Managing thrombocytopenia in cats and dogs: part 2

Last week we discussed the causes and diagnostic pathway for investigating immune-mediated thrombocytopenia. This week we will go through the management of this condition.

Despite the fact red blood cells are not actually being destroyed, a severe anaemia can develop from blood loss due to coagulopathy – a common reason for why they present to emergency practices. The management of these patients is broken down into three main areas:

• improving oxygen delivery
• commencing immunosuppression
• management of the underlying cause (if identified)

Optimising oxygen delivery in the acute phase is going to keep them alive long enough for immunosuppression to work. This is achieved through IV fluids to help improve perfusion and blood transfusions to replace red blood cells. If fresh whole blood is available, it can assist in increasing platelet numbers, but generally it is not very effective.

Platelet transfusions using platelet-rich plasma can be considered if it is available. Plasma transfusion is not effective at managing the coagulopathy as it is due to a loss of platelets, not a loss of coagulation factors.

Immunosuppression

Immunosuppression therapy is often commenced concurrently as the patient is being stabilised.

The first choice is either dexamethasone 0.5mg/kg IV every 24 hours if the patient is not stable enough for oral medications; otherwise, once stable, start prednisolone at 2mg/kg by mouth per day divided every 12 hours.

Other immunosuppressive agents include:

• Azathioprine – 2mg/kg by mouth every 24 hours then 0.5mg/kg by mouth every other day. The main concerns are bone marrow suppression and hepatoxicity – also, it is very toxic in cats.
• Ciclosporin – 5mg/kg to 10mg/kg by mouth divided twice a day; cats 5mg/kg by mouth every 24 hours.
• Chlorambucil could also be used at a dose of 0.1mg/kg/day to 0.2mg/kg/day by mouth if the response to prednisolone is insufficient.

Management

Management of the underlying cause should be commenced if a cause is identified, but this is often not the case.

Other management options include:

• Vincristine can be trialled to increase platelet number as it stimulates the release of platelets from the bone marrow.
• Gastroprotectants can be considered if gastrointestinal bleeding has occurred – these include proton pump inhibitors and sucralfate.
• Strict confinement, potentially sedatives and minimal blood sampling are important to minimise injury that may result in further bleeding and blood loss.
• Antithrombotic therapy is not part of standard management as, unlike immune-mediated haemolytic anaemias, thrombotic events rarely occur.

When it comes to monitoring, platelet counts are performed daily until more than 40 × 10⁹/L – this can take up to two weeks to occur.

Once above this level, take weekly counts until the numbers have normalised. Once they have, taper immunosuppressive medications over four to six months, with 20% dose reduction every couple weeks, generally with the adjunctive immunosuppressants first and prednisolone last.