Pathophysiology
Digoxin
- Inotropic = NA+/K+ ATPase pump causing ↑ in intracellular Ca++, Na+ and ↓ in intracellular K+
- Chronotropic = Slows conduction in AV node (but increased spontaneous firing by Purkinje tissues)
- Toxic effect mainly ATPase pump effects
History
- Fatigue
- Palpitations, DOE rare
- Pre-syncope or light headed
- Confusion
- Changes in colour vision
- Diplopia or blurred vision
- Nausea, anorexia, diarrhoea
Examination
- Poor perfusion, CCF
- Dysrhythmia
- PVCs usually benign
- PAF with 2:1 block
- Junctional rhythm
- Torsade de pointes
- Sinus or AF bradycardias
Classically see tachy/brady with VT ± bradycardia unresponsive to atropine
Treatment
- Stop digoxin!
- Treat arrhythmias
- Correct electrolyte imbalance
- Beware drugs that raise plasma digoxin levels
- Amiodarone, Ca++ channel blockers, quinine
- DigiFab®: 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 DigiFab®. Repeated doses should be given only on clinical ground, not on repeat dig levels (which may appear higher that before DigiFab is given