No abstract

The most important clinical properties of local anaesthetic agents are potency, onset, duration of action and relative blockade of sensory and motor fibres. These qualities are related primarily to the physicochemical properties of the various compounds. In general, lipid solubility determines the relative intrinsic potency of the various agents, while protein binding influences the duration of anaesthesia and pKa is correlated with the onset of action. In general, the local anaesthetics for infiltration, peripheral nerve blockade, and extradural anaesthesia can be classified into three groups: agents of low potency and short duration, for example procaine and chloroprocaine; agents of moderate potency and duration, for example lignocaine, mepivacaine and prilocaine; and agents of high potency and long duration, for example amethocaine, bupivacaine and etidocaine. These local anaesthetics also vary in terms of onset: chloroprocaine, lignocaine, mepivacaine, prilocaine and etidocaine have a rapid onset, while procaine, amethocaine and bupivacaine are characterized by a longer latency period.

No abstract

No abstract

No abstract

No abstract

No abstract

Local anesthetic agents may be classified according to their intrinsic anesthetic potency and duration of activity. Procaine and chloroprocaine are relatively weak, short-acting drugs. Lidocaine, mepivacaine, and prilocaine represent agents of intermediate potency and duration of action. Tetracaine, bupivacaine, and etidocaine are highly potent, long-acting agents. The toxicity of local anesthetic drugs is usually due to inadvertent rapid intravascular injection or extravascular administration of an excessive amount. Intravascular toxicity is correlated with intrinsic anesthetic potency, whereas toxicity following extravascular injections is a function of physiological disposition characteristics of the various agents, such as rate of vascular absorption, rate of tissue redistribution, and rate of metabolism. The central nervous system is most susceptible to the toxic effects of local anesthetic agents. Signs and symptoms of CNS excitation followed by depression are the most common manifestations of local anesthetic toxicity. Cardiovascular depression may also occur following administration of excessive doses of local anesthetic agents or following high spinal or epidural anesthesia.