Oncologic Emergencies

When chemotherapy kills a large, rapidly dividing tumor, millions of cells rupture at once and dump their contents into the blood. Each cell holds potassium at roughly 120–130 mEq/L — an order of magnitude above serum — plus phosphate and nucleic acids that are metabolized to uric acid. The classic laboratory signature is ↑K⁺, ↑phosphate, ↑uric acid, ↓calcium: the released phosphate chelates calcium, and the resulting calcium-phosphate precipitates in tissues — including the kidney and the heart.

Two organs pay the price. In the kidney, uric acid crystallizes in the tubules (obstruction), scavenges nitric oxide (vasoconstriction and ischemia), and drives inflammation — acute kidney injury — while calcium-phosphate deposits add a second crystal insult. In the heart, hyperkalemia plus cardiac calcium-phosphate deposits produce arrhythmias, and hypocalcemia adds tetany, seizures, and arrhythmias of its own — the sources call the hypocalcemia more hazardous than the hyperphosphatemia that caused it.

TLS strikes within 72 hours of cytotoxic therapy, classically after the first chemo doses for highly proliferative hematologic malignancies — and it can occur spontaneously, before any treatment, in high-grade disease. By the Cairo–Bishop criteria, laboratory TLS is ≥ 2 derangements within 24 hours (uric acid ≥ 8.0 mg/dL, K⁺ ≥ 6.0 mEq/L, phosphorus ≥ 4.5 mg/dL, calcium ≤ 7.0 mg/dL, or a 25% change from baseline); clinical TLS adds creatinine > 1.5× normal, seizure, arrhythmia, or sudden death. Clinical TLS carries an in-hospital mortality around 21% — which is why the strategy is prevention: aggressive hydration started 48 hours before chemo, allopurinol beforehand to block new uric acid formation (it cannot clear uric acid already made), and rasburicase — which converts existing uric acid to soluble allantoin — preferred for prevention and treatment in high-risk patients. Urine alkalinization with bicarbonate is no longer routine: it dissolves urate but promotes calcium-phosphate precipitation in the tubules — a classic “old teaching” exam distractor.

Chemotherapy suppresses the marrow: neutropenia is an ANC < 1,500 cells/µL, severe below 500/µL, profound below 100/µL. Here is the trap: neutrophils are what produce the signs of infection. With the inflammatory response eroded, "representative signs of infection (erythema, swelling, pus) may be absent," and "Clinical signs of infection may be subtle or absent due to impaired neutrophil response, so fever may be the only presenting symptom" — and sometimes "Pain and tenderness may be the only indicators of infection."

That is why the numbers are non-negotiable: a single oral temperature ≥ 38.3 °C (101 °F), or ≥ 38.0 °C (100.4 °F) sustained for one hour, in any neutropenic patient is treated as an emergency. The sequence is fixed — obtain two sets of blood cultures (a peripheral vein plus every lumen of every venous catheter) and site-specific specimens, then start empiric broad-spectrum antibiotics within 1 hour of triage. The evidence behind the clock is blunt: a door-to-needle time beyond 60 minutes is significantly associated with ICU admission. Never hold antibiotics waiting for culture results or for the ANC to come back.

The empiric choice (per IDSA, as relayed by StatPearls) is an antipseudomonal beta-lactam alone — cefepime, ceftazidime, piperacillin-tazobactam, or a carbapenem — with vancomycin added only for suspected catheter, skin/soft-tissue, or lung infection, or hemodynamic instability. Risk scores (MASCC ≥ 21 = low risk; CISNE ≥ 3 = high risk) let selected low-risk patients go home on oral therapy; high-risk patients (anticipated ANC < 500/µL for over 7 days, uncontrolled comorbidities) stay on IV treatment, antibiotics continuing until the ANC recovers to ≥ 500 cells/mm³ and/or the infection clears — with empiric antifungals added if fever persists past 4–7 days.

