Thrombocytopenia in critically ill patients

 

 

 

 

Definition:

1. Plt count less than 150, 000/micL, generally not significant until less than 100,000.
2. Relative  thrombocytopenia - acute drop from a higher platelet count may be pathologic.

Pathophysiology:

1. Decreased production
 a) Isolated thrombocytopenia
 b) Multiple cytopenias

2. Increased destruction and consumption

 a) Immune or alloimmune: primary (idiopathic) or secondary -associated with other autoimmune disease (e.g. SLE), associated with malignancy, maybe complication of infection and drug associated thrombocytopenia

b) Nonimmune -isolated or combined platelet consumption

3. Increased sequestration in enlarge spleen

a) portal hypertension
b) myloproliferative disease
c) lymphoma
d) storage and infiltrative deseases of spleen
e) chronic hemolysis
f) granulomatoses -eg tuberculosis, sarcoidosis

4. Dilutional - effect of massive transfusion and fluid resuscitation

5. States with multiple causes of thrombocytopenia:

a) cirrhosis with portal hypertension
b) hepatitis
c) HIV
d) other viral illnesses
e) patients with multiple medical problems on multiple drugs

Diagnosis

1. FBP with peripheral smear: -Review of rbc abnormalities e.g. schistocytes, teardrops, nucleated RBC. Rule out pseudothrombocytopenia due to platelet clumping.
2. Coagulation testing: Identify associated coagulation abnormalities
3. Additional blood tests, if required:  

• viral titres and antibodies
• autoimmune disorders (e.g. collagen vascular disease)
• other disorders

     4. Radiologic

• abdominal US -evaluation of spleen size
• CT scan -evaluation for lymphoproliferative disease

    5. Indication for bone marrow examination

• unclear pathology
• multiple cytopenias
• suspected infiltrative process

Therapy

1. Transfusion therapy indications:

• bleeding or necessary invasive procedures
• prophylactic - for very severe (less than 10,000) thrombocytopenia
• other blood components as indicated to correct coagulation abnormalities

2. Platelet transfusion relatively contraindicated:

• TTP unless bleeding present
• ITP unless bleeding present
• HIT without bleeding - unknown

3. Primary thrombocytopenia - depends on specific disorder

4. Secondary thrombocytopenia -direct therapy at underlying causes