Blood products in ICU Flashcards
Describe the transfusion trigger in the ICU
Generally: Hb of < 7g/dL
Exceptions
1. Active bleeding
2. Active ischaemia
3. Evidence of poor tissue oxygenation
Then the trigger is Hb < 10g/dL
Summarise the types of acute transfusion reactions
ACUTE and potentially life threatening
- TRALI (donor anti-HLA or anti-PMN antibodies)
- TACO
- Acute hemolysis (ABO incompatibility)
- Anaphylaxis
- Sepsis
- Allergic (Itching and hives)
- Febrile non-haemolytic (Fever only - cytokine release)
- Hypotensive (vasoactive kinins - bradykinin - associated with recipient on ACEI)
OTHER associated effects
TRIM - Transfusion Related Immunomodulation
- Immunosuppressant effect
STORAGE Lesions
- Prolonged storage of blood products leads to:
1. Depletion 2.3 DPG (reduced O2 carriage)
2. Hyperkalaemia, Hypocalcaemia, Hyponatraemia)
3. Acid/Base abnormality
4. Reduced RBC deformability
What is the differential diagnosis for low platelets in the critically ill patients
NB - exclude plt clumping:
Plt s can clump in EDTA tube. Repeat in heparin or citrate tube and correlate.
- DIC
- Infections (Increased phagocytosis of plts by macrophages)
- HIV - plts destroyed via immune mechanisms
- Hypersplenism
- TTP
- HELLP
- HITT: Heparin Induced Thrombocytopaenia
- Drugs: Bactrim. Rifampicin
What are the different types of HITT
Heparin Induced Thrombocytopaenia
Type 1 - Direct toxic effect of heparin
Type 2 - Ag-Ab response against heparin-PF4 complex. Leads to activation of plts that are cleared by the RES.
What is DIC
Disseminated Intravascular Coagulation
Widespread endothelial damage due to sepsis/trauma leads to TF activation.
- Activation of coagulation cascade (Fibrinogen, plts drop with increase PTT)
- Inhibition of anticoagulant pathways
- Activation of fibrinolytic pathways (Increase D-dimers)
Net result is widespread microvascular thrombosis which may lead to multi-organ dysfunction
Describe how the diagnosis of DIC is made
Score global coagulation tests
- Platelets: > 100 = 0. <100 = 1. <50 = 2.
- D-dimer: No increase 0. > 0.4 = 2. > 4.0 = 3.
- Prothrombin time < 3 secs = 0. > 3 secs = 1. > 6 secs = 2
- Fibrinogen > 1 = 0. < 1 = 1.
Calculate score:
If > or = to 5 then compatible with DIC
If < 5 unlikely DIC. Repeat 1-2 days time
Describe the causes of abnormal platelet function
- Drug related (Aspirin/Plavix)
- Renal failure - Impaired fibrinogen binding to platelets and abnormalities in vWF –> so platelets cannot anchor to damaged endothelium
What can be used to treat platelet dysfunction secondary to uraemia
- Premarin (oestrogen)
- ? mechanism
- Works < 24 hrs and lasts 2 weeks - DDAVP
- Increase endothelial release of vWF and factor VIII
What are the limitations of adminstration of DDAVP for platelet dysfunction in uraemia
Tachyphylaxis can develop
Limit use to 3 - 4 days
What are the indications for a platelet transfusion
< 10 000 in adult stable patient
< 20 000 if risk of bleeding significant (e.g. PUD)
< 50 000 if broncho-endoscopic biopsy planned. (Except neurosurgery or eye surgery: > 100 000)
What is the target Plts for a trauma patient with massive transfusion?
> 100 000 to decrease risk of ICH
What is the concern with transfusing platelets to patients with TTP or HIT
Increase risk of thrombosis
What platelet level can a CVP, bone marrow aspirate/biopsy be done
Platelets > 10 000 provided platelet function is normal
What is HIV related TTP and what is the pathophysiology
Thrombotic Thrombocytopaenic Purpura
Deficiency of a specific von Willebrand factor-cleaving protease (ADAMTS13) - autoantibodies directed against ADAMTS13.
- leads to accumulation of abnormally large vWF multimers –> platelet clumping and deposition of platelet rich thrombi in tissues
What is the management of TTP
- Start ARVS
- FFPs: 30 ml/kg/day until normalization of platelet count
- Unresponsive patients should be referred for plasma exchange +- biologicals
