Digoxin toxicity: Difference between revisions
Line 8: | Line 8: | ||
*Renally cleared | *Renally cleared | ||
* Hemodialysis does not work | * Hemodialysis does not work | ||
*1 fab vial binds 0.5mg of digoxin | |||
== Risk Factors == | == Risk Factors == |
Revision as of 07:23, 18 March 2011
Background
- Positive inotropic effect
- Inhibits Na-K pump -> incr extracelluar K, incr intracellular Na -> incr intracellular Ca
- Increases vagal tone
- Decreases refractory time; increases automaticity
- Increases risk of dysrhythmias
- Renally cleared
- Hemodialysis does not work
- 1 fab vial binds 0.5mg of digoxin
Risk Factors
- Hypokalemia
- Hypovolemia
- Hypoxia
- cardiac ischemia
- renal insufficiency
- Meds
- CCBs, amiodarone
Work-Up
- Dig level
- Normal = 0.8-2 ng/mL
- May have toxicity even with "therapeutic" levels
- Measure serum level at least 6 hours after acute ingestion, immediately for chronic ingestion
- If measure before this may be falsely elevated due to incomplete drug distribution
- Normal = 0.8-2 ng/mL
- Chemistry
- Hyperkalemia level correlates with degree of toxicity
- Hyperkalemia does not cause death; lowering K+ does not reduce mortality
- Hypokalemia increases susceptibility in chronic toxicity
- Hypomagnesemia is common
- Hyperkalemia level correlates with degree of toxicity
- Cr/BUN
- Urine output
- ECG (serial)
Clinical Manifestations
Cardiac
- Any type of dysrhythmia is possible except for rapidly conducted atrial arrhythmias
- Most common:
- PVCs
- Bradycardia
- Digitalis Effect
- T wave changes
- QT interval shortening
- Scooped ST segments with depression in lateral leads
GI
- Nausea/vomiting
- Abdominal pain
Neuro
- Confusion
- Weakness
- Visual disturbances
- yellow halos
- Scotomas
- Delirium
Treatment
Fab Fragment Therapy
- Indications
- Severe rhythm disturbances refractory to conventional therapy
- End-organ dysfunction
- Hyperkalemia >5 after acute overdose
- Pacemaker (may mask cardiac dysrhythmia)
- Consider for:
- Dig level > 10 in acute ingestion
- Dig level > 4 in chronic ingestion
- If adult acutely ingests > 10mg
- If child acutely ingests > 4mg
- How To Use
- Neither amount ingested nor digoxin level are known:
- Adult dose
- 10 vials over 30 minutes
- Peds dose
- 5 vials
- Peak effect occurs after 90min, initial response after 20min
- Repeat dose if clinical response is inadequate
- Adult dose
- Amount ingested is known but digoxin level is unknown
- Step 1: Calculate total body load (TBL)
- TBL = dose (in mg) ingested
- Step 2: Calculate number of vials needed
- Number of vials = TBL X 2 (round up to nearest whole number)
- Steady state digoxin level is known
- Number of vials = (dig level(in ng/mL) X pt wt) / 100
- Neither amount ingested nor digoxin level are known:
Chronic toxicity without severe signs
- Give half the recommended dose
- Otherwise may unmask the condition for which the pt is taking digoxin
- Give half the recommended dose
Fab side-effects
- Allergic reaction
- Withdrawal of dig effect:
- CHF, a fib w/ RVR
- Hypokalemia
Activated charcoal
- Only an adjunctive tx; NOT an alternative to fab fragment therapy
- Consider only if present within 2 hr of ingestion
- 1g/kg (max 50g)
- Hyperkalemia
- Do not treat! Do not give calcium!
- Once fab is given hyperkalemia will rapidly correct
- Aggressive tx with potassium-lowering agents could cause sig hypokalemia following therapy
- Once fab is given hyperkalemia will rapidly correct
- Do not treat! Do not give calcium!
- Hypokalemia
- Treat!
- Hypomagnesemia
- Treat
- Rhythm Disturbance
- Bradycardia (symptomatic)
- Atropine 0.5mg IV
- Pacing
- Tachyarrhythmias
- K
- Mag
- Lidocaine
- Phenytoin
- Cardioversion
- Bradycardia (symptomatic)
Source
Rosen's, UpToDate