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Flashcards in Haem1 Deck (417)
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151

What blood can an O- and O+ person receive?

O- can only receive O-

O+ can receive both O+ and O-

No A or B can be given because the recipient will have antibodies
Negative can only receive negative
O does not have A or B antigens

152

How much will 1 unit of PRBCs raise the HCT by?

Approx 4%

153

When are frozen red blood cells used?

Rare blood types
Occasionally - severe leukoagglutinin reactions or anaphylactic reactions

154

Why are the A and B antigen important in blood types?

If you lack one, you have an IgM isoantibody to it (isoagglutinin) --> complement gets activated --> rapid intravascular lysis.

155

Why is type O negative blood used in emergencies?
What needs to be done to it?

It does not have A or B antigens, and thus can be given to anyone.

PRBCs can only be given (the plasma has to be separated out)  because the donor plasma contains Anti-A or Anti-B antibodies.

156

Why is the Rhesus antigen important in blood typing?

Rh D antigen is highly immunogenic
Anyone who receives D+ blood when they are D- will subseuqnetly make highly active anti-D antibodies that cause severe lysis of subsequent transfusions of D+ red cells or to a future rhesus positive baby

157

Why is anti-D given to rhesus-negative mothers?

Stops allo-immunisation by destroying any Rh-D positive fetal erythrocytes that get through to the maternal system before the mother can make her own antibodies.

Prevents haemolytic disease (rhesus disease) of the newborn.

Okay if you have an RH+ mother and an Rh- fetus

158

What causes haemolytic transfusion reactions?

Acute
ABO incompatibility - isoagglutinin mediated
Mostly due to clerical errors and mislabelled specimens
Rapid intravascular haemolysis - most severe usually when the patient is under anaesthesia

Delayed
Minor RBC antigen discrepancies, less severe, IgG alloantibody mediates
5-10 days post transfusion
Most common antigens are duffy, Kidd, Kell and Rh C and E

SSx
Fever, chills, backache and headache
Apprehension, dyspnoea and hypotension
Generalised bleeding and oliguria
Severe:  DIC, ARF due to ATN

Delayed:  usually w/o SSx

Tx - hydration, maybe forced diuresis with mannitol

159

What is a leukoaggluttinin transfusion reaction?

Leucocyte rich blood products esp platelets cause - happens in 1-2% of transfusion
Fevers and chills within 12 hours post
No haemolysis
Responds to panadol and dipenhydramine, steroids

Less of an issue now with leuco depletion
Different to a hypersensitivity reaction

160

What is the cause of a blood product hypersensitivity reaction?

Exposure to allogeneic plasma proteins (not leukocytes)

Anaphylactic shock may develop in IgA deficient patients because of IgA antibodies in the plasma component of the donor product.

May require washed or frozen PRBCs next time.

161

Under what circumstances does contamination of blood products occur?

Platelets especially because they cannot be refrigerated

Gram positive contaimination will cause fever and bacteraemia but rarely sepsis.

Gram negative will cause septic shock, acute DIC and ARF due to transfused endotoxin - usually fatal.

Reduced by
Aseptic technique
Diverting first few ml of donated blood
Single donor products (instead of pooled)
POC bacterial screening to discard dodgy units

162

Which blood products can transmit viral diseases?

All blood products can.
Risk of post-transfusion viral hepatitis is very low.
Leukodepletion has greatly reduced CMB transmission, possibly equivalent to CMV-screened negative blood products.

163

What is tranfusion graft-versus-host disease?

Usually fatal, fever, rash, diarrhea, hepatitis, lymphadenopathy and severe pancytopaenia

Usually in patients with immune defects, malignant lymphoproliferative disorders, chemo or immunotherapy, immunosuppression, old patients getting cardiac surgery

HIV alone does not increase risk

Leukodepletion doesn't avoid, need to irradiate the blood products if high risk.

164

What is TRALI?  What causes it and how does it present?

Transfusion-related Acute Lung Injury

Allogeneic antibodies in donor plasma bind to recipient leukococyte antigens including HLA, granulocyte and monocyte specific.

Definition:  Non-cardiogenic pulmonary oedema after a blood product transfusion without other explanation.  Surgical and critically ill patients most susceptible.

Reduced with male only plasma, treated with supportive care.

165

At what platelet level is there a higher risk of spontaneous bleeds?

Life threatening bleeding?

When do you transfuse?

What do you aim for?

<80

<5

Given when less then 10

In thrombocytopaenia pre-op patients, goal is to get the platelet count >50

166

What are the causes of poor platelet response post transfusion?

