Risk reduction of thromboembolic complications → hematocrit value (Hk: volume fraction of cellular elements in the blood; because erythrocytes physiologically represent 99% of the total volume of blood cells, Hkt corresponds to the volume fraction of all erythrocytes in total blood ): < 45 %
Therapy recommendations in polycythaemia vera (PV)
For mild risk:
Bloodletting – to lower hematocrit (goal: lower hematocrit to <45% in men or <42% in women); approximately 500 ml of blood is drawn. Caution. The iron deficiency resulting from bloodletting must not be compensated for under any circumstances, as this would stimulate erythropoiesis (blood formation). If necessary, blood plasma must be replaced to prevent protein loss.
If the risk is high, i.e., insufficient hematocrit reduction by phlebotomy or thromboembolic complications under ASA therapy with normal hematocrit and /or there is progression (progression) of myeloproliferation (leukocytosis/increase in the number of white blood cells (leukocytes) in the blood (> 25. 000/μl), thrombocytosis/increase in the number of platelets (thrombocytes) in the blood (> 600,000/μl), leukoerythroblastic blood count; splenomegaly/spleen enlargement) and/or there is a high risk of thrombosis (e.g., microcirculatory disorders despite ASA, known cardiovascular risk factors):
If necessary, also use of Janus kinase inhibitors/JAK inhibitors (ruxolitinib; JAK1 + 2) in patients who do not respond to hydroxyurea; improvement of symptoms, improvement of hematocrit as well as spleenvolume reduction.
