Rosen & Barkin's 5-Minute Emergency Medicine Consult (214 page)

• Accidental adult or pediatric overdose of a known amount
  
• Intentional acute overdose in a patient not taking digoxin chronically
  
• Intentional acute or chronic overdose in a patient taking digoxin chronically
  
• Unintentional chronic ingestion of digoxin in which renal clearance decreases or the dose chronically increases
  
• Unintentional toxicity from recent antibiotic use (esp. macrolides) that alter GI flora, primarily by decreasing
  Eubacterium lentum
  , increasing absorption
  

• Altered mental status
  
• Bradycardia
  
• Tachycardia
  
• Irregular rhythm
  
• Hypotension
  

• ECG:
  
  • For dysrhythmia
    
• Digoxin level:
  
  • Normal range: 0.5–2 ng/mL
    
  • Distribution after oral intake not complete until 6 hr; therefore, >6-hr level is most accurate steady state concentration.
    
  • False elevations possible with spironolactone use, pregnancy, hyperbilirubinemia, chronic renal failure, liver failure, CHF
    
  • May be falsely elevated after digoxin-specific Fab fragments given
    

• Electrolytes, BUN, creatinine, glucose:
  
  • Hypokalemia contributes to digitalis toxicity.
    
  • Hyperkalemia seen in acute toxicity and correlates with acute digitalis mortality better than digoxin serum levels.
    
  • Follow K
    ⁺
    serially
    
• Calcium, magnesium
  

• Overdoses:
  
  • Calcium channel blockers
    
  • β-Blockers
    
  • Quinidine, procainamide
    
  • Clonidine
    
  • Organophosphates
    
  • Antidysrhythmics
    
  • Other antihypertensives
    
• Primary cardiac dysrhythmias
  
• Acute gastroenteritis
  

TREATMENT

• Establish IV access
  
• Continuous cardiac monitoring
  
• Apply pads for potential cardioversion
  

ABCs:

• IV, oxygen, monitor:
  
  • IV fluid bolus if hypovolemic
    
• Administer naloxone, thiamine, dextrose for altered mental status.
  

• Cardiac arrest resuscitation:
  
  • Defibrillate for ventricular fibrillation, pulseless VT.
    
  • Standard advanced cardiac life support (ACLS) protocol
    
  • Administer digoxin-specific antibody Fab fragments (Digibind), up to 5–20 vials IV push (IVP).
    
  • MgSO
    ₄
    , 2 g IVP
    
  • Continue resuscitation for 30 min after digoxin-specific antibody Fab fragments.
    
• General measures:
  
  • Activated charcoal if acute ingestion
    
  • Replenish magnesium.
    
  • Treat hyperkalemia with insulin, dextrose, bicarbonate, sodium polystyrene sulfonate.
    
    • Calcium can probably be used to treat hyperkalemia, but because other safer alternatives exist it is not recommended, unless life-saving membrane stabilization is needed secondary to hyperkalemia, in the unstable patient.
      
    • If the patient has hyperkalemia from digoxin toxicity treatment with digoxin-specific Fab fragments are indicated 1st in the hemodynamically stable patient.
      

DYSRHYTHMIA MANAGEMENT

• 1st choice: Digoxin-specific antibody Fab fragments (Digibind, DigiFab)
  
  • Indications:
    
    • SDC ≥15 ng/mL at any time or ≥10 ng/mL at steady state (6 hr)
      
    • Ingestion of >10 mg in adults or 0.2 mg/kg or 4 mg in children
      
    • Hyperkalemia >5–5.5 mEq/L
      
    • Hemodynamically unstable or life-threatening dysrhythmias
      
    • VT, ventricular fibrillation
      
    • Atrial tachycardia
      
    • Variable AV block
      
    • Bradycardia with no response to atropine
      
    • Hypotension
      
  • Onset: 20–30 min
    
  • Digoxin levels may increase, decrease, or stay in therapeutic range after therapy owing to Fab digoxin complexes and redistribution.
    
