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AP III > Blood, Anemia > Flashcards

Blood, Anemia Flashcards

1
Q

What are the components of the CPDA1 Preservative?

A

1) Citrate: Chelates Calcium, disrupting clotting mechanism
2) Phosphate: Buffer
3) Dextrose: energy source for cellular metabolism
4) Adenine: Substrate source for cells to produce ATP
-Extends shelf life to 35 days
-Preserves blood and prevents coagulation

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2
Q

What is the difference in shelf life between CPD (without adenine) vs CPDA1?

A

CPD (without adenine): 2 weeks
CPDA1: 35 days

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3
Q

What are the benefits of Component Therapy?

A

Maximizes the number of recipients and preserves function of essential blood elements.

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4
Q

What are the basic purposes of transfusing each component?

A

-Packed RBCs: oxygen carrying capacity
-Platelet concentrates: thrombocytopenia
-Fresh frozen plasma: coagulation proteins
-Cryoprecipitate: Fibrinogen, Factors VIII vWF, XIII
-Leukocyte poor RBCs: filtration to remove WBCs

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5
Q

Describe the process of separating blood components:

A

1) First centrifuge at room temperature produces platelet concentrates
-By separating plasma (containing platelets) from RBCs
2) Then the other products are separated by centrifuging at cold temperatures (1-6˚ C)

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6
Q

Describe PRBCs with CPDA-1

A

Hct 70-75%
50-70 mL of residual plasma
Volume 250-275 mL
Shelf life 35 days
-Similar pH and K+ content to additive solution

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7
Q

Describe PRBCs with Additive Solution:

A

Hct 60%
Less plasma (10-15 mL)
Volume 250-350 mL
Less citrate
Longer shelf life–42 days
Regenerates 2,3-DPG more quickly
Less TRALI
-Similar pH and K+ content to CPDA-1

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8
Q

1 unit of PRBCs should increase Hgb by ___ g/dL or the Hematocrit by approx. ____%

A

1 unit of PRBCs should increase Hbg by 1g/dL or the hematocrit by approximately 3%

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9
Q

Describe biochemical changes that occur in stored PRBCs.

A

1) pH decreases to 6.7 by 21 days
2) K+ = 4 mEq day of donation → 76 mEq at 35 days (slow leak of K+ from banked blood)
3) Dextrose:
-Day of donation raises blood sugar to 400 mg/dL
-At 35 days glucose level drops to 100 mg/dL
4) Decreased 2,3 DPG:
-Levels at 10% of baseline at 35 days, left shift in Oxy-Hgb curve

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10
Q

What is 2,3 DPG?

A

A compound that binds deoxyhemoglobin and increases oxygen delivery to cells).
-Decreased levels shift oxyhemoglobin dissociation curve to the left (increased O2 affinity for Hgb)
- 2,3 diphosphoglycerate and it comes from glycolysis

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11
Q

What are saline-washed RBCs?

A

For patients who experience reactions to foreign proteins that attach themselves to RBCs
-↓allergic reactions due to IgE or IgA antibodies
-Washed with isotonic saline solution
-Resulting units must be transfused within 24 hours

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12
Q

What are Leukocyte-reduced RBCs?

A

-Filtration or irradiation
-Done to eliminate or reduce white blood cell passengers
-Prevent non-hemolytic febrile transfusion reactions

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13
Q

What is the Hgb level that triggers transfusion?

A

There is NO transfusion trigger or Hgb level at which to transfuse.

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14
Q

What is Chronic Anemia?

A

-S/Sx begin to develop at a Hgb of <7/8 g/dL
Compensatory mechanisms:
-Increased cardiac output
-Increased 2,3 DPG so that oxygen unloads at lower oxygen saturation of hemoglobin
-Healthy bone marrow can increase production up to 6-fold

Decision to transfuse depends on pt’s underlying health status, the s/sx of decompensation due to anemia, cardiorespiratory reserve, and activity level
Chronic anemia patients rarely require transfusion until Hgb levels drop to 5g/dL overwhelming compensatory mechanisms.

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15
Q

Tolerance of acute anemia depends on what?

A

-Maintenance of intravascular volume
-Ability of the patient to increase cardiac output
-Health of the patient

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16
Q

What is the major function of RBCs (erythrocytes)?

A

To transport Hemoglobin.
-The bound hemoglobin carries oxygen from the lungs to the tissues of the body.

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17
Q

Describe the structure of hemoglobin.

