Oncologic Emergencies: SIADH, DIC, Neutropenic Fever, Tumor Lysis Syndrome

Oncologic Emergencies: SIADH, DIC, Neutropenic Fever, Tumor Lysis Syndrome

A high-density, practical guide for nurses, medical students, and clinicians.

What Is This?

Oncologic emergencies are life-threatening complications of cancer or its treatment. This guide covers four critical emergencies: - SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion) – Fluid overload and hyponatremia from excessive ADH. - DIC (Disseminated Intravascular Coagulation) – Simultaneous clotting and bleeding due to systemic coagulation activation. - Neutropenic Fever – Life-threatening infection in immunocompromised patients (ANC < 500). - Tumor Lysis Syndrome (TLS) – Metabolic chaos from rapid tumor cell death, releasing potassium, phosphate, and uric acid.

Why it matters today: Cancer patients are living longer with aggressive treatments, increasing the risk of these emergencies. Early recognition and intervention save lives—delayed treatment can be fatal.

Why It Matters

• SIADH: Untreated hyponatremia-seizures, coma, death.
• DIC: 50–80% mortality if unmanaged; survivors may lose limbs or organs.
• Neutropenic Fever: 10–20% mortality if antibiotics are delayed >1 hour.
• TLS: 20–50% mortality if untreated; renal failure and arrhythmias are common.

Real-world impact: - Hospitals: Oncology units, ICUs, and EDs must be prepared. - Clinicians: Nurses and doctors must act fast—these are time-sensitive emergencies. - Patients: Early intervention improves survival and reduces long-term damage.

Core Concepts

1. SIADH (Syndrome of Inappropriate Antidiuretic Hormone)

• Pathophysiology: Excess ADH-water retention-dilutional hyponatremia (Na+ < 135 mEq/L).
• Causes in cancer:
• Small cell lung cancer (SCLC) (most common).
• Brain tumors, chemotherapy (cyclophosphamide, vincristine).
• Key signs:
• Mild (Na+ 125–134): Nausea, headache, confusion.
• Severe (Na+ < 120): Seizures, coma, respiratory arrest.
• Diagnosis:
• Serum Na+ < 135 mEq/L + low serum osmolality (< 275 mOsm/kg).
• Urine osmolality > serum osmolality (kidneys retain water).
• Normal adrenal/thyroid/renal function (rule out other causes).

2. DIC (Disseminated Intravascular Coagulation)

• Pathophysiology: Widespread clotting-consumption of clotting factors-bleeding.
• Causes in cancer:
• Acute promyelocytic leukemia (APL) (most common).
• Sepsis, metastatic solid tumors (prostate, lung, GI).
• Key signs:
• Clotting: DVT, PE, stroke, organ ischemia.
• Bleeding: Oozing from IV sites, petechiae, GI bleeds.
• Diagnosis:
• ? Platelets + ? PT/INR & aPTT + ? D-dimer.
• ? Fibrinogen (consumed in clots).

3. Neutropenic Fever

• Pathophysiology: ANC < 500-increased infection risk-sepsis.
• Causes:
• Chemotherapy (nadir 7–14 days post-treatment).
• Hematologic malignancies (leukemia, lymphoma).
• Key signs:
• Fever-38.3°C (101°F) once or-38.0°C (100.4°F) for ?1 hour.
• No obvious source (may lack classic infection signs due to neutropenia).
• Diagnosis:
• ANC = (WBC × % neutrophils) / 100.
• Blood cultures ×2 (peripheral + central line if present).
• CXR, urine culture, sputum culture (if symptomatic).

