General: The safety and effectiveness of lidocaine depend on proper
dosage, correct technique, adequate precautions, and readiness for
emergencies. Standard textbooks should be consulted for specific
techniques and precautions for various regional anesthetic procedures.
Resuscitative equipment, oxygen, and other resuscitative drugs
should be available for immediate use. (See WARNINGS and ADVERSE REACTIONS). The lowest dosage that results in effective anesthesia
should be used to avoid high plasma levels and serious adverse effects.
Syringe aspirations should also be performed before and during each
supplemental injection when using indwelling catheter techniques. During
the administration of epidural anesthesia, it is recommended that a test
dose be administered initially and that the patient be monitored for
central nervous system toxicity and cardiovascular toxicity, as well as
for signs of unintended intrathecal administration before proceeding.
When clinical conditions permit, consideration should be given to
employing local anesthetic solutions that contain epinephrine for the
test dose because circulatory changes compatible with epinephrine may
also serve as a warning sign of unintended intravascular injection. An
intravascular injection is still possible even if aspirations for blood
are negative. Repeated doses of lidocaine may cause significant
increases in blood levels with each repeated dose because of slow
accumulation of the drug or its metabolites. Tolerance to elevated blood
levels varies with the status of the patient. Debilitated, elderly
patients, acutely ill patients and children should be given reduced
doses commensurate with their age and physical condition. Lidocaine
should also be used with caution in patients with severe shock or heart
block.
Lumbar and caudal epidural anesthesia should be used with extreme
caution in persons with the following conditions: existing neurological
disease, spinal deformities, septicemia and severe hypertension.
Local anesthetic solutions containing a vasoconstrictor should be
used cautiously and in carefully circumscribed quantities in areas of
the body supplied by end arteries or having otherwise compromised blood
supply. Patients with peripheral vascular disease and those with
hypertensive vascular disease may exhibit exaggerated vasoconstrictor
response. Ischemic injury or necrosis may result. Preparations
containing a vasoconstrictor should be used with caution in patients
during or following the administration of potent general anesthetic
agents, since cardiac arrhythmias may occur under such conditions.
Careful and constant monitoring of cardiovascular and respiratory
(adequacy of ventilation) vital signs and the patient’s state
of consciousness should be accomplished after each local anesthetic
injection. It should be kept in mind at such times that restlessness,
anxiety, tinnitus, dizziness, blurred vision, tremors, depression or
drowsiness may be early warning signs of central nervous system
toxicity.
Since amide-type local anesthetics are metabolized by the liver,
lidocaine injection should be used with caution in patients with hepatic
disease. Patients with severe hepatic disease because of their inability
to metabolize local anesthetics normally, are a greater risk of
developing toxic plasma concentrations. Lidocaine should also be used
with caution in patients with impaired cardiovascular function since
they may be less able to compensate for functional changes associated
with the prolongation of A-V conduction produced by these drugs.
Many drugs used during the conduct of anesthesia are considered
potential triggering agents for familial malignant hyperthermia. Since
it is not known whether amide-type local anesthetics may trigger this
reaction and since the need for supplemental general anesthesia cannot
be predicted in advance, it is suggested that a standard protocol for
the management of malignant hyperthermia should be available. Early
unexplained signs of tachycardia, tachypnea, labile blood pressure and
metabolic acidosis may precede temperature elevation. Successful outcome
is dependent on early diagnosis, prompt discontinuance of the suspect
triggering agent(s) and institution of treatment, including oxygen
therapy, indicated supportive measures and dantrolene (consult
dantrolene sodium intravenous package insert before using).
Injections containing epinephrine or other vasoconstrictors
should not be used for intravenous regional anesthesia.
Lidocaine should be used with caution in persons with known drug
sensitivities. Patients allergic to para-amino-benzoic acid derivatives
(procaine, tetracaine, benzocaine, etc.) have not shown cross
sensitivity to lidocaine.
Use in the Head and Neck
Area: Small doses of local anesthetics injected into the head and
neck area, including retrobulbar, dental and stellate ganglion blocks,
may produce adverse reactions similar to systemic toxicity seen with
unintentional intravascular injections of larger doses. Confusion,
convulsions, respiratory depression and/or respiratory arrest and
cardiovascular stimulation or depression have been reported. These
reactions may be due to intra-arterial injections of the local
anesthetic with retrograde flow to the cerebral circulation. Patients
receiving these blocks should have their circulation and respiration
monitored and be constantly observed. Resuscitative equipment and
personnel for treating adverse reactions should be immediately
available. Dosage recommendations should not be exceeded. (See DOSAGE AND
ADMINISTRATION).
Information for Patients: When appropriate, patients should be informed in advance that
they may experience temporary loss of sensation and motor activity,
usually in the lower half of the body following proper administration of
epidural anesthesia.
