Hematology

Question 1

P50

Answer 1

partial pressure of oxygen at which the oxygen carrying protein is 50% saturated.

Question 2

P50 for hemoglobin vs. myoglobin under normal conditions

Answer 2

Under normal conditions for temperature (37 C) and pH (7.4), the P50 for hemoglobin is approximately 27 mmHg while the P50 for myoglobin is 2.75 mmHg.

Question 3

Utility of myoglobin

Answer 3

Intracellular storage of oxygen, where the concentration of oxygen is low enough that myoglobin will let go!

Question 4

Mnemonic 30-60 60-90 40-75

Answer 4

partial pressure of 30 mmHg, the % saturation is ~60 %, at 60 mmHg it’s ~90% and at 40 mmHg it’s ~75%. Also, at 10 mmHg the % saturation is ~10 %.

Question 5

Bohr Effect

Answer 5

Increase in pH leads to increased oxygen affinity (Left Shift)
(CO2 and lactic acid make high activity tissues more acidic)

Question 6

Temperature effect on Hb O2 affinity

Answer 6

Increase in temperature leads to decreased oxygen affinity (right shift) allows oxygen to unload in tissues affected by exercise or fever

Question 7

2,3 BPG - + Hb O2 affinity

Answer 7

A product of Glycolytic pathway

2,3 BPG binds and stabilizes the T form of Hb, allowing the oxygen to be released into the tissues. (left shift)

Question 8

Hb Gower 1

Answer 8

Zeta 2 eta 2

Question 9

Hemoglobin Gower 2

Answer 9

alpha 2 eta 2

Question 10

Hemoglobin Portland

Answer 10

zeta 2 gamma 2

Question 11

HbA vs. embryonic Hb

Answer 11

Embryonic Hb has higher Hb affinity

Question 12

Fetal hemoglobin

Answer 12

alpha 2 gamma 2

Question 13

Fetal hemoglobin and 2-3 BPT

Answer 13

2,3-BPG binds HbF less well than HbA, so the oxygen affinity is higher

Question 14

Bohr effect in fetal hemoglobin

Answer 14

Increased by 20%
Fetal blood transfers H+ ions to the intravillous space of the placenta, which leads to increased pH in fetal blood and increased oxygen affinity, promoting transfer of oxygen to blood

Question 15

Prolonged fetal hemoglobin

Answer 15

premature babies
babies of mothers with diabetes
people with hemolytic anemia
people with diseases like myelodysplasia and leukemia

Question 16

Hg A2

Answer 16

Same bohr effect, cooperativity, and 2,3 BPG affinity

More heat stable, slightly higher O2 affinity

Question 17

Heinz bodies

Answer 17

precipitated denatured hemoglobin that can be seen with a special stain.
Caused by mutations producing an unstable hb molecule leading to a mild hemolytic anemia

Question 18

Hb Chesapeake

Answer 18

Hb with increased O2 affinity

asociated with erythrocytosis

Question 19

Hemoglobin Zurich

Answer 19

-point mutation that doesn’t affect O2 binding but increases CO affinity
Carboxyhemoglobin levels approach those of smokers

Question 20

Hemoglobin Koln

Answer 20

Most common unstable HbG. Mild anemia, reticulocytosis, and splenomegaly

Question 21

Methemoglobin

Answer 21

Fe+2 binds oxygen (ferrous)
Fe+3 does not (ic)
Methemoglobin has Fe 3+ and can’t bind O2

Question 22

Causes of Methemoglobinemia

Answer 22

1) Methemoglobin overproduction
2) Decreased methemoglobin reduction by NADPH methemoglobin reductase pahtway
3) Heme oxidation by free radicals, H202, NO, or Oh

Question 23

Acquired Methemoglobinemia

Answer 23

Typically caused by exposure to chemicals (benzocaine, nitrates in drinking water)
Infants are especially at risk

Question 24

Hereditary methemoglobinemia

Answer 24

Commonly due to homozygous deficiency in cytochrome b5 reductase
Also can be caused due to mutation of Hb that produces HbM by inhibiting reduction of Fe

Question 25

Methemoglobin Clinical findings

Answer 25

• High amounts of methemoglobin reduces O2 capacity and increases O2 affinity
• People with up to 40% of methemoglobin are typically asymptomatic but cyanotic

Question 26

Dx of Methemoglobinemia

Answer 26

Suspected: person looks cyanotic but arterial PO2 is normal

-Conclusive - Blood looks chocolate or brown blue and does not change with additional o2 exposure

Question 27

Treatments

Answer 27

HgM: None

Cytochrome b5 deficient: treat w/ methylene blue or ascorbic acid for cosmetic reasons

Question 28

Acquired Methemoglobinemia

Answer 28

Levels above 60% can be lethal

Treated by removing chemical and methylene blue (provides electron acceptor for Fe reduction via NADPH pathway)

Question 29

Dx and treatment of Carbon monoxide poisoning

Answer 29

Dx: Co-oximetry (Pulse oximetry with 4 diodes)

Treatment= oxygen or Hyperbaric oxygen (decreases 1/2 life of CO hemoglobin)

Question 30

Pulse Oximetry

Answer 30

Photo detector and 2 light diodes (660 nm and 940 nm)
Hemoglobin and Deoxyhemoglobin have different absorption spectrums at the region
Methemoglobin and carboxyhemoglobin aren’t distinguished with this.