4. Tumor Lysis Syndrome (TLS)

• Pathophysiology: Rapid tumor cell death-release of intracellular contents-metabolic chaos.
• Causes:
• High tumor burden (lymphoma, leukemia, bulky solid tumors).
• Chemotherapy/radiation (especially in first 12–72 hours).
• Key signs:
• Hyperkalemia (K+ > 6.0 mEq/L)-arrhythmias, cardiac arrest.
• Hyperphosphatemia (PO4 > 4.5 mg/dL)-hypocalcemia (tetany, seizures).
• Hyperuricemia (uric acid > 8 mg/dL)-acute kidney injury (AKI).
• Diagnosis (Cairo-Bishop Criteria):
• Lab TLS: ?2 metabolic abnormalities (K+, PO4, uric acid, Ca2+).
• Clinical TLS: Lab TLS + AKI, arrhythmia, or seizure.

How It Works (Management Overview)

SIADH Management

1. Fluid restriction (500–1000 mL/day) – First-line for mild cases.
2. Hypertonic saline (3% NaCl) – For severe hyponatremia (Na+ < 120).
3. Goal: Increase Na+ by 0.5–1 mEq/L/hour (max 12 mEq/L in 24h).
4. Risk: Central pontine myelinolysis if corrected too fast.
5. Vasopressin receptor antagonists (tolvaptan) – For chronic SIADH.
6. Treat underlying cancer (chemotherapy for SCLC).

DIC Management

1. Treat the underlying cause (e.g., chemotherapy for APL, antibiotics for sepsis).
2. Supportive care:
3. FFP (fresh frozen plasma) – Replaces clotting factors.
4. Cryoprecipitate – Replaces fibrinogen.
5. Platelets – If < 50,000 and bleeding.
6. Heparin (controversial) – Only for thrombotic DIC (e.g., purpura fulminans).
7. Monitor:
8. PT/INR, aPTT, fibrinogen, D-dimer every 4–6 hours.

Neutropenic Fever Management

1. Start empiric antibiotics within 1 hour (even before cultures).
2. Low-risk (ANC > 100, no comorbidities): Oral ciprofloxacin + amoxicillin-clavulanate.
3. High-risk (ANC < 100, hypotension, comorbidities): IV piperacillin-tazobactam or cefepime.
4. Add vancomycin if:
5. Hemodynamic instability, pneumonia, skin/soft tissue infection, MRSA risk.
6. Add antifungal (e.g., micafungin) if:
7. Fever persists >4–7 days despite antibiotics.
8. G-CSF (filgrastim) if:
9. ANC < 100, sepsis, or high-risk features.

Tumor Lysis Syndrome Management

1. Prevention (high-risk patients):
2. IV fluids (3–5 L/day) – Maintain urine output > 100 mL/hour.
3. Allopurinol (300–600 mg/day) – Blocks uric acid formation.
4. Rasburicase (0.2 mg/kg IV) – For high uric acid (>8 mg/dL) or AKI.
5. Treatment (established TLS):
6. Hyperkalemia:
   • Calcium gluconate (stabilizes cardiac membrane).
   • Insulin + dextrose (shifts K+ into cells).
   • Kayexalate or dialysis (removes K+).
7. Hyperphosphatemia:
   • Phosphate binders (sevelamer, aluminum hydroxide).
   • Dialysis if severe.
8. Hypocalcemia:
   • Only treat if symptomatic (tetany, seizures)-calcium gluconate.
9. AKI:
   • IV fluids, loop diuretics (furosemide), dialysis if needed.

Hands-On / Getting Started

Prerequisites

• Knowledge:
• Basic understanding of electrolytes, coagulation, and infection control.
• Familiarity with chemotherapy side effects.
• Skills:
• IV access, blood draws, medication administration.
• Interpreting lab values (CBC, CMP, coagulation panel).

Step-by-Step Minimal Example: Neutropenic Fever

Scenario: A 55-year-old with AML presents with fever (38.5°C) 10 days post-chemo. ANC = 200.

