Digoxin toxicity
Pathophysiology
Digoxin
- Inotropic = NA+/K+ ATPase pump causing rise in intracellular Ca++, Na+ and fall in intracellular K+
- Chronotropic = Slows conduction in AV node (but increased spont firing by Purkinje tissues)
- Toxic effect mainly ATPAse pump effects
History
- Fatigue
- Palpitations, DOE rare
- Pre-sncope or light headed
- Confusion
- Changes in colour vision
- Diplopia or blurred vision
- Nausea, anorexia, diarrhoea
Examination
- Poor perfusion, CCF
- Dysrhtthmias
- PVCs usually benign
- PAF with 2:1 block
- Junctional rhythm
- Torsade de pointes
- Sinus or AF bradycardias
Clasically see tachy/brady with VT +/- bradycardia unresponsive to atropine
Treatment
- Stop digoxin!
- Treat arrhythmias
- Correct electrolyte imbalance
- Beware drugs that raise plasme digoxin levels
- Amiodarone, Ca++ channel blockers, quinine
- Digibind: digoxin specific antigen binding fragment for life threatening dig toxicity
- t1/2 16 hours (with normal renal fxn)
- Beware that serum dig levels are unreliable after Digibind. Repeated doses should be given only on clinical ground, not on repeat dig levels (which may appear higher that before Digibind in given.
