Co-existence of thrombocytopenia and hyperleukocytosis ('critical period') as a risk factor of haemorrhage into the central nervous system in patients with acute leukaemias.

The aim of this work was to examine whether the risk of death i.a. due to haemorrhage into the central nervous system (CNS) is higher during some phases of acute myeloblastic leukaemia (AML), lymphoblastic leukaemia (ALL), and the blastic phase of chronic myelogenous leukaemia (BP) when two important risk factors that worsen the prognosis are simultaneously present: low thrombocytopenia and hyperleukocytosis. Clinical and post-mortem neuropathological examination was performed in 143 patients, aged 17-76 years, who died from AML (80 cases), BP (38), and ALL (25). Periods with co-existence of thrombocytopenia below 25 x 10(9) per l and hyperleukocytosis above 100 x 10(9) per l were identified after plotting the results and were termed the 'critical period' (CP). The study showed that the risk of death was disproportionately high during the CP. This finding was obtained in all patient groups, although it involved mainly patients with AML and BP, i.e. leukaemias with the highest frequency of hyperleukocytosis in peripheral blood. It is suggested that the risk of death during the CP is so high because leukaemic cells are a potent synergistic factor to thrombocytopenia in causing CNS haemorrhage. When a CP is detected, hyperleukocytosis and thrombocytopenia should be controlled and treated aggressively: leukapheresis and platelet concentrates should be administered. Patients with CP should not be given packed red blood cells, in order to avoid a further increase in blood viscosity, which is already high due to hyperleukocytosis. In fact, anaemia during the CP should be regarded as a potentially life-saving factor.