Lignocaine injection

Lignocaine injections are indicated for production of local or regional anaesthesia by infiltration techniques such as percutaneous injection, peripheral nerve block, spinal or subarachnoid block. 

Lignocaine, originally introduced as a local anesthetic, is now widely used for the treatment and prevention of ventricular arrhythmias. When used for this purpose, it is usually administered either by intramuscular injection, or as a bolus intravenously, or, more commonly, by constant intravenous infusion. For clinical purposes, lignocaine measurements arc usually carried out on plasma collected either while the patient is receiving a constant intravenous infusion or at a specified time after the last intramuscular injection. Colorimetric methods have been used in the past (S29), but, because they lack both sensitivity and specificity, may yield false and misleading results. They have largely been replaced by GLC techniques (A3, El, K5). 

Animal experiments have shown (A3) that equilibration of lignocaine between blood and brain occurs relatively slowly. This may explain why plasma levels of lignocaine that can readily be tolerated, without cerebral side effects, after intravenous bolus injection nevertheless are associated with serious toxic symptoms when produced by constant intravenous infusion or when resulting from impaired metabolic degradation. 

Infiltration anaesthesia is applied fan-shaped, with as few needle punctures as possible, in close proximity of the wound or the skin area to be treated. An aspiration should always take place to avoid intravascular injection. Suitable alternatives are lidocaine (lignocaine) or prilocaine for injection 5-10 mg/ml, with or without adrenaline. When making an incision of an abscess it is sometimes difficult to use a local anaesthetic if there is a pronounced inflammatory reaction, since the effect of the anaesthetic is reduced due to an increased acidity level. While adrenaline reduces bleeding and delays dispersion of the anaesthetic, local anaesthetic/adrenaline combinations are contraindicated for local anaesthesia of digits, on the face or where the skin survival is at risk. 

Dental anaesthesia—The total amount of local anaesthetics injected is much smaller (20-80 mg of lignocaine) than that used for othr purpose. Lignocaine (2%) with adrenaline (1 80,000) is the standard local anaesthetic preparation used in dentistry which produces good soft tissue and pulpal anaesthasia and also reduce postextraction bleeding. 

The elimination half-life of lignocaine following an intravenous bolus injection is 1.5 to 2.0 hours. 

Intra-arterial injection of thiopentone is a serious complication as crystals of the thiobarbiturate can form in the arterioles and capillaries, causing intense pain, vasoconstriction, thrombosis, and even tissue necrosis. Accidental intra-arterial injections should be treated promptly with intra-arterial administration of a vasodilator (papaverine 20 mg) and lignocaine (lidocaine) Note leave the needle/cannula in the artery), as well as a regional anaesthesia-induced sympathectomy (stellate ganglion block, brachial plexus block) and anticoagulation with intravenous heparin. The risk of ischaemic damage is much higher with a 5% solution and the use of this concentration is not recommended. 

Pain on injection is more common (8-20%) than with thiopentone, especially if a small vein is used for administration but can be reduced by flushing the vein with lidocaine (lignocaine) prior to methohexitone administration. 

Pain on injection. The 35% propylene glycol solvent is a significant contributor to the high incidence of pain on injection (80% with small veins, 10% with large veins) that can be further reduced by the prior administration of 1% lidocaine (lignocaine). 

Lidocaine (synonyme lignocaine) was introduced as the first amide in 1944 and is the most commonly used LA today. It has a rapid onset of action with intermediate duration and an intermediate toxicity. The maximum tolerated dose with infiltration or injection is 200 mg (500 mg when combined with adrenaline). Lidocaine is dealkylated in the liver to monoethylglycine xylidide and glycine xylidide which retain local anesthetic activity. It is available in a variety of preparations including creams, gels, patches and solutions, often in combination with adrenaline. 

Dose. For local anaesthesia, the total dose of lignocaine hydrochloride by injection should not exceed 300 mg (4.5 mg/kg), unless administered with adrenaline. For ventricular arrhythmias, initally 50 to 100 mg intravenously, followed by an infusion. 

Lignocaine (lidocaine) is a first choice drug for surface use as weU as for injection, combining efficacy with comparative lack of toxicity the t/ is 1.5 h. It is also useful in cardiac arrhythmias although it is being replaced by amiodarone for this purpose. 

Intravenous regional ane.sthesia is used to anesthetize a large region, such us a limb. The anesthetic is injected into a suitable vein in a limb that has had its blood flow restricted by a tourniquet. The efficiency and safety of the technique depends on preventing arterial flow for the duration of the anesthesia. Lignocaine is frequently used to produce intravenous regional anesthesia, but bupivacaine is not approved for this purpose because of its long duration of action. 

Scott, D. B. et ah. Plasma lignocaine levels after intravenous and intramuscular injection. Lancet, 1 41, 1970. 

Figure 3.11 Chromatograms obtained using the ESA Coulochem in screen mode (PGEs, Ej +0.6 V, E2 +0.9 V v5 Pd). Column 150x4.6 (i.d.) mm Spherisorb S5CN cyanopropyTmodified silica Eluent acetonitrile-aq. phosphoric acid (14 mmol L ) (30+70). Flow-rate 0.8 mL min Injections (a) 50 xL aqueous 2-methylaniline (1) (0.01 mg IT ) and prilocaine (2) (1 mg L ) (b) 50 J,L aqueous 3-hydroxylignocaine (3) (0.1 mg L ) and lignocaine (4) (1 mg L ).

Injection of Lignocaine and Adrenaline, B,P. Contains the equivalent of 0 00125 per cent w/v of adrenaline. 

The adrenaline is determined as Lignocaine and Adrenaline Injection omitting the ether extraction. 

---