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