1) List the differential diagnoses of a low platelet count in the critically ill.
2) A 68-year-old man commenced on continuous renal replacement therapy for Acute Kidney Injury (AKI) following repair of a ruptured abdominal aortic aneurysm is noted to have a platelet count of 40 x 109/L. What is your management of this problem?
Management consists of establishing the diagnosis and specific and supportive treatment.
The most likely causes in this patient are:
Other causes to be considered if indicated from history or examination
The differential diagnosis of thrombocytopenia in general is presented in a table in the discussion section of Question 11.3 from the first paper of 2012.
At risk of damaging SEO, I will reproduce it here:
Decreased platelet production
Increased platelet destruction
Dilution of platelets
No sensible or specific additions can be made to the non-specific manageemnt suggested by the college in the second part of this question. This patient is probably having his platelets eaten by the dialysis filter, or is developing DIC from sepsis, or he has developed HITS. The bottom line is, you would stop anticoagulating him.
The following list of generic steps applies to thrombocytopenia of any cause:
Minimise platelet destruction
Maximise platelet production
Protect the patient from complications of thrombocytopenia
Stasi, Roberto. "How to approach thrombocytopenia." ASH Education Program Book 2012.1 (2012): 191-197.
UpToDate: Approach to the adult patient with thrombocytopenia.
Casonato, A., et al. "EDTA dependent pseudothrombocytopenia caused by antibodies against the cytoadhesive receptor of platelet gpIIB-IIIA." Journal of clinical pathology 47.7 (1994): 625-630.
Castro, Christine, and Mark Gourley. "Diagnostic testing and interpretation of tests for autoimmunity." Journal of Allergy and Clinical Immunology 125.2 (2010): S238-S247.
Arepally, Gowthami M., and Thomas L. Ortel. "Heparin-induced thrombocytopenia." New England Journal of Medicine 355.8 (2006): 809-817.
Chong, B. H., J. Burgess, and F. Ismail. "The clinical usefulness of the platelet aggregation test for the diagnosis of heparin-induced thrombocytopenia." Thrombosis and haemostasis 69.4 (1993): 344-350.