Transfusion, Transplant and Radiation Flashcards
1
Q
LINAC
A
- X-rays from linear accelerator (LINAC); electron accelerated toward positive target –> when it hits target it decelerates and gives off a photon which interacts w/ electrons in tissue (knocks a tissue electron out of its orbit)–> indirect damage via free radicals OR direct DNA damage
- Electron interacts w/ water –> radical which damage DNA
- OR electron directly interacts w/ DNA
2
Q
Radiation Units
A
- Absorbed dose - Rads or Grays
- 1 gray = 100 rads
- Equivalent dose = absorbed dose x radiation quality (measured in Sieverts)
- Gamma and Xrays have radiation quality of 1 so 1 gray = 1 Sievert
3
Q
4 R’s of Radiation
A
- 1- Repair - normal tissue can repair the sublethal DNA breaks that tumor cells cannot (must wait enough time b/n fractions for normal tissue to repair)
- 2- Reassortment - during specific phases of cell cycle there are different radio-sensitivities so waiting for next fraction gives time for tumor cells to reach a new, more susceptible phase of cell cycle (inc damage to tumor)
- Mitotic most susceptible
- Late S phase least susceptible
- 3- Re-oxygenation - oxygenated cells more sensitive b/c more free radical production
- Killing oxygenated cells near capillaries dec diffusion distance to less oxygenated cells (these cells now closer to capillary - more susceptible to next fraction of radiation)
- 4- Re-population - if radiation not completed soon enough the tumor cells can regrow
4
Q
What are the 2 main uses of HSC transplant?
A
- 1- RESCUE; use chemo +/- radiation to ablate existing BM then replace w/ HSCT
- 2- IMMUNOTHERAPEUTIC; use donor cells that recognize antigens on tumor cells as foreign and mediate immune response against them (“graft v leukemia” GVL)
- More intense - higher mortality - lower chance relapse
5
Q
HLA System
A
- Found on chromosome 6; usually inherit complete haplotype from ea parent so siblings have 25% chance matching
- Major
- Class I - HLA-A, B, C
- Class II - HLA-DR, DQ, DP
- Minor - initiate weaker immune response
- Need 6/8 or 8/10 match in adult donor
6
Q
Pre-HSC Transplant Regimen
A
- Goal = destroy tumor cells + immunosuppress for engraftment
- Myeloablatives = busulfan, cyclophosphamide, melphalan, etoposide
- Immunosup = fludarabine, ATG, alemtuzumab
7
Q
GVHD
A
- (graft v host disease) - mediated by minor HLA; tissue injury –> inflammation and cytokines –> donor T cells attack host cells
- Immunosuppress for 100+ days after transplant to prevent (steroids, calcineurin inhibitors, ATG)
- Seen as maculopapular rash, nausea/vomiting, diarrhea, elevated LFTs
8
Q
3 Phases of Post HSC Transplant Infection + Prophylaxis
A
- Phase I - (b/f engraftment) HSV/RSV/Candida
- Phase II - (100 days post-engraftment) - CMV, RSV, enteric, EBV, Candida, Aspergillus, PJP
- Phase III - (after day 100) encapsulated bacteria (functional asplenia), CMV, VZV, aspergilus, PJP, other fungi
- **Typical prophylaxis = antiviral (acyclovir), antifungal (fluconazol), abx (cipro)
- PJP prophylaxis = bactrim, pentamide, dapsone
9
Q
ABO Serology
A
- Carb antigens on RBC surface added to surface by glycosyl transferase (A and B genes code for the enzyme that adds the carb to the RBC surface)
- A (40%) - n-acetylgalactosamine on surface; anti-B antibodies
- B (10%) - galactose on surface; anti-A antibodies
- AB (5%) - no antibodies
- O (45%) - both anti-A and anti-B antibodies
- Antibodies form by 3-4 mo
- Usually IgM
- Cause hemolytic transfusion reactions and organ transplant rejection
10
Q
Rh Serology
A
- Rh - protein antigen that spans RBC membrane; most important is D antigen in 85% individuals
- Rh - patient can make anti-D antibody if exposed to Rh+ blood (pregnancy or transfusion)
- IgG antibodies that can cause extravascular hemolysis
- Hemolytic disease of newborn - when mom’s anti-D hemolyzes fetal red cells (prevent w/ Rh Ig anti-D that neutralizes mom’s anti-D)
11
Q
Type
Screen
Crossmatch
A
- Type - determine ABO/Rh type and
- To determine type, incubate pt RBCs w/ anti-A, anti-B and anti-D ab then look for agglutination (ex- blood type A will agglutinated if given anti-A ab)
- Screen - screen pt plasma for unexpected antibodies w/ indirect anti-globulin test
- Indirect anti-globulin - add reagent red cells to pt serum to sensitize it then enhance w/ Coombs reagent
- IgG more sig than IgM b/c bind at body temp or higher
- Ex) Rh, Kell, Kidd, Duffy, Ss
- Use type and screen when transfusion may be needed but not expected
- Indirect anti-globulin - add reagent red cells to pt serum to sensitize it then enhance w/ Coombs reagent
- Crossmatch - pt serum incubated w/ donor RBCs to sensitize them; then add Coomb’s reagent to enhance
- Full 30 min if antibody screen is pos
- Abbreviated 5 min if antibody screen is neg
- Type and cross is used when transfusion is expected
- Uncrossmatched- give Group O if life threatening
12
Q
Packed Red Cells
A
- 350 cc (RBCs, anti-coagulant preservative for storage and some plasma)
- Ea unit is expected to inc Hb by 1gram/dl and inc HCT by 3%
- Can store for 42 days w/ anti-coag preservative
- Indications - symptomatic anemia
- Acute MI, infarction need higher HCT
- Esp if cardio-pulmonary problems
- If HCT < 21%
13
Q
Whole Blood Platelets
A
- Ea unit derived from one unit of whole blood = 8 x 10^10 platelets and all coagulation factors
- Recommend 4 units for adults
- Stored for 5 days at room temp
- Indications
- Prophylaxis if platelets <10,000
- Sig bleeding or undergoing procedure and platelets <50,000
- Platelets <30,000 if less significant procedure
14
Q
Apharesis Platelets
A
- 1 dose equal to 4 units of whole blood platelets; so can come from single donor (HLA type)
- Also store for 5 days at room temp
15
Q
Plasma (FFP)
A
- 200-250 ml of plasma coming from 1 unit whole blood
- Frozen for up to 1 yr and thawed when needed
- Give 3-5 units in an adult
- Contains all coagulation factors
- Indications
- To reverse coagulopathy (INR >1.5) if bleeding or undergoing surgery
- Immediate reversal of Warfarin
