Local and Regional Anesthesia: Clinical Considerations

Local and regional anesthesia, in discrepancy to systemic, general anesthesia, involves the reversible deadening of a specific region of the body to help any sensation of pain. Pain may be blocked on different situations of its signal transduction pathway,e.g., at the point of origin, along the jitters, or in the brain. Consequently, local and regional anesthesia can be divided into local topical and infiltration anesthesia, regional supplemental whim-whams blocks( PNB), and neuraxial anesthesia(e.g., spinal and epidural). Local anesthesia can be combined with general anesthesia, allowing the boluses of anesthetic and analgesic medicines to be reduced during surgery, and may exclude the need for other measures to achieve


INTRODUCTION
Local anesthetics( LAs) are medicines that block the sensation of pain in the region where they're administered. LAs act by reversibly blocking the sodium channels of whimwhams filaments, thereby inhibiting the conduction of whimwhams impulses. whim-whams filaments that carry pain sensation have the lowest periphery and are the first to be blocked by LAs. Loss of motor function and sensation of touch and pressure follow, depending on the duration of action and cure of the LA used. LAs can be sneaked into skin/ subcutaneous apkins to achieve local anesthesia or into the epidural/ subarachnoid space to achieve regional anesthesia(e.g., spinal anesthesia, epidural anesthesia). 1,2,3 Some LAs( lidocaine, prilocaine, tetracaine) are effective on topical operation and are used before minor invasive procedures( venipuncture, bladder catheterization, endoscopy/ laryngoscopy). LAs are divided into two groups grounded on their chemical structure. The amide group( lidocaine, prilocaine, mepivacaine,etc.) is safer and, hence, further generally used in clinical practice. The ester group( procaine, tetracaine) has a advanced threat of causing antipathetic responses or systemic toxin and is, thus, reserved for cases with known disinclinations to medicines of the amide group. Overdose or unintentional injection of an LA into a blood vessel can beget systemic toxin, which substantially affects the CNS( tinnitus, seizures,etc.) and the CVS( bradycardia, arrhythmias,etc.). 4,5 Corresponding Author: Félix Osuna Gutiérrez

Indications
Local anesthetic agents have a big range of clinical uses: Topical application (lidocaine, tetracaine, prilocaine), useful in children, e.g., in form of a lidocaine patch, before performing minor invasive procedures, such as venipuncture or intravenous catheter placement. 6 As a gel prior to catheterizing the bladder (as a lubricant and as an LA). 6 As a mouth gargle/spray, prior to performing indirect laryngoscopy, endoscopy, in pharyngitis with odynophagia, etc. 6

Infiltration
Into the skin/subcutaneous tissue: for skin surgery (skin biopsy, suturing, foreign body extraction, etc.). 6 Into the epidural space for epidural anesthesia. 6 Into the subarachnoid space for spinal anesthesia. 6

Peripheral nerve block
Local anesthetic is injected near a specific nerve or nerve bundle. 7

Indications
Surgery of the upper extremities, interscalene block, supraclavicular plexus block, vertical infraclavicular plexus block, axillary brachial plexus block, surgery of the lower extremities, sciatic and femoral nerve block, inguinal block and paravertebral plexus block, surgery of the scalp, neck, and trunk, block of selected peripheral nerves (e.g., digital nerve block).

Procedure
Injection site: depends on the nerves that need to be blocked. 7

Technique
The patient is placed in a confortable position that is tolerable for him or and allows the physician to access the relevant nerve easily. 7 Hygiene: hand disinfection, sterile gloves, sterile face mask, utensils for wipe disinfection of the puncture site afterward, (if catheter is inserted, also sterile gown and sterile fenestrated drape). 7 Ultrasound: ultrasound-guided needle advancement towards the target nerve. 7

Nerve stimulation test
There are 2 approaches to inject the local anesthetic drugs: Single-shot technique: A single dose of the local anesthetic drug is injected (e.g., bupivacaine). 7 Catheter placement with the advantage of repeated/continuous administration of anesthetic drugs. 7

Epidural anesthesia
Local anesthetics with or without opioids and alphaadrenergic agonists are injected into the epidural space and act on the spinal nerve roots. 8

Procedure
May be performed at any vertebral level (cervical, thoracic and lumbar spine). 8 Needle inserted into the epidural space alwayas looking to be between the ligamentum flavum and dura mater Approaches to inject the local anesthetic: Catheter placement, which has the advantage of repeated/continuous administration of anesthetic drugs (most commonly performed). 8 Single-shot technique. 8