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Local Anesthesia With Sedation

Overview

Local anesthesia with sedation offers anesthesia personnel and the surgeon great flexibility in tailoring the degree of anesthesia to the needs of the patient. Procedures that once required patients to stay overnight in the hospital are now performed safely in office and outpatient surgical suites.
The utilization of these anesthetic applications enables patients to undergo lengthy and complex procedures as outpatients and then more readily and safely be discharged home.
The choice and route of anesthesia administration is paramount to the patient’s overall surgical experience. If, upon discharge, the patient is alert, has minimal pain, and has no nausea or vomiting, then the surgical experience was a positive one.

Monitored anesthesia care

Monitored anesthesia care (MAC) combines intravenous sedation with local anesthetic injection, infiltration including tumescent anesthesia, or nerve blocks.

Procedures such as otoplasty, facelift, blepharoplasty, or liposuction are examples of surgeries routinely performed under MAC. Patients given monitored anesthesia rather than general anesthesia experience fewer incidences of nausea and vomiting and typically can be discharged home safely and quickly.

The image below depicts intraoral approach for an infraorbital block. 

Intraoral approach for an infraorbital block.

Intraoral approach for an infraorbital block.

The primary disadvantages of MAC are the lack of airway control and the threat of aspiration or obstruction. To minimize these risks, the anesthesia personnel must titrate the medications carefully to maintain spontaneous respirations while maintaining an anesthetic depth, allowing the patient to remain comfortable. Careful selection and administration of medications is essential in producing the desired and optimal intraoperative anesthetic effect and postoperative outcomes.

Local anesthesia

Local anesthesia encompasses infiltration of the operative site, tumescent techniques, and nerve blocks.

A nerve block can be labeled minor if one nerve is affected or major if more than one nerve or conduction in a nerve plexus is impeded.

Local anesthetic agents are usually of the amino amides class and include such agents as lidocaine, bupivacaine, prilocaine, mepivacaine, and etidocaine. The potency, onset of action, and duration of these agents varies (see table below). For additional information on the classes of local anesthetics, see Local Anesthetic Agents, Infiltrative Administration.

Table. Local Anesthetic Dosage Ceiling and Duration of Action (Open Table in a new window)

Anesthetic Agent

Dosage Ceiling

Duration of Action

Lidocaine

7.0 mg/kg with EPI*

4.5 mg/kg without EPI

30-60 minutes

Bupivacaine

225 mg with EPI

175 mg without EPI

30-90 minutes

Prilocaine

600 mg with EPI

500 mg without EPI

30-90 minutes

Mepivacaine

7.0 mg/kg with EPI

45-90 minutes

Etidocaine

8.0 mg/kg with EPI

6.0 mg/kg without EPI

120-180 minutes

*EPI: epinephrine

Depending on the area to be anesthetized, varying techniques can be implemented. For incisional sites, a local anesthetic such as 1% lidocaine with epinephrine (EPI) is ideal for direct injection into the incisional site with rapid onset of the anesthetic effect. For procedures in which flaps are to be elevated, as in a facelift or coronal forehead lift, the incision site is anesthetized as previously mentioned, and the flap area can be infiltrated with a diluted anesthetic such as 0.5% lidocaine with EPI. This is a tumescent anesthetic technique. As an example, in a facelifting procedure both short-acting (lidocaine) and longer-acting (bupivacaine) anesthetics with EPI are injected into the incision line from the temple area, the preauricular and tragal incision site, and posteriorly into the posterior ear sulcus and postauricular scalp and neck areas, which are injected using a 30 gauge x 0.5 inch or 27 gauge x 1.25 inch needle. A diluted anesthetic such as 0.25% lidocaine with 1:400,000 EPI can be injected with a spinal needle (25 gauge x 3.5 inches) in a tumescent fashion, infiltrating (swelling) the subcutaneous area with this diluted mixture. The dilution can be made by combining 1% lidociane with 1:100,000 EPI with normal saline injectable in a 3:1 ratio.

For the local anesthetic, 1% lidocaine often is used with 1:200,000 or 1:100,000 EPI. The latter prolongs the anesthetic effect of lidocaine as a result of its vasoconstrictive properties. If more prolonged anesthesia is desired, lidocaine can be mixed with bupivacaine, providing the rapid but shorter lasting anesthesia effect of the former coupled with the slower but prolonged anesthetic effect of the latter.

In tumescent techniques, vastly larger amounts of anesthetic are used, albeit in diluted concentrations. Adipose tissue is suffused via an infusion cannula in the subcutaneous space, with large volumes of diluted lidocaine (0.05-0.1%) and a diluted concentration of EPI (1:1,000,000) for both anesthetic and hemostatic effects. The safety of this technique lies in the fact that the anesthetic concentration is extremely small, allowing large amounts of solution to be used without reaching toxic levels. For example, a mixture of 500 mL of normal saline with 50 mL of 2% lidocaine will result in a concentration of lidocaine of less than 0.2%. In addition, a tissue plane is created that aids in later dissection.

General anesthesia

Although monitored anesthesia care (MAC) is a safe method for providing anesthesia, general anesthesia is preferred for lengthy or complex procedures. General anesthesia provides amnesia, analgesia, and muscle relaxation. In addition, the patient’s airway is secured with an endotracheal tube or laryngeal mask, and the risk of aspiration or obstruction is minimized.
The primary disadvantage of general anesthesia is the increased incidence of nausea and vomiting and the somnolence of patients postoperatively. However, in properly selected patients, local anesthesia with MAC is a safe and effective method of providing anesthesia for operative procedures. Another form of anesthesia, total intravenous anesthesia (TIVA), involves the use of full intravenous sedation and airway management via a laryngeal mask. This offers an alternative between MAC and general anesthesia.

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