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The evidence behind the guideline 2 - Coagulopathy and central venous access

8/6/2015

8 Comments

 
Every so often we have a patient who has had their coagulopathy corrected before the insertion of a central line.  Although this is done with the best of intentions, it’s not my own practice and I think it increases rather than reduces risk.  In fact, it’s one of those areas where I’ve always thought there’s an evidence base, but until writing this was never sure where I heard/read it.
Happily, Scandinavian guidelines say that if a coagulopathy is present “an easily compressible vessel should be chosen and the catheter inserted by an experienced operator using optimal techniques” and that coagulopathy should not be reversed, which is great because that backs up my position perfectly.  These guidelines are however not from the UK, and differ from those that are.

The British Committee for Standards in Haematology (all be it back in 2007) tells us that it is ‘generally accepted’ that the platelet count should be >50x109/l before insertion of a central line, and that the correction of coagulopathy should be considered ‘on an individual patient basis’.  They are consistent, with this document produced in 2012 by NHS Blood and Transplant quoting the same value.  The AAGBI use the BCSH guidance as the sole reference for their recommendation that platelets should be above 50x109/l for a central line as well. 

In the UK at least, thrombocytopenia seems to be getting special attention….     

The general acceptance referred to by the BCSH is, I’m assuming, their own 2003 guideline on the use of platelets, which says:

“For lumbar puncture, epidural anaesthesia, gastroscopy and biopsy, insertion of indwelling lines, transbronchial biopsy, liver biopsy, laparotomy or similar procedures, the platelet count should be raised to at least 50x109/l” 

I am somewhat sceptical of 50 being a very round number, so thought it was worth having a look to see whether it has any basis beyond accepted wisdom, not really expecting to find any.  The key reference for the BCSH guidance is another guideline which is always suspicious, written in 2001 by the American Society of Clinical Oncology, who give a level C recommendation of 40-50x109/l for invasive procedures.  As suspected, 50 seems to be a round number rather than an evidence based threshold, but one that has been accepted for many years.

But what is the evidence that a platelet count of less than this will cause significant bleeding?  And even if the risk is increased, at what level does that risk outweigh the risk and cost of giving a platelet transfusion? 

The only clues to help answer these questions (accepting that the answer will be different for each patient) will be from case series – what have people been ‘getting away with’?

One such example is this paper by Doerfler et al, reporting a series of 104 central line insertions in patients who all had disorders of coagulation.  41 had platelets of <50x109/l, 24 had a raised PT with INR>1.5 and 13 had both raised PT and thrombocytopenia (the others had a platelet count of <100 but >50 or INR>1.2, so really there were only 78 with what I would consider to be significant coagulopathy).  Seven patients had bleeding, and these all came from the thrombocytopenia group (<50x109/l).  5/7 had bleeding from the puncture or sutures, and the other 2 developed 2-3cm haematomas.  One of these patients had Kaposi's sarcoma of the skin and a platelet count of 6x109/l.  This patient received a transfusion of 5 bags of donor platelets (which seems a lot), requiring 1 h of direct pressure to stop the bleeding from the skin.  The others just required 10-20mins of pressure.  So from this series, thrombocytopenia seems to be the only significant risk, with bleeding that required platelet transfusion in one patient. 

Whether transfusion to >50x109/l in that patient would have prevented the bleeding is not certain (or whether the platelets were what stopped the bleeding), neither is whether any harm came of transfusing once the bleeding had become an issue rather than prophylactically.  How many more patients would have had lines inserted before another significant bleeding episode is also unknown, so it wouldn’t be fair to say that the rate is 1/78.  There are plenty of other series out there, and it’s not worth trailing through them all now but they all come down on the side of showing safety with thrombocytopenia (there will of course be publication bias).

But does any of this matter?  Well it turns out it does.  This paper looked at why patients meeting criteria for EGDT for sepsis (in 2013, when it was still in fashion!) didn’t get central access.  The OR for not attempting central access was just shy of 4 for those patients with a platelet count of <50x109/l.   It’s too big a leap to say that harm resulted, but if this threshold is stopping active management then that can’t be a good thing.  The paper also reports local bleeding rates, adding support to 50x109/l being conservative.

As for the costs of platelet transfusion, there’s a financial one (about £250) as well as the risks of TRALI, allergy and infection, all of which are more common with platelets than other blood products.  There’s also the issue of platelets not being a limitless resource.  According to this document the demand on platelets in the UK is increasing, with 15% of platelets being given pre-procedure.  The same document quotes the magical 50x109/l threshold however, so they’re maybe not helping their cause!

