Hematologic & Oncologic Emergencies
Critical emergency hematology and oncology: Thrombotic Thrombocytopenic Purpura (TTP) recognition (why platelets are strictly contraindicated), febrile neutropenia 60-minute antibiotic bundles, Tumor Lysis Syndrome (TLS) Rasburicase protocols, and malignant spinal cord compression.
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In Thrombotic Thrombocytopenic Purpura (TTP), NEVER TRANSFUSE PLATELETS—giving platelets fuels widespread microvascular thrombosis and causes stroke, myocardial infarction, and death. TTP is a medical emergency managed with emergent plasma exchange (plasmapheresis) and Caplacizumab. In febrile neutropenia (ANC < 500/uL), administer broad-spectrum anti-pseudomonal monotherapy (Cefepime 2g IV) within 60 minutes. In Tumor Lysis Syndrome (TLS), manage hyperkalemia and hyperuricemia with aggressive hydration and Rasburicase (contraindicated in G6PD deficiency). In spinal cord compression, give Dexamethasone 10–16 mg IV immediately before MRI.
Thrombotic Thrombocytopenic Purpura (TTP) is a life-threatening thrombotic microangiopathy caused by severe deficiency (< 10% activity) of the von Willebrand factor-cleaving protease ADAMTS13. Ultra-large vWF multimers accumulate, causing spontaneous platelet aggregation, microvascular thrombi, and widespread end-organ ischemia. The classic 'Pentad' (FAT RN) is present in under 10% of patients; Microangiopathic Hemolytic Anemia (MAHA) + Thrombocytopenia alone is sufficient to initiate emergent therapy:
| TTP Pentad Feature | Clinical / Laboratory Hallmarks | Underlying Pathophysiology |
|---|---|---|
| 1. Thrombocytopenia | Severe thrombocytopenia (platelets typically 10,000–30,000/uL), petechiae, purpura | Platelets are consumed in widespread microthrombi throughout arterioles and capillaries. |
| 2. Microangiopathic Hemolytic Anemia (MAHA) | Marked anemia, elevated indirect bilirubin, elevated LDH (> 1,000 U/L), low haptoglobin (< 10 mg/dL), SCHISTOCYTES on peripheral smear | Erythrocytes are mechanically sheared as they navigate fibrin-rich microthrombi in small vessels. |
| 3. Neurologic Symptoms | Fluctuating confusion, headache, transient ischemic attack (TIA), aphasia, seizures, coma | Transient cerebral microvascular thrombosis; symptoms wax and wane rapidly. |
| 4. Renal Dysfunction | Elevated serum creatinine, microscopic hematuria, proteinuria (usually mild/moderate) | Renal microthrombi (less severe than in Hemolytic Uremic Syndrome - HUS). |
| 5. Fever | Low-grade fever in 25–50% of patients | Systemic inflammatory cytokine release from tissue ischemia. |
The Absolute Platelet Transfusion Contraindication in TTP: Transfusing platelets into a patient with active TTP is like 'throwing gasoline on a fire'. Exogenous platelets are immediately bound by ultra-large vWF multimers, producing widespread acute thrombotic occlusions that trigger fatal myocardial infarction, acute ischemic stroke, and sudden circulatory arrest. Withhold platelet transfusions unless there is catastrophic, life-threatening intracranial or internal hemorrhage.
- Definitive Emergency Therapy: Immediate Plasma Exchange (PLEX / Plasmapheresis). Removes ultra-large vWF multimers and autoantibodies while infusing donor ADAMTS13. If PLEX is delayed, infuse Fresh Frozen Plasma (FFP 15–30 mL/kg) as a temporizing bridge.
- Immunosuppression: Methylprednisolone 1 g IV daily (or Prednisone 1 mg/kg PO) to suppress autoantibody production against ADAMTS13.
- Caplacizumab (Cablivi): 10 mg IV bolus followed by 10 mg SubQ daily. Anti-vWF nanobody that rapidly prevents platelet adhesion to ultra-large vWF multimers, halting microthrombus formation within hours.
Febrile Neutropenia is defined as an oral temperature >= 38.3°C (101.0°F) once, or >= 38.0°C (100.4°F) sustained over 1 hour, in a patient with an Absolute Neutrophil Count (ANC) < 500 cells/uL (or expected to drop < 500 in 48h). Neutropenic patients cannot mount an inflammatory response (pyuria, sputum, or fluctuance may be completely absent). Bacteremia rapidly progresses to fatal septic shock:
| Antimicrobial Strategy | First-Line Empiric Regimen | Administration Route & Dose | Specific Clinical Indications |
|---|---|---|---|
| Anti-Pseudomonal Monotherapy (Standard) | Cefepime OR Piperacillin-Tazobactam OR Meropenem | Cefepime 2g IV q8h (or Zosyn 4.5g IV q6h; Meropenem 1g IV if penicillin anaphylaxis) | Administer within 60 minutes of arrival. Covers Pseudomonas aeruginosa, Gram-negative rods, and Enterobacteriaceae. |
| Add Vancomycin (Gram-Positive Coverage) | Vancomycin 15–20 mg/kg IV (max 2g) | IV piggyback | INDICATED ONLY IF: 1) Hemodynamic instability / septic shock; 2) Pneumonia on radiograph; 3) Suspected central venous catheter site infection; 4) Severe mucositis; 5) Known MRSA colonization. |
| High-Risk vs Low-Risk (MASCC Score) | MASCC Score >= 21 = Low Risk; MASCC Score < 21 = High Risk | Low-risk outpatients may qualify for oral Ciprofloxacin + Augmentin | High-risk patients (ANC < 100, prolonged neutropenia > 7 days, renal/hepatic dysfunction) require mandatory inpatient admission. |
| Oncologic Emergency | Pathophysiologic Mechanism | Key Diagnostic Markers | Emergency Medical Management |
|---|---|---|---|
| Tumor Lysis Syndrome (TLS) | Massive breakdown of malignant cells following chemotherapy (hematologic malignancies: ALL, Burkitt lymphoma). Intracellular contents flood circulation. | Cairo-Bishop Criteria (>= 2 of 4): 1) Uric acid >= 8 mg/dL; 2) Potassium >= 6.0 mEq/L; 3) Phosphate >= 4.5 mg/dL; 4) Calcium <= 7.0 mg/dL (hypocalcemia secondary to phosphate binding). | Aggressive IV hydration (200–300 mL/hr); Rasburicase 0.2 mg/kg IV (recombinant urate oxidase converts insoluble uric acid to soluble allantoin; CONTRAINDICATED in G6PD deficiency due to methemoglobinemia); manage hyperkalemia; emergent hemodialysis. |
| Malignant Spinal Cord Compression (MSCC) | Metastatic tumor expands in epidural space (prostate, breast, lung, myeloma), compressing the thecal sac and spinal cord. | Thoracic or lumbar back pain worsening when recumbent or coughing, followed by progressive bilateral lower extremity weakness, sensory level, urinary retention (post-void residual > 150 mL), and loss of anal sphincter tone. | Dexamethasone 10 to 16 mg IV bolus immediately (reduces vasogenic spinal cord edema); emergent whole-spine MRI; emergent radiation oncology and spine surgery consultation for surgical decompression. |
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