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Adverse effects and drug interactions associated with local and regional anaesthesia
M Naguib1, M M Magboul, A H Samarkandi
1Department of Anaesthesia, Faculty of Medicine at King Khalid University Hospital, Riyadh, Saudi Arabia.
Insights
Local anesthetics can cause serious CNS and cardiovascular toxicity, especially with overdose or IV injection. Careful patient selection and administration are crucial to avoid adverse effects like seizures and cardiac arrest.
Area of Science:
- Anesthesiology
- Pharmacology
- Toxicology
Background:
- Local anesthetic drugs are widely used for pain management.
- Adverse effects can occur due to excessive dosage, rapid absorption, or inadvertent intravascular injection.
- Certain patient populations, like small children, are more susceptible to specific toxicities.
Purpose of the Study:
- To review the systemic and localized adverse effects of local anesthetic drugs.
- To highlight the mechanisms and treatments for central nervous system (CNS) and cardiovascular toxicity.
- To discuss neurotoxicity risks associated with specific administration methods and drug formulations.
Main Methods:
- Literature review of adverse effects associated with local anesthetics.
- Analysis of case reports and clinical studies on local anesthetic toxicity.
- Discussion of pharmacological interactions and patient-specific risk factors.
Main Results:
- Systemic toxicity (CNS and cardiovascular) can arise from increased plasma concentrations.
- Bupivacaine is frequently linked to seizures and cardiotoxicity; lidocaine carries neurotoxicity risks intrathecally.
- Methaemoglobinaemia is a risk in children with prilocaine and sulfonamides; true allergy is rare.
Conclusions:
- Understanding local anesthetic toxicity is vital for safe clinical practice.
- Appropriate dosing, administration techniques, and patient monitoring are essential.
- Awareness of drug interactions and patient comorbidities can prevent severe adverse events.
Abstract:
Systemic and localised adverse effects of local anaesthetic drugs usually occur because of excessive dosage, rapid absorption or inadvertent intravascular injection. Small children are more prone than adults to methaemoglobinaemia, and the combination of sulfonamides and prilocaine, even when correctly administered, should be avoided in this age group. The incidence of true allergy to local anaesthetics is rare. All local anaesthetics can cause CNS toxicity and cardiovascular toxicity if their plasma concentrations are increased by accidental intravenous injection or an absolute overdose. Excitation of the CNS may be manifested by numbness of the tongue and perioral area, and restlessness, which may progress to seizures, respiratory failure and coma. Bupivacaine is the local anaesthetic most frequently associated with seizures. Treatment of CNS toxicity includes maintaining adequate ventilation and oxygenation, and controlling seizures with the administration of thiopental sodium or benzodiazepines. Cardiovascular toxicity generally begins after signs of CNS toxicity have occurred. Bupivacaine and etidocaine appear to be more cardiotoxic than most other commonly used local anaesthetics. Sudden onset of profound bradycardia and asystole during neuraxial blockade is of great concern and the mechanism(s) remains largely unknown. Treatment of cardiovascular toxicity depends on the severity of effects. Cardiac arrest caused by local anaesthetics should be treated with cardiopulmonary resuscitation procedures, but bupivacaine-induced dysrhythmias may be refractory to treatment. Many recent reports of permanent neurological complications involved patients who had received continuous spinal anaesthesia through a microcatheter. Injection of local anaesthetic through microcatheters and possibly small-gauge spinal needles results in poor CSF mixing and accumulation of high concentrations of local anaesthetic in the areas of the lumbosacral nerve roots. In contrast to bupivacaine, the hyperbaric lidocaine (lignocaine) formulation carries a substantial risk of neurotoxicity when given intrathecally. Drugs altering plasma cholinesterase activity have the potential to decrease hydrolysis of ester-type local anaesthetics. Drugs inhibiting hepatic microsomal enzymes, such as cimetidine, may allow the accumulation of unexpectedly high (possibly toxic) blood concentrations of lidocaine. Reduction of hepatic blood flow by drugs or hypotension will decrease the hepatic clearance of amide local anaesthetics. Special caution must be exercised in patients taking digoxin, calcium antagonists and/or beta-blockers.