local anesthetic (LA):

University of Babylon
College of Nursing Anesthesia Lec.7
_Dr. Naji Yassesr Al-Mayyahi 4th Years ____________________________________________________________

A local anesthetic (LA):
is a medication that causes reversible absence of pain sensation, although other senses are often affected, as well. Also, when it is used on specific nerve pathways (local anesthetic nerve block), paralysis (loss of muscle power) also can be achieved.
Clinical LAs belong to one of two classes: aminoamide and aminoester local anesthetics. Synthetic LAs are structurally related to cocaine. They differ from cocaine mainly in that they have a very low abuse potential and do not produce hypertension or (with few exceptions) vasoconstriction.
They are used in various techniques of local anesthesia such as:
• Topical anesthesia (surface)
• Topical administration of cream, gel, ointment, liquid, or spray of anaesthetic dissolved in DMSO or other solvents/carriers for deeper absorption
• Infiltration
• Brachial plexus block
• Epidural (extradural) block
• Spinal anesthesia (subarachnoid block)
• Iontophoresis
Medical uses
1-Acute pain:
Acute pain may occur due to trauma, surgery, infection, disruption of blood circulation, or many other conditions in which tissue injury occurs. In a medical setting, pain alleviation is desired when its warning function is no longer needed. Besides improving patient comfort, pain therapy can also reduce harmful physiological consequences of untreated pain.
Acute pain can often be managed using analgesics. However, conduction anesthesia may be preferable because of superior pain control and fewer side effects. For purposes of pain therapy, LA drugs are often given by repeated injection or continuous infusion through a catheter. Low doses of LA drugs can be sufficient so that muscle weakness does not occur and patients may be mobilized.
Some typical uses of conduction anesthesia for acute pain are:
• Labor pain (epidural anesthesia, pudendal nerve blocks)
• Postoperative pain (peripheral nerve blocks, epidural anesthesia)
• Trauma (peripheral nerve blocks, intravenous regional anesthesia, epidural anesthesia)
2-Chronic pain:
Chronic pain is a complex and often serious condition that requires diagnosis and treatment by an expert in pain medicine. LAs can be applied repeatedly or continuously for prolonged periods to relieve chronic pain, usually in combination with medication such as opioids, NSAIDs, and anticonvulsants.
3-Surgery:
Virtually every part of the body can be anesthetized using conduction anesthesia. However, only a limited number of techniques are in common clinical use. Sometimes, conduction anesthesia is combined with general anesthesia or sedation for the patient s comfort and ease of surgery.


Side effects:
1-Localized side effects:
The local adverse effects of anesthetic agents include neurovascular manifestations such as prolonged anesthesia (numbness) and paresthesia (tingling, feeling of "pins and needles", or strange sensations). These are symptoms of localized nerve impairment or nerve damage. Of particular note, the use of topical anesthetics for relief of eye pain can result in severe corneal damage.
2-Risks
The risk of temporary or permanent nerve damage varies between different locations and types of nerve blocks
3-General side effects[edit]
General systemic adverse effects are due to the pharmacological effects of the anesthetic agents used. The conduction of electric impulses follows a similar mechanism in peripheral nerves, the central nervous system, and the heart. The effects of local anesthetics are, therefore, not specific for the signal conduction in peripheral nerves. Side effects on the central nervous system and the heart may be severe and potentially fatal. However, toxicity usually occurs only at plasma levels which are rarely reached if proper anesthetic techniques are adhered to. High plasma levels might arise, for example, when doses intended for epidural or intrasupport tissue administration are accidentally delivered as intravascular injection.

Drugs of local aneasthesia:
Introduction:
Local anaesthetic drugs are used widely for the provision of anaesthesia and analgesia both intra- and post-operatively. Understanding the pharmacology of these agents as a group, as well as the differences between specific drugs, enables the anaesthetist to use them safely to maximum effect. This tutorial focuses on the basic structure and function of local anaesthetics.
Definition of a local anaesthetic

A local anaesthetic can be defined as a drug which reversibly prevents transmission of the nerve impulse in the region to which it is applied, without affecting consciousness. There are many drugs which exert local anaesthetic activity in addition to their main clinical uses,





Administration of Local Anesthetics
Drug Onset Maximum Dose (with Epinephrine)
Lidocaine Rapid 4.5 mg/kg (7 mg/kg)
Mepivacaine Rapid 5 mg/kg (7 mg/kg)
Bupivacaine Ropivacaine Levobupivacaine Slow Medium Medium 2.5 mg/kg (3 mg/kg) 2-3 mg/kg 2.0 mg/kg or 400mg in 24 hrs
Procaine Slow 8 mg/kg (10 mg/kg)
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