A

-Hemoglobin has four protein subunits
-The binding affinity of hemoglobin for O2 is increased by the oxygen saturation of the molecule
-When the first oxygen binds, it influences the shape of the binding sites for the next O2 molecule, making it easier to bind
-Alterations or abnormalities in these subunits or hemoglobin chains can alter the physical characteristics of the hemoglobin molecule. Ex: Sickle Cell

18
Q

What is the Oxygen-Hemoglobin Dissociation Curve?

A

Describes the relationship between available oxygen and amount of oxygen carried by hemoglobin.
-The horizontal axis is Pa02, or the pressure of oxygen in the blood (mmHg).
-The vertical axis is SaO2, or the amount of hemoglobin saturated with oxygen, shown as a percent.
-Once the PaO2 reaches 60 mmHg the curve is almost flat, indicating there is little change in saturation above this point. So, PaO2 of 60 or more is usually considered adequate.
-But, at less than 60 mmHg the curve is very steep, and small decreases in the PaO2 greatly reduce the percent saturation of hemoglobin.

19
Q

What is “p50”?

A

The partial pressure of O2
at which hemoglobin is 50% saturated.
-The P50 is 26-27 mmHg.

20
Q

What does an increased p50 mean?

A

Indicates a rightward shift of the curve, which means that a larger partial pressure is necessary to maintain a 50% oxygen saturation.
-This indicates a decreased affinity of the oxygen to hemoglobin.

21
Q

What does a decreased p50 mean?

A

Indicates a leftward shift and a higher affinity of the oxygen to hemoglobin.

22
Q

What factors cause a Left Shift in the O-H Dissociation Curve?

A

P50< 26-27 mmHg
-Decreased Temperature
-Increased pH (decreased H+ concentration)
-Decreased PCO2
-Decreased 2,3 DPG

Fetal Hemoglobin
Carboxyhemoglobin
Methemoglobin

23
Q

What factors cause a Right Shift in the O-H Dissociation Curve?

A

P50 > 26-27 mmHg
-Increased Temperature
-Decreased pH (increased H+ concentration)
-Increased PCO2 (Bohr effect)
-Increased 2,3 DPG

Sickle Cell
Maternal Hgb
Renal failure

24
Q

What is the Bohr effect?

A

As the blood passes through the tissues, CO2 diffuses from the tissue cells into the blood. This diffusion increases the blood PCO2, which in turn raises the blood H2CO3 (carbonic acid) and the hydrogen ion concentration. These effects shift the oxyhemoglobin dissociation curve to the right and downward, forcing O2 away from the hemoglobin and therefore delivering increased amounts of O2 to the tissues. Exactly the opposite is seen in the lungs – CO2 diffuses from the blood to the alveoli, reducing the blood PCO2 and decreasing the hydrogen ion concentration – causing a leftward and upward shift of the curve to facilitate increased binding of O2 to hemoglobin – allowing greater O2 transport to the tissues.

25
Q

What is Henry’s Law?

A

At a constant temperature the amount of a gas that dissolves in a liquid is proportional to the partial pressure of the gas in the gas phase.

26
Q

What is the PaO2 if the FiO2 is 40%? How much O2 is dissolved?

A

PaO2 x 0.003 = amount of O2 dissolved (in mL) per 100 mL of blood (!!)

-If the inspired O2 is given, estimate the PaO2 by multiplying inspired concentration by 5
-40 x 5 = 200 mmHg (estimated PaO2)
-Amount dissolved: 200 x 0.003 = 0.6 mL O2 per every 100 mL of blood

27
Q

What is the Oxygen Delivery equation?

A

DO2 = Cardiac Output x Arterial Oxygen Content
DO2 = CO x CaO2
-CO = HR x SV
-CaO2 = (Hgb x 1.34 x SaO2) + (0.003 x PaO2)

28
Q

How do you calculate arterial O2 content (CaO2)?

A

CaO2 = (Hbg X 1.34 X SaO2) + (0.003 X PaO2)
-Each gram of Hgb can carry up to 1.34 to 1.39 mL of O2.
-SaO2 is expressed as a fraction, not the whole number percentage. This accounts for the bound O2 content and the dissolved O2 portion.

29
Q

If Hgb is 15 gm and is 100% saturated, and the PaO2 is 120, then what is CaO2?

A

CaO2 = (15 x 1.34 X 1) + (0.003 X 120)
=(20.1) + (0.36) = 20.46 ml/dL
CaO2 = 20 mL of O2/dL or 200 mL of O2/L

30
Q

What is the equation for Oxygen consumption?

