Chemistry Flex Bench

Question 1

contribute most to serum osmo

Answer 1

Na
Glucose
Urea

Question 2

purpose of osmo

Answer 2

kidney’s concentration ability

Question 3

typical causes for ↑ osmo

Answer 3

dehydration
kidney issues

Question 4

osmo equation

Answer 4

1.86(Na) + (glu/18) + (BUN/2.8) + 9

Question 5

osmo normal ranges

Answer 5

serum – 275-300 mOsm/kg
urine – 50-1200 mOsm/kg

Question 6

osmo gap equation

Answer 6

measured osmo - calculated osmo
normal <10

Question 7

causes of ↑ osmo gap and ↑ anion gap

Answer 7

• PO4, SO4 (renal failure)
• acetone, BHOB (DKA)
• alcohol
• lactate (tissue hypoxia)
• ethylene glycol (antifreeze)
• ANION gap – salicylate (aspirin OD)

Question 8

anion gap (no K) equation and RR

Answer 8

Na - Cl + tCO2

RR: 7-16 mEq/L
RR with K: 10-20 mEq/L

Question 9

excess anions/acids

Answer 9

↑ anion gap

Question 10

sample size for osmo (in pipette)

Answer 10

20 μL

Question 11

the osmo sample must be…
(size)

Answer 11

slightly longer than it is wide
no convex meniscus

Question 12

osmo procedure for pts

Answer 12

run in duplicate
must be within 2 mOsm

Question 13

1000 mOsm/kg depresses FP by…

Answer 13

-1.86° C

Question 14

steps of FP osmometer

Answer 14

1. fast cool
2. reaches 0° – slow cool
3. mechanical pulse freezes sample
4. heat of fusion – asymptotically warms sample to its freezing point – temp approaches equilibrium
5. plateau – osmolality is read

Question 15

automated multi-wavelength spectrophotometric method used on ABG instruments

Answer 15

co-oximetry

Question 16

test method for co-oximetry

Answer 16

1 μL blood heated to 37° and sonically hemolyzed by vibrating the cuvette walls at 30 kHz

Beer’s law is used to measure components

fractions of total Hgb are given

Question 17

↑ Hgb affinity for O2

Answer 17

↑ pH
↓ pCO2
↑ pO2
↓ 2,3-DPG
↓ temp

Question 18

↓ Hgb affinity for O2

Answer 18

↓ pH
↑ pCO2
↓ pO2
↑ 2,3-DPG
↑ temp

Question 19

corrected barometric pressure

Answer 19

BP value - 47 mmHg [VP of water] = corrected BP

Question 20

calibrate BP for gas content

Answer 20

corrected BP(% gas) = mmHg

Question 21

ABG sample requirements

Answer 21

• tightly stoppered
• balanced heparinized syringe
• on ice (2 hr) – 30 min no ice
• no bubbles
• perform ASAP

Question 22

non-balanced heparin effects…

Answer 22

electrolytes, especially cCa2+

Question 23

lipid therapy affects…

Answer 23

OXI measurements (Beer’s law)

Question 24

opposite arrows vs same arrows on either side of HH equation

Answer 24

opposite – respiratory
same – metabolic

Question 25

calibration for electrode drift

Answer 25

one-point

Question 26

calibration for electrode slope changes

Answer 26

two-point

Question 27

HH equation for blood gases

Answer 27

pH = 6.1 + log[HCO3/(pCO2)(0.03)]

Question 28

pKa for blood gases

Answer 28

6.1

Question 29

normal pH, HCO3, and pCO2

Answer 29

pH – 7.35-7.45
HCO3 – 22-26 mEq/L
pCO2 – 35-45 mmHg

Question 30

alkalosis/acidosis with normal pH

Answer 30

fully compensated

Question 31

P/F ratio equation and ranges

Answer 31

pO2/% inspired O2 = P/F

mild resp distress – 200-300
moderate – 100-200
severe – <100

room air is 21% O2
indicates ARDS or resp failure

Question 32

—–% O2 saturation for a capillary specimen is acceptable

Answer 32

> 70

Question 33

as pH ↓, iCa —-, because…

Answer 33

↑
decreasing pH causes less Ca to be protein-bound

Question 34

iCa sample

Answer 34

dark green (heparinized plasma) tube with no gel

on ice (4hr) or not on ice (30 min)

half full

WB

Question 35

released with iCa to account for false changes

Answer 35

pH

Question 36

— iCa causes seizures, cardiac arrest

Answer 36

↓

Question 37

— iCa causes nausea, constipation, kidney failure

Answer 37

↑

Question 38

if osmo gap is >25…

Answer 38

suspect ingestion of substance

Question 39

high osmo gap with HAGMA

high anion gap metabolic acidosis

Answer 39

MEELK
- methanol
- ethylene glycol
- ethanol
- lactic acidosis
- ketoacidosis

Question 40

high osmo gap without HAGMA

high anion gap metabolic acidosis

Answer 40

• isopropyl alcohol
• mannitol
• sorbitol
• glycine
• maltose

glycine, sorbitol, mannitol used for transurethral resection of prostate

Question 41

hyponatremia + euvolemia

Answer 41

• SIADH
• adrenal insufficiency
• hypothyroidism

Question 42

hyponatremia + hypovolemia

Answer 42

• diuretics
• osmotic diuresis
• vomiting
• diarrhea

Question 43

hyponatremia + hypervolemia

Answer 43

• kidney failure
• cardiac arrest
• cirrhosis
• nephrotic syndrome

Question 44

↓ serum osmo
↓ serum Na
↑ urine output
↓ urine osmo

Answer 44

water overload

Question 45

↑ serum osmo
↑ serum Na
↑ urine output
↓ urine osmo

Answer 45

DI

Question 46

↓ serum osmo
↓ serum Na
↓ urine output
↑ urine osmo

Answer 46

SIADH

Question 47

causes of water overload

Answer 47

psychogenic/primary polydipsia

• hypothalamic disease
• drugs
• altered mental status/psychiatric disease

Question 48

polyuria + polydipsia
>2.5 L/day urine output
crave water/ice
extreme fatigue, muscle weakness

Answer 48

DI

Question 49

2 types of DI

Answer 49

central – failure of pituitary to secrete normal ADH
nephrogenic – renal resistance to action of ADH

Question 50

fluid overload/weight gain
low urine output with high SG

Answer 50

SIADH

Question 51

causes of SIADH

Answer 51

• malignant production of vasopressin
• diseases of CNS
• pulmonary disorders
• side effects of drugs