Toxicity of local anesthetic agents

The toxicity of local anesthetic agents can be divided into two categories: (1) systemic toxic reactions due usually to an accidental intravascular injection and (2) local tissue toxicity. The systemic toxicity of local anesthetic agents is primarily characterized by CNS excitation and convulsive activity. The cardiovascular system is more resistant to the toxic actions of local anesthetics. However, local anesthetics can exert a negative chronotropic and inotropic action and cause profound peripheral vasodilation. The combination of cardiac depression and peripheral vascular dilation results in irreversible circulatory collapse. The more potent agents such as bupivacaine appear to be more cardiotoxic and may precipitate ventricular arrhythmias and ventricular fibrillation. Local tissue toxicity is rare following the administration of local anesthetics. However, large doses of chloroprocaine solutions administered intrathecally have been associated with prolonged sensory-motor deficits in a few patients due probably to the low pH and presence of sodium bisulfite in the chloroprocaine solutions. In general, local anesthetic agents are relatively safe if administered properly. However, as with any pharmacological agents, local anesthetics may cause severe toxic reactions due to the improper use of these drugs.