Local Anesthesia Armamentarium + Positioning PDF

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SYRINGE 

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Type of syringes o Aspirating standard syringe: thumb ring has to be purposefully pulled back for aspiration. The harpoon inserts into the rubber stopper to allow aspiration. o Self-aspirating standard syringe: releasing of the thumb ring provides automatic aspiration by applying negative pressure to the cartridge. The harpoon is replaced by a flat disc at the end of the piston rod. o Safety syringe: sheath “locks” over the needle when it is removed from the patient’s tissues. This mechanism helps prevent needle stick injuries. + Designed for single-use. + Reuse of the same syringe for a second cartridge is discouraged. o Computer-controlled local anesthetic delivery system (C-CLAD): the syringe is held like a pen and the drug is delivered at a preprogrammed flow. This prevents patient discomfort associated with rapid anesthetic delivery. Components of the standard syringe o Needle adapter: hole through which the end of the needle that pierces through the diaphragm of the cartridge is inserted. o Piston with harpoon: piece of sharp metal that inserts into the rubber stopper. + The harpoon can become dull after repeated usage. + A dull harpoon increases the chance for disengagement when the thumb ring is pulled back during aspiration. o Finger grip: allows the index and middle finger to hold and stabilize the syringe. o Thumb ring: loop in which the thumb is placed to push or pull the piston. Small and large thumb rings are available. o Threaded hub: threaded component that attaches the needle to the syringe. o Window opening: large rectangular opening on the barrel that allows the cartridge solution to be seen and confirm positive/negative aspirations.

Dental Syringe CARE AND HANDLING OF SYRINGES   

Syringes should be autoclaved just like other surgical instruments. After five autoclave episodes, disassemble the syringe and lubricate all threaded joints. The harpoon should be cleaned with a brush after each use.

NEEDLE 

Components of the needle o Bevel: slanted portion at the end of the needle.

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+ In general, the greater the angle of the bevel, the greater the degree of deflection. o Shaft: tubular metal from the tip of the needle to the hub. o Hub: plastic or metal part that attaches the needle to the syringe. + It is the weakest part of the needle where needle breakage occurs. Avoid inserting the needle all the way to the hub. o Cartridge penetrating end: opposite end of the needle that pierces the diaphragm of the cartridge. Gauge: diameter of the needle lumen. Available in 25, 27, and 30-gauge. o The bigger the gauge, the smaller the diameter. o 25-gauge is the thickest, followed by 27-gauge, and 30-gauge. o Needle gauges are coded by colors. Below is the common color system used in North America: + 25-gauge: red (largest diameter) + 27-gauge: yellow + 30-gauge: blue (smallest diameter) o Advantages of using smaller gauge needles (large diameter needles): + Less deflection of the needle as it passes through the oral tissues. + Bi-Rotational Insertion Technique (BRIT): the operator rotates the needle back and forth while advancing the needle through the tissues. This can help minimize deflection. + More resistant to breakage. + More accurate aspiration of blood. Smaller gauge (larger diameter) needles are recommended with injections in highly vascular areas (IA, PSA, mental/incisive nerve block). + Ease of solution deposition Length: long, short and ultrashort are available.

o Long needle: 30-35 mm (average 32 mm). + Used for all injections penetrating oral tissues more deeply. e.g., IA, Gow-Gates mandibular, infraorbital (ASA) nerve blocks. o Short needle: 20-25 mm (average 20mm). o Ultra-short needle: 10-12 mm. Only available in 30-gauge (smallest diameter). Care and handling of needles o Needles should never be used on more than one patient. o Needles should be changed after 3-4 insertions as the tip becomes dull. A dull tip can increase patient discomfort. o Recap needles using the one-hand “scoop” technique (needle is reinserted into its cap, using one hand only). Never touch the cap with

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the other hand. + Needle holders can also be used. o Dispose needles in specific “sharps” containers. Contaminated needles should never be discarded into open trash containers. o A fishhook-like barb at the tip of the needle can cause discomfort when the needle is withdrawn. In such case, change the needle. + Barbs can develop when the tip contacts the bone. + Barbs can be detected by lightly dragging the needle tip against a sterile cotton gauze. If a barb is present, the gauze will “catch.” Patient movement is the main cause of needlestick injuries.

