10 OVERDOSAGE
Clinical Presentation
Acute emergencies from MARCAINE SPINAL are generally related to hypoventilation (and perhaps apnea) secondary to upward extension of spinal anesthesia or high plasma levels encountered during therapeutic use [see Warnings and Precautions (5.3), Adverse Reactions (6)]. Hypotension is commonly encountered during the conduct of spinal anesthesia due to loss of sympathetic tone, and sometimes, contributory mechanical obstruction of venous return due to the gravid uterus exerting pressure on the great vessels [see Warnings and Precautions (5.2), Adverse Reactions (6)].
If not treated immediately, convulsions with simultaneous hypoxia, hypercarbia, and acidosis plus myocardial depression from the direct effects of the local anesthetic may result in cardiac arrhythmias, bradycardia, asystole, ventricular fibrillation, or cardiac arrest. Respiratory abnormalities, including apnea, may occur. Hypoventilation or apnea due to a high or total spinal may produce these same signs and also lead to cardiac arrest if ventilatory support is not instituted. If cardiac arrest should occur, successful outcome may require prolonged resuscitative efforts.
Management
The first step in the management of systemic toxic reactions, as well as hypoventilation or apnea due to a high or total spinal, consists of immediate attention to the establishment and maintenance of a patent airway and effective assisted or controlled ventilation with 100% oxygen with a delivery system capable of permitting immediate positive airway pressure by mask. Endotracheal intubation, using 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.
If necessary, use drugs to manage the convulsions. A bolus intravenous dose of benzodiazepine will counteract the CNS stimulation related to MARCAINE SPINAL. Immediately after the institution of ventilatory measures, evaluate the adequacy of the circulation. Supportive treatment of circulatory depression may require Advanced Cardiac Life Support measures.
Hypotension due to sympathetic relaxation may be managed by giving intravenous fluids (such as isotonic saline or lactated Ringer's solution), in an attempt to relieve mechanical obstruction of venous return, or by using vasopressor agents (such as ephedrine which increases myocardial contractility) and, if indicated, by giving plasma expanders or blood products.