Toxic Tuesday: the Digoxin Debates

DIGOXIN: The drug, the myth, the poisoning
* 60% renal eliminated; RENAL FAILURE makes it stick around longer (6 days!) 
* Cellular effect = INCREASED potassium OUTSIDE the cell
* Systemic effect = INCREASED inotropyslowed AV nodal conduction
* When do I suspect it?? Because chronic toxicity may have a normal digoxin level...
 = Lethal combination of hyperkalemia, dysrhythmia and cardiac arrest
- In cases where the digoxin level is normal: 
* increased automaticity/irritability (PACs, PVCs) gives you a 70% chance of dig toxicity; 
* increased automaticity with ANY OTHER FEATURE (bradycardia, GI symptoms...) give you >80% likelihood of dig toxicity
* For more about normal dig levels with toxicity:
Prevent cardiac arrest. Period.
Symptomatic control: 
- Atropine and adrenaline (but may increase cardiac irritability)
- Pacing: usually doesn't work
* Tachyarrhythmias:
- Consider MAGNESIUM
- Cardioversion: usually doesn't work
* Hyperkalemia:
Calcium: To give or not to give, that is the question. (This is its own POD. For now, read this:
- Insulin, glucose, bicarbonate
* Take this in the clinical context that one vial of digibind = $700
* Hard indications = digoxin at home plus:
cardiac arrest
life-threatening dysrhythmia
bad GI s/s
any of the above + new renal failure
ACUTE# vials needed = dose (mg) x 1.6  OR: 
stable = 5 vials
unstable = 10 vials then repeat doses of 5 vial q30mins until improved EKG
cardiac arrest 2/2 digoxin toxicity = 20 vials (if you have that much!)
CHRONIC# vials needed = dig level (ng/L) x wt (kg) / 100 OR: if unk dose = 2 ampules, observe for clinical response