Calcium channel blocker toxicity

Background

• Hemodialysis is ineffective
• Precipitous deterioration is common (esp w/ verapamil)
• 2 Classes:
  • 1. Dihydropyridines (nifedipine, amlodipine, nicardipine)
    • Systemic vasodilation, mild effect on heart
    • Toxicity = Hypotension, reflex tachycardia
      • Note: with higher doses peripheral selectivity is lost
        • I.e. may see decreased inotrophy, bradycardia
  • 2. Non-dihydropyridines (Verapamil, diltiazem)
    • Stronger effect on heart, weak vasodilators
    • Toxicity = Bradycardia, decreased inotropy

Diagnosis

• Cardiovascular
  • Hypotension (any CCB overdose)
  • Bradycardia (usually only seen with verapamil/dilt)
  • AV/sinus block
  • CHF
• Pulmonary
  • Respiratory depression
  • Pulmonary edema
• GI
  • Nausea/vomiting
• Neurologic
  • Lethargy, confusion, coma
• Metabolic
  • Hyperglycemia

Work-Up

• ECG
  • PR prolongation
  • Bradydysrhythmia
• Glucose
• Chemistry

DDx

• Beta blockers
  • More likely to cause CNS changes
  • Hypoglycemia is more common
• Digoxin
  • Nausea/vomiting is more common
• Clonidine
  • Miosis, somnolence
• Cholinergic agents
  • SLUDGE

Treatment

• Charcoal 1g/kg (max 50g)
  • Consider if present within 1-2hr with delayed-release preparation

• Hypotension
  • IV fluids

• Bradycardia (symptomatic)
  • Atropine
    • Adult: 0.5-1mg IV q2-3min to max of 3g
    • Ped: 0.02mg/kg (minimum is 0.1mg)

Calcium

• Calcium gluconate 30-60mL of 10% soln
• Calcium chloride 10-20mL of 10% soln (requires central line)

Glucagon

• 5mg IV bolus q10min x 2

Vasopressors

• Norepinephrine is agent of choice

High-dose insulin and glucose

• Takes 30-60min for effect
• Glucose:
  • Adult: 50mL of D50W
  • Ped: 2.5mL/kg of D10
• Insulin bolus 1 Unit/kg followed by 0.5units/kg/hr
  • Titrate infusion until hypotension is corrected or max 2u/kg/hr
• Potassium
  • If <3 administer 20mEq IV

Disposition

• Admit all symptomatic pts
• Admit all sustained-release ingestions
• D/C if asymptomatic x 6-8hrs

Source

Rosen's