heparin induced thrombocytopenia, audit & international survey
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The Monitoring of Heparin Induced Thrombocytopenia Following Orthopaedic Surgery
An audit and international survey
Benedict Rogers
Sam Simmonds Meeting
2nd May 2008
Low-molecular-weight heparins
• widely used– Clexane® (enoxaparin sodium)– Fragmin® (dalteparin sodium)– Innohep® (tinzaparin sodium)
• prevention of DVT and PE
• orthopaedic & general surgery patients
Anastasios K. Lilikakis, Theodoros Papapolychroniou, Georgios Macheras and Emmanuel MichelinakisJ Bone Joint Surg Am. 2006;88:634-638.
Case 1
• 46 yr, DDH• Total Hip Replacement• Clexane 40 mg od• Headache & motor
disturbance day 6
Platelet count
(103 per mm3 )
Pre-Op 250
Post-Op 180
Day 6 126
Day 10 35
CT
Day 11
Bilateral parasagittal haemorrhages
Died day 11
Case 1
Case 2
• 47 yr, DDH, Total Hip Replacement• Clexane 40 mg • Fit & well, no previous heparin• Discharged on s/c clexane & readmitted day 13• Headache and abnormal left arm sensation
Day 13 MRI , platelet 70
High signal intensity involving the left thalamus
? thrombosis
Day 22 MRI, platelet 40
Large bilateral haematomas
Discharged quadriplegic
Heparin-induced thrombocytopenia (HIT)
• HIT commonest drug-induced thrombocytopenia
• Complicating 1-4% of exposures to standard & LMW
heparin.
• Immune (IgG) mediated, (ie non-dose related)
• High thrombotic morbidity (30-50%)
& mortality (10-15%) due to platelet activation and DIC.
Pathoaetiology
•Heparin forms a complex with platelet factor 4 (PF4) which is released from platelets by platelet activation.
•The antibody-heparin-PF4 immune complex binds to the Fc receptor on the surface of the platelet leading to activation of the platelet.
Why important ?
• Bleeding post-joint replacement– Operative site – Epidural– Intrahepatic– Retroperitoneal– Gastrointestinal– Intra-cerebral
British Society for HaematologyHaemostasis & Thrombosis Task Force
Keeling et alBJH, May 2006 133, 259-269,
Guidelines on Management of
Heparin-Induced thrombocytopenia
Study Aim
To audit the monitoring of heparin induced
thrombocytopenia in patients receiving
LMWH following orthopaedic surgery
Risk of Heparin-induced Thrombocytopenia (HIT) identified
Initial survey of 56 patients to assess monitoring of platelet
count in post-oporthopaedic patients
Comparison of initial survey to BSH published guidelinesDissemination and implementation
of BSH guidelines
Repeat survey 53 patients to assess implementation of BSH
guidelines
Audit Loop
56 Patients Receiving LMWH > 4 days post-op
8 patientsMedically unwell or on
warfarin
48 patientsWell post-op
2 patientsFBC after 4 days
46 patientsNo FBC after 4 days
Initial Survey
2/48 (4.1%) of at risk patients had platelet counts monitored
Risk of Heparin-induced Thrombocytopenia (HIT) identified
Initial survey of 56 patients to assess monitoring of platelet
count in post-oporthopaedic patients
Comparison of initial survey to BSH published
guidelines
Dissemination and implementation of BSH guidelines
Repeat survey 53 patients to assess implementation of BSH
guidelines
Audit Loop
1. All patients receiving heparin (of any sort) should have a platelet count on day of starting treatment
2. All surgical patients receiving LMWH, platelet counts should be performed every 2-4 days from days 4 - 14
Guidelines on Monitoring of Heparin-Induced Thrombocytopenia
Keeling et al BJH, May 2006, 133, 259-269
If platelet count falls • by 50%+ or• below normal lab limits
And/or patients develops thrombosis or skin allergy
…consider HIT, stop LMWH & inform haematologist
Guidelines on Management of Heparin-Induced Thrombocytopenia
Keeling et al BJH, May 2006, 133, 259-269
Risk of Heparin-induced Thrombocytopenia (HIT) identified
Initial survey of 56 patients to assess monitoring of platelet
count in post-oporthopaedic patients
Comparison of initial survey to BSH published guidelinesDissemination and implementation
of BSH guidelines
Repeat survey 53 patients to assess implementation of BSH
guidelines
Audit Loop
Risk of Heparin-induced Thrombocytopenia (HIT) identified
Initial survey of 56 patients to assess monitoring of platelet count
in post-oporthopaedic patients
Comparison of initial survey to BSH published guidelinesDissemination and implementation of
BSH guidelines
Repeat survey 53 patients to assess implementation of BSH
guidelines
Audit Loop
53 Patients Receiving LMWH > 4 days post-op
13 PatientsMedically unwell
or on warfarin
40 patientsWell post-op
23 patientsFBC after 4 days
17 patientsNo FBC after 4 days
Secondary Survey
23/40 (57.5%) of at risk patients had platelet counts monitored
0
10
20
30
40
50
60
Primary Survey Secondary Survey
Per
cen
tag
e
Percentage of at risk patients monitored for heparin induced thrombocytopenia
P < 0.05
Post-Op Platelet CountSecondary Survey
0
2
4
6
8
10
12
> 75% 50 - 75 % < 50 %
Percentage of pre-operative platelet count
Nu
mb
er o
f P
atie
nts
•23 patients correctly monitored
•11 plt 50 - 75 % pre-op
•2 plt < 50 % pre - op
Survey
Aware of BSH HIT guidelines
Monitor platelet count for pts on LMWH
Canada / Australia N/A 2/12
UK District General Hospital
1/25 0/25
Teaching Hospital 1/6 0/6
General Practitioner 0/22 0/22
Conclusion
• Poor awareness of HIT monitoring
• Simple audit improved monitoring (4% to 57%)
• Incidence : 1 % of patients on LMWH
• DGH orthopaedic dept : 10 cases per year(assuming up to 1000 patients per year with LMWH)
• This study identified 2 cases non-symptomatic HIT
Conclusion
• Published case reports• Published guidelines• If LMWH used• HIT should be monitored• Medicolegal implications
• All surgical patients receiving LMWH, platelet counts should be performed every 2-4 days from days 4 – 14
If platelet count falls • by 50%+ or• below normal lab limits• And/or patients develops
thrombosis or skin allergy
…consider HIT, stop LMWHinform haematologist
Conclusion
Acknowledgements
Mr Rosson,
Andrew Cowie,
Jason Fleming &
Chris Alcock
The Royal Surrey County Hospital,
Guildford, England.
Thank You
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