Rhythm Nation December 2014 – Answer!

 is a lipid soluble class 1C antidysrhythmic that works by stabilizing sodium channels in their inactivated state and prolonging phase 0 depolarization of the cardiac action potential. This results in QRS widening and the tall terminal R’ wave in lead aVR. In toxic doses, it can also block slow calcium channels and cause slowed conduction. Flecainide toxicity can cause both bradyarrhythmias and ventricular tachyarrhythmias.

Sodium bicarbonate! Give if QRS > 100 msec or a ventricular arrhythmia. It narrows the QRS, improves systolic blood pressure, and decreases ventricular arrhythmias. Bicarb pushes act via a Na depended effect. It essentially competes for binding at the Na channel with the Na-Channel blocking drug. Bicarb drips act via a pH-dependent effect by converting the Na-channel blocker to its non-ionized form, which reduces its ability to bind to the Na-channel binding site. Some authors advocate a goal pH of 7.50-7.55 (can also hyperventilate if the patient is intubated).

Sodium bicarbonate can induce hypokalemia (likely by shifting potassium intracellularly), leading to prolonged QTc. Serum pH and potassium levels should be checked hourly until pH levels are within desired range. Replete potassium as needed.

If patients present within 2 hours of ingestion, one dose of activated charcoal may be given.

Supportive care such as airway management prn, cardiac monitoring, IV fluids and vasopressors prn.

Dispo: Patients with mild symptoms and no signs of conduction abnormalities (i.e QRS <100) after being observed for several hours may be admitted to a non-critical care setting with telemetry.

Intravenous fat emulsion can be used as an antidote for highly lipophilic drugs (i.e flecainide, propofol, etc.). There are 3 proposed mechanisms, the most popular being the lipid sink/sponge model where the drug is removed from its site of toxicity and deposited into areas with high lipid content (like Intralipid) where it is then excreted. Current indications for lipid emulsion include patients not responding to standard therapy (including sodium bicarbonate) and cardiac arrest. Consider it early! Up to three IV boluses can be given, followed by an infusion for up to one hour or until hemodynamic recovery.

Lidocaine is recommended in some textbooks but may not be a great choice as it can also block sodium channels and further widen the QRS in toxicity. Again, think Intralipid!

Dispo: Patients with AMS, conduction abnormalities, hypotension, or seizures should be admitted to MICU.