Clinical Chemistry Cls 2213 Unit 7 Blood Gas

Front 1

Normal values for arterial and venous blood pH, and critical values

Back 1

Arterial 7.35-7.45
Venous 7.32-7.42
Critical below 7.2 and above 7.6

Front 2

Normal values for pCO2

Back 2

35-45 mmHg

Front 3

Normal values for pO2

Back 3

83-108 mmHg

Front 4

Normal values for arterial and venous TCO2

Back 4

Arterial 22-29 mEq/L
Venous 23-30 mEq/L

Front 5

Normal values for arterial and venous bicarb

Back 5

Arterial 21-28 mEq/L
Venous 22-29 mEq/L

Front 6

Normal values for base excess

Back 6

+/- 3 mEq/L

Front 7

Normal values for O2 saturation

Back 7

95% or greater

Front 8

Explain the principles of pH indicator electrode

Back 8

Greater H+ on the outside of glass membrane makes the outside more + than inside of membrane and causes e- potential across membrane
As acidity increases e- potential increases

Front 9

Explain the principles of calomel reference electrode

Back 9

-Has Hg/HgCl2 paste cathode
- Takes into account the e- potential independent of potential due to H+ differences

Front 10

Explain the principles of severinghaus CO2 electrode

Back 10

Teflon permeable to CO2 gas, sample reacted with H2SO4
- CO2 reacts with water in bicarb buffer solution forming carbonic acid
- pH change is measured by pH electrode

Front 11

Explain the principles of Clark pO2 electrode

Back 11

O2 unites with H2 gass and reduces resistance

Front 12

Explain specimen collection procedure

Back 12

- Specimen of choice is heparinized arterial whole blood
- drawn in heparin-coated glass syringe
- don't excite patient (causes hyperventilation)
- apply tourniquet loosely
- mix specimen as soon as it is drawn

Front 13

Common sources of blood gas analysis error

Back 13

- improper mixing
- improper handling (exposing to air, not putting on ice)
- incorrect calibration or pH calibrator buffers are contaminated
- incorrect barometric pressure
- improper temp control (must be kept at exactly 37 C)
- Dirty sample chamber (protein buildup)
- Dirty electrode membranes (protein buildup)
- Damaged electrode membranes

Front 14

Effects on sample from increased temp or failing to perform assay immediately

Back 14

RBC's will catabolize glucose and cause falsely low pH and increased pCO2. pO2 will not be affected

Front 15

Effects on sample from poor mixing and partial clotting

Back 15

will cause falsely high pH (alkaline)

Front 16

Effects on sample from exposure to ambient air

Back 16

pCO2 will be falsely low, and pO2 will be high

Front 17

Tricks used by the kidney to secrete more H+ when blood is to acidic

Back 17

Excretion of ammonia and phosphates.
Excreted ammonia comes from modified glutamine

Front 18

Effects of renal failure on pH, pCO2, pO2, and bicarb

Back 18

-decreased pH (acidic)
- no direct effect on CO2 or O2
- low bicarbonate (bicarb is lost in urine)

Front 19

Normal range for lactic acid

Back 19

.5-1.9 mMol/L
at 4.5 mMol/L patient is considered to be in lactic acidosis

Front 20

Importance of lactic acid levels in burn patients

Back 20

-pO2 and pCO2 measurments are not reliable in a severely burned patient, they are falsely elevated due to decreased capillary resistance
- if lactic acid is increased then the physician knows that O2 is not being used by the body, and a transfusion is needed to increase O2 carrying capacity