Morning Report

Morning Report: 3/29/2013

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Here’s Dr. Willis with today’s Morning Report!

 

Lidocaine Toxicity

Epidemiology

  • Inadvertent injection
  • Repeated use of a therapeutic dose
  • Unintentional administration of a toxic dose

 

Pharmacology

  • Amide
  • Toxic dose: 5mg/ml and with epi 7mg/ml
  • Blocks sodium channels (fast in, slow out mechanism)
  • Toxicity potentiated by
    • Med interactions (cimetidine, cipro, clonidine, phenytoin, beta blockers)
    • Rate of injection
    • Metabolic or respiratory acidosis
    • Hypoxia

 

CNS Manifestations

  • Occur at lower doses and earlier
  • Early: tinnitus, lightheadedness, circumoral numbness, disorientation, confusion, auditory and visual disturbances, and lethargy
  • Objective: shivering, tremors, and ultimately generalized tonic-clonic seizures
  • Higher concentrations: producing coma, apnea, and cardiovascular collapse
  • First blocks inhibitory CNS pathways and then blocks excitatory

 

CV Manifestations

  • Related to effects on vascular tone, inotropy, and dysrhythmias related to indirect CNS and direct cardiac and vascular effects
  • Sodium channel blockade causes negative inotropy by affecting excitation-contraction coupling
  • Slows impulse conduction in the SA and AV nodes, His-Purkinje system, and atrial and ventricular muscle
  • Low doses vasocontrictive and high doses causing relaxation
  • Widened PR, widened QRS, sinus tach, sinus arrest, AV dissociation
  • CV toxicity is greatest in patients with underlying cardiac conduction problems or post MI
  • At progressively higher anesthetic concentrations, hypotension, sinus arrest with junctional rhythm, and eventually cardiac arrest

 

Treatment

  • Benzos for seizures. Avoid phenytoin (Na channel blockade)
  • Manage hypoxemia and met acidosis b/c may potentiate CV toxicity. Use sodium bicarb, early airway management
  • Hyperventilation in theory might decrease CNS toxicity
  • No vasopressin, epi preferred
  • Use Amio for arrhythmia
  • Lipid infusions in animal models, case reports
The views expressed on this blog are the author's own and do not reflect the views of their employer. Please read our full disclaimer here. Any references to clinical cases refer to patients treated at a virtual hospital, Janus General Hospital.
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Jay Khadpe MD

Editor in Chief of "The Original Kings of County" Assistant Professor of Emergency Medicine Assistant Residency Director SUNY Downstate / Kings County Hospital
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