Anesthesia Student Survival Guide.pdf - Index of

PhArMAColoGY of loCAl AnesthetiCs ● 71
Uses of Local Anesthetics in Anesthesia Practice
In addition to its use by the surgeon to infiltrate the incision site, local anesthetics
are used by anesthesiologists in a variety of settings. For example, local anesthetics
are used for IV placement, epidural placement, spinal or other regional block
placement, pain management practice (patch), or lido for propofol pain.
Local Anesthetic Side Effects and Toxicity
● Central nervous system effects: Dysfunction of the central nervous system
is often the first sign of local anesthetic toxicity. Signs and symptoms of
local anesthetic toxicity tend to follow a stereotypical sequence. Early
symptoms may include lightheadedness, perioral or tongue numbness,
or a metallic taste. Higher levels may lead to tinnitus, visual dysfunction,
agitation, and anxiety. Central nervous system depression can follow, with
unconsciousness, respiratory arrest, and seizure activity. Local anestheticinduced
seizures can be treated with hyperventilation, benzodiazepines, or
small doses of thiopental or propofol.
● Cardiovascular effects: If blood concentrations rise high enough, the
●
local anesthetics can bind to sodium channels present on myocardial cells.
This reduces myocardial automaticity and shortens the refractory period.
Cardiac arrhythmias, depressed contractility, and cardiac arrest can ensue.
In general, the high-potency agents such as bupivacaine and ropivacaine
have greater cardiotoxicity than the lower-potency agents. Successful
resuscitation of a patient with local anesthetic-induced cardiotoxicity can
require prolonged efforts and may prove to be difficult (or impossible). Of
note, cardiotoxic effects of bupivacaine and ropivacaine have been observed
to occur without promontory central nervous system effects.
Neurotoxicity:
Lidocaine: Permanent neurologic injury (cauda equina syndrome) has
been associated with infusion of 5% lidocaine through spinal microcatheters.
It has rarely been observed after single-dose spinal injections.
It is thought that pooling of this concentrated local anesthetic solution
around nerve fibers may cause neurotoxic effects.
2-Chloroprocaine: 2-chloroprocaine was used for spinal anesthesia in the
1950s, and is still commonly used for epidural anesthesia (particularly
in obstetrics). In the early 1980s, multiple cases of neurological injury
were associated with accidental intrathecal injections of large doses of
chloroprocaine. Investigations showed that a likely cause of injury was