21.3 Pleural Effusions and Arrhythmias

CPHON TCO V.E.3–4 tests pleural effusions and arrhythmias as cardiopulmonary emergencies. Domain IV already covered bleomycin lung, chyle as a lymphatic effect, anthracycline cardiomyopathy, and QTc monitoring as late-effect work. This section is the acute drain and the acute rhythm: get the fluid off safely, put the child on telemetry, and know when bradycardia is increased intracranial pressure (ICP), not a primary heart problem.

A 5-year-old drowning in a malignant effusion, an 8-year-old with milky chest-tube output after thoracic neuroblastoma surgery, and a child with peaked T waves on tumor-lysis morning are the pictures. Generic names only: doxorubicin, daunorubicin, arsenic trioxide, ondansetron. Brand antiemetics and brand anthracyclines do not appear on ONCC items.

Pleural effusions: three sources, one respiratory exam

Three high-yield sources share dyspnea and decreased breath sounds:

• Malignant effusion — lymphoma (especially T-lymphoblastic and Hodgkin), leukemia, metastatic solid tumors. Fluid may be the presenting finding and, as the mediastinal-mass section taught, a safer diagnostic specimen than a sedated central biopsy.
• Chylothorax — thoracic-duct injury after mediastinal or chest surgery (thoracic neuroblastoma, selected lymphoma or germ-cell resections, occasional line or thoracotomy complications). Output is milky and triglyceride-rich, often lymphocyte-predominant.
• Infection — parapneumonic effusion, empyema, or effusion during fever and neutropenia. Do not assume every effusion is malignant in a neutropenic child with pneumonia, and do not assume every febrile effusion is “only infection” when a mediastinal mass is sitting next to it.

Confirm with upright chest radiograph and/or bedside ultrasound. A supine portable film underestimates layering fluid. Infants feed poorly, grunt, and prefer to sit. Do not skip imaging because “the lung sounds a little soft.”

Thoracentesis or chest-tube drainage relieves distress and can diagnose. Nursing is positioning (upright or as tolerated—except the mediastinal-mass child who cannot lie flat), oxygen, pain control, and monitoring output character and volume.

Do not drain massive volumes instantly in small children without monitoring. Rapid evacuation of a large collection can cause re-expansion pulmonary edema, violent cough, hypoxia, and hemodynamic swings. Controlled drainage, pause if the child crashes, and intensive-care backup for a huge effusion in a toddler are the CPHON moves. ONCC does not publish a single milliliter-per-kilogram stop number as exam fact. The principle is controlled drainage and reassessment, not a race to empty the bottle because the intern wants a dry film before rounds.

Chylothorax after the drain: respiratory support, chest-tube care, nutrition as ordered (low long-chain fat, medium-chain triglyceride formulas, or parenteral nutrition), and sometimes octreotide. Persistent leak is a surgical conversation. Do not strip the tube harder because milky output looks thick, and do not start a high-fat celebration diet the night of surgery.

Malignant fluid may reaccumulate until the cancer is treated. The drain is a bridge; chemotherapy, corticosteroids, or radiation treat the source. Infection needs antibiotics and sometimes video-assisted drainage for loculated empyema—team decisions after you have protected breathing.

Walk the 5-year-old. Decreased breath sounds, oxygen 88%, upright film with a white-out hemithorax, ultrasound showing a large free collection. The plan is oxygen, controlled tube or catheter drainage with monitoring, and a sample to cytology and culture—not a single massive syringe pull to “get it all now,” and not a trip to the playroom until the lung is heard again.

Arrhythmias: electrolytes, drugs, fever, and the ICP signpost

Put the child on telemetry when tumor lysis, arsenic, a wide-complex rhythm, syncope, or a crashing potassium is in play. Keep a crash cart on the unit and know the code-button path. Hold QT-prolonging medicines when QTc is already long.

High-yield pediatric oncology triggers:

• Tumor-lysis hyperkalemia — peaked T waves, widened QRS, sine-wave risk. This is the metabolic-emergency playbook: no potassium in fluids, insulin-glucose, cardioprotective calcium, dialysis. Arrhythmia here is a potassium emergency, not a lidocaine-first puzzle. Hypokalemia and hypomagnesemia, conversely, seed ectopy and torsades when arsenic or a 5-HT3 antagonist is on board.
• Anthracyclines (doxorubicin, daunorubicin) — acute pericarditis or arrhythmia during infusion blocks, and later cardiomyopathy that seeds ventricular arrhythmia. New ectopy after an anthracycline day is not “anxiety from being in the hospital.”
• Arsenic trioxide — classic QTc prolongation and torsades risk in acute promyelocytic leukemia (APL). Replete potassium and magnesium, obtain protocol electrocardiograms, and hold arsenic when the team’s QTc threshold is crossed. Do not invent a single millisecond cutoff as ONCC fact; use the protocol in front of you.
• 5-hydroxytryptamine-3 (5-HT3) antagonists such as intravenous ondansetron — QTc prolongation is uncommon but real at higher intravenous doses, especially when stacked with arsenic, low potassium, or other QT-active drugs. Hold or change the antiemetic when QTc is already long. Do not stack a large rapid ondansetron bolus onto a prolonged QTc because “everyone gets it before chemotherapy.”
• Fever — sinus tachycardia is expected. Do not treat sinus tach from fever as ventricular tachycardia and do not charge a defibrillator for a febrile sinus rate. Do treat the fever workup (sepsis chapter).

Bradycardia from increased ICP is the signpost that saves a life. Cushing physiology is hypertension, bradycardia, and irregular respirations. A 7-year-old with a posterior-fossa or other brain tumor whose heart rate falls while blood pressure rises is herniation physiology, not a primary sinoatrial problem and not “the child is finally calm after morphine.” Escalate the neurologic-emergency pathway: airway, head of bed, urgent team, osmotherapy as ordered. Do not treat that bradycardia with atropine as the only move and go back to charting. Full ICP algorithms live in the next emergency chapter; this chapter’s job is to refuse to mislabel the rhythm.

The CPHON product is a toddler whose effusion was drained in a controlled way, a chyle tube that was named chyle, a QTc that stopped the next ondansetron bolus, a potassium that was treated as a cardiac emergency, and a falling heart rate that was called ICP rather than a quiet, reassuring pulse.