A 40 year old previously well male presents with a ruptured appendix and associated peritonitis (Day 0). He returns to theatre 3 days later with ischaemic colitis and requires a right hemicolectomy. At laparotomy, he is noted to have extensive thrombosis in his superior mesenteric vein and portal vein. Attempts to anticoagulate him postoperatively (day 5 onwards) with intravenous heparin have been unsuccessful.
His post op haematology results are as follows:
|
Day 0 |
Day 1 |
Day 3 |
Day 5 |
Day 7 |
Day 9 |
Range |
|
|
INR |
1.2 |
1.7 |
1.8 |
1.6 |
0.8 – 1.3 seconds |
||
|
APTT |
36 |
38 |
36 |
28* |
31* |
37* |
24 – 35 seconds |
|
Fibrinogen |
5.8 |
1.8 |
1.4 |
1.7 |
2.0 – 5.0 g/L |
||
|
INR mix |
1.9 |
0.8 – 1.3 seconds |
|||||
|
APTT mix |
32.5 |
30 – 40 seconds |
|||||
|
D dimer |
>4.0 |
< 0.5 mg/L |
* On I.V. heparin
APTT therapeutic range for I.V. heparin therapy: 60 – 90 seconds
Additional tests performed on Day 7
A. Tests of hypercoagulability (plasma)
Antithrombin (functional) 20% (Reference: 80 – 120%)
B. Factor assays (plasma)
Factor VIII 4.10 IU/ml (Reference: 0.5 – 1.5)
C. Anti-Factor Xa assay (plasma)
Anti-Factor Xa 0 IU/ml (Reference for IV heparin therapy: 0.3 – 0.7)
a) What are the possible factors preventing therapeutic anticoagulation in this patient?
b) List 2 strategies to effect anticoagulation with intravenous heparin.
a) What are the possible factors preventing therapeutic anticoagulation in this patient?
• Disseminated intravascular coagulation
• High clot burden
• Antithrombin III deficiency
• High Factor VIII levels
b) List 2 strategies to effect anticoagulation with intravenous heparin.
• Change to low molecular heparin, instead of unfractionated heparin
• Give cryoprecipitate and/or fresh frozen plasma (if there is confirmed ATIII deficiency )
• Give antithrombin III concentrate
Some discussion of the management of heparin resistance goes on in the end of my brief pharmacological entry on unfractionated heparin. In short, there are several strategies one can employ. The specific choice relies on what exactly is causing the heparin resistance.
• Change to low molecular heparin, instead of unfractionated heparin
• Give cryoprecipitate and/or fresh frozen plasma (if there is confirmed ATIII deficiency )
• Give antithrombin III concentrate
This CICM question asks specifically about increasing the effect of heparin, and candidates who suggested using something else (such as a direct thrombin inhibitor) would probably have earned no marks.
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Hirsh, J., et al. "Heparin kinetics in venous thrombosis and pulmonary embolism." Circulation 53.4 (1976): 691-695.
Beresford, C. H. "Antithrombin III deficiency." Blood reviews 2.4 (1988): 239-250.
The PROTECT Investigators for the Canadian Critical Care Trials Group and the Australian and New Zealand Intensive Care Society Clinical Trials Group Dalteparin versus Unfractionated Heparin in Critically Ill Patients N Engl J Med 2011; 364:1305-1314April 7, 2011
Koster, Andreas, et al. "Management of heparin resistance during cardiopulmonary bypass: the effect of five different anticoagulation strategies on hemostatic activation." Journal of cardiothoracic and vascular anesthesia 17.2 (2003): 171-175.
Isil, Canan Tulay, et al. "Management of heparin resistance in an emergency cardiac surgical patient." Indian journal of anaesthesia 56.4 (2012): 430.