I think it’s fair to say at this point that with coagulopathy not caused by thrombocytopenia my stance is definitely unchanged.  With regards thrombocytopenia, a threshold of 50x109/l is not evidence based and there are numerous examples showing a lower threshold would be fine.  I don’t think that the platelet count can be ignored, but I also don’t buy into the concept that the risk of bleeding at laparotomy is the same as inserting a 16G needle under USS guidance.

It is difficult to know for the individual patient what my threshold should be (especially when thinking about function as well as number).  Maybe <10x109/l would be better, but that’s just another round number………

8 Comments
Allistair Dodds
9/6/2015 07:49:07 am

A little off topic perhaps, but our regions 2 fatalities related to a NOAC (dabigatran) this year have both been referred for Haemodialysis. Neither has had a canula sited, admittedly in the face of uncontrolled comprimising haemorrage, because of the fear of cannulation and poor prognosis.

Reply
Brian Wilkinson
9/6/2015 07:37:48 pm

It's very interesting, have any studies looked at platelet function rather than number - e.g. Bleeding time? It's interesting how may patients we insert lines into who are on anti-platelets (most commonly aspirin +/- clopidogrel but now it's not uncommon to see prasugrel or ticagrelor - but it seems that these patients seem to get lines without major problems (from what I have seen). In terms of platelet transfusion it is also notable that any patient with antibodies often requires platelets to be delievred from Sheffield, and there may well be risk associated with delay in therapy attributable to waiting for platelets.

I find it fascinating that the BSCH give the same guidance for indwelling lines and epidural anaesthesia, which clearly have have different benfit and risk profiles and are unlikely to be covered by a magic number.


I think site of line is an interesting point in coagulopathic patients - I think most of us would avoid subclavian but it's interesting as to whether people would insert femoral or IJ lines in the first instance - I must admit I favour IJ lines due to them usually being technically easier and I find I can usually apply direct pressure until the bleeding stops.

Reply
Laura
10/6/2015 09:26:46 am

Great topic!
I must say i agree with you pete and tend not to wait or give products for line insertion. Having worked in other areas where it is often not desirable to correct coagulapathy ( liver failure/transplant) the ethos is to get the most skilled technician available insert the line in an appropriate site. In my experience this doesnt seem to result in major issues with bleeding.
Brian I also agree with your point. Keeping platelets above a threshold doesnt neccesarily assure fewer bleeding complications as our lab measures of coagulation & numerical platelet count fail to take into account other unmeasured deficiencies/drugs.
We have a similar 'evidence light guidance' approach to septic patients who are sedated on ICCU to keep the PLT>20. I think the observational data from septic haematology patients showed bleeding still occured in those with PLT>20 and despite correction with products.

Reply
Alistair
10/6/2015 02:07:34 pm

Do a Hickman line list!
Those with myelodysplastic syndromes and other haematological catastrophes need a line for "life saving" chemo. The platelet count /clotting may never be "normal".
Just crack on .......

Reply
Andrew (Hawthorne)
10/6/2015 03:26:30 pm

Suppose it goes without saying that there are some circumstances in which raising the platelet count would actually be undesirable, e.g. TTP

Reply
Edward Pugh
16/6/2015 10:44:14 pm

I agree with Brian that functional tests of coagulation are of much greater value than in vitro studies. For example in the patient with liver disease, both pro and anti-coagulant factors are depleted so a patient with coagulopathy on lab tests may not bleed excessively in vivo. Anecdotally I've found this to be the case with line insertions.
As far as recommendations go there has to be a line drawn in the sand somewhere and this area is not going to be a hot bed of medical research - getting quality evidence to support any figure is nigh-on impossible. A platelet count of 50x10 9 does sound conservative, especially for USS guided techniques in compressible areas. Is there evidence out there to show that giving a platelet transfusion actually decreases bleeding complications? Or does it just make us feel better...

Reply
Pete Hersey
1/12/2015 03:53:31 pm

UPDATE!!

The new NICE guidelines for transfusion have just come out, and this statement is included

"Do not offer prophylactic platelet transfusions to patients having
procedures with a low risk of bleeding, such as adults having central venous cannulation or any patients having bone marrow aspiration and trephine biopsy."

Within the guidelines you would however give platelets if the count is <10, whether getting a central line or not.

The guidance is available at

http://www.nice.org.uk/guidance/ng24/resources/algorithm-2178655021

Reply
Pete
5/12/2015 07:20:32 pm

There's also a Cochrane review on the way...

http://www.ncbi.nlm.nih.gov/pubmed/26627708?utm_source=hootsuite

It concludes "There is no evidence from RCTs to determine whether platelet transfusions are required prior to central line insertion in patients with thrombocytopenia, and, if a platelet transfusion is required, what is the correct platelet transfusion threshold".

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