What are the signs of systemic absorption of local anesthesia with lignocaine (lidocaine) and adrenaline (epinephrine), including effects on blood pressure and risk of myocardial infarction (MI), in a patient undergoing a procedure?

Signs and Management of Systemic Absorption of Lignocaine with Adrenaline

Clinical Presentation of Local Anesthetic Systemic Toxicity (LAST)

Systemic absorption of lignocaine (lidocaine) with adrenaline manifests initially with central nervous system symptoms followed by cardiovascular collapse if severe, and immediate recognition with lipid emulsion therapy is the cornerstone of saving the patient on the table. 1

Early Warning Signs (CNS Toxicity Phase)

The progression follows a predictable pattern that you must recognize immediately:

• Circumoral numbness and facial tingling - often the first symptoms patients report 1, 2, 3
• Metallic taste in the mouth 1
• Slurred or pressured speech 1
• Auditory changes (tinnitus) 1, 3
• Dizziness, lightheadedness, and disorientation 1
• Visual disturbances (double vision, blurred vision) 1
• Muscle twitching and tremor 1
• Nausea and drowsiness 1
• Hallucinations 1

Progression to Severe Toxicity

As toxicity worsens, the clinical picture deteriorates rapidly:

• Seizures or frank convulsions - occur at plasma levels above 6 mcg/mL free base 1, 4
• CNS depression following initial excitation 1
• Respiratory depression or arrest 1
• Altered consciousness progressing to unconsciousness 1

Cardiovascular Effects and Blood Pressure Changes

Hemodynamic Response to Epinephrine Component

The blood pressure rise from systemic epinephrine absorption is typically modest (4-5% increase in systolic BP) with corresponding 5% increase in heart rate in patients without complications. 5

• Hypertension and tachycardia accompany early CNS symptoms 1
• Rate-pressure product increases by approximately 10% 5
• Cardiac index increases by 14% while total peripheral resistance decreases by 10% 5
• In the test dose scenario (10-15 mcg epinephrine), expect a transient "epinephrine response" within 45 seconds consisting of increased heart rate (≥20 bpm for ≥15 seconds) and systolic blood pressure rise 4
• Circumoral pallor, palpitations, and nervousness may accompany the cardiovascular response 4

Severe Cardiovascular Toxicity

When lignocaine toxicity progresses beyond CNS effects:

• Bradycardia and sinus arrest 1
• Hypotension (despite initial hypertensive phase) 1
• Cardiac dysrhythmias 1
• Fulminant cardiovascular collapse refractory to standard resuscitation 1
• Cardiac failure or cardiac arrest 1

Risk of Myocardial Infarction

The risk of MI from therapeutic doses of lignocaine with epinephrine in properly selected patients is extremely low, with studies showing safety even in patients with stable cardiovascular disease. 1, 5

• Patients with stable cardiac disease can safely receive local anesthesia with epinephrine 1
• In a study of 27 patients with cardiovascular disease (including NYHA class I-III), no patient complained of cardiac symptoms following 1.8 mL of 2% lidocaine with 1:80,000 epinephrine 5
• The hemodynamic changes are minimal and well-tolerated even in compromised patients 5

High-Risk Scenarios for Cardiac Events

Exercise extreme caution in:

• Patients with recent MI or unstable cardiac disease - consult cardiology before proceeding 1
• Patients on cocaine or other sympathomimetic drugs - avoid epinephrine entirely 1
• Solvent abuse patients - epinephrine poses significant risk 1

Life-Saving Management on the Table

Immediate Actions (First 60 Seconds)

Stop injecting immediately and call for help the moment you recognize early CNS symptoms. 1

1. Discontinue local anesthetic administration 1
2. Call for emergency assistance and lipid emulsion 1
3. Maintain airway and provide 100% oxygen 1
4. Establish IV access if not already present 1

Seizure Management

If seizures develop:

• Provide ventilatory support - bag-valve-mask with 100% oxygen 1
• Consider small doses of benzodiazepines for seizure control 1
• Avoid propofol in large doses - may worsen cardiovascular instability 1

Intravenous Lipid Emulsion (ILE) Therapy - The Definitive Treatment

Administer 20% lipid emulsion immediately for cardiovascular collapse from LAST - this is the single most important intervention. 1

ILE Dosing Protocol

• Initial bolus: 1.5 mL/kg lean body mass over 1 minute (approximately 100 mL for 70 kg patient) 1
• Continuous infusion: 0.25 mL/kg per minute for 30-60 minutes 1
• Repeat bolus: Can repeat 1-2 times for persistent cardiovascular collapse 1
• Maximum total dose: 10 mL/kg over the first hour 1

Mechanism and Efficacy

• Creates a lipid compartment in serum that sequesters lipophilic lidocaine away from tissues 1
• Increases cardiac inotropy through additional mechanisms 1
• All 21 published cases of ILE for bupivacaine LAST demonstrated clinical improvement 1
• Registry data shows 81/103 cases (79%) reported clinical improvement with ILE 1

Cardiovascular Resuscitation

If cardiac arrest occurs:

• Begin CPR at 100 compressions/minute 1
• Defibrillate for VF/VT - do not delay for other interventions 1
• Administer epinephrine 1 mg IV every 3-5 minutes for non-VF/VT rhythms 1
• Use caution with epinephrine - the patient already has sympathomimetic toxicity 1
• Continue lipid emulsion therapy throughout resuscitation 1

Supportive Care

• Continuous cardiovascular monitoring is mandatory 1
• Flush peripheral IV with 20 mL saline after drug administration to ensure central circulation delivery 1
• Prepare for prolonged resuscitation - LAST can cause refractory arrest requiring extended efforts 1

Prevention Strategies

Dosing Safeguards

• Maximum safe dose: 7 mg/kg with epinephrine (approximately 500 mg for 70 kg adult) 2, 4
• Use lowest effective dose and concentration 1, 2
• Fractionate doses - inject incrementally rather than as single bolus 1, 4

Technical Precautions

• Aspirate before each injection to detect intravascular placement 1, 2
• Inject slowly to allow time for recognition of early symptoms 1
• Use intravascular marker - add 10-15 mcg epinephrine to test dose 1
• Consider ultrasound guidance for high-risk blocks 1

High-Risk Patient Modifications

Reduce doses significantly in:

• Patients >70 years - prolonged half-life 1, 4
• Congestive heart failure - clearance reduced by 50% or more 1, 4
• Hepatic dysfunction - metabolism severely impaired 1, 4
• Severe renal dysfunction - metabolite accumulation 1, 4

Critical Timing Consideration

Never administer lidocaine within 4 hours of other local anesthetic interventions to prevent cumulative toxicity 2, 3