Needle recapping techniques CARTRIDGE 

Components of the cartridge o Cartridge: color band on the cartridge identifies the anesthetic (required by the ADA). + Pressure can shatter the glass cartridge. When such an event happens, suction the patient’s mouth thoroughly and report the incident.| + The thin Mylar plastic label on the outside of the cartridge reduces the incidence of “shattering.” + “Hitting” the thumb ring when engaging the harpoon into the stopper may put pressure on the neck of the cartridge which is the weakest part of the cartridge. o Stopper (plunger): rubber piece where the harpoon inserts. + The width of the stopper is equivalent to about 0.2 ml of solution. + The stopper is slightly indented from the lip of the glass cylinder (not flushed with the cylinder edge). + An extended stopper indicates that the solution has been frozen or that other liquid has diffused into the cartridge. Discard such cartridge. o Diaphragm: thin semipermeable membrane through which the needle penetrates. + The needle should penetrate the center of the round diaphragm. If

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the diaphragm is punctured eccentrically, the solution may leak during an injection. o Aluminum cap: holds the diaphragm. + Corrosion and rust can occur from other solutions. Discard such cartridge. Content of the cartridge: a cartridge contains approximately 1.8 ml of solution (in North America). o Some manufacturers label their cartridges 1.7 ml (even though there is about 1.76 ml of anesthetic). o Local anesthetic: drug that produces the anesthetic effects. + In a 1.8 ml cartridge, 2% solution contains 36 mg, 3% solution contains 54 mg, and 4% solution contains 72 mg of local anesthetic. + In a 1.7 ml cartridge, 2% solution contains 34 mg, 3% solution contains 51 mg, and 4% solution contains 68 mg of local anesthetic. o Vasoconstrictor (vasopressor): added in some cartridges to counteract the vasodilating activity of local anesthetics. + In a 1.8 ml cartridge, 1:50,000 solution contains 0.036 mg, 1:100,000 solution contains 0.018 mg, and 1:200,000 solution contains 0.009 mg of vasoconstrictor. + In a 1.7 ml cartridge, 1:50,000 solution contains 0.034 mg, 1:100,000 solution contains 0.017 mg, and 1:200,000 solution contains 0.0085 mg of vasoconstrictor. o Sodium bisulfite: prevents oxidation of the vasoconstrictor. o Sodium chloride: makes the solution isotonic with body tissues. o Distilled water: provides volume. o Methylparaben: makes the solution bacteriostatic. No longer used in single-cartridge local anesthetics. o Nitrogen gas: prevents oxygen from being trapped inside the cartridge. This gas creates a small 1-2 mm bubble which is considered normal. Care and handling of cartridges o Store dental cartridges at room or body temperature (20-22 °C or 6871.6 °F) in a dark place. + Do not warm the cartridge. This can cause a burning sensation to the patient. o Clean the diaphragm with alcohol-soaked gauze. + Do not soak the cartridge in alcohol (the diaphragm is semipermeable and allows diffusion). Latex allergy: latex-free cartridges are now commonly used. Regardless, studies have concluded that there are no reports of documented allergy due to the latex component of cartridges. Bubble larger than 2 mm: indicates a frozen cartridge. Discard such cartridges.

PATIENT POSITIONING 

Place the patient in a supine position to prevent syncope. + Syncope (fainting) is the most common medical emergency in dentistry. This emergency occurs typically during, or shortly after dental injections.

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+ With anxiety, blood flow is directed toward the skeletal muscles rather than the head. As a result, dizziness, tachycardia, lightheadedness, loss of consciousness, etc. can occur. Sit the patient up after the IA nerve block and Gow Gates technique to allow the solution to diffuse to the desired areas.

CLINICIAN POSITIONING 

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Establish a fulcrum to stabilize the syringe. + Clinician’s finger can rest on the patient’s face. + Clinician’s elbow can rest on the patient’s stable body parts (if other fulcrum techniques are not available). + Clinician may draw his/her elbow close to his/her side. Avoid placing the hand/arm holding the syringe against the patient’s arm. Keep the syringe out of the patient’s sight by moving it behind the patient’s head or across the patient’s chest but below the patient’s line of sight. Also, avoid displaying the syringe on a bracket that is visible to the patient.

COMMUNICATION   

During the process, speak to the patient. + e.g., “I am applying topical anesthetic.” Use positive words such as “comfortable, freeze,” while avoiding negative words such as “pain, injection, shot, and hurt.” Observe the patient’s facial expressions and body language that may indicate discomfort, allergic reactions, or overdose.

RECORD 

Entry must include: type of local anesthetic, amount of local anesthetic (in mg), type of vasoconstrictor, amount of vasoconstrictor (in mg), number of cartridges, needle gauge and length, injection type, time injection occurred, patient’s reaction, and post-op instructions. Topical anesthetic should also be noted. + e.g., 5% benzocaine topical. Right infraorbital nerve block injection, using 2% lidocaine, 1:100,000 epinephrine, 36 mg of lidocaine, 0.018 mg of epinephrine (1.8 ml cartridge), 25-gauge long needle. Patient tolerated procedure well. Post-operation instructions: avoid hot food or drink for 3-4 hours and call if any concerns....