BLOOD, DCR & FLUIDS (62) Flashcards
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1
Q
INTRA-OSSEOUS BLOODS
A
IO Bloods appear Leukaemic, so:
- cant be used for cell counts, eg WCC and Platelets
- can be used for Hb measurement and X match
- but are unreliable for some electrolytes
2
Q
WHATS IN A UNIT OF FFP?
A
- traditionally, one unit of FFP = the snap frozen plasma fraction of a single blood donation after the cells have been spun off
- it’s typically ~250 mls and contains most of the clotting factors, but only ~1/2 the FIBRINOGEN, so Fibrinogen topups (CRYOPRECIPITATE or concentrates) are required in Massive Transfusion
- increasingly, Plasma is being sieved off directly from donors by APHERESIS
3
Q
WHY DO WE FREEZE (OR FREEZE DRY) PLASMA?
A
- Freshly collected Plasma has a short storage life of 5 days at 1-6C, so most is snap frozen soon after collection for long term storage
- Plasma can also be FREEZE DRIED (aka LYOPHILISED) to produce a a lightweight product with a long room temperature shelf life. It was widely used in WW2 but discontinued soon after as it was a pooled product with infectious concerns. It is undergoing renewed interest for austere use.
Note: the 2nd World War plasma must have been universal donor sourced from AB donors, given the lack of field cross match
4
Q
HOW TO THAW FFP
A
- FFP is thawed in a 37C waterbath for 20m
5
Q
STORAGE LIFE OF THAWED FFP?
A
- thawed FFP should be used within 6h, or stored at 1-6C for 5 days
6
Q
WHATS IN CRYO-PRECIPITATE ?
A
- Cryoprecipitate is a clotting factor concentrate produced by thawing a unit of FFP to just above zero degrees C, and collecting the ‘cold insoluble’ proteins that precipitate
- it contains high levels of Fibrinogen, F8 and VWF
- it was originally used for F8 replacement in Haemophillia, but is now mostly used for Fibrinogen replacement in coagulopathy
7
Q
STORAGE OF CRYOPRECIPITATE
A
- paradoxically, perhaps, CRYO is stored at room temperature and is ruined by freezing
8
Q
WHATS IN A UNIT OF PLATELETS?
A
- traditionally, one unit of platelets contained the pooled platelets from 4 RANDOM blood donations (ie unmatched), suspended in a small amount of plasma
- increasingly, platelet ‘4 packs’ are being ‘APHERESED’ from SINGLE DONORS (allowing matching if desired).
9
Q
HOW ARE PLATELETS STORED?
A
- Traditionally, platelets can be stored at room temperature for 5 days with constant agitation, but are ruined if cooled
- Alternatively, platelets can be Deep Frozen for long term storage if DMSO* treated first.
- Surprisingly, the freeze/thaw process increases platelet activity, (producing thrombo-embolic concerns) although the resultant clots are less stable, possibly increasing rebleeding risk.
* Di-methyl-sulphoxide : thawed platelets smell of sulphur!
10
Q
RBC STORAGE
A
-
traditionally, RBC can be stored for 4-6 weeks at 1-6 degrees C by adding of one of the proprietary preservatives, eg ACD or CPD, but accumulate an increasing STORAGE LESION as they age, including 2-3DPG depletion, which
- impairs their ability to give up O2 at the tissues
- persists for hours after transfusion
- and is only partly reversible.
- For this reason, RBC given in massive transfusion should be as fresh as possible, preferably <21 days
- alternately, RBC can be suspended in Glycerol and deep frozen for many years, but take 90 minutes to thaw and de-glycerolise for use.
11
Q
HYPOCALCAEMIA AND STORED BLOOD PRODUCTS
A
- all 3 major blood products (RBC, FFP and PLATELETS) are ‘CITRATED’ to bind CALCIUM and prevent activation of the coagulation cascade in storage.
- As such, hypocalcaemia can occur early in massive transfusion and Calcium administration should not be forgotten.
12
Q
STORAGE OF FWB
A
- FWB can be kept at room temperature for 18h only, after which it needs to be refrigerated at 1-6C, which permanently inactivates the platelets
13
Q
WHAT ARE THE ABO, RHESUS AND MINOR BLOOD GROUPS?
A
- A patient’s blood may be classified or ‘typed’ according to the presence or absence of a variety of antigens on the Red Cell surface.
- Incompatibility between RBCSAg and plasma antibodies, eg after transfusion, can cause cell lysis
- The most important RBCSAg are the A and B antigens, because the reciprocal plasma antibodies are always expressed, irrespective of prior transfusion
- The patient’s blood type is classified
- ‘A’ if A antigens are present
- ‘B’ if B are
- ‘AB’ if both are
- and ‘O’ if neither are.
- Similarly, blood may be further subtyped according to the presence or absence of a host of other ‘minor’ antigens, including RHESUS, KELL etc.
14
Q
CROSS MATCHING BLOOD - RBC
A
- it is essential to ensure that the recipient plasma does not contain antibodies which can attack cell surface antigens on the donor RBC.
