Local Anesthetic Systemic Toxicity (LAST): Risks, Symptoms, and Management for Nurses

Understanding Local Anesthetics

• 💡 Local anesthetics work by blocking nerve impulses, preventing pain signals from reaching the brain, resulting in numbness in the affected area.
• 🔑 Common local anesthetics include roivocaine, bupivocaine, and lidocaine, often identifiable by the "-caine" suffix.
• 🎯 These medications are widely used in dentistry, surgery, for invasive procedures, post-operatively, and during labor and delivery.
• 💉 Administration routes vary, including injection, topical application (like EMLA cream or patches), airway instillation, epidural, intrathecal (spinal), per neural injection, and intravenous regional blocks.

Local Anesthetic Systemic Toxicity (LAST)

• ⚠️ LAST occurs when local anesthetics reach toxic levels in the systemic circulation, typically due to accidental intravascular injection or local overdose.
• 📈 Factors contributing to LAST include an imbalance between drug absorption and biotransformation (metabolism and excretion), often in the liver.
• 📉 Patients at higher risk include the very young, elderly, and those with comorbidities like heart, lung, liver, or renal disease, as well as pregnant individuals and those with metabolic syndromes.
• 🔗 Epinephrine is sometimes added to local anesthetics to cause vasoconstriction, limiting the anesthetic's spread into systemic circulation.

Pathophysiology and Symptoms of LAST

• 💔 Cardiac toxicity from LAST involves binding to and inhibiting sodium channels, disrupting cardiac cell action potentials and potentially leading to arrhythmias and collapse.
• 🧠 Central nervous system (CNS) toxicity is thought to stem from disturbances in potassium channels, increasing neuronal excitability and often manifesting as seizures.
• 🗣️ Early CNS symptoms can include confusion, unease, dizziness, agitation, ringing in the ears, numbness/tingling around the mouth, metallic taste, and slurred speech.
• 📉 Cardiac symptoms can progress from tachycardia and hypertension to bradycardia, hypotension, and severe arrhythmias.
• 🚨 Serious manifestations of unmanaged LAST include respiratory arrest, seizures, ventricular fibrillation, cardiovascular collapse, coma, and death.

Management and Nursing Interventions for LAST

• 🛑 The immediate priority is to stop any infusing local anesthetics and notify the physician.
• 🩺 Initial management focuses on supporting the patient's airway, oxygenation, and circulation, potentially requiring oxygen, ventilation, or mechanical ventilation.
• 💊 For seizures, benzodiazepines are used, and if seizures persist, paralytic agents may be considered.
• ❤️ Cardiac issues like bradycardia, hypotension, and arrhythmias are managed with appropriate medications, and lipid emulsion therapy is a potential treatment for severe cases.
• ✅ In the case of Mr. Thompson, mild symptoms resolved with oxygen, alternative pain management, discontinuation of the local anesthetic infusion, and ICU observation, leading to a full recovery.