Should digoxin immune fab be administered based solely on reported ingested amount in acute digoxin poisoning?

Abstract

Acute digoxin poisoning is increasingly uncommon in emergency medicine. Furthermore, controversy exists regarding indications for antidotal digoxin immune fab in acute poisoning. In healthy adults, the fab prescribing information recommends administration based on “known consumption of fatal doses of digoxin: ≥10mg,” while many emergency medicine textbooks suggest fab administration be driven by clinical features or potassium concentration. A 54 kg adult, not on digoxin, presented one hour after ingesting 12.5 mg. Electrocardiogram revealed only ST depression and first degree heart block. Initial pulse was 102 beats/min, systolic blood pressure was 170 mmHg. The patient was otherwise asymptomatic. Poison center recommended immediately obtaining serum potassium and digoxin concentrations; call-back was planned for two hours. The emergency physician was instructed to have ≥10 fab vials bedside and to administer if instability ensued. Thirty-five minutes later (≈90 min post-ingestion) ventricular fibrillation cardiac arrest occurred; initial serum potassium resulted at this time at 3.3 mEq/L. Bicarbonate, insulin and glucose, amiodarone, magnesium, calcium, and 10 fab vials were administered. Cardioversion resulted in wide-complex tachycardia which became ventricular fibrillation then asystole and the patient died. Serum digoxin concentration drawn on hospital arrival resulted after death at 44 ng/mL. In this fatal case of acute digoxin poisoning, fab was not empirically recommended because the patient initially did not have significant signs or symptoms that accompanied the history of ingesting ≥10 mg digoxin. While the bedside team was given clear anticipatory guidance by the regional poison center, the patient died despite fab administration once instability occurred.