LIDOCAINE

The method of administration of lidocaine varies according to the procedure (infiltration anaesthesia, intravenous regional anaesthesia or nerve block). The dosage should be adjusted according to the response of the patient and the site of administration.

The lowest concentration and smallest dose producing the required effect should be given. The maximum dose for healthy adults should not exceed 200 mg. Children and elderly or debilitated patients require smaller doses, commensurate with age and physical status.

In common with other local anaesthetics, adverse reactions to lidocaine are rare and are usually the result of raised plasma concentrations due to accidental intravascular injection, excessive dosage or rapid absorption from highly vascular areas, or may result from a hypersensitivity, idiosyncrasy or diminished tolerance on the part of the patient.

9). Blood and Lymphatic System Disorders Lidocaine may also produce methaemoglobinaemia. Immune system disorders Hypersensitivity reactions (allergic or anaphylactoid reactions, anaphylactic shock) – see also Skin & subcutaneous tissue disorders) are rare.

They may be characterised by cutaneous lesions, Skin testing for allergy to lidocaine is not considered to be reliable. Localised nerve damage at the site of injection (very rare). Nervous & Psychiatric disorders Neurological signs of systemic toxicity include dizziness or light-headedness, nervousness, tremor, circumoral paraesthesia, tongue numbness, drowsiness, convulsions, coma.

Nervous system reactions may be excitatory and or depressant. Signs of CNS stimulation may be brief, or may not occur at all, so that the first signs of toxicity may be confusion and drowsiness, followed by coma and respiratory failure.

CNS (central nervous system) reactions may be excitatory and/or depressant.. Signs of CNS stimulation may be brief or may not occur at all, so that the first signs of toxicity may be confusion and drowsiness, followed by coma and respiratory failure.

Neurological complications of spinal anaesthesia include transient neurological symptoms such as pain of the lower back, buttock and legs. These symptoms usually develop within twenty-four hours of anaesthesia and resolve within a few days.

Isolated cases of arachnoiditis or cauda equina syndrome, with persistent paraesthesia, bowel and urinary dysfunction, or lower limb paralysis have been reported following spinal anaesthesia with lidocaine and other similar agents.

The majority of cases have been associated with hyperbaric concentrations of Lidocaine or prolonged spinal infusion. Psychotic reactions have been reported following infusion for the control of arrhythmia. Eye disorders Blurred vision, diplopia and transient amaurosis may be signs of lidocaine toxicity.

Bilateral amaurosis may also be a consequence of accidental injection of the optic nerve sheath during ocular procedures. 4) Ear and labyrinth disorders Tinnitus, hyperacusis Cardiac and vascular disorders Cardiovascular reactions are depressant and may manifest as hypotension, bradycardia, myocardial depression, cardiac arrhythmias and possibly cardiac arrest or circulatory collapse.

Hypotension may accompany spinal and epidural anesthesia. Isolated cases of bradycardia and cardiac arrest have also been reported. Profound hypotension may be associated with B blockade, widespread sympathetic block from spinal or epidural block, intercostal nerve block administration or supine hypotension in pregnancy.

The major adverse effects on the CNS and CVS are primarily due to the absorption of lidocaine into the systemic circulation. Ventricular fibrillation occurs less frequently than that seen with bupivacaine. Respiratory, thoracic or mediastinal disorders Dyspnoea, bronchospasm and respiratory depression Gastrointestinal Nausea, vomiting.

Skin and subcutaneous tissue disorders Rash, urticaria, oedema (including angioedema, face oedema) Prolonged neural blockade following epidural may be due to delayed spread. Permanent neural blockade may be more likely associated with hypotension and cord ischaemia.

Following regional blockade as when lidocaine is injected intrathecally or extradurally, hypotension, hypoventilation, Horners Syndrome and hypoglycaemia may be seen. The degree of these effects will depend on the dose and the height of the block.

Urinary retention may occur following sacral or lumbar epidural block. It should not outlast the duration of the block. Apnoea and coma followed by aphasia and hemiparesis may occur following stellate ganglion block. The probable cause is a direct injection of lidocaine into the vertebral or carotid arteries.

Profound lethargy and death have been reported following the injection of only 10 – 32 mg of lidocaine for dental blocks. The initial CNS toxic effects are demonstrated by a gradual onset of drowsiness or inebriation similar to alcoholic intoxication.

Balance is disturbed, dizziness or light-headedness, nervousness, circumoral pins and needles (circumoral paraesthesia), tongue numbness, tinnitus, hyperacusis, visual disturbances, restlessness and twitching may occur. Severe intoxication of rapid onset may immediately lead to convulsions followed by circulatory depression.

Major overdosage may depress all systems simultaneously.

Lidocaine should be administered by persons with resuscitative skills and equipment. Facilities for resuscitation should be available when administering local anaesthetics. g. g. hepatic or end renal insufficiency where the metabolites of Lidocaine may accumulate, or if the dose or site of administration is likely to produce high blood levels.

Lidocaine is metabolised in the liver and it should be used with caution in patients with impaired hepatic function. The effect of local anaesthetics may be reduced if the injection is made into an inflamed or infected area. Intramuscular Lidocaine may increase creatinine phosphokinase concentrations which can interfere with the diagnosis of acute myocardial infarction.

Lidocaine has been shown to be porphyrinogenic in animals and should be avoided in persons suffering from porphyria. Hypokalaemia, hypoxia and disorder of acid-base balance should be corrected before treatment with intravenous lidocaine begins.

: - Central nerve blocks may cause cardiovascular depression, especially in the presence of hypovolaemia, and therefore epidural anaesthesia should be used with caution in patients with impaired cardiovascular function. - Retrobulbar injections may rarely reach the cranial subarachnoid space, causing serious / severe reactions, including cardiovascular collapse, apnoea, convulsions and temporary blindness.

- 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 and/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 anaesthetics, the lowest effective concentration and dose of local anaesthetic should be used. - Injections in the head and neck regions may be made inadvertently into an artery, causing cerebral symptoms even at low doses.

6). Epidural anaesthesia may lead to hypotension and bradycardia. This risk can be reduced by preloading the circulation with crystalloidal or colloidal solutions. Hypotension should be treated promptly Lidocaine Injection is not recommended for use in neonates.

The optimum serum concentration of lidocaine required to avoid toxicity, such as convulsions and cardiac arrhythmias, in this age group is not known. 59 mmol) sodium. 18 mmol) sodium.

Known hypersensitivity to anaesthetics of the amide type Complete heart block Hypovolaemia