OVERDOSAGE
Acute emergencies from local anesthetics are generally related to
high plasma levels encountered during therapeutic use of local
anesthetics or to unintended subarachnoid injection of local anesthetic
solution (see
ADVERSE REACTIONS,
WARNINGS
and
PRECAUTIONS
).
Management of Local Anesthetic
Emergencies:
The first consideration is prevention, best accomplished by
careful monitoring of cardiovascular and respiratory vital signs and the
patient’s state of consciousness after each local anesthetic
injection. At the first sign of change, oxygen should be administered.
The first step in the management of convulsions, as well as
under-ventilation or apnea due to unintended subarachnoid injection of
drug solution, consists of immediate attention to the maintenance of a
patent airway and assisted or controlled ventilation with oxygen and a
delivery system capable of permitting immediate positive airway pressure
by mask. Immediately after the institution of these ventilatory
measures, the adequacy of the circulation should be evaluated, keeping
in mind that drugs used to treat convulsions sometimes depress the
circulation when administered intravenously. Should convulsions persist
despite adequate respiratory support, and if the status of the
circulation permits, small increments of an ultra-short acting
barbiturate (such as thiopental or thiamylal) or a benzodiazepine (such
as diazepam) may be administered intravenously. The clinician
should be familiar, prior to use of local anesthetics, with these
anticonvulsant drugs. Supportive treatment of circulatory depression may
require administration of intravenous fluids and, when appropriate, a
vasopressor as directed by the clinical situation (e.g., ephedrine).
If not treated immediately, both convulsions and cardiovascular
depression can result in hypoxia, acidosis, bradycardia, arrhythmias and
cardiac arrest. Underventilation or apnea due to unintentional
subarachnoid injection of local anesthetic solution may produce these
same signs and also lead to cardiac arrest if ventilatory support is not
instituted. If cardiac arrest should occur standard cardiopulmonary
resuscitative measures should be instituted.
Endotracheal intubation, employing drugs and techniques familiar
to the clinician, may be indicated, after initial administration of
oxygen by mask, if difficulty is encountered in the maintenance of a
patent airway or if prolonged ventilatory support (assisted or
controlled) is indicated.
Dialysis is of negligible value in the treatment of acute
overdosage with lidocaine.
The oral LD50 of lidocaine HCl in non-fasted female
rats is 459 (346-773) mg/kg (as the salt) and 214 (159-324) mg/kg (as
the salt) in fasted female rats.
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