Patient Preparation and Counseling, Therapeutic plasma exchange, Clinical Pathology - Full Vignette

Описание: A 60-year-old man with complex cardiac, pulmonary, and gastrointestinal history is admitted to the ICU for confusion and agitation during his first therapeutic plasma exchange, subsequently developing perioral tingling, carpopedal spasms, and arrhythmias. What clinical features and laboratory findings should guide your evaluation of his sudden symptoms during plasma exchange? Which aspects of the presentation are crucial for narrowing the differential diagnosis in this critical care setting?

VIDEO INFO
Category: Patient Preparation and Counseling, Therapeutic plasma exchange, Clinical Pathology
Difficulty: Easy - Basic level - Suitable for medical students
Question Type: Diagnosis - Identify conditions based on clinical presentation
Case Type: Critical Condition

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QUESTION
A 60-year-old man with a history of hypertrophic cardiomyopathy (recently reclassified as dilated cardiomyopathy on follow-up), silicosis, vesicoureteral reflux, chronic fatigue syndrome, hearing loss, laryngopharyngeal reflux, and prior gastric adenocarcinoma (resected; immunohistochemistry CK7+, HER2-, pMMR) is admitted to the ICU with agitation and confusion. He has a sedentary lifestyle, occasionally uses marijuana, and is in treatment for opioid use disorder (on methadone)....

OPTIONS
A. Symptomatic hypocalcemia from citrate anticoagulation during albumin-replacement TPE, presenting with perioral tingling, carpopedal spasm, and ventricular ectopy despite stable blood pressure and oxygenation.
B. Immediate hypersensitivity to 5% human albumin, causing anaphylaxis with hypotension, bronchospasm, and urticaria during the exchange.
C. Air embolism from central venous access, causing abrupt hypoxemia, chest pain, and a drop in end-tidal CO2 with cardiovascular collapse.
D. Sepsis from catheter-related infection, causing fever, rigors, hypotension, and rising lactate within minutes of starting the exchange.

CORRECT ANSWER
A. Symptomatic hypocalcemia from citrate anticoagulation during albumin-replacement TPE, presenting with perioral tingling, carpopedal spasm, and ventricular ectopy despite stable blood pressure and oxygenation.

EXPLANATION
This patient develops classic citrate toxicity during albumin-replacement TPE: perioral tingling, carpopedal spasm, and ventricular ectopy, with documented low ionized calcium (0.88 mmol/L) and concurrent mild respiratory alkalosis (pH 7.47, PaCO2 31 mm Hg), which further lowers ionized calcium. Citrate in ACD-A chelates ionized calcium in the extracorporeal circuit and, when returned to the patient, transiently reduces systemic ionized calcium until hepatic metabolism clears citrate. Even if albumin-corrected total calcium looks near-normal, ionized calcium best correlates with symptoms. Prompt intravenous calcium (often calcium gluconate) and magnesium repletion abort symptoms and mitigate arrhythmias; slowing the citrate load or increasing prophylactic calcium infusion can prevent recurrence.

Alternative diagnoses do not fit the pattern and timing. Immediate hypersensitivity to 5% albumin would more often show hypotension, bronchospasm, urticaria, or flushing, which are absent. Air embolism typically causes sudden hypoxemia, chest pain, a drop in end-tidal CO2, and hemodynamic collapse-not present here with PaO2 110 mm Hg on low-flow oxygen. Sepsis within minutes of starting an exchange is implausible; fever, rigors, hypotension, and rising lactate are not reported....


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