Regional nerve block

Peripheral or sympathetic nerve block (regional anesthesia) Topical Up to 200 ml of a... 

Nerve Block Regional anesthetic injected directly into a nerve (intraneural) or adjacent to the nerve (paraneural). 

After local anaesthetic injection, onset of nerve block and duration depends mainly on lipid solubility and on the region in where the diug is injected. In some formulations adrenaline is added to prolong the blocking action by inducing regional vasoconstriction and hereby reduce absorption and metabolisation. 

Local anesthetics are used for topical anesthesia, local infiltration, peripheral nerve block, paravertebral anesthesia, intravenous block also known as regional anesthesia, epidural block, and spinal i.e. subarachnoid blockade. The local anesthetics may be divided into two main groups, the esters and the amide-type agents. 

Amide-type agents include articaine, lidocaine, bupivacaine, prilocaine, mepivacain and ropiva-caine. These are metabolized in the liver by microsomal enzymes with amidase activity. The amide group is preferred for parenteral and local use. If by accident rapidly administered intravascularly these agents, especially bupivacaine but also lidocaine, can produce serious and potentially lethal adverse effects including convulsions and cardiac arrest. They can more easily accumulate after multiple administrations. Intravenous lidocaine is sometimes used for regional anesthesia, for infiltration procedures, for the induction of nerve blockade and for epidural anesthesia. However, it is also used as an antiarrhythmic. Bupivacaine is a long-acting local anesthetic used for peripheral nerve blocks and epidural anesthesia. 

The first clinical uses of a local anesthetic agent occurred in 1884, when cocaine was employed as a topical agent for eye surgery and to produce a nerve block. These events inaugurated a new era, that of regional anesthesia. New applications were developed, including spinal, epidural, and caudal anesthesia. The search for a better local anesthetic led to chemical synthesis of a number of other compounds that have more selective local anesthetic properties and few systemic side effects. 

Lidocaine hydrochloride Xylocaine) is the most commonly used local anesthetic. It is well tolerated, and in addition to its use in infiltration and regional nerve blocks, it is commonly used for spinal and topical anesthesia and as an antiarrhythmic agent (see Chapter 16). Lidocaine has a more rapidly occurring, more intense, and more prolonged duration of action than does procaine. 

Regional nerve block anesthesia— injection of a small amount of local anesthetic into the tissue immediately surrounding a nerve supplying the region to be anesthetized... 

Local anaesthetics are employed routinely in dentistry by nerve block or by infiltration and/or regional block techniques to cary out varous operative procedures. 

Lignocaine injections are indicated for production of local or regional anaesthesia by infiltration techniques such as percutaneous injection, peripheral nerve block, spinal or subarachnoid block. 

Chloroprocaine Nesacaine Rapid Short Infiltration Peripheral nerve block Epidural Intravenous regional block... 

Local Anesthetics for Regional Infiltration and Peripheral Nerve Block... 

In most minor surgical procedures of the eye, local infiltrative anesthesia is adequate. However, patients having multiple lesion removal or those exceptionally sensitive to pain may require a more complete regional anesthesia using an orbital nerve block. Nerve blocks provide excellent regional anesthesia without distortion of tissues but do not allow local epinephrine-induced hemostasis. 

Administration of an orbital nerve block requires intimate familiarity with both the anatomic locations of the sensory nerve fibers of the orbit (Figure 19-5) and the sensory distribution of these nerve branches (Figure 19-6). A description of orbital nerve blocks and distribution of regional anesthesia associated with these injections is included in Table 19-1. Care must be taken to avoid nerve laceration that may manifest as severe pain or paresthesias during needle insertion. 

Orbital Nerve Block and Distribution of Regional Anesthesia ... 

Nerve block means to anaesthetise a region, which may be small or large, by injecting the drug around, not into, the appropriate nerves, usually either a peripheral nerve or a plexus. Nerve block provides its own muscular relaxation as motor fibres are... 

The vertex of the scalp is innervated by all the nerve endings that sensitize the skull. This region is therefore sometimes difficult to anesthetize completely without doing a full circular nerve block of the scalp. 

The skin of the forehead is thoroughly anesthetized by the nerve blocks, and the phenol application should extend slightly into the temporal zone. Patients should be warned that they will feel a burning sensation on the temples for 15-20 seconds as the phenol is applied to this unanesthetized area. The temporal regions are treated gradually up to a virtual horizontal line that goes through the center of the pupils. The extension zone includes part of the wrinkles of the crow s feet the phenol is first applied at the base of these wrinkles the left hand stretches the skin to make it easier to reach the base of the wrinkles with the applicator. The peel solution is then applied to the rest of the area. 

There is one small lateral region that has not been treated. This region can be anesthetized with a lateral nerve block (see Chapter 33) or can be treated slowly and gradually. This latter option is always chosen when the ftiU-face peel is performed under deep sedation. 

Lidocaine hydrochloride is a local anesthetic/vasopressor preparation. Lidocaine stabilizes neuronal membranes by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action. Epinephrine stimulates both alpha and beta receptors within sympathetic nervous system relaxes smooth muscle of bronchi and iris and is an antagonist of histamine. They are indicated for production of local or regional anesthesia by infiltration techniques such as percutaneous injection, by peripheral nerve block techniques such as brachial plexus and intercostals, and by central neural techniques such as lumbar and caudal epidural blocks. 

Mepivacaine is indicated in production of local or regional analgesia and anesthesia by local infiltration, peripheral nerve block techniques, and central neural techniques including epidural and caudal blocks (see also Figure 31). 

It is a long-acting local anaesthetic of the amide type, similar to mepivacaine and lidocaine but about four times more potent. The effects of bupivacaine last longer to lidocaine hydrochloride. It is mainly employed for regional nerve block, specifically epidural block, when a prolonged effect is required. 

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