Introduction:
Short-term anesthesia can be achieved with injectable anesthetics. Local anesthetics have high lipid solubility and quick onset and allow passage into the blood-brain barrier; to perform simple diagnostic and surgical operations or to induce general anesthesia followed by inhalation anesthesia maintenance for a lengthy procedure. It should be selected based on the inherent pharmacological effects, the type of surgery or diagnostic test conducted, and the duration of the operation. Because of their established safety profile, affordability, storage convenience, broad availability, and rapid onset of action, infiltrative anesthetics are extensively used. Local anesthetics allergy is due to the preservative used in the drug. The use of Epinephrine or longer-acting drugs can prolong anesthesia. Anesthetic injections can be made less painful by buffering the local anesthetic with bicarbonate; the solution can be warmed up and injected slowly.
What Are the Common Infiltration Anesthetics?
A few commonly injectable amide and ester anesthetics are routine in-office procedures like
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Amides: Lidocaine, Bupivacaine, Mepivacaine, Prilocaine, and Etidocaine.
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Esters: Procaine, Chloroprocaine,Tetracaine.
How to Choose the Right Anesthetic Agent for Injection?
Local anesthetics are classified as amides or ester anesthetics. Traditionally, both amide (Lidocaine, Bupivacaine) and ester anesthetics (Procaine, Tetracaine) were utilized, but esters lost popularity due to their increased sensitivity. Hence, amide anesthetics are used widely for routine in-office procedures.
Lidocaine is the first amino amide local anesthetic to take place in clinical practice due to its quick onset and short duration of action. In addition, it comes in concentrations ranging from 0.5 to 4 percent. Therefore, it may be advantageous when only a tiny amount is needed.
Bupivacaine has a slow onset and a longer duration of action. Therefore, it is particularly beneficial when anesthesia is required for a prolonged period (for joint injections and digital nerve blocks). Other amide anesthetics can be utilized as in-office procedures, although they are typically reserved for spinal and regional anesthesia.
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Adding Epinephrine at a concentration of 1:100,000 to 200,000 (5 to 10 g per mL) can help to extend the anesthesia duration and reduce bleeding from the operation site. When operating on highly vascular areas like the scalp, the clinician may need to wait between injection and surgery. The optimum vasoconstrictive action of Epinephrine needs about five minutes to begin. The maximum dose of Lidocaine is increased from 4 to 7 mg per kg with the vasoconstrictive agent Epinephrine. Adrenaline should never be administered in locations with an end-arterial supply, such as the fingers, pinna, penis, or nose since vasoconstriction might produce ischemia and gangrene.
What Are the Benefits of a Mixture of Anesthetic Solutions?
Suppose an anesthetic effect is required for longer than thirty to sixty minutes. In that case, Lidocaine with Epinephrine or Bupivacaine with or without Epinephrine is recommended if an anesthetic effect is necessary for more than thirty to sixty minutes. Numerous studies have proved the advantages of combining Lidocaine with Epinephrine.
What Are the Techniques of Infiltration Anesthesia?
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When injecting infiltration anesthesia, it must permeate the whole surgical field, allowing the anesthetic to work on the nerve endings that feed the region from all directions.
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Before starting the procedure, look for the expiration date and concentration. Then, warm the anesthetic solution to reduce the discomfort caused by the injection. Simultaneously, prior to injection, alcohol wipes should be employed to clean both the anesthetic vial and the skin. On healthy skin, alcohol wipes are equally beneficial as Chlorhexidine or Povidone-iodine.
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Begin by using a fine-bore needle. Then, once the injection site has been numbed, a long, broad needle can be utilized following the first invasion.
What Are the Methods of Infiltration?
There are two methods of injecting anesthesia: static and continuous modes.
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Static: Insert the needle, aspirate to check there is no blood flow into the syringe, and then inject.
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Continuous: Insert the needle into the surrounding region, constantly moving the hand.
Attempt to pierce the skin as few times as possible. Rotate the needle to facilitate maximum infiltration through a single injection site. Additional punctures should be made through an already penetrated region if necessary. The needle should be removed slightly to reduce the risk of an injection directly into the vascular space. To decrease the pain of reinsertion, the anesthetic should be administered slowly into the tissue, shifting the needle from treated to untreated areas. Check sensation before any procedure, such as by pinching lightly with toothed forceps, to ensure that the region has been sufficiently anesthetized. An accidental infusion of local anesthetic into the circulation can cause paraesthesia, light-headedness, heart arrhythmias, and even cardiac arrest.
What Are the Methods to Reduce the Pain During the Injection?
Injection pain is induced by the prick of the needle and the infiltration of the anesthetic into the skin. Generally, one should use 25 to 30-gauge needles for injection. May use adjunctive treatments such as topical anesthetics, cryotherapy, or distraction in addition to Lidocaine. Pinching the skin activates local sensory nerves, obstructing other painful impulses reaching the brain. Injecting gently and steadily can help to reduce the discomfort of the anesthetic. In addition, administration into the subcutaneous tissues is less painful than administering directly into the dermis, which results in a bruise or scar.
What Are the Complications of Infiltration Anesthetics?
Side effects caused by local infiltration anesthetics are infrequent. Tremors and shivering accompany early symptoms such as metallic taste, convulsions, light-headedness, and disorientation. Finally, generalized seizures and respiratory failure are possible.
In the cardiovascular system (CVS) - At low doses, they cause vasoconstriction of the blood vessels and thereby increase blood pressure. However, high doses cause a negative inotropic effect on the heart, leading to heart block.
Conclusion:
It is the decision of the surgeon to choose the right anesthetic drug based on the availability of the drug, the time taken for surgery, and the area to be operated on. In addition, while administering a local anesthetic with a vasoconstrictor, the drug's pharmacokinetics should be considered, which is different in children and adults.
