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When any local anaesthetic agent is used, resuscitative equipment and drugs, including oxygen, should be immediately available in order to manage possible adverse reactions involving the cardiovascular, respiratory or central nervous systems.
Because of the possibility of hypotension and bradycardia following major blocks an IV cannula should be inserted before the local anaesthetic is injected. Delay in proper management of dose-related toxicity, under ventilation from any cause and/or altered sensitivity may lead to the development of acidosis, cardiac arrest and death.
Injection should always be made slowly with frequent aspirations to avoid inadvertent intravascular injection which can produce toxic effects (see Dosage & Administration: test dose). Careful and constant monitoring of cardiovascular and respiratory vital signs and the patient's state of consciousness should be accomplished after each local anaesthetic injection. It should be kept in mind that at such times restlessness, anxiety, tinnitus, dizziness, blurred vision, tremors, depression or drowsiness may be early warning signs of CNS toxicity.
The use of local anaesthetics for major peripheral nerve block may involve the administration of large volumes in highly vascularised areas, often close to large blood vessels. As such there is an increased risk of intravascular injection and/or systemic absorption which can lead to high plasma concentrations. There have been reports of cardiac arrest or death during the use of bupivacaine for epidural anaesthesia or peripheral nerve blockade. In some instances, resuscitation has been difficult or impossible despite apparently adequate preparation and management.
Central nerve blocks may cause cardiovascular depression, especially in the presence of hypovolaemia. Epidural anaesthesia should be used with caution in patients with impaired cardiovascular function. Epidural anaesthesia may lead to hypotension and bradycardia.
LOW MOLECULAR WEIGHT HEPARINS AND HEPARINOIDS (Spinal/Epidural Haematomas): When neuraxial anaesthesia (epidural/spinal anaesthesia) is employed, patients anti-coagulated or scheduled to be anti-coagulated with low molecular weight heparins or heparinoids are at risk of developing an epidural or spinal haematoma which can result in long-term or permanent paralysis. The risk of these events is increased by the use of indwelling epidural catheters, traumatic or repeated epidural/spinal puncturem, and the concomitant use of drugs affecting haemostatis such as NSAID, platelet inhibitors or other anticoagulants. Patients should be frequently monitored for signs and symptoms of neurological impairment.
The safety and efficacy of Bunascan 0.5% depend on proper dosage, correct technique and adequate precautions.
Standard textbooks should be consulted regarding specific techniques and precautions for various regional anaesthetic procedures.
The lowest dosage that results in effective anaesthesia should be used (see Dosage & Administration). Repeated injection of Bunascan 0.5% may cause accumulation of bupivacaine or its metabolites and result in toxic effects. Tolerance to elevated blood levels varies with the status of the patient. Elderly, young or debilitated patients, including those with partial or complete conduction block, advanced liver disease or severe renal impairment, should be given reduced doses commensurate with their age and physical condition.
Caution should be used when administering bupivacaine to children under 12 years of age.
Bupivacaine may cause acute toxicity affects on the central nervous and cardiovascular systems if utilized for local anaesthetic procedures resulting in high blood concentrations of the drug. This is especially the case after unintentional intravascular administration. Ventricular arrhythmia, ventricular fibrillation, sudden cardiovascular collapse and death have been reported in connection with high systemic concentrations of bupivacaine.
Bupivacaine should be given with caution to patients with epilepsy, impaired cardiac conduction, bradycardia, severe shock or digitalis intoxication. It should also be administered with caution to patients with impaired cardiovascular function as they may be less able to compensate for functional change associated with the prolongation of AV conduction produced by bupivacaine. Patients being treated with antiarrhythmic drugs class III (e.g. amiodarone) should be under close surveillance and ECG monitoring since cardiac effects may be additive.
In patients with Stokes-Adams syndrome or Wolff-Parkinson-White syndrome extreme care should be taken to avoid accidental arterio-venous injection.
Local anaesthetics should be given with great caution (if at all) to patients with pre existing neurological or neuromuscular disease e.g. myasthenia gravis. Use with extreme caution in epidural, caudal and spinal anaesthesia when there are senous diseases of the CNS or of the spinal anaesthesia when there are serious diseases of the CNS or of the spinal cord, e.g. meningitis, spinal fluid block, cranial or spinal haemorrhage, tumours, poliomyelitis, syphilis, tuberculosis or metastatic lesions of the spinal cord.
