Chemistry Flex Bench Flashcards
contribute most to serum osmo
Na
Glucose
Urea
purpose of osmo
kidney’s concentration ability
typical causes for ↑ osmo
dehydration
kidney issues
osmo equation
1.86(Na) + (glu/18) + (BUN/2.8) + 9
osmo normal ranges
serum – 275-300 mOsm/kg
urine – 50-1200 mOsm/kg
osmo gap equation
measured osmo - calculated osmo
normal <10
causes of ↑ osmo gap and ↑ anion gap
- PO4, SO4 (renal failure)
- acetone, BHOB (DKA)
- alcohol
- lactate (tissue hypoxia)
- ethylene glycol (antifreeze)
- ANION gap – salicylate (aspirin OD)
anion gap (no K) equation and RR
Na - Cl + tCO2
RR: 7-16 mEq/L
RR with K: 10-20 mEq/L
excess anions/acids
↑ anion gap
sample size for osmo (in pipette)
20 μL
the osmo sample must be…
(size)
slightly longer than it is wide
no convex meniscus
osmo procedure for pts
run in duplicate
must be within 2 mOsm
1000 mOsm/kg depresses FP by…
-1.86° C
steps of FP osmometer
- fast cool
- reaches 0° – slow cool
- mechanical pulse freezes sample
- heat of fusion – asymptotically warms sample to its freezing point – temp approaches equilibrium
- plateau – osmolality is read
automated multi-wavelength spectrophotometric method used on ABG instruments
co-oximetry
test method for co-oximetry
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
↑ Hgb affinity for O2
↑ pH
↓ pCO2
↑ pO2
↓ 2,3-DPG
↓ temp
↓ Hgb affinity for O2
↓ pH
↑ pCO2
↓ pO2
↑ 2,3-DPG
↑ temp
corrected barometric pressure
BP value - 47 mmHg [VP of water] = corrected BP
calibrate BP for gas content
corrected BP(% gas) = mmHg