Local Anaesthetics Systemic Effects Quiz

Systemic Effects of Local Anaesthetics (LA)

• Local anaesthetics (LA) agents are not easily absorbed through intact skin.
• LA agents are absorbed into the bloodstream when applied to mucous membranes or injected into tissues.
• Systemic distribution of LAs occurs throughout the body.
• LAs undergo metabolism and elimination processes.

Systemic Actions of Local Anaesthetic Agents

• LAs cause a reversible blockade of nerve conduction in nerve endings and nerve trunks.
• LAs directly relax smooth muscle.
• LAs cause myocardial depression (reduced conduction rate, force of contraction, and electrical excitability).
• LAs can depress the central nervous system, and initial signs may be excitatory.

Absorption of Local Anaesthetic Agents into the Circulation

• Absorption of LA agents into the bloodstream causes the effect of the LA to wear off.
• Systemic absorption may lead to toxicity.
• The rate of systemic absorption depends on factors such as the anaesthetic agent, tissue vascularity, presence/absence of vasoconstrictors, and accidental intravascular injection.

Metabolism and Elimination of Local Anaesthetics (LA)

• LA metabolism depends on patient physiology.
• Most commonly used LAs are metabolized in the liver, yielding inactive metabolites.
• Artiacaine is also metabolized in the plasma.
• LAs are typically eliminated through the urine.
• Reduced liver and kidney function may necessitate adjusting the LA dose for safety.

Signs of Systemic Toxicity of Local Anaesthetics (LA)

• Systemic LA toxicity is extremely rare in dentistry procedures.
• Early signs may include tingling and numbness around the mouth.
• Other potential signs include visual and hearing disturbances (e.g., tinnitus).
• Mood changes (e.g., irritability, agitation, anxiety, and restlessness).
• Lightheadedness or dizziness.
• Increased respiratory rate and depth.
• Drowsiness
• Coma and convulsions.
• Respiratory arrest
• Cardiac arrest

Reducing Systemic Toxicity

• Avoid intravascular injection (always aspirate before injecting).
• Inject slowly.
• Use safe dosages.
• Choose less toxic drugs (e.g., 3% prilocaine with felypressin).
• Use vasoconstrictors.

Maximum Safe Dose of Local Anaesthetic Agents (LA)

• The provided table lists maximum safe doses for different LA agents (lidocaine, prilocaine, mepivacaine, articaine) in mg/kg and maximum cartridge numbers for adults and 5-year-old children.

Contraindications and Cautions of Local Anaesthetic Agents (LA)

• Lidocaine: Contraindicated in hypersensitivity (rare). Caution with beta-blockers.
• Prilocaine: Contraindicated in hypersensitivity (very rare). Caution with sulphonamides and beta-blockers.
• Mepivacaine: Contraindicated in hypersensitivity (very rare) and children under age 4. Caution with pregnancy, breastfeeding, and beta-blockers.
• Articaine: Contraindicated in hypersensitivity, children under age 4, and plasma cholinesterase deficiency. Cation with pregnancy (use with caution), avoid breastfeeding for 48 hours after use, and use beta-blockers cautiously. Patients need to be monitored for post-operative paraesthesia.
• Epinephrine (adrenaline): Contraindicated in recent cocaine use (within 24 h). Caution with tricyclic antidepressants, monoamine oxidase inhibitors, beta-blockers, calcium channel blockers, diuretics, cardiac conditions, and hypertension and circulatory problems
• Felypressin: Cautions concern late stages of pregnancy, as it might induce labour (theoretical), and it is similar to oxytocin.

LA Equipment

• Cartridges: Various types of LA cartridges are available.
• Plunger (handle): Used to administer LA
• Needles: Different lengths and gauges of safety needles for LA administration.
• Bevel indicator: Used to check orientation of the needle.
• Traditional LA system: Involves a syringe, needle, and cartridge.

Summary of Today's Session

• Different LA agents used in dentistry and their functions discussed.
• Systemic effects of LAs were explained.
• Contraindications and cautions concerning adminstration of LA were identifed.
• Safety measures for use of LA equipment were shown.