  • Renal clearance of drug–antibody complexes:
    
    • Too large to be removed by dialysis
      
  • 2nd dose if rebound toxicity
    
  • Complications:
    
    • Exacerbation of CHF
      
    • Hypokalemia
      
    • Atrial fibrillation with rapid ventricular response
      
• If digoxin-specific antibody Fab fragments not immediately available initiate the following:
  
  • Lidocaine:
    
    • For ventricular dysrhythmias without AV block
      
    • Not harmful but not very effective
      
  • For bradydysrhythmias:
    
    • Atropine
      
  • Pacing for symptomatic bradydysrhythmia
    
  • MgSO
    ₄
    for ventricular dysrhythmias with torsades de pointes
    
  • Quinidine, procainamide contraindicated
    
• Cardioversion is last resort for severe, life-threatening tachydysrhythmia:
  
  • Start at low energy 10–50 J, then increase to high levels if ineffective.
    
  • Safe if digoxin level <2 ng/mL
    

• Activated charcoal slurry:
  
  • 1 g/kg if within 1 hr
    
• Digoxin-specific antibody Fab fragments:
  
  • 40-mg vial neutralizes 0.5 mg of digoxin.
    
  • If amount ingested known:
    
  • Number of vials needed to treat equals [amount ingested (mg)/0.5 (mg/vial)]
    
  • If steady serum level known:
    
    • Number of vials needed equals [SDC (ng/mL) × weight (kg)]/100
      
  • If neither amount ingested nor serum level known:
    
    • Acute toxicity: 5–10 vials adults or children
      
    • Chronic toxicity: 1--2 vials in adults or children
      
  • Bolus digoxin-specific antibody Fab fragments for cardiac arrest
    
  • Additional doses as needed
    
• Standard treatment for hyperkalemia and bradycardia (calcium only if necessary)
  

• Dosage is based on weight and serum concentration. There is no change in the setting of renal or hepatic dysfunction.
  
• Recrudescence of toxicity has been reported in patients with concomitant renal failure. Redosing of digoxin-specific antibody Fab fragments should be used again when indicated.
  

• Weight-based dosing for children is the same as it is for adults.
  
• On some occasions, accidental dose ingested by a child is known and the number of vials is indicated by the amount of digoxin bound by each vial. See dosing.
  

Digoxin-specific Fab fragments are pregnancy class C.

FOLLOW-UP

• ICU:
  
  • Unstable cardiovascular status in acute or chronic toxicity
    
• Telemetry:
  
  • Asymptomatic or mildly symptomatic dysrhythmia
    
  • High risk for developing toxicity
    

Acute/chronic ingestion:

• Digoxin level <2 ng/mL
  
• Asymptomatic for 6 hr and no ECG abnormalities
  

Psychiatric referral for stable patients who are suicidal

When it is known that the patient is on digoxin and presents with cardiovascular instability, and/or hyperkalemia, treatment should begin with the antidote: Digoxin-specific Fab fragments.

• Erickson CP, Olson KR. Case files of the medical toxicology fellowship of the California poison control system-San Francisco: calcium plus digoxin-more taboo than toxic?
  J Med Toxicol
  . 2008;4(1):33–39.
  
• Levine M, Nikkanen H, Pallin DJ. The effects of intravenous calcium in patients with digoxin toxicity.
  J Emerg Med.
  2011;40(1):41–46.
  

CODES

972.1 Poisoning by cardiotonic glycosides and drugs of similar action

BASICS

• Double vision
  
  • Simultaneous perception of 2 images
    
  • Can be oriented horizontally, vertically, or diagonally from one another.
    
• Diplopia is usually due to abnormal movement of the extraocular muscles (EOMs), which are innervated by 3 cranial nerves (CNs):
  
  • CN 3 – superior, inferior, and medial rectus and inferior oblique muscles
    
  • CN 4 – superior oblique muscle
    
  • CN 6 – lateral rectus muscle
    
• Brainstem lesions can damage CN nuclei or their connections (medial longitudinal fasciculus, MLF), causing an internuclear ophthalmoplegia (INO)
  
• CN dysfunction
  
  • Compression as they traverse the subarachnoid space and venous sinuses
    
  • Inflammation
    
  • Elevation (or reduction) of CSF pressure can cause CN 6 palsy
    
• Disease affecting the orbits and the bony skull can cause restriction of motion of one or both eyes or EOMs