- Antibodies to the A&B antigens are most important, given their universal expression, then Rhesus, then the minor groups
- the first test for compatibility is the ‘TYPE AND SCREEN’:
- the ABO TYPE of the recipients Red cells is determined (and thus by reciprocity whether A or B antibodies will be present in their plasma)
- then their plasma is SCREENED for a standard battery of minor group antibodies.
- These 2 steps determine which antibodies are present in the recipient, and allows identification of potentially compatible donor units.
- secondly, the selected donor unit is CROSS MATCHED by physically mixing it with the recipient plasma, to check it doesn’t clot or Lyse.
15
Q
CROSS-MATCHING BLOOD : FFP
A
- whilst Donor FFP contains no RBCSAg, and hence is not at risk of attack by antibodies in the recipient plasma, it may contain sufficient Antibodies of its own to launch an attack on the recipient RBC.
- hence FFP should be ABO matched, or Universal Donor AB FFP used*.
- If unavailable, A is the next safest choice.
* Dave Roxby says Rh compatibility is not important
16
Q
CROSS-MATCHING BLOOD: PLATELETS
A
- whilst platelets do not have RBCSAg, and hence are not at risk of lysis by recipient antibodies, they do contain some plasma which could theoretically mount an attack on the recipient red cells, but these reactions are generally minor and the traditional platelet ‘4 PACK’ is a POOLED RANDOM DONOR product so it cant be matched anyway
- APHERESIS PLATELETS are single donor, so can be matched if desired, but most platelets are still given unmatched in trauma
17
Q
WHO IS THE UNIVERSAL DONOR FOR RBC, PLASMA AND WHOLE BLOOD?
A
- UNIVERSAL DONOR RBC come from O- donors, because they have no A, B or Rhesus (D) RBCSAg, hence cannot be attacked by the reciprocal antibodies
- conversely, Universal donor Plasma is AB*, as it comes from donors with both A and B antigens on their RBC, hence neither of the reciprocal Antibodies are expressed in their plasma
- NOTE: these 2 reciprocal requirements mean that, strictly speaking, THERE IS NO UNIVERSAL DONOR FOR FWB, although in practice, RBC compatibility is much more important than plasma compatibility, and O Neg FWB can usually be safely given, particularly if sourced from donors known to naturally produce low Anti-A and Anti-B antibody titres.
* not, as is often stated, AB+: Rh compatibility is unimportant with plasma
18
Q
HOW TO CROSS MATCH FRESH WHOLE BLOOD
A
tba
19
Q
WHAT WARMERS AND FILTERS SHOULD BE USED TO GIVE BLOOD PRODUCTS?
A
- cold blood products (RBC and (thawed) FFP) should be given via 37 degree warming devices, but PLATELETS are stored at room temperature so warming is less important, and indeed is generally avoided due to (unfounded) concerns it damages them
- all blood products should be given through 200 micron filters* to remove larger clots, AND platelets should only be given thru virgin filters that have not had other blood products through them, or risks activation of the platelets in the filter, clogging it
- some advocate using finer 40 micron filters to remove micro clots and reduce TRALI, but these clog quickly & evidence of benefit is weak
* these are found in standard giving sets
20
Q
INR: ORIGINAL USE AND NR
A
- the INR was initially developed to monitor Warfarinisation
- it tests ONLY the INITIATION PHASE of the coagulation cascade.
- N = 0.8-1.2
- DVT Rx = 2-3
- Valve prophylaxis = 3-4
21
Q
APTT: ORIGINAL USE AND NORMAL & THERAPEUTIC RANGES
A
- the APTT tests Heparinisation
- Normal = 26-40 s
- Heparinised = 50-80 s
22
Q
WHAT IS HEPARIN? & BASIC DOSING
A
- Heparin is a naturally occurring anticoagulant found in the Mast cells of all animals*
- it enhances the activity of ANTI-THROMBIN III, an endogenous THROMBIN (Factor 2) inhibitor.
-
Dose:
- LD 5000u IV, then 1000u/hr vs APTT
- PERIOPERATIVELY: T1/2 = 1h, stop 4h preop
* but originally isolated from canine liver, hence Hepar-in
23
Q
WHAT ARE the LMW HEPARINS?
A
- NATURAL HEPARIN consists of a spectrum of molecules of different sizes.
- Heparin preparations containing only the LOW MOLECULAR WEIGHT (LMW) fractions have the following advantages
- can be given BD S/C instead of requiring IV infusion
- do not require APTT monitoring
- have less risk of bleeding
- less risk of HITS
- but, are less reversible by PROTAMINE
24
Q
WHAT IS PROTAMINE?
A
- PROTAMINE is a Heparin binding and inactivating protein, originally derived from salmon spermatozoa, but now synthetic
-
DOSE:
- 1mg of Protamine neutralises 100u of Heparin (or 1 x 50mg Amp neutralises 5000u)
- Give very slow IV as it causes Anaphylactoid reactions
