ELECTROLYTES

Question 1

Major extracellular electrolytes

Answer 1

Na⁺, Cl⁻, HCO₃⁻

Question 2

Major intracellular electrolytes

Answer 2

K⁺, Mg²⁺, phosphates

Question 3

Active transport

Answer 3

Energy-requiring movement of ions across membranes against a gradient

Question 4

Passive transport

Answer 4

Movement of ions down a concentration gradient without energy

Question 5

Osmolality

Answer 5

Concentration of solute particles per kg of solvent (mOsm/kg)

Question 6

Normal serum osmolality

Answer 6

275–295 mOsm/kg

Question 7

Osmolality formula (mg/dL)

Answer 7

(2(Na)) + (glucose/18) + (BUN/2.8)

Question 8

Clinical significance of osmolality

Answer 8

Evaluates electrolyte and acid-base disorders

Question 9

Osmotic pressure

Answer 9

Solvent movement across a semipermeable membrane driven by solute concentration

Question 10

Colligative properties

Answer 10

Properties dependent on number of particles, not type

Question 11

Four colligative properties

Answer 11

Vapor pressure ↓, freezing point ↓, boiling point ↑, osmotic pressure ↑

Question 12

Major function of sodium

Answer 12

Primary determinant of plasma osmolality and water balance

Question 13

Normal serum sodium

Answer 13

135–145 mmol/L

Question 14

Sodium measurement method

Answer 14

Ion-selective electrode (ISE)

Question 15

Cause of hyponatremia (2)

Answer 15

Excess water retention or increased ADH

Question 16

Cause of hypernatremia

Answer 16

Water loss or decreased water intake

Question 17

Indirect ISE sodium error

Answer 17

Falsely decreased Na with increased lipids or proteins

Question 18

Major location of potassium

Answer 18

Intracellular fluid (20× higher inside cells)

Question 19

Normal serum potassium

Answer 19

3.5–4.5 mmol/L

Question 20

Potassium ISE membrane

Answer 20

Valinomycin

Question 21

Major potassium pre-analytical error and what does it cause

Answer 21

Hemolysis falsely increases K

Question 22

Pseudohyperkalemia causes

Answer 22

Hemolysis, EDTA, fist clenching, ↑ platelets or WBCs

Question 23

Hypokalemia symptoms

Answer 23

Muscle weakness, paralysis, cardiac arrhythmias

Question 24

Hyperkalemia symptoms

Answer 24

Cardiac effects, weakness, respiratory muscle paralysis

Question 25

Major chloride function (3)

Answer 25

Maintains osmolality, blood volume, and electrical neutrality

Question 26

Normal serum chloride

Answer 26

98–107 mmol/L

Question 27

Chloride measurement methods

Answer 27

ISE and coulometric titration

Question 28

Principle of coulometric titration (Cl-)

Answer 28

Ag⁺ reacts with Cl⁻ to quantify chloride

Question 29

Sweat chloride test purpose

Answer 29

Diagnosis of cystic fibrosis

Question 30

Sweat chloride diagnostic value

Answer 30

>60 mmol/L indicative of cystic fibrosis

Question 31

Primary role of bicarbonate

Answer 31

Major blood buffering system

Question 32

Normal serum bicarbonate

Answer 32

23–29 mmol/L

Question 33

Increased bicarbonate indicates

Answer 33

Metabolic alkalosis or compensated respiratory acidosis

Question 34

Decreased bicarbonate indicates

Answer 34

Metabolic acidosis or diabetic ketoacidosis

Question 35

Specimen requirement for bicarbonate

Answer 35

Serum or plasma collected anaerobically

Question 36

Magnesium distribution

Answer 36

2nd most abundant intracellular cation

Question 37

Normal serum magnesium

Answer 37

1.6–2.4 mg/dL

Question 38

Magnesium testing method

Answer 38

Colorimetric (calmagite or methylthymol blue)

Question 39

Magnesium specimen error and what does it cause

Answer 39

Hemolysis falsely increases Mg

Question 40

Anticoagulants to avoid for Mg

Answer 40

EDTA, citrate, oxalate (bind Mg)

Question 41

Hypomagnesemia symptoms

Answer 41

Cardiac arrhythmias, tremors, tetany

Question 42

Percentage of ionized calcium

Answer 42

50% (biologically active)

Question 43

Other calcium forms

Answer 43

40% protein-bound, 10% complexed

Question 44

Normal total calcium

Answer 44

8.6–10.3 mg/dL

Question 45

Normal ionized calcium

Answer 45

4.6–5.3 mg/dL

Question 46

Hormones regulating calcium

Answer 46

PTH, vitamin D, calcitonin

Question 47

Hypocalcemia causes (3)

Answer 47

Hypoalbuminemia, renal failure, vitamin D deficiency

Question 48

Hypercalcemia causes

Answer 48

Hyperparathyroidism, malignancy

Question 49

Ionized calcium specimen requirement

Answer 49

Anaerobic collection

Question 50

Phosphate distribution

Answer 50

Primarily intracellular and in bone

Question 51

Normal serum phosphate

Answer 51

2.5–4.5 mg/dL

Question 52

Calcium-phosphate relationship

Answer 52

Inverse relationship

Question 53

Phosphate measurement method

Answer 53

Molybdate reaction forming molybdenum blue

Question 54

Hyperphosphatemia symptoms

Answer 54

Tetany and seizures

Question 55

Lactate clinical significance (2)

Answer 55

Marker of anaerobic metabolism and tissue hypoxia

Question 56

Normal plasma lactate

Answer 56

0.5–2.2 mmol/L

Question 57

Lactate specimen requirements (3)

Answer 57

Fluoride tube, on ice, avoid tourniquet

Question 58

Lactate measurement principle

Answer 58

Lactate oxidase produces H₂O₂ measured colorimetrically

Question 59

Anion gap definition

Answer 59

Difference between measured cations and anions

Question 60

Anion gap formula

Answer 60

Na − (Cl + HCO₃)

Question 61

Normal anion gap

Answer 61

~10–20 mmol/L

Question 62

Causes of increased anion gap

Answer 62

Lactic acidosis, ketoacidosis, renal failure

Question 63

Causes of decreased anion gaps

Answer 63

Low albumin, increased Mg/Ca, lithium therapy

Question 64

Is sodium a cation or anion

Answer 64

Cation

Question 65

What organ reabsorbs 85% of sodium

Answer 65

Kidney