LIGNOCAINE
Introduction:
- Also referred as “Lidocaine/xylocaine”.
- Most commonly used LA.
- Is an amide.
Properties:
- Rapidly acting drug.
- Rapidly distributes to well-perfused tissues (brain & heart).
Dosage:
- Maximum safe dose of plain lidocaine = 300 mg (4.5 mg/kg).
- Maximum safe dose of lidocaine with epinephrine = 500 mg (7 mg/kg).
Duration of action:
- Without adrenaline = 45-60 mins.
- With adrenaline = 2-3 hrs.
Uses:
- Used as topical application on mucous membrane & skin.
- Lidocaine without adrenaline – DOC for Bier’s block.
- As regional anesthesia – Used in different concentrations for different anesthesia:
- Surface (topical) analgesia: 4%
- Nerve block: 1 – 2%.
- Spinal anesthesia: 5%
- Epidural: 1 – 2 %
- Beir’s block (intravenous regional anesthesia): 0.5%.
- Infiltration block: 1 – 2%.
- For treating ventricular arrhythmias –
- Has anti-arrhythmic effect.
- To blunt cardiovascular response to laryngoscopy & intubation (i.v. or intrathecal administered lidocaine).
- EMLA – Eutectic mixture of lignocaine & prilocaine.
Adverse effects:
- Causes malignant hyperthermia.
- CNS involvement occurs at much lesser dose than CVS involvement.
Lidocaine toxicity:
- Circulatory failure – Characterized by decreased cardiac output –> Decreasing hepatic blood flow –> Diminished metabolic clearance in liver –> Increased elimination.
- Consequently, Lidocaine concentration is initially increased in these relatively well-perfused tissues (brain & heart) even with usual doses & toxicity results.
Exam Important
- Dose of lignocaine for spinal anesthesia is 5%
- Maximum safe dose of lignocaine with adrenaline is 7 mg/kg wt
- Maximum safe dose of lignocaine for spinal anesthesia is 25-100 mg
- Concentration of lignocaine is used in epidural anesthesia is 2%
- Maximum dose of lignocaine which can be given with adrenaline for ocular blocks is 7mg/kg
- Local anesthetics act by blocking nerve conduction.
- Small fibers and non-myelinated fibers are blocked more easily than large myelinated fibers.
- Lignocaine is used as anesthetic and class IB antiarrhythmic in 2% jelly, 4% injection form
- 2-10% is the concentration of lignocaine used for topical anesthesia
- High first pass metabolism is seen in Lignocaine
- Lignocaine is used in Ventricular tachycardia
- Best used in digoxin induced arrhythmia Lignocaine
- Drug of choice in lignocaine toxicity is Diazepam
- Lignocaine can be used in Ventricular fibrillation, Spinal anesthesia & Epidural anesthesia
- A patient selected for surgery was induced with Thiopentone iv through one of anti cubital vein complains of severe pain of whole hand. The next line of management IV lignocaine through same needle
- Lignocaine is a amide
- Lignocaine in high dose produces Convulsion, Respiratory depression & Hypotension
- Adrenaline is added to Lignocaine injection for Less bleeding at the site, Higher doses can be given & Prolonged duration of action
- Lignocaine Can penetrate through mucous membrane
- Lignocaine can precipitate malignant hyperthermia
- Percentage of adrenaline with lignocaine for local infiltration is 1:50000.
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