Leucostasis and hyperviscosity — Rapid

Synopsis

Recognise cellular and paraprotein-mediated microcirculatory emergencies, distinguish their mechanisms, reduce viscosity safely and coordinate immediate definitive treatment of the underlying clone.

Hyperleukocytosis is a numerical finding, commonly leukocytes above 100 × 10⁹/L; leukostasis is clinical organ dysfunction and can occur at lower AML counts.
Key leukostasis organs are lung and brain: dyspnoea, hypoxia, confusion, headache, focal deficit, seizure and retinal change with blast-rich disease require emergency cytoreduction.
First-line tests are urgent FBC and film, coagulation and fibrinogen, renal, calcium, phosphate, potassium, urate, LDH, cultures, group sample and leukaemia flow and molecular samples.
Start tumour-lysis prevention and definitive leukaemia treatment immediately; hydroxycarbamide is a rapid oral bridge when full induction cannot begin at once.
Leukapheresis is not routine for an asymptomatic high count and does not replace systemic treatment; consider it only in selected severe symptomatic cases through the apheresis and leukaemia teams.
In suspected APL, start ATRA immediately and correct coagulopathy; avoid leukapheresis because line placement and extracorporeal circulation can worsen catastrophic bleeding.
Paraprotein hyperviscosity classically causes visual change, mucosal bleeding and neurological symptoms; urgent therapeutic plasma exchange is first-line and must not wait for a universal viscosity threshold.
Defer non-essential red-cell transfusion until the cellular or protein burden falls because increasing haematocrit can worsen microcirculatory flow.

Key red flags

Hypoxia, tachypnoea or bilateral pulmonary infiltrates with marked myeloid leukocytosis may be leukostasis and can worsen during early cell lysis.

Confusion, focal neurology, seizure, visual change, retinal haemorrhage or papilloedema indicates threatened cerebral or retinal microcirculation and needs immediate specialist action.

Mucosal bleeding or DIC with suspected acute promyelocytic leukaemia requires immediate ATRA and blood-product support; leukapheresis is generally avoided.

Pulmonary leukostasis

Tachypnoea, hypoxia, diffuse infiltrates and respiratory failure with blast-rich hyperleukocytosis can mimic infection or oedema and demand parallel treatment.

Neurological leukostasis

Headache, confusion, ataxia, focal deficit, seizure or reduced consciousness may reflect microvascular ischaemia or haemorrhage.

Investigation priorities

First-line FBC and expert blood filmFirst stepFirst line

Identify cell burden, lineage clues, anaemia, thrombocytopenia and an APL-like morphology.

Management branches

Suspected leukostasisCytoreduce while protecting organs

Acute pulmonary, neurological, retinal or priapic dysfunction occurs with blast-rich hyperleukocytosis.

Call acute leukaemia, critical care and apheresis teams and obtain clonal, lysis, coagulation, culture and group samples.
Start monitored hydration and tumour-lysis prophylaxis and use immediate definitive therapy or hydroxycarbamide bridging.
Consider leukapheresis only for selected severe symptomatic disease without allowing it to delay effective systemic therapy.

Key medicines

Hydroxycarbamide for emergency cytoreductionGive 50 to 100 mg/kg/day orally in 2 or 3 divided doses under the acute-leukaemia protocol, with a maximum and dose adjustment defined by renal function and response, until definitive therapy controls the count.Monitor FBC, lysis chemistry and renal and liver function at least daily and more often when unstable. It is not definitive therapy, can worsen cytopenia, requires safe handling and is avoided in pregnancy unless specialist life-saving benefit dominates.

Therapeutic plasma exchangeExchange approximately 1 to 1.5 calculated plasma volumes with the apheresis replacement protocol urgently, repeating according to symptoms, fundal findings, immunoglobulin and viscosity rebound.Monitor vascular access, calcium, coagulation and haemodynamics. Exchange is temporary and must be followed by clone-directed treatment; avoid routine red-cell transfusion before viscosity falls.

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