11.6 Hematologic & Endocrine Emergencies: DIC, Leukostasis, Hyperviscosity & SIADH

11.6 Hematologic & Endocrine Emergencies: DIC, Leukostasis, Hyperviscosity & SIADH

Blueprint focus: ONCC Domain III — completing the emergency set. These four syndromes account for a disproportionate share of early mortality in hematologic malignancy and small cell lung cancer.

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1. Disseminated Intravascular Coagulation (DIC)

Etiology. Systemic activation of coagulation consumes platelets and clotting factors while activating fibrinolysis, producing simultaneous thrombosis and bleeding. Triggers in oncology are acute promyelocytic leukemia (APL), other acute leukemias, mucin-secreting adenocarcinomas (pancreas, stomach, prostate, lung), and — most commonly overall — sepsis.

Assessment.

Clinically: oozing from venipuncture sites, mucosal and gastrointestinal bleeding, petechiae and ecchymoses, and simultaneously acral cyanosis, digital ischemia, or organ infarction.

Management.

1. Treat the underlying cause. Nothing else is definitive — antimicrobials for sepsis, chemotherapy for the leukemia.
2. Blood product support guided by bleeding, not by numbers alone. Platelets for a count below roughly 50,000/µL with bleeding (or below 20,000 to 30,000/µL prophylactically in this setting), cryoprecipitate for fibrinogen below approximately 100 to 150 mg/dL, and fresh frozen plasma for prolonged PT and aPTT with bleeding.
3. Heparin is reserved for the thrombosis-predominant phenotype — digital ischemia, large-vessel thrombosis — and is dangerous in the bleeding-predominant phenotype.
4. Antifibrinolytics such as tranexamic acid are generally avoided in DIC because they can precipitate catastrophic thrombosis; APL is a specific exception managed by hematology.

The APL emergency

Acute promyelocytic leukemia deserves its own line. The classic presentation is a new acute leukemia with DIC and bleeding, and early hemorrhagic death — often intracranial or pulmonary — is the leading cause of treatment failure. All-trans retinoic acid (ATRA) is started immediately on clinical suspicion, before PML-RARA confirmation returns, because ATRA rapidly reverses the coagulopathy. Aggressive product support targets a fibrinogen above about 150 mg/dL and platelets above 30,000 to 50,000/µL. Watch for differentiation syndrome — fever, dyspnea, hypoxemia, pulmonary infiltrates, weight gain, hypotension, and effusions — treated with dexamethasone 10 mg twice daily started at first suspicion.

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2. Hyperleukocytosis and Leukostasis

Definitions. Hyperleukocytosis is a laboratory finding, usually a white cell count above 100,000/µL. Leukostasis is the clinical syndrome that follows when leukemic blasts — which are large, stiff, and adhesive — plug the microvasculature.

Risk. Highest in acute myeloid leukemia, particularly monocytic subtypes, where symptoms can appear above roughly 50,000 to 100,000/µL. Chronic lymphocytic leukemia can reach counts above 300,000/µL without leukostasis, because small mature lymphocytes are far less obstructive.

Presentation.

• Pulmonary: dyspnea, hypoxemia often out of proportion to the chest radiograph, diffuse infiltrates.
• Neurologic: headache, confusion, visual change, tinnitus, focal deficit, retinal hemorrhage, and in severe cases intracranial hemorrhage.
• Fever without documented infection, priapism, and limb ischemia.
• Frequently accompanied by DIC and tumor lysis syndrome.

Management.

1. Aggressive intravenous hydration.
2. Emergent cytoreduction: induction chemotherapy is the definitive treatment; hydroxyurea provides rapid interim control; leukapheresis may be used for severe symptomatic leukostasis, though it does not improve long-term outcome and is not a substitute for chemotherapy.
3. Tumor lysis prophylaxis with rasburicase or allopurinol and hydration.
4. Avoid red cell transfusion until after cytoreduction unless the patient is critically anemic — adding red cells raises whole-blood viscosity and can worsen leukostasis. This is the classic exam trap.
5. Diuretics are avoided because hemoconcentration worsens viscosity.

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3. Hyperviscosity Syndrome

Etiology. A large paraprotein load raising serum viscosity. Waldenström macroglobulinemia (pentameric IgM, which is confined to plasma and highly viscous) is the archetype; IgA and IgG3 myeloma are less common causes. Polycythemia vera and severe leukocytosis raise viscosity by different mechanisms.

Classic triad.

1. Mucosal bleeding — epistaxis, gingival bleeding, gastrointestinal bleeding.
2. Visual change — blurred vision or vision loss, with dilated, tortuous, sausage-link retinal veins, papilledema, and retinal hemorrhage on funduscopy. Funduscopic examination is a fast bedside confirmation.
3. Neurologic symptoms — headache, vertigo, tinnitus, ataxia, confusion, seizure, and rarely coma.

Congestive heart failure from expanded plasma volume may accompany it.

Management.

• Urgent plasmapheresis rapidly removes the paraprotein and reverses symptoms. It is the immediate intervention.
• Definitive control requires systemic therapy for the underlying plasma cell or lymphoplasmacytic disorder.
• Avoid red cell transfusion before plasmapheresis — it raises viscosity further, and this is an exact parallel to the leukostasis rule.
• Rituximab in Waldenström macroglobulinemia can cause an IgM flare that transiently worsens hyperviscosity, so plasmapheresis often precedes it.

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4. Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Etiology. Ectopic ADH production, most classically by small cell lung cancer, and also by head and neck cancers, CNS disease, pulmonary infection, and a long list of drugs including cyclophosphamide, vincristine, vinblastine, cisplatin, and SSRIs.

Diagnostic profile.

Euvolemia is what separates SIADH from hypovolemic hyponatremia (vomiting, diuretics, adrenal insufficiency) and hypervolemic hyponatremia (heart failure, cirrhosis).

Presentation. Severity tracks both the sodium level and the speed of the fall: anorexia, nausea, headache, and lethargy at moderate levels; confusion, seizure, and coma below roughly 120 mEq/L or with rapid decline.

Management.

• Asymptomatic or mild: fluid restriction, commonly 500 to 1,000 mL per day, plus increased dietary salt and protein. Treat the malignancy — SIADH from small cell lung cancer often resolves with effective chemotherapy.
• Severe symptomatic hyponatremia (seizure, coma): hypertonic 3% saline in small boluses with frequent sodium monitoring in a monitored setting.
• The correction-rate rule: do not raise serum sodium faster than approximately 8 mEq/L in 24 hours (some guidance permits up to 10 to 12 mEq/L, with 8 as the safer working target, and a lower limit in high-risk patients). Over-rapid correction causes osmotic demyelination syndrome, presenting days later with dysarthria, dysphagia, quadriparesis, and locked-in syndrome. It is irreversible.
• Tolvaptan and other vasopressin receptor antagonists are options for persistent SIADH but require inpatient initiation with sodium monitoring, carry hepatotoxicity limits on duration, and must not be combined with fluid restriction during initiation.
• Demeclocycline is a rarely used alternative with slow onset.