Morning Report: 3/29/2013

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 following two tabs change content below.

• Bio
• Latest Posts

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

Latest posts by Jay Khadpe MD (see all)

• Save of the Month! December 2015 - December 23, 2015
• Morning Report: Unprovoked First Seizure in Adults - September 11, 2015
• Morning Report: Extramural Deliveries in the Emergency Room - September 10, 2015