Local Anesthetics Armamentarium

Dr. Rahaf Y. Al-Habbab BDS. MsD. DABOMSDiplomat of the American Boards of Oral and

Maxillofacial Surgery2012

Armamentarium used for Local Anesthesia

• The Syringe

• The Needle

• The Cartridge

The Syringe

Types

• Non-Disposable (Metallic non-aspirating or aspirating)

• Disposable

Syringes (Non-Disposable)

Non-Aspirating Syringe Aspirating Syringe

Syringes (Disposable)

Component of the Syringe

Metal Barrel

Piston (Plunger) with the Harpoon

Finger Grip

Thumb Ring

Needle Adaptor (Hub)

Barrel

Finger Grip

Thumb Ring

Piston Rod/Plunger

Harpoon

Threaded Hub

Syringes

The Harpoon ended plunger is designed to pierce the lower rubber stopper of the cartridge, to help withdrawn for aspiration

Rubber Stopper

Loading the Cartridge

• The cartridge is inserted into the syringe either from the side or from the base.

• Aspirating syringe has a device (Harpoon) that is attached to the piston which penetrates the rubber stopper.

• Fixate the needle into the threaded hub, making sure it goes through the rubber diaphragm

Armamentarium used for Local Anesthesia

• The Syringe

• The Needle

• The Cartridge

Components of the Needle

• The Bevel

• The Shank

• The Hub

• The Syringe Penetrating End

Bevel

Shank

Hub Needle End

The Needle

The Bevel: It is the point or tip of the needle.

The Shank (Shaft): Consist of the diameter of the lumen (needle gauge).

The Hub: It is the plastic or metallic piece that attaches to the syringe.

The Syringe Penetrating End: It is placed into the needle adaptor and perforates the rubber diaphragm of the cartridge.

Bevel

The Needle

• Needles are selected according to the length and gauge.

• Gauge: The diameter of needle lumen (27 or 30 most commonly used)

• The smaller the number, the greater the lumen diameter (30-gauge needle has smaller diameter than 25-gauge)

The Needle

• The Length: Measured from the hub to the tip Maybe long or short.

• Long: It is about 1 5/8 inches or 40mm• Short: It is about 1 inch or 25mm

• To allow different depth penetration in the tissue with different techniques, leaving safety length of the needle during use.

The weakest portion of the needle is at the hub, so never insert a needle into the tissue up to the hub.

Safe Needle Management

One Hand Recapping Method

Plastic Housing

Management of Occupational Blood Exposure

If an exposure occurs:

• Should stop immediately.

• Wash wound with soap and water.

• Antiseptic use and/or bleeding the wound have not been proven to reduce infection, however antiseptic use is not contraindicated.

• Bleach and other caustic agents should not be poured directly into the wound.

Armamentarium used for Local Anesthesia

• The Syringe

• The Needle

• The Cartridge

Anesthetic Carpule (Cartridge)

Cartridges

• Referred to as a Carpule.

• Alkali and Pyrogen-free glass are used in the manufacture of the cartridges.

• Cartridges contain either 2.2ml or 1.8ml of local anesthetic solution

Components of the Cartridges

Consist of Four Parts:

• Cylindrical glass tube

• Stopper (Plunger)

• Aluminum Cap

• Diaphragm

StopperGlass CartridgeAluminum cap with Rubber Diaphragm

Cartridges

• The Stopper is Located at the end of the cartridge that receive the Harpoon of the aspirating syringe.

• The stopper used to be treated with glycrin or wax as a lubericant, but now it is treated with silicone.

• The upper rubber sealing cap is present at the top of the cartridge and surrounded by aluminum diaphragm.

• The needle pierce the upper rubber cap when the cartridge is loaded.

• Storage of cartridges in sterilizing solution is contraindicated because of the danger of contamination by seepage.

