Local anesthesia/anesthetics regional intravenous

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 vasoconstrictor actions of epinephrine and norepinephrine have been used to prolong the action of local anesthetics by reducing local blood flow in the region of the injection. Epinephrine has been used as a topical hemostatic agent for the control of local hemorrhage. Norepinephrine is infused intravenously to combat systemic hypotension during spinal anesthesia or other hypotensive conditions in which peripheral resistance is low, but it is not used to combat the hypotension due to most types of shock. In shock, marked sympathetic activity is already present, and perfusion of organs, such as the kidneys, may be jeopardized by norepinephrine administration. 

Intravenous regional anesthesia—injection of local anesthetic into a suitable vein supplying the limb to be anesthetized the blood flow from this limb is then restricted by a tourniquet... 

Convulsions have occurred after inadvertent intravenous injection of ropivacaine during regional anesthesia (4,5). CNS adverse effects from ropivacaine occur before or without severe cardiovascular toxicity, as there have been several similar reports of CNS toxicity, but not yet one with severe or fatal cardiotoxicity. This reinforces the claim of increased safety from cardiovascular toxicity with this enantiomeric local anesthetic compared with racemic bupivacaine. 

Local anesthetics are widely used to provide anesthesia via local subcutaneous Injection topical application to skin and mucous membranes and epidural, spinal, and regional nerve blocks. In addition, lidocaine (see p 462) is used intravenously as an antiarrhythmic agent and cocaine (see p 171) is a popular drug of abuse. Gommonly used agents are divided into two chemical groups ester-linked and amide-linked (Table 11-2). 

Local anesthetics are used to locally anesthetize a wide range of specific body parts or areas to allow painless surgery. Local anesthetics are most commonly used for dental procedures and repair of lacerations. They can also be used to provide neural blockade for larger, more painful procedures. Sites of LA application include localized injection, peripheral nerve blocks as well as central nerve blockade. The only safe agents which can be utilized for intravenous regional anesthesia (Bier block) are lidocaine and prilocaine. Other typical indications are outlined in Table 64.1. 

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