Reactions to CARBOCAINE (mepivacaine) are characteristic of those associated with other amide-type
local anesthetics. A major cause of adverse reactions to this group of drugs
is excessive plasma levels, which may be due to overdosage, inadvertent intravascular
injection, or slow metabolic degradation.
Systemic
The most commonly encountered acute adverse experiences which demand immediate
counter-measures are related to the central nervous system and the cardiovascular
system. These adverse experiences are generally dose related and due to high
plasma levels which may result from overdosage, rapid absorption from the injection
site, diminished tolerance, or from unintentional intravascular injection of
the local anesthetic solution. In addition to systemic dose-related toxicity,
unintentional subarachnoid injection of drug during the intended performance
of caudal or lumbar epidural block or nerve blocks near the vertebral column
(especially in the head and neck region) may result in underventilation or apnea
(“Total or High Spinal”). Also, hypotension due to loss of sympathetic
tone and respiratory paralysis or underventilation due to cephalad extension
of the motor level of anesthesia may occur. This may lead to secondary cardiac
arrest if untreated. Factors influencing plasma protein binding, such as acidosis,
systemic diseases which alter protein production, or competition of other drugs
for protein binding sites, may diminish individual tolerance.
Central Nervous System Reactions
These are characterized by excitation and/or depression. Restlessness, anxiety,
dizziness, tinnitus, blurred vision, or tremors may occur, possibly proceeding
to convulsions. However, excitement may be transient or absent, with depression
being the first manifestation of an adverse reaction. This may quickly be followed
by drowsiness merging into unconsciousness and respiratory arrest. Other central
nervous system effects may be nausea, vomiting, chills, and constriction of
the pupils.
The incidence of convulsions associated with the use of local anesthetics varies
with the procedure used and the total dose administered. In a survey of studies
of epidural anesthesia, overt toxicity progressing to convulsions occurred in
approximately 0.1% of local anesthetic administrations.
Cardiovascular Reactions
High doses or, inadvertent intravascular injection, may lead to high plasma
levels and related depression of the myocardium, decreased cardiac output, heart
block, hypotension (or sometimes hypertension), bradycardia, ventricular arrhythmias,
and possibly cardiac arrest. (See WARNINGS, PRECAUTIONS,
and OVERDOSAGE sections.)
Allergic
Allergic-type reactions are rare and may occur as a result of sensitivity to
the local anesthetic or to other formulation ingredients, such as the antimicrobial
preservative methylparaben, contained in multiple-dose vials. These reactions
are characterized by signs such as urticaria, pruritus, erythema, angioneurotic edema (including laryngeal edema), tachycardia, sneezing, nausea, vomiting,
dizziness, syncope, excessive sweating, elevated temperature, and possibly,
anaphylactoid-like symptomatology (including severe hypotension). Cross sensitivity
among members of the amide-type local anesthetic group has been reported. The
usefulness of screening for sensitivity has not been definitely established.
Neurologic
The incidences of adverse neurologic reactions associated with the use of local
anesthetics may be related to the total dose of local anesthetic administered
and are also dependent upon the particular drug used, the route of administration,
and the physical status of the patient. Many of these effects may be related
to local anesthetic techniques, with or without a contribution from the drug.
In the practice of caudal or lumbar epidural block, occasional unintentional
penetration of the subarachnoid space by the catheter or needle may occur. Subsequent
adverse effects may depend partially on the amount of drug administered intrathecally
and the physiological and physical effects of a dural puncture. A high spinal
is characterized by paralysis of the legs, loss of consciousness, respiratory
paralysis, and bradycardia.
Neurologic effects following epidural or caudal anesthesia may include spinal
block of varying magnitude (including high or total spinal block); hypotension
secondary to spinal block; urinary retention; fecal and urinary incontinence;
loss of perineal sensation and sexual function; persistent anesthesia, paresthesia,
weakness, paralysis of the lower extremities, and loss of sphincter control
all of which may have slow, incomplete, or no recovery; headache; backache;
septic meningitis; meningismus; slowing of labor; increased incidence of forceps
delivery; cranial nerve palsies due to traction on nerves from loss of cerebrospinal
fluid.
Neurologic effects following other procedures or routes of administration may
include persistent anesthesia, paresthesia, weakness, paralysis, all of which
may have slow, incomplete, or no recovery.