Superior vena cava syndrome is plumbing: a mediastinal mass (small-cell lung cancer first, non-Hodgkin lymphoma second) compresses the SVC — or a thrombus around a central catheter or pacemaker wire occludes it — and every manifestation traces to venous congestion above the blockage: face, neck, and arm swelling, distended neck and chest-wall veins, dyspnea that is often worse lying flat (orthopnea), hoarseness, and head fullness or headache. Most cases build insidiously over days to weeks as collateral veins open, so first aid is positional — keep the head of the bed elevated to lower venous pressure — while definitive care (endovascular stenting, now widely considered first-line, plus steroids, diuretics, and tumor-directed radiation or chemo) is arranged. The rare killers are laryngeal edema (stridor) and cerebral edema (confusion → stupor → coma) — those cues convert a subacute problem into an immediate one.

Malignant spinal cord compression starts as a metastasis in a vertebral body — seeded classically from prostate cancer via Valsalva-driven venous shunting through the Batson plexus, with lung, prostate, and multiple myeloma the leading primaries and the thoracic spine the most common site. The enlarging mass (or a collapsing vertebra) compresses the cord, and the injury is partly vasogenic edema — which responds to steroids. The earliest symptom, in 80–95%, is back pain: constant, aching, worse at night (it wakes the patient) and with Valsalva — coughing, sneezing, straining. The only well-validated red flag for MSCC in back pain is a history of malignancy, so new or changed back pain in a cancer patient is MSCC until proven otherwise: immediate whole-spine gadolinium MRI and IV dexamethasone now, then surgery and/or radiation. The urgency is brutal math — function at diagnosis predicts function after treatment: severe weakness or more than 48 hours unable to walk before diagnosis predicts a poor outcome, and complete loss of function is rarely reversible.

Hypercalcemia of malignancy touches ~20% of cancer patients. About 80% is humoral — tumor-secreted PTHrP binds the PTH receptor and strips calcium from bone — with osteolytic metastases (myeloma, breast) causing most of the rest and a steroid-responsive calcitriol-mediated form in lymphomas. The picture follows the classic mnemonic, stones, bones, groans, thrones, and psychiatric overtones: calcium blunts renal concentrating ability, so polyuria and polydipsia dehydrate the patient; GI hypomotility brings constipation, anorexia, and nausea; muscles weaken, bones ache; and lethargy slides into confusion and coma, especially in older adults. Severity bands: mild 10–12 mg/dL, moderate 12–14, severe > 14 mg/dL — symptoms usually appear above 12, and ≥ 14 mg/dL (or hypercalcemia with confusion) is a crisis demanding immediate isotonic saline, then antiresorptive therapy. One related recognition note: some cancers secrete excess ADH (SIADH of malignancy) — water retention and hyponatremia managed with fluid restriction of 500–1,000 mL/day and neuro monitoring.

Rank these syndromes by how fast irreversible harm arrives — this is applied clinical judgment assembled from the facts above, not a published triage scale. Febrile neutropenia owns the tightest clock: cultures then antibiotics within one hour, in a patient who may show no sign but the fever — so it outranks every stable-appearing patient on the unit. New neurologic deficit, or new or worsening back pain, in a cancer patient is possible cord compression, where the hours before dexamethasone and MRI decide whether the patient walks again. TLS threatens fatal arrhythmia and AKI inside the 72-hour post-chemo window — an abnormal K⁺ or a rhythm change acts first. Hypercalcemia ≥ 14 mg/dL or with confusion is a crisis. SVC syndrome usually built over days to weeks and can wait behind all of the above — unless stridor or falling mental status signals airway or cerebral edema, which vaults it to the front of the line.

The pattern underneath the ranking: an invisible infection on a one-hour clock beats a visible-but-stable problem; a threatened spinal cord beats pain alone; laboratory values that can stop the heart (K⁺, calcium) beat laboratory values that merely trend badly; and any airway cue beats everything.