5 WARNINGS AND PRECAUTIONS
5.1 Use of Spinal Anesthetics During Uterine Contractions
Spinal anesthetics including MARCAINE SPINAL should not be injected during uterine contractions because cerebrospinal fluid current may carry the drug further cephalad than desired, resulting in a high motor block.
5.2 Patients with Hypertension
Sympathetic blockade due to spinal anesthesia may result in peripheral vasodilation and hypotension, the extent of which depends on the number of dermatomes blocked. Patients over 65 years, particularly those with hypertension, may be at increased risk for experiencing the hypotensive effects of MARCAINE SPINAL. Monitor blood pressure frequently, especially in the early phases of anesthesia. Hypotension may be controlled by administration of vasoconstrictor agents in titrated dosages depending on the severity of hypotension and response to treatment. Monitor the onset of adequate spinal anesthesia because it is not always possible to control the level of anesthesia after subarachnoid injection of MARCAINE SPINAL.
5.3 Dose-Related Toxicity
The safety and effectiveness of MARCAINE SPINAL depend on proper dosage, correct technique, adequate precautions, and readiness for emergencies. Careful and constant monitoring of cardiovascular and respiratory (adequacy of oxygenation and ventilation) vital signs and the patient's state of consciousness should be performed after injection of MARCAINE SPINAL solutions.
Possible early warning signs of central nervous system (CNS) toxicity are restlessness, anxiety, incoherent speech, lightheadedness, numbness and tingling of the mouth and lips, metallic taste, tinnitus, dizziness, blurred vision, tremors, twitching, CNS depression, or drowsiness. Delay in proper management of dose-related toxicity, hypoventilation from any cause, and/or altered sensitivity may lead to the development of acidosis, cardiac arrest, and possibly death.
The patient should have an indwelling intravenous catheter to assure adequate intravenous access. Use the lowest dosage of MARCAINE SPINAL that results in effective anesthesia to avoid serious adverse reactions. Avoid rapid injection of a large volume of MARCAINE SPINAL.
Injection of repeated doses of MARCAINE SPINAL may cause significant increases in plasma bupivacaine levels with each repeated dose due to slow accumulation of the drug or its metabolites, or to slow metabolic degradation. Tolerance to elevated blood levels varies with the status of the patient. Debilitated, elderly patients and acutely ill patients should be given reduced doses commensurate with their age and physical status. Reduced doses may be indicated in patients with increased intra-abdominal pressure (including obstetrical patients), if otherwise suitable for spinal anesthesia.
5.4 Risk of Systemic Toxicities with Unintended Intravascular Injection
Unintended intravascular injection of MARCAINE SPINAL may be associated with systemic toxicities, including CNS or cardiorespiratory depression and coma, progressing ultimately to respiratory arrest [see Adverse Reactions (6)].
Aspirate for blood and cerebrospinal fluid before injecting MARCAINE SPINAL, for both the initial dose and all subsequent doses (where applicable), to confirm entry into the subarachnoid space and to avoid intravascular injection. Aspiration of cerebrospinal fluid into a MARCAINE SPINAL-filled syringe will result in an identifiable swirl in the solution. A negative aspiration for blood does not ensure against an intravascular injection.
Cases of methemoglobinemia have been reported in association with local anesthetic use. Although all patients are at risk for methemoglobinemia, patients with glucose 6 phosphate dehydrogenase deficiency, congenital or idiopathic methemoglobinemia, cardiac or pulmonary compromise, infants under 6 months of age, and concurrent exposure to oxidizing agents or their metabolites are more susceptible to developing clinical manifestations of the condition [see Drug Interactions (7.2)]. If local anesthetics must be used in these patients, close monitoring for symptoms and signs of methemoglobinemia is recommended.
Signs of methemoglobinemia may occur immediately or may be delayed some hours after exposure, and are characterized by a cyanotic skin discoloration and/or abnormal coloration of the blood. Methemoglobin levels may continue to rise; therefore, immediate treatment is required to avert more serious CNS and cardiovascular adverse effects, including seizures, coma, arrhythmias, and death. Discontinue MARCAINE SPINAL and any other oxidizing agents. Depending on the severity of the signs and symptoms, patients may respond to supportive care, i.e., oxygen therapy, hydration. A more severe clinical presentation may require treatment with methylene blue, exchange transfusion, or hyperbaric oxygen.
5.6 Risk of Cardiac Arrest with Use of Epidural Bupivacaine in Obstetrical Anesthesia
There have been reports of cardiac arrest with difficult resuscitation or death during use of MARCAINE for epidural anesthesia in obstetrical patients. In most cases, this has followed use of MARCAINE 0.75%, not MARCAINE SPINAL. The package insert for MARCAINE hydrochloride for epidural, nerve block, etc., has a more complete discussion of preparation for, and management of cardiac arrest following epidural administration. MARCAINE SPINAL (bupivacaine hydrochloride in dextrose injection) is recommended for spinal anesthesia in obstetrical patients.
5.7 Chondrolysis with Intra-Articular Infusion
Intra-articular infusions of local anesthetics including bupivacaine following arthroscopic and other surgical procedures is an unapproved use, and there have been post-marketing reports of chondrolysis in patients receiving such infusions. The majority of reported cases of chondrolysis have involved the shoulder joint; cases of gleno-humeral chondrolysis have been described in pediatric and adult patients following intra-articular infusions of local anesthetics with and without epinephrine for periods of 48 to 72 hours. There is insufficient information to determine whether shorter infusion periods are not associated with chondrolysis. The time of onset of symptoms, such as joint pain, stiffness, and loss of motion can be variable, but may begin as early as the 2nd month after surgery. Currently, there is no effective treatment for chondrolysis; patients who experienced chondrolysis have required additional diagnostic and therapeutic procedures and some required arthroplasty or shoulder replacement.
5.8 Risk of Cardiac Arrest with Intravenous Regional Anesthesia Use (Bier Block)
There have been reports of cardiac arrest and death during the use of bupivacaine for intravenous regional anesthesia (Bier Block). Information on safe dosages and techniques of administration of MARCAINE SPINAL in this procedure is lacking. Therefore, MARCAINE SPINAL is contraindicated for use with this technique [see Contraindications (4)].
5.9 Patients with Severe Disturbances of Cardiac Rhythm, Shock, or Heart Block
Consider alternate anesthetic techniques in patients with severe disturbances of cardiac rhythm, shock, or heart block [see Contraindications (4)].
5.10 Risk of Toxicity in Patients with Hepatic Impairment
Because amide-type local anesthetics such as bupivacaine are metabolized by the liver, consider reduced dosing and increased monitoring for bupivacaine systemic toxicity in patients with moderate to severe hepatic impairment who are treated with MARCAINE SPINAL [see Use in Specific Populations (8.6)]. Most information regarding dose-related hepatic impairment is based on larger dosages of bupivacaine administered for other neuraxial, peripheral nerve, or fascial plane blocks.
5.11 Risk of Use in Patients with Impaired Cardiovascular Function
MARCAINE SPINAL should be given in reduced doses in patients with impaired cardiovascular function (e.g., hypotension, heartblock, valvular abnormalities) because they may be less able to compensate for functional changes associated with the sympathetic blockade observed after subarachnoid administration of MARCAINE SPINAL and the prolongation of AV conduction produced by the drug. Monitor patients closely for blood pressure, heart rate, and ECG changes.