Clinically Significant Drug
Interactions: The administration of local anesthetic solutions containing
epinephrine or norepinephrine to patients receiving monoamine oxidase
inhibitors or tricyclic antidepressants may produce severe prolonged
hypertension.
Phenothiazines and butyrophenones may reduce or reverse the
pressor effect of epinephrine.
Concurrent use of these agents should generally be avoided. In
situations when concurrent therapy is necessary, careful patient
monitoring is essential.
Concurrent administration of vasopressor drugs (for the treatment
of hypotension related to obstetric blocks) and ergot-type oxytocic
drugs may cause severe persistent hypertension or cerebrovascular
accidents.
Drug Laboratory Test
Interactions: The intramuscular injection of lidocaine may result in an
increase in creatine phosphokinase levels. Thus, the use of this enzyme
determination without isoenzyme separation as a diagnostic test for the
presence of acute myocardial infarction may be compromised by the
intramuscular injection of lidocaine.
Carcinogenesis, Mutagenesis,
Impairment of Fertility: Studies of lidocaine in animals to evaluate the carcinogenic
and mutagenic potential or the effect on fertility have not been
conducted.
Pregnancy: Teratogenic Effects. Pregnancy Category B. Reproduction
studies have been performed in rats at doses up to 6.6 times the human
dose and have revealed no evidence of harm to the fetus caused by
lidocaine. There are, however, no adequate and well-controlled studies
in pregnant women. Animal reproduction studies are not always predictive
of human response. General consideration should be given to this fact
before administering lidocaine to women of childbearing potential,
especially during early pregnancy when maximum organogenesis takes
place.
Labor and Delivery: Local anesthetics rapidly cross the placenta and when used
for epidural, paracervical, pudendal or caudal block anesthesia, can
cause varying degrees of maternal, fetal and neonatal toxicity (See
CLINICAL
PHARMACOLOGY-Pharmacokinetics). The potential for toxicity depends upon the procedure
performed, the type and amount of drug used, and the technique of drug
administration. Adverse reactions in the parturient, fetus and neonate
involve alterations of the central nervous system peripheral vascular
tone and cardiac function.
Maternal hypotension has resulted from regional anesthesia. Local
anesthetics produce vasodilation by blocking sympathetic nerves.
Elevating the patient’s legs and positioning her on her left
side will help prevent decreases in blood pressure. The fetal heart rate
also should be monitored continuously, and electronic fetal monitoring
is highly advisable.
Epidural, spinal, paracervical, or pudendal anesthesia may alter
the forces of parturition through changes in uterine contractility or
maternal expulsive efforts. In one study, paracervical block anesthesia
was associated with a decrease in the mean duration of first stage labor
and facilitation of cervical dilation. However, spinal and epidural
anesthesia have also been reported to prolong the second stage of labor
by removing the parturient’s reflex urge to bear down or by
interfering with motor function. The use of obstetrical anesthesia may
increase the need for forceps assistance.
The use of some local anesthetic drug products during labor and
delivery may be followed by diminished muscle strength and tone for the
first day or two of life. The long term significance of these
observations is unknown. Fetal bradycardia may occur in 20 to 30 percent
of patients receiving paracervical nerve block anesthesia with the
amide-type local anesthetics and may be associated with fetal acidosis.
Fetal heart rate should always be monitored during paracervical
anesthesia. The physician should weigh the possible advantages against
risks when considering paracervical block in prematurity, toxemia of
pregnancy and fetal distress. Careful adherence to recommended dosage is
of the utmost importance in obstetrical paracervical block. Failure to
achieve adequate analgesia with recommended doses should arouse
suspicion of intravascular or fetal intracranial injection. Cases
compatible with unintended fetal intracranial injection of local
anesthetic solution have been reported following intended paracervical
or pudendal block or both. Babies so affected present with unexplained
neonatal depression at birth, which correlates with high local
anesthetic serum levels, and often manifest seizures within six hours.
Prompt use of supportive measures combined with forced urinary excretion
of the local anesthetic has been used successfully to manage this
complication.
Case reports of maternal convulsions and cardiovascular collapse
following use of some local anesthetics for paracervical block in early
pregnancy (as anesthesia for elective abortion) suggest that systemic
absorption under these circumstances may be rapid. The recommended
maximum dose of each drug should not be exceeded. Injection should be
made slowly and with frequent aspiration. Allow a 5-minute interval
between sides.
Nursing Mothers: It is not known whether this drug is excreted in human milk.
Because many drugs are excreted in human milk, caution should be
exercised when lidocaine is administered to a nursing woman.
Pediatric Use: Dosages in pediatric patients should be reduced, commensurate
with age, body weight and physical condition. See DOSAGE AND
ADMINISTRATION.