If you are a #medicine resident you will be called by your colleague to consult on this topic ๐๐ป
**๐๐๐ฉ๐๐ซ๐ข๐ง ๐๐ง๐๐ฎ๐๐๐ ๐๐ก๐ซ๐จ๐ฆ๐๐จ๐๐ฒ๐ญ๐จ๐ฉ๐๐ง๐ข๐**
If you wanna revise, read this thread ๐๐ป
#MedTwitter
1/18
**๐๐๐ฉ๐๐ซ๐ข๐ง ๐๐ง๐๐ฎ๐๐๐ ๐๐ก๐ซ๐จ๐ฆ๐๐จ๐๐ฒ๐ญ๐จ๐ฉ๐๐ง๐ข๐**
If you wanna revise, read this thread ๐๐ป
#MedTwitter
1/18
Let's get this right, you'll get a lot of consults for suspected HIT. Most of them won't turn out to be HIT but you must know what to do in case it is HIT !
Is every TCP in a patient receiving heparin, HIT?
NOOOO, obviously NOT
The incidence is <1% of all pts on heparin๐ฎ
2/18
Is every TCP in a patient receiving heparin, HIT?
NOOOO, obviously NOT
The incidence is <1% of all pts on heparin๐ฎ
2/18
Why is it so important to recognise it?
Because HIT is not simply thrombocytopenia ๐ฎ
It's TCP + THROMBOSIS.
That's bad, very bad !!
Can be limb or life threatening ๐ญ๐ญ
3/18
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Because HIT is not simply thrombocytopenia ๐ฎ
It's TCP + THROMBOSIS.
That's bad, very bad !!
Can be limb or life threatening ๐ญ๐ญ
3/18
#MedTwitter
So, when should you suspect HIT?
๐ธSudden โคต๏ธ in platelet count (>50%)
๐ธWeek or 2 after starting hep
๐ธLesions at heparin inj. site
๐ธThrombosis despite hep
๐ธLimb gangrene
Remember, patients don't ๐ฉธdespite the TCP๐ฎ
Suspect HIT, calculate 4T score, more on that later !!
4/18
๐ธSudden โคต๏ธ in platelet count (>50%)
๐ธWeek or 2 after starting hep
๐ธLesions at heparin inj. site
๐ธThrombosis despite hep
๐ธLimb gangrene
Remember, patients don't ๐ฉธdespite the TCP๐ฎ
Suspect HIT, calculate 4T score, more on that later !!
4/18
So who is at risk of HIT ?
Everyone who receives heparin, but these patients are at HIGH RISK ๐๐ป
๐ธโ๏ธ
๐ธadults >kids
๐ธpost ortho sx
๐ธPost CABG
๐ธIV >SC route
๐ธUnfractionated hep (UFH)>LMWH
Why is that so?
For that we need to dive deeper, into the pathogenesis of HIT!
5/18
Everyone who receives heparin, but these patients are at HIGH RISK ๐๐ป
๐ธโ๏ธ
๐ธadults >kids
๐ธpost ortho sx
๐ธPost CABG
๐ธIV >SC route
๐ธUnfractionated hep (UFH)>LMWH
Why is that so?
For that we need to dive deeper, into the pathogenesis of HIT!
5/18
HIT is an immune process, so that's antigens and antibodies and stuff !!
What's the ANTIGEN here?
It's platelet factor4 (PF4), a component of platelet alpha granule
When PF4 is exposed to heparin, it undergoes a conformational CHANGE and is now immunogenic ๐ฒ
6/18
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What's the ANTIGEN here?
It's platelet factor4 (PF4), a component of platelet alpha granule
When PF4 is exposed to heparin, it undergoes a conformational CHANGE and is now immunogenic ๐ฒ
6/18
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PF4 is โ charged
Heparin is โ charged
Heparin & PF4 = ultra large complexes (ULC) and technically these ULC are the ANTIGEN !
Long heparin chain=โคด๏ธULC formation
So, UFH forms ULC > LMWH ULC !
Thus, HIT is more likely with UFH ๐๐ป
7/18
Heparin is โ charged
Heparin & PF4 = ultra large complexes (ULC) and technically these ULC are the ANTIGEN !
Long heparin chain=โคด๏ธULC formation
So, UFH forms ULC > LMWH ULC !
Thus, HIT is more likely with UFH ๐๐ป
7/18
The heparin + PF4 complex has a variable proportion of both components.
It's been shown that โคด๏ธ โcharge =โคด๏ธimmunogenicity !
So โคด๏ธPF4 component=โคด๏ธimmunogen.
โคด๏ธโคด๏ธPF4 is released during ortho SX.
So, Ortho SX=โคด๏ธPF4=โคด๏ธimmunogenicity=โคด๏ธHIT incidence
8/18
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It's been shown that โคด๏ธ โcharge =โคด๏ธimmunogenicity !
So โคด๏ธPF4 component=โคด๏ธimmunogen.
โคด๏ธโคด๏ธPF4 is released during ortho SX.
So, Ortho SX=โคด๏ธPF4=โคด๏ธimmunogenicity=โคด๏ธHIT incidence
8/18
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Let's recap the pathogenesis:
๐ธโคด๏ธULC = โคด๏ธHIT
๐ธโคด๏ธPF4 component = โคด๏ธHIT
UFH=โคด๏ธULC formation=โคด๏ธHIT
OrthoSX=โคด๏ธPF4=โคด๏ธimmunogen=โคด๏ธHIT
9/18
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๐ธโคด๏ธULC = โคด๏ธHIT
๐ธโคด๏ธPF4 component = โคด๏ธHIT
UFH=โคด๏ธULC formation=โคด๏ธHIT
OrthoSX=โคด๏ธPF4=โคด๏ธimmunogen=โคด๏ธHIT
9/18
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Now we know when to SUSPECT HIT, who is at HIGH RISK and WHY !!