1. Assess:
2. Vital signs: BP 100/60, HR 110, RR 22, SpO2 94%.
3. Exam: No focal infection signs, but central line in place.
4. Labs:
5. CBC: WBC 0.8, ANC 200, Hgb 8, Plt 40.
6. CMP: Na+ 135, K+ 4.0, Cr 1.2.
7. Blood cultures ×2 (peripheral + central line).
8. CXR: No infiltrates.
9. Intervene:
10. Start IV piperacillin-tazobactam (4.5 g IV q6h) within 1 hour.
11. Add vancomycin (15 mg/kg IV q12h) (central line present).
12. IV fluids (NS 100 mL/hour).
13. Monitor:
14. Vitals q1h, repeat CBC/CMP in 6 hours.
15. If fever persists >48h, add micafungin (100 mg IV daily).

Expected outcome: - Fever resolves in 24–48 hours if bacterial infection. - If fungal, may take 5–7 days to improve.

Common Pitfalls & Mistakes

Best Practices

SIADH

Fluid restriction first (unless Na+ < 120). ? Check urine osmolality (should be > serum osmolality). ? Avoid hypotonic fluids (D5W, 0.45% NS).

DIC

Treat the cause (e.g., chemo for APL, abx for sepsis). ? Monitor fibrinogen (give cryoprecipitate if < 100 mg/dL). ? Avoid heparin unless thrombotic DIC (e.g., purpura fulminans).

Neutropenic Fever

Start abx within 1 hour (even if cultures pending). ? Add vancomycin if central line, pneumonia, or hypotension. ? Consider fungal coverage if fever persists >4 days.

TLS

Hydrate before chemo (3–5 L/day, maintain UOP > 100 mL/hour). ? Give allopurinol/rasburicase prophylactically in high-risk patients. ? Monitor K+, PO4, uric acid, Ca2+ every 6–12 hours.

Tools & Frameworks

Real-World Use Cases

1. SIADH in Small Cell Lung Cancer (SCLC)

Scenario: A 65-year-old smoker presents with confusion and Na+ 118 mEq/L. - Action: - Fluid restriction (800 mL/day). - 3% NaCl (50 mL/hour) to raise Na+ by 0.5 mEq/L/hour. - Chemotherapy for SCLC (etoposide + cisplatin). - Outcome: Na+ normalizes in 48 hours; confusion resolves.

2. DIC in Acute Promyelocytic Leukemia (APL)

Scenario: A 30-year-old with APL develops petechiae, oozing from IV sites, and INR 3.0. - Action: - ATRA (all-trans retinoic acid) + arsenic trioxide (treats APL). - FFP + cryoprecipitate (replaces clotting factors). - Platelets if < 50,000 and bleeding. - Outcome: Bleeding stops in 24 hours; DIC resolves in 3–5 days.

3. Neutropenic Fever in AML Post-Chemo

Scenario: A 45-year-old with AML has fever (39°C) 10 days post-induction chemo (ANC = 100). - Action: - IV piperacillin-tazobactam + vancomycin (central line present). - Blood cultures ×2 (peripheral + central line). - G-CSF (filgrastim) 5 mcg/kg SC daily. - Outcome: Fever resolves in 36 hours; cultures grow Staph epidermidis (line infection).

4. Tumor Lysis Syndrome in Burkitt Lymphoma

Scenario: A 25-year-old with bulky Burkitt lymphoma starts R-CHOP chemo and develops K+ 6.5, PO4 6.0, uric acid 12. - Action: - IV fluids (NS 200 mL/hour) + furosemide (40 mg IV). - Rasburicase (0.2 mg/kg IV) + allopurinol (300 mg PO). - Calcium gluconate (1 g IV) for hyperkalemia. - Dialysis if AKI worsens. - Outcome: Electrolytes normalize in 48 hours; no arrhythmias.

Check Your Understanding (MCQs)

Question 1

A 60-year-old with small cell lung cancer presents with confusion and Na+ 115 mEq/L. Urine osmolality is 400 mOsm/kg, serum osmolality is 250 mOsm/kg. What is the most appropriate initial treatment?

A. 0.9% NaCl at 125 mL/h