A

CO x ([O2]a – [O2]v)
-Normal, non-exercising difference in arterial and venous O2 content is 5 mL/dL or 50 mL/L
-O2 consumption = CO x ([O2]a – [O2]v)
= 5 L/m x 50 mL O2/L
= 250 mL O2/min

31
Q

What is the equation for Oxygen Extraction Ratio?

A

OER = Oxygen Consumption/Oxygen Delivery

OER = 250 mL O2/min / 1000 mL O2/min = 0.25 or 25%

Normal is 22-32%

32
Q

What is the Oxygen Extraction Ratio?

A

At rest:
-4x more oxygen available than oxygen consumed
-Therefore, the O2 reserve is high
-Global extraction ratio of 25%
-75 % oxygen reserve

Extraction ratios vary throughout the body:
-Heart: 55-70%
-Hepatic: 45-55%
-Renal: < 15%
-Skin: 7-10%

33
Q

Rule of Thumb for transfusion:

A

**Assuming no preoperative anemia
-Blood loss 5-10% - min replacement
-Blood loss <20% - volume expansion
-Blood loss >25% - red cell transfusion & volume expansion

34
Q

What factors should you use to judge an individual’s transfusion trigger?

A

-Increased oxygen demand (fever)
-Impaired oxygen delivery (decreased CO)
-Ability to use compensatory mechanisms

35
Q

What compensatory mechanisms are associated with anemia?

A

-Increase in cardiac output (Inc SV, dec SVR)
-Redistribution of the cardiac output
-Increased oxygen extraction
-Change in oxygen-hemoglobin affinity

36
Q

How does CO increase during anemia?

A

-Isovolumetric hemodilution is self correcting
-↓ oxygen-carrying = improvement in oxygen transport
-Oxygen delivery constant between Hct 30-45%
-Optimal oxygen transport at Hct 30%
-Further reductions in Hct result in ↑ cardiac output
-O2 transport = HCT/viscosity
-Exact Hgb at which C.O. increases is variable

37
Q

How does CO redistribute during anemia?

A

Organs with higher extraction ratios (brain and heart) receive more of the increase in blood flow.
-Coronary blood flow can increase 500%
Organs with lower extraction ratios, (muscle, skin, viscera) receive less of increase in flow.
-The heart is the organ which will determine the lower limit of anemia tolerated. When the heart can no longer increase cardiac output or coronary blood flow further hemodilution will not be tolerated

38
Q

How can oxygen extraction increase during anemia?

A

Normal basal extraction rates:
-Heart: 55-70% of oxygen delivered
-Brain: 30-35%
-Other tissue: 7-30%

Tissues can increase oxygen extraction ratios → critical compensatory mechanism
-When Hct < 25%, whole body extraction ratios increase as evidenced by decreases in SVO2
-When Hct 15%, extraction ratios increase to 60% and SVO2 decreases from 70% to 50%

39
Q

How do changes in Oxygen-Hgb Affinity occur during anemia?

A

Left shift in oxy-hgb dissociation curve:
-Lower P50: Hgb molecule “stingy”—requires lower PO2 to release O2 to tissues
-May impair tissue oxygenation

Right shift in oxy-hgb dissociation curve:
-Increased P50: ↓ affinity for oxygen—will release oxygen to tissues at higher PO2

2,3 DPG increases in slowly developing anemia.
-Shifts the oxy-hgb curve to right
-↑ synthesis of 2,3 DPG starts at Hgb = 9 g/dL
-Remember that banked blood in depleted of 2,3 DPG. Once infused, resynthesis of 2,3-DPG requires from 12-36 hours.

40
Q

What is the first compensatory mechanism in chronic anemia?

A

↑ 2,3 DPG first compensatory mechanism followed by ↑ in C.O.
-inc 2,3 dpg occurs at a Hgb <9

41
Q

What compensatory mechanisms occur with Acute blood loss?

A

Redistribution of blood flow and ↑ extraction rates are compensatory mechanisms.
-Vasoconstriction occurs, no increase in C.O.

42
Q

What are the different hematocrit endpoints for transfusion?

A

-Hct 18: Patients with long-standing chronic anemia who are well compensated; Young healthy patients with large blood loss and no other problems

-Hct 25: Middle aged patient; No cardiac disease

-Hct 30: Patients with coronary artery disease for non-cardiac surgery; Patients with LVH; Tachycardia

AP III (20 decks)

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