehydration

• inadequate water intake
• pure water loss (panting, fever, diabetes insipidus)

Question 21

hypernatremia is less commonly due to

Answer 21

excessive Na+ intake or retention

Question 22

Chloride

Answer 22

Major extracellular fluid (ECF) anion

Important in transport of electrolytes and water

Anion involved in acid base metabolism

Question 23

who is chloride’s BFF

Answer 23

Na

Question 24

if changes in Cl- and Na+ are proportional:

Answer 24

consider differentials that pertain to abnormalities in Na+ (Cl- is following Na+)

Question 25

if the changes in Cl- are greater than Na+

Answer 25

consider acid-base abnormalities

Question 26

how is chloride regulated

Answer 26

Controlled by electrochemical gradients Corresponds to the active transport of sodium

Question 27

what interferes with Cl transport

Answer 27

furosemide GI enterotoxins

Question 28

T/F Cl is usually regulated secondary to Na

Answer 28

true: usually parallels [Na]

Question 29

T/F All causes of ↓Na+ are causes of ↓Cl-

Answer 29

true

Question 30

most common cause of Cl- loss being greater than Na+ loss

Answer 30

hypochloremia metabolic alkalosis - severe vomiting - abomasal disorders, high GI obstructions

Question 31

what can selective chloride loss lead to

Answer 31

Hypochloremic metabolic alkalosis +/- Paradoxical aciduria

Question 32

when should selective chloride loss be suspected

Answer 32

corrected Cl- is below the reference interval

Question 33

what 2 things does paradoxical aciduria require

Answer 33

volume depletion chloride depletion

Question 34

mechanism of paradoxical aciduria

Answer 34

Kidney: • Resorbs Na+ to correct dehydration • Resorbs HCO3- instead of Cl- (electoneutrality) Result: exacerbated alkalosis (more HCO3-)

Question 35

causes of hyperchloremia

Answer 35

Generally parallels increases with Na+ Hyperchloremic metabolic acidosis − GIT loss of HCO3- Alkalemia / HCO3- excess

Question 36

functions of potassium

Answer 36

Major intracellular (IC) cation- IC osmotic pressure and fluid volume Resting cell membrane potential Carbohydrate metabolism Electron transport

Question 37

clinical signs of abnormal serum K+

Answer 37

cardiac dysfunction skeletal muscle dysfunction

Question 38

regulation of potassium

Answer 38

adequate intake renal excretion sweat GI loss

Question 39

causes of hyperkalemia

Answer 39

Failure of renal Excretion: most common Redistribution ↑ intake: Parenteral administration of K+

Question 40

examples of redistribution leading to hyperkalemia

Answer 40

* Inorganic acidosis * Insulin deficiency * Muscle trauma: rhabdomyolysis, seizures * Massive hemolysis

Question 41

hyperkalemia: examples of failure of renal excretion

Answer 41

Oliguria/ Anuria Urethral obstruction Ruptured urinary bladder Hypoadrenocorticism (Addison’s): ↓ aldosterone Drugs that decrease K+ excretion • “Potassium Sparing Diuretics”

Question 42

T/F redistribution is a major mechanism of hyperkalemia

Answer 42

true

Question 43

T/F H+ & K+ balance maintains electroneutrality between ICF and ECF

Answer 43

true

Question 44

pseudohyperkalemia

Answer 44

Generally in vitro, not in vivo Marked thrombocytosis: leakage of intracellular K+ Hemolysis: K+ released from RBCs EDTA CONTAMINATION!!

Question 45

hypokalemia

Answer 45

Usually indicates marked depletion of cellular K+

Question 46

causes of hypokalemia

Answer 46

Decreased intake or low K+ IV fluids Loss - Alimentary: vomiting, diarrhea, abomasal disorders - Renal - Horse sweat Redistribution - Alkalemia - INSULIN injection (or glucose bolus)

Question 47

consequences of hypokalemia

Answer 47

* Weakness * Neurologic signs * EKG abnormalities

Question 48

potassium in diarrhea

Answer 48

loss of bicarb and K+ - leads to an acidosis - H+ entersinto the cells and K+ leaves cells - may mask total body K+ deficit

Question 49

T/F With diarrhea, potassium supplementation may be indicated despite normal serum K+

Answer 49

true