Awesome ๐ช๐ผ๐ช๐ผ
Let's move on to some scoring to strengthen your suspicion, the 4T scoreโ
Always calculate it, if >3 there is a possibility of HIT, need to test further
10/18
Awesome ๐ช๐ผ๐ช๐ผ
Let's move on to some scoring to strengthen your suspicion, the 4T scoreโ
Always calculate it, if >3 there is a possibility of HIT, need to test further
10/18
4T is >3, what do you do first ??
STOP ALL HEPARIN, STAT ๐ค
THIS INCLUDES EVEN FLUSHING CENTRAL LINES, CATHETERS ETC.
Next, get an immunoassay !!
Wait, what's that ?
11/18
STOP ALL HEPARIN, STAT ๐ค
THIS INCLUDES EVEN FLUSHING CENTRAL LINES, CATHETERS ETC.
Next, get an immunoassay !!
Wait, what's that ?
11/18
This brings us to the lab !!
There are 2 types of tests for diagnosing HIT:
๐ธImmunoassay (IA)
๐ธFunctional assay (FA)
IA = ELISA = easier & good sensitivity
FA = difficult to do but good specificity
FA = specific = confirmatory test
12/18
There are 2 types of tests for diagnosing HIT:
๐ธImmunoassay (IA)
๐ธFunctional assay (FA)
IA = ELISA = easier & good sensitivity
FA = difficult to do but good specificity
FA = specific = confirmatory test
12/18
If 4T score >3 โก๏ธget an immunoassay
It is reported as an optical density (OD)
๐ธIf OD >2, it's HIT and can avoid FA
๐ธIf OD <0.6 it's NOT HIT
If OD between the 2 values, needs FA to confirm the DX ! FA is available only in a few labs.
13/18
It is reported as an optical density (OD)
๐ธIf OD >2, it's HIT and can avoid FA
๐ธIf OD <0.6 it's NOT HIT
If OD between the 2 values, needs FA to confirm the DX ! FA is available only in a few labs.
13/18
Recap, again:
๐ธHIT, rare but serious
๐ธMore with UFH, ortho SX etc
๐ธ4T score important
๐ธSTOP HEPARIN if suspecting HIT
๐ธ2 types of tests, IA and FA
๐ธIf high 4T, order IA first, then FA
14/18
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๐ธHIT, rare but serious
๐ธMore with UFH, ortho SX etc
๐ธ4T score important
๐ธSTOP HEPARIN if suspecting HIT
๐ธ2 types of tests, IA and FA
๐ธIf high 4T, order IA first, then FA
14/18
#MedTwitter
One more thing, get B/L lower limb Doppler, silent DVT are common !
Do we need more than just stopping heparin?
Yes โ
What about platelet transfusions?
๐ธAVOID
๐ธmay โคด๏ธthrombosis
๐ธGive only if active bleeding !
What anticoagulant to use now?
๐ธNon-heparin
15/18
#MedTwitter
Do we need more than just stopping heparin?
Yes โ
What about platelet transfusions?
๐ธAVOID
๐ธmay โคด๏ธthrombosis
๐ธGive only if active bleeding !
What anticoagulant to use now?
๐ธNon-heparin
15/18
#MedTwitter
How long to anticoagulate ?
๐ธ12 wks if thrombosis present
๐ธ4 wks if HIT but no thrombosis.
****So anticoagulate even if no thrombosis is found on imaging****
What are the non-heparin AC?
๐ธFondaparinux
๐ธArgatroban
๐ธBivalirudin
What's best ?
16/18
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๐ธ12 wks if thrombosis present
๐ธ4 wks if HIT but no thrombosis.
****So anticoagulate even if no thrombosis is found on imaging****
What are the non-heparin AC?
๐ธFondaparinux
๐ธArgatroban
๐ธBivalirudin
What's best ?
16/18
#MedTwitter
No one correct answer, choose as per availability and clinical scenario !
Fondaparinux advantage:
๐ธSubcutaneous
๐ธEasy availability
Argatroban & Bivalirudin:
๐ธOnly IV route
๐ธNeed continuous infusion
ARGATROBAN is SAFE in patients who need DIALYSIS!
DOAC =No data yet
17/18
Fondaparinux advantage:
๐ธSubcutaneous
๐ธEasy availability
Argatroban & Bivalirudin:
๐ธOnly IV route
๐ธNeed continuous infusion
ARGATROBAN is SAFE in patients who need DIALYSIS!
DOAC =No data yet
17/18
Recap the treatment:
๐ธSTOP HEPARIN including flushes
๐ธScreening Doppler
๐ธAvoid platelet transfusion
๐ธNon heparin anticoagulation
๐ธ12 wks if thrombosis
๐ธ4 wks if HIT w/o thrombosis
18/18
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๐ธSTOP HEPARIN including flushes
๐ธScreening Doppler
๐ธAvoid platelet transfusion
๐ธNon heparin anticoagulation
๐ธ12 wks if thrombosis
๐ธ4 wks if HIT w/o thrombosis
18/18
#MedTwitter
Once again, I thank you for reading this far ๐๐ป
This is by no means a comprehensive thread. There is a lot more to HIT !!
#MedTwitter share this if you find this useful ๐ช๐ผ
This is by no means a comprehensive thread. There is a lot more to HIT !!
#MedTwitter share this if you find this useful ๐ช๐ผ
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