Carpule Contents

• Local Anesthetic Agent (To be discussed later)

• Vasoconstrictor

• Preservative

• Vehicle

Carpule Contents

• Local Anesthetic Agent

• Vasoconstrictor

• Preservative

• Vehicle

Vasoconstrictor

• Duration and Depth of local anesthesia can be modified by the Amount of vasoconstrictor in the local anesthetic.

• The lower the concentration of vasoconstrictor, the less the depth and duration of anesthesia.

• Concentration of 1:80,000 or 1:100,000 is most commonly used.

Vasoconstrictor

Vasoconstrictor used are:• Adrenaline (epinephrine, supranol) 1:50 000 to 1:200 000

• Noradrenalin (nor-epinephrine) 1:30 000

• Neo-Synephrine: 1:2500

• Neo-Cobefrin: 1:20 000

• Octapressin (Felypressin) similar to that excreted by human posterior pituitary gland.

Why add vasoconstrictor to LA?

All LA has some degree of VD effect that leads to:

• Increase rate of absorption.

• Higher plasma level.

• Decrease duration of action.

• Increase bleeding at site of injection.

Advantages of Adding Vasoconstrictor

• Decrease incidence of Toxicity by retarding drug Absorption as toxicity depends on drug amount in bloodstream.

• Confines the anesthetic agent to localized area so it increase the effect and duration of anesthesia.

• Reduce blood flow to the injected area, so produces bloodless field, prolong the effect of anesthesia with minimum amount of LA to produce the desired effect.

• Retard the absorption of local anesthetic drug.

Side Effects of Vasoconstrictor Use

• Marked elevation of blood pressure.

• Tachycardia, as epinephrine stimulate the heart by direct action on the myocardium which result in increase heart rate and cardiac output.

• Arrhythmia.

• Severe Headache.

• Elevate blood sugar level.

• May participate in Thyroid crisis in Hyperthyroid patients.

Side Effects of Vasoconstrictor Use

Intravascular injection or increased concentration of the VC may producetoxic manifestation such as Tachycardia, Hypertension, Palpitation, Tremors,Headache, and Ventricular Fibrillation in rare cases.

These side effects last as long as the blood level of the drug remain elevated.

Dilution of VC Agent

• Dilution referred to as ratio.

• 1 to 1000 means that there is 1g (1000mg) of drug in 1000ml of solution.

• Dilution of 1:100 000 or 1:200 000 are commonly used

Pharmacological Action of Adrenaline

• It stimulates both alpha and beta receptors (responsible for excitatory and inhibitory effects)

• It inhibits the action of vasodilatation of blood vessels of voluntary muscles and causes relaxation of bronchial muscles

• It dilates blood vessels in skeletal muscle and myocardium

• It constrict blood vessels in the skin

Pharmacological Action of Adrenaline

• It increases the heart rate and forces myocardium contraction (patient may complain of palpitation)

• It increases cardiac output and elevate blood pressure (systolic) and decrease diastolic pressure as it dilates blood vessels of skeletal muscles and of the heart causing decrease in peripheral resistance.

Carpule Contents

• Local Anesthetic Agent

• Vasoconstrictor

• Preservative

• Vehicle

Preservative (Reducing Agent)

• Vasoconstrictors are unstable in solution and may oxidize especially if exposed to sunlight, so solution color is turned into brown color.

• Small quantity (0.1%) of sodium bisulphite is added to compete for the available oxygen and maybe oxidized to sodium bisulphate turning the solution into brown color (should be discarded)

Carpule Contents

• Local Anesthetic Agent

• Vasoconstrictor

• Preservative

• Vehicle

Vehicle

• LA are weak bases that are insoluble in water.

• Ringer’s lactate solution is added to minimize discomfort during injection and gives the required volume of anesthetic solution.

Ringer’s lactate Solution

Composed of:• 0.5gm Sodium Chloride • 0.04gm Calcium Chloride • 0.02gm Potassium Chloride• Dissolved in 100ml water