Bupivacaine is eliminated primarily by hepatic metabolism and changes in hepatic function may have significant consequences. Bupivacaine has an intermediate clearance which depends on its unbound fraction and intrinsic metabolic clearance. Bupivacaine should therefore be used with caution in patients with severe hepatic disease.
Bupivacaine should be used with caution in patients with reduced plasma protein concentration, which are frequently seen in these patients, may increase the risk of systemic toxicity. Patients with hyperthyroidism are also more susceptible to toxicity with bupivacaine.
Inadvertent intravascular or subarachnoid infection of small doses of local anaesthetics 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. Injections made inadvertently into an artery may cause immediate cerebral symptoms even at low doses. Clinicians who pertorm retrobulbar blocks should be aware that there have been reports of cardiovascular collapse and apnoea following the use of local anaesthetic injections for retrobulbar block. Prior to retrobulbar block, necessary equipment, drugs and personnel should be immediately available as with all other regional procedures. Retrobulbar injections may very occasionally reach the subarachnoid space, causing temporary blindness, cardiovascular collapse, apnoea, convulsions etc. These must be diagnosed and treated promptly.
Retro and peribulbar injections of local anaesthetics carry a low risk of persistent ocular muscle dysfunction. The primary causes include trauma and/or local toxic effects on muscles or nerves. The severity of such tissue reactions is related to the degree of trauma, the concentration of the local anaesthetic and the duration of exposure of the tissue to the local anaesthetic. For this reason, as with all local anaesthetic, the lowest effective concentration and dose of local anaesthetic should be used. Vasoconstrictors may aggravate tissue reactions and should be used only when indicated.
Fetal bradycardia/tachycardia frequently follows paracervical block with some amide type local anaesthetic and maybe associated with fetal acidosis and hypoxia. Added risk appears to be present in prematurity, toxaemia of pregnancy, and foetal distress. Careful monitoring of the fetal heart rate is necessary (see Contraindications).
Bupivacaine should be used with caution in patients with known drug sensitivities.
Carcinogenecity/Mutagenicity/Impairment of fertility: Long-term studies in animals of most local anaesthetics, including bupivacaine, to evaluate the carcinogenic potential have not been conducted. Formal studies of mutagenic potential have not been carried out. Effects on fertility have not been determined.
Effects on ability to drive and operate machinery: Depending on the dosage local anaesthetics may have a mild effect on mental function and coordination and may temporarily impair locomotion and coordination.
Use in Pregnancy: Category A.
After epidural administration of bupivacaine to women in labour bupivacaine crosses the placental barrier. However, concentrations in umbilical veins are lower than those found in the maternal circulation. Bupivacaine has been effectively used for obstetrical analgesia and adverse effects on the course of labour or delivery are rare. It has been suggested that blood glucose levels should checked in newborns after obstetric regional anaesthesia.
Fetal adverse effects due to bupivacaine, such as fetal bradycardia, seem to be most apparent in paracervical block anaesthesia. Such effects may be due to high concentrations of anaesthetics reaching the fetus (see Contraindications).
The safe use of bupivacaine during pregnancy, other than labour, has not been established. Although bupivacaine has been used extensively for surgical procedures during pregnancy with no reports of ill effects to mother or fetus, there are no adequate and well-controlled studies in pregnant women of the effect of bupivacaine on the developing fetus. It should therefore be used cautiously during pregnancy other than labour.
Use during lactation Bupivacaine passes into breast milk. The amount of bupivacaine appearing in breast milk from a nursing mother receiving parenteral bupivacaine is unlikely to lead to a significant accumulation of the parent drug in the breast-fed infant.
At maternal serum levels of up to 0.45 µg/mL produced by the epidural use of bupivacaine for vaginal delivery, bupivacaine could not be detected in breast milk during the first 24 hours after delivery (detection limit 0.02 µg/mL).
The possibility of an idiosyncratic or allergic reaction in the breast-fed infant from bupivacame remains to be determined.
