Unexpected Cardiac Arrest After Cardiopulmonary Bypass Initiation, Likely Due to Cardioplegia Migration: A Case Report.

ECG changes appeared immediately after CPB initiation, followed by severe bradycardia and flaccid cardiac arrest within minutes.

• The cardiac arrest occurred in a pediatric cardiac surgery patient shortly after cardiopulmonary bypass was initiated.
• The sequence of events progressed from ECG changes to severe bradycardia to flaccid cardiac arrest within minutes.
• The presentation was unexpected given the safe design of CPB and cardioplegia circuits.

Lab analysis revealed severe hyperkalemia at 13.1 mEq/L and metabolic acidosis, strongly suggesting cardioplegia solution contamination of the CPB circuit.

• Blood potassium concentration was measured at 13.1 mEq/L, consistent with cardioplegia solution contamination.
• Metabolic acidosis was also identified alongside the hyperkalemia.
• The findings 'strongly suggest contamination with cardioplegia solution in the CPB circuit system' per the authors.

Cardiac function was restored after potassium removal via hemodialysis while CPB was continued.

• CPB was maintained throughout the event to support circulation.
• Hemodialysis was used to remove excess potassium from the patient.
• The heartbeat resumed following potassium removal, allowing the surgery to proceed as planned.

Contamination of the CPB circuit with cardioplegia solution remains a potential cause of unexpected cardiac arrest following CPB initiation, despite safe circuit design.

• The case highlights a risk that persists even with modern safety-designed CPB and cardioplegia circuits.
• This mechanism of cardiac arrest—cardioplegia migration into the CPB circuit—should be considered in the differential diagnosis when unexpected arrest follows CPB initiation.
• The authors note this as a previously underappreciated complication warranting clinical awareness.