Fever, sepsis
Splenomegaly
Lagre habitus
Low platelet dose in transfusion
Platelet alloimmunisation from prior transfusion
Prior pregnancy
Prior organ transplantation
May get alloantibodies directed at HLA antigens - can get HLA matched antigens if this is the case.

167

In the rare circumstance that you would have to get a granulocyte transfusion (ie failed G-CSF), what needs to happen?

Must be ABO matched
Must be irradiated to prevent lymphocyte proliferation and prevent GVHD without funcitonal harm to the granulocytes or containing platelets.

BUT not commonly used anyway

168

What are febrile non-haemolytic transfusion reactions mostly due to?

Recipient has antibodies to donor antigens on leukocytes (granulocytes) due to previous transfusion or pregnancy.

Leucodepletion reduces febrile non-haemolytic transfusion reactions as a result.

169

A 19-year-old woman presents with recent-onset of right leg swelling and pleuritic chest pain and is found to have iliofemoral thrombosis on Doppler ultrasound examination.  Results of a ventilation-perfusion lung scan indicate a high probability for pulmonary emboli.  She had been taking the oral contraceptive pill for the last three years but has now ceased.  She is a non-smoker.  There is no significant medical history and no known family history of venous thromboembolism. 
 
Which one of the following investigations for an underlying hypercoagulable state is most likely to be affected by the presence of the extensive thrombosis? 
 
A. Antiphospholipid antibody screen. 
 
B. Antithrombin level. 
 
C. Factor V and prothrombin genotype assessment. 
 
D. Activated partial thromboplastin time (APTT). 
 
E. Full blood count including blood film. 

B

170

What is the mechanism of ITP?

Antiplatelet antibody to glycoprotein IIb/IIa or Ib/IX on the platelet membrane --> platelet destruction --> mucocutaneous bleeding

171

What is the aetiology of ITP?

Primary / idiopathic
Medication related (Thiazides, penicillin, GPIIB/IIIa inhibitors (ie tirofiban, Heparin)
Hep-C
HIV

172

What is the mechanism of ITP in HIV?  Hep-C?

HIV:  Direct suppression of platelet production

Hep-C:  Cirrhosis related splenomegaly

173

What are the clinical findings in ITP?

Mucocutaneous bleeding:  nosebleeds, gingiva
Spontaneous bruising
Usually at PLT counts <20-30

Disease specific findings if HIV or Hep-C

174

What are the lab findings in ITP?

Isolated thrombocytopaenia
Anaemia if they've bled
Exclude HIV and Hep-C
BMBx for cytopaenias if over 60 or failed to respond to ITP therapy

Megakaryocyte abnormalities are not ITP

175

What is the treatment of ITP?

Treat when PLT <20-30 or significant bleeding

Mainstay:  short course of corticosteroids however most relapse.  Plus or minus IVIG or anti-D (WinRho)

Persistent plt count <30 after roids:  second line treatment (anti D, IviG are both temporary), rituxmiab works in up to 50%.  Splenectomy an option

176

Name the thrombopoietin receptor agonists

Eltrombopag
Romiplostin

Used in chronic ITP for people who have not responded to corticosteroids, IvIG or splenectomy or in cirrhosis due to hep-C. Must be taken indefintely

177

What vaccinations should be administered pre-splenectomy?

Patients should receive pneumococcal, Haemophilus influenzae type b, and meningococcal vaccination at least 2 weeks before the procedure

178

What are the goals and management of pregnancy-associated ITP?

The goal of management of pregnancy-associated ITP is a platelet count of 10,000–30,000/mcL in the first trimester, >30,000/mcL during the second or third trimester, and >50,000/mcL prior to cesarean section or vaginal delivery. Moderate-dose oral prednisone or intermittent infusions of IVIG are standard. 

179

How is the thrombocytopaenia of HIV and Hep-C managed?

Treatment of either infection improves platelet count in most cases

Refractory thrombocytopenia may be treated with infusion of IVIG or anti-D (HIV and hepatitis C virus), splenectomy (HIV), or interferon-alpha or eltrombopag (hepatitis C virus, including eradication). 

Treatment with corticosteroids is not recommended in hepatitis C virus infection.

180

A 30-year-old man has previously undergone splenectomy (six months prior) for chronic idiopathic thrombocytopenic purpura (ITP). Apart from occasional bruising, there are no haemorrhagic symptoms. 

His full blood examination shows:
 
_
Repeated autoimmune and viral serology remain negative. 

The most appropriate management of his thrombocytopenia is: 

A. danazol. 

B. immunoglobulin. 

C. prednis(ol)one. 

D. azathioprine. 

E. observation. 

E.  Platelet count gets treated when <30 in refractory cases or if bleeding.