1. Overview of Clinical Presentations

Early recognition of hallmark signs and symptoms directs timely diagnosis and management of spinal cord compression, tumor lysis syndrome (TLS), and neutropenic fever in the ICU.

1.1 Spinal Cord Compression Signs

Pathophysiology: Tumor invasion or vertebral collapse compresses the spinal canal. Irreversible paraplegia may occur within 24–48 hours of onset.

• Key Symptoms: Progressive back pain (often worse when supine, causing nocturnal awakenings), motor deficits (gait disturbance, limb weakness graded 0–5), sensory changes (dermatomal hypesthesia, ascending paresthesias), and autonomic dysfunction (urinary retention, fecal incontinence).
• Examination: Assess reflexes, Babinski sign, and ankle clonus.

1.2 Tumor Lysis Syndrome Symptoms

Timing: Typically occurs 6–72 hours after cytotoxic therapy but may be spontaneous in high-burden malignancies. Monitor vital signs, urine output, and serial labs every 4–6 hours in high-risk patients.

• Hyperuricemia: Nausea, vomiting, acute kidney injury.
• Hyperkalemia: Muscle weakness, life-threatening arrhythmias.
• Hyperphosphatemia → Secondary Hypocalcemia: Tetany, seizures, neuromuscular irritability.

1.3 Neutropenic Fever Indicators

Definition: A single oral temperature ≥ 38.3 °C (101 °F) or a temperature ≥ 38.0 °C (100.4 °F) for over one hour, combined with an absolute neutrophil count (ANC) < 500 cells/mm³.

• Presentation: May be culture-negative. Look for subtle signs like respiratory symptoms, mucositis, or diarrhea.
• High-Risk Features: Hemodynamic instability, pneumonia on imaging, new-onset organ dysfunction.

2. Laboratory Diagnostic Interpretation

Key laboratory criteria confirm diagnoses, stratify risk, and trigger specific interventions for oncologic emergencies.

2.1 Uric Acid and Metabolic Panels (TLS)

The Cairo-Bishop classification defines Tumor Lysis Syndrome:

• Laboratory TLS: Requires ≥2 of the following abnormalities occurring within 3 days before or 7 days after therapy:
  • Uric acid ≥ 8 mg/dL or 25% increase from baseline
  • Potassium ≥ 6 mmol/L or 25% increase from baseline
  • Phosphorus ≥ 4.5 mg/dL or 25% increase from baseline
  • Calcium ≤ 7 mg/dL or 25% decrease from baseline
• Clinical TLS: Defined as laboratory TLS plus one of the following: creatinine ≥ 1.5× baseline, cardiac arrhythmia or sudden death, or a seizure.

2.2 Electrolytes (Calcium, Potassium, Phosphorus)

• Hyperkalemia: Monitor the EKG for peaked T waves and QRS widening. Treat immediately if ECG changes are present or if serum K⁺ > 6 mmol/L.
• Hypocalcemia: Can cause tetany and QT prolongation. Replace with IV calcium cautiously to avoid calcium-phosphate precipitation, especially if phosphorus is high.
• Hyperphosphatemia: Consider oral phosphate binders when serum phosphate is persistently elevated (e.g., > 2 mmol/L).

2.3 Neutrophil Counts and Infectious Markers

The Absolute Neutrophil Count (ANC) is calculated as: Total WBC × (% neutrophils + % bands).

• Severe Neutropenia: ANC < 500 cells/mm³
• Profound Neutropenia: ANC < 100 cells/mm³ (highest infection risk)

Inflammatory markers like C-reactive protein (CRP) and procalcitonin are adjunctive but can be nonspecific in this population. De-escalation of antibiotics is typically guided by clinical improvement and evidence of bone marrow recovery (rising ANC).

3. Imaging Modalities

Targeted imaging is crucial to confirm structural emergencies like spinal cord compression and to identify occult sources of infection in neutropenic patients.

3.1 MRI for Cord Compression

Contrast-enhanced MRI of the entire spine is the gold standard diagnostic test.

• T1-weighted sequences: Best for visualizing vertebral body involvement by tumor.
• T2/STIR sequences: Highly sensitive for detecting cord edema, a sign of compression.
• Gadolinium contrast: Helps delineate epidural tumor from surrounding nerve roots.

CT myelography is a viable alternative if MRI is contraindicated (e.g., incompatible hardware, patient instability).

3.2 CT and Ultrasound Applications

• Chest CT (non-contrast): Useful for detecting subtle pulmonary infiltrates or nodules not visible on chest X-ray in patients with neutropenic fever.
• Abdominal CT/Ultrasound: Can localize sources of infection such as typhlitis (neutropenic enterocolitis) or intra-abdominal abscesses.
• Renal Ultrasound: Serves as an adjunctive tool to assess for hydronephrosis or urate nephropathy in TLS-associated kidney injury.
• Point-of-Care Ultrasound (POCUS): Enables rapid bedside assessment for pericardial effusion, pleural effusions, or intra-abdominal free fluid in hemodynamically unstable patients.

4. Risk Stratification Tools

Validated scoring systems and classification criteria guide crucial decisions on the level of care (inpatient vs. outpatient) and the urgency of specific interventions.

4.1 MASCC Score for Febrile Neutropenia

The Multinational Association for Supportive Care in Cancer (MASCC) score helps identify patients with febrile neutropenia who are at low risk for complications. A total score ≥ 21 suggests the patient may be a candidate for outpatient management with oral antibiotics.

4.2 CTCAE Grading for Hypercalcemia

The Common Terminology Criteria for Adverse Events (CTCAE) grades hypercalcemia severity, which guides the intensity of treatment:

• Grade 1 (Mild): > Upper limit of normal to 11.5 mg/dL
• Grade 2 (Moderate): 11.6–12.5 mg/dL
• Grade 3 (Severe): 12.6–13.5 mg/dL
• Grade 4 (Life-threatening): > 13.5 mg/dL

Interventions escalate from IV fluids (all grades) to bisphosphonates (Grade ≥2), calcitonin (Grade ≥3), and potentially dialysis for refractory Grade 4 cases.

4.3 Cairo-Bishop Classification for TLS

As described in Section 2.1, this system differentiates between laboratory and clinical TLS. Risk stratification based on tumor type, burden, and baseline renal function determines the appropriate prophylaxis: aggressive hydration for low-risk, allopurinol for intermediate-risk, and rasburicase for high-risk patients.

5. Algorithmic Assessment of Urgency

A systematic approach integrating clinical, laboratory, and imaging data is essential for rapid triage and initiation of time-sensitive therapies.