Osmolality and Osmolal gap, ACID-BA

Question 1

Characteristic finding that shows the concentration of solutes in a solution

Answer 1

Osmolality

Question 2

Reference range for serum osmolality

Answer 2

275–295 mOsm/kg

Question 3

Effect of anticoagulant on plasma in osmolality testing

Answer 3

Falsely increases osmolality

Question 4

Method for measuring osmolality that uses freezing point or vapor pressure decrease

Answer 4

Osmometry

Question 5

Formula for calculating osmolality

Answer 5

2Na + (Glucose x 0.0555 / 18) + (BUN / 2.8)

Question 6

Formula for calculating osmolal gap

Answer 6

Measured osmolality - Calculated osmolality

Question 7

Reference range for osmolal gap

Answer 7

5–10 mOsm/kg

Question 8

Clinical significance when osmolal gap is greater than 12 mOsm/kg

Answer 8

Uremia, DKA, Lactic Acidosis, Alcohol intoxication (methanol, ethanol), Ethylene glycol poisoning

Question 9

Characteristic finding that shows difference between cations and anions

Answer 9

Anion gap

Question 10

Formula for calculating anion gap

Answer 10

AG = (Na+ + K+) – (Cl- + HCO3-) or AG = Na+ – (Cl- + HCO3-)

Question 11

Reference range for anion gap

Answer 11

10-20 mmol/L or 7-16 mmol/L

Question 12

Clinical significance of an increased anion gap

Answer 12

Increased unmeasured anions (MUDPILES: Methanol, Uremia, DKA, Paraldehyde, Inhalants, Lactic acidosis, Ethylene glycol, Salicylate)

Question 13

Condition associated with decreased anion gap

Answer 13

Hypoalbuminemia, Hypercalcemia, Multiple myeloma

Question 14

Laboratory error affecting anion gap

Answer 14

Increased Na, Cl, or HCO3, Decreased Na, F, Cl

Question 15

Characteristic finding that shows a substance that yields hydrogen ions

Answer 15

Acid (donor)

Question 16

Characteristic finding that shows a substance that yields hydroxyl ions

Answer 16

Base

Question 17

Definition of a buffer

Answer 17

Combination of a weak acid and its salt or conjugate base that resists changes in pH

Question 18

Second most important blood buffer

Answer 18

Hemoglobin

Question 19

Buffer that contains 38 histidine residues that bind H+

Answer 19

Hemoglobin

Question 20

Buffer with free carboxyl and amino groups that bind H+

Answer 20

Plasma proteins

Question 21

Buffer system that uses HPO4^2- and H2PO4- to minimize pH changes

Answer 21

Phosphate buffer system

Question 22

Most important buffer system in blood

Answer 22

Bicarbonate/carbonic acid buffer system

Question 23

Chemical equilibrium for carbonic acid and bicarbonate

Answer 23

CO2 + H2O ←→ H2CO3 ↔ HCO3− + H+

Question 24

Acid-base ratio of H2CO3 and HCO3

Answer 24

0.05555555555555558

Question 25

Henderson-Hasselbalch equation

Answer 25

pH = pKₐ + log([A⁻]/[HA])

Question 26

Estimate of carbonic acid

Answer 26

pCO₂ x 0.03

Question 27

Kidney function and pH

Answer 27

HCO₃⁻ is directly related to pH

Question 28

Lung function and pH

Answer 28

pCO₂ (H₂CO₃) is inversely related to pH