1/ Prolonged APTT tweetorial

Quick tip; A prolonged APTT is more likely to indicate an underlying factor deficiency than a prolonged PT
BUT factor deficiency is not the most common cause for a prolonged APTT
2/ The most common causes include

- Heparin (either circulating in blood or in the line the sample was taken from)
- Lupus anticoagulant
- Liver disease (expect prolonged PT also)
- DIC (expect prolonged PT and low fibrinogen also)
- Factor deficiencies
3/ The coagulation factors associated with the APTT test are;

- VIII
- IX
- XI
- XII
4/ When working up a cause for a long APTT, the first question must be - is there any chance the patient is on heparin/heparin has been given through the line the sample was taken from?

If in doubt ➡️ repeat

This leads to a normal result in a significant number of cases
5/ Helpful tests if suspecting heparin contamination are thrombin time and protamine time;
🔴 Heparin will cause a PROLONGED thrombin time
🔵 But protamine time will NOT be prolonged (protamine is the antidote to unfractionated heparin)
6/ To differentiate between factor deficiency and a lupus anticoagulant we perform a 50:50 mix of patient plasma to normal donor plasma

🔵If there is a factor deficiency, it should be ‘replaced’ with donor factors and normalise
🔴 If there is a lupus anticoagulant it will not
7/ ‘Lupus anticoagulants’ are a misnomer.

They are not just seen in patients with lupus, and actually confer a prothrombotic state, not a predisposition to bleeding.

They are usually positive in anti-phospholipid syndrome
8/ Now for an example real-life walkthrough of how the lab and haematologists work through a prolonged APTT result;

a) Sample received in lab 🔥 clinical details really helpful here🔥*. If taking a coag screen please say if bleeding (or thrombosis) as that helps our workup
9)
b) APTT prolonged (PT and fibrinogen normal in this case)
c) Thrombin time performed ➡️ if prolonged, suggests heparin so protamine or reptilase time performed
d) If protamine or reptilase normal, this is in keeping with heparin

If does not normalise...
10)
e) 50:50 mix performed
➡️ if it corrects this suggests factor deficiency and usually ➡️ lab performing factor assays VII,XI, IX, XII and/or haematologists speaking to the clinical team

However often a repeat is asked for in first instance
11)
f) ➡️ if no correction on 50:50 mix, this suggests a lupus anticoagulant (LA). An LA is an antibody which interferes with the APTT test, giving the appearance of a bleeding phenotype
BUT - LA’s are clinically associated with thrombosis risk

A DRVVT test is used to confirm
12) SO, although not straightforward, working out the cause of a long APTT is logical, and is about ruling out more common issues (e.g heparin contamination, lupus anticoagulant) before testing factor levels.
#meded #FOAMed #MedTwitter
13) * We get some excellent clinical details in many cases but also some that leave themselves more open to interpretation 😂. Highlights include;

- “No”
- “None”
- “Mon”
- “L”
- “Known to Mythologists”
- “Clinical details”

• • •

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More from @BukuHaematology

4 Mar
1/ When transfusing platelets, the mantra of;

'Why use two when one will do?'

Is supported by data from the PLADO study + others (see refs) which show that giving more than a standard dose of platelets (1 pool/unit* in an adult) did not ⬇️ bleeding incidence
2/ Each platelet exposure has (uncommon but significant) risks of allergic reaction, virus transmission and...

Each exposure to platelets is also another potential exposure to HLA antigens which the recipient does not have
3/ This may not have a big impact for many patients but for those awaiting transplants (haem or solid organ @BukuRenal) it increases the chance of graft rejection.

Why does this happen?
Read 11 tweets
3 Mar
1/ Neutropenic sepsis tweetorial
 
Febrile neutropenia is a common and serious complication of chemotherapy treatment and can rapidly progress to life-threatening severe sepsis. Patients with bone marrow failure conditions (e.g. AML, Myelodysplastic syndrome) are also at risk.
2/ Outcomes have improved with increased recognition of the importance of prompt treatment and better supportive care, driven by initiatives such as the Surviving Sepsis Campaign.

🔥IV antibiotics must be given within one hour in all suspected neutropenic sepsis 🔥
3/ Patient education is crucial, as is a failsafe, 24/7 contact line for prompt assessment and treatment in secondary care: once there, antimicrobials should be given within the hour.

🔬History, examination, imaging and cultures are then used to pinpoint the source.
Read 7 tweets
18 Jan
1/ Tweetorial: DOACs in cancer
 
The risk of venous thromboembolism (VTE) is up to 7 x higher in patients with cancer, and contributes to morbidity and mortality

Overall prognosis is worse in patients with cancer and VTE, compared to those with cancer and no VTE
2/ The treatment of VTE in cancer is complex due to concerns around;

-Interactions with anti-cancer treatment 💊
-Timing of surgery and procedures 🪚 (no scalpel emoji)
-Low platelet counts due to treatment 🩸
-Higher risk of bleeding related to some cancers 🩹
3/ LMWH was traditionally the treatment of choice, with data from the CLOT study (2003) showing improved efficacy vs warfarin & no ⬆️ bleeding risk

It is a useful option as no monitoring (usually) required, less interactions and short T1/2. It is however given by injection...
Read 9 tweets
16 Sep 20
1/ Antidote news! There has been promise recently regarding antidotes being developed for DOACs. Before we get onto that, a quick summary of what we have so far...
2/ In the case of bleeding while on warfarin, this should be stratified by severity. Usual rule is if life/limb/sight threatening bleeding, prothrombin complex concentrate + vit K is used. If not, vitamin K +- pause/cessation of warfarin is advised.
3/ Warfarin works by inhibiting vitamin K-dependent clotting factor production. These factors are II, VII, IX and X. The 'antidote' is prothrombin complex concentrate (e.g beriplex) which is a concentrated 'soup' of factors II, VII, IX and X (and some protein C and S)
Read 11 tweets
17 Feb 20
1/19. When considering whether a patient is at risk of bleeding before a procedure/surgery or if a patient is bleeding and you want to assess if there are any 'correctable' clotting abnormalities, a thorough approach is needed to ensure all factors are identified.
2/19. The patient might have a PT of 19 seconds but this will probably make little/no difference in terms of bleeding risk, but the clopidogrel they have continued to take without telling the nurses/medical staff really will. I.e the coagulation screen isn't the whole picture..
3/19. The 3 main elements are platelets, fibrinogen and clotting factors.
Platelet function depends on platelet number and function. Count can be reduced by many causes. Major surgery can occur with a platelet count of 50x10^9 or more (BSH guidelines. Note neurosurgery >100)
Read 19 tweets
15 Jan 20
1/7. Prothrombin time (PT) measures the extrinsic coagulation cascade. The only 'major' clotting factor in the extrinsic pathway is factor VII. This is the clotting factor with the shortest half life, and explains why the PT is so often prolonged in unwell patients
2/7. It also makes a long PT relatively easy to investigate and manage. The absolute majority of patients with a long PT will either be vitamin K deficient, have factor VII deficiency due to consumption in sepsis/bleeding or liver disease.
3/7. Warfarin and the DOACS (to a varying degree) will represent most of the rest of prolonged PT results. Factor VII deficiency is incredibly rare, and will have been present from birth, therefore if the patient has had a normal PT in the past...
Read 7 tweets

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