Local anesthesia
Encyclopedia
Local anesthesia is any technique to induce the absence of sensation
in part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain
, although other local senses may be affected as well. It allows patients to undergo surgical and dental
procedures with reduced pain and distress. In many situations, such as cesarean section
, it is safer and therefore superior to general anesthesia. It is also used for relief of non-surgical pain and to enable diagnosis of the cause of some chronic pain conditions. Anesthetists sometimes combine both general and local anesthesia techniques.
The following terms are often used interchangeably:
that causes reversible local anesthesia and a loss of nociception
. When it is used on specific nerve pathways (nerve block
), effects such as analgesia (loss of pain
sensation) and paralysis
(loss of muscle
power) can be achieved.
Clinical local anesthetics belong to one of two classes: aminoamide and aminoester local anesthetics. Synthetic local anesthetics are structurally related to cocaine
. They differ from cocaine mainly in that they have no abuse potential and do not act on the sympathoadrenergic system, i.e. they do not produce hypertension
or local vasoconstriction
, with the exception of Ropivacaine
and Mepivacaine
that do produce weak vasoconstriction.
Local anesthetics vary in their pharmacological
properties and they are used in various techniques of local anesthesia such as:
Adverse effects depend on the local anesthetic
agent, method, and site of administration and is discussed in depth in the local anesthetic
sub-article, but overall, adverse effects can be:
that uses other techniques than analgesic
medication include:
Sensation
Sensation is the fiction-writing mode for portraying a character's perception of the senses. According to Ron Rozelle, “. . .the success of your story or novel will depend on many things, but the most crucial is your ability to bring your reader into it. And that reader will be most completely...
in part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
, although other local senses may be affected as well. It allows patients to undergo surgical and dental
Dentistry
Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...
procedures with reduced pain and distress. In many situations, such as cesarean section
Caesarean section
A Caesarean section, is a surgical procedure in which one or more incisions are made through a mother's abdomen and uterus to deliver one or more babies, or, rarely, to remove a dead fetus...
, it is safer and therefore superior to general anesthesia. It is also used for relief of non-surgical pain and to enable diagnosis of the cause of some chronic pain conditions. Anesthetists sometimes combine both general and local anesthesia techniques.
The following terms are often used interchangeably:
- Local anesthesia, in a strict sense, is anesthesiaAnesthesiaAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
of a small part of the body such as a tooth or an area of skin. - Regional anesthesia is aimed at anesthetizing a larger part of the body such as a leg or arm.
- Conduction anesthesia is a comprehensive term, which encompasses a great variety of local and regional anesthetic techniques.
Medical
A local anesthetic is a drugMedication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
that causes reversible local anesthesia and a loss of nociception
Nociception
Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...
. When it is used on specific nerve pathways (nerve block
Nerve block
Regional nerve blockade, or more commonly nerve block, is a general term used to refer to the injection of local anesthetic onto or near nerves for temporary control of pain. It can also be used as a diagnostic tool to identify specific nerves as pain generators...
), effects such as analgesia (loss of pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
sensation) and paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
(loss of muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
power) can be achieved.
Clinical local anesthetics belong to one of two classes: aminoamide and aminoester local anesthetics. Synthetic local anesthetics are structurally related to cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
. They differ from cocaine mainly in that they have no abuse potential and do not act on the sympathoadrenergic system, i.e. they do not produce hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
or local vasoconstriction
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
, with the exception of Ropivacaine
Ropivacaine
Ropivacaine is a local anaesthetic drug belonging to the amino amide group. The name ropivacaine refers to both the racemate and the marketed S-enantiomer...
and Mepivacaine
Mepivacaine
Mepivacaine is a local anesthetic of the amide type. Mepivacaine has a reasonably rapid onset and medium duration of action and is marketed under various trade names including Carbocaine and Polocaine.Mepivacaine became available in the United States in the 1960s.Mepivacaine is used in any...
that do produce weak vasoconstriction.
Local anesthetics vary in their pharmacological
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
properties and they are used in various techniques of local anesthesia such as:
- Topical anesthesiaTopical anestheticA topical anesthetic is a local anesthetic that is used to numb the surface of a body part. They can be used to numb any area of the skin as well as the front of the eyeball, the inside of the nose, ear or throat, the anus and the genital area. Topical anesthetics are available in creams,...
(surface) - InfiltrationInfiltration (medical)Infiltration is the diffusion or accumulation of substances not normal to it or in amounts in excess of the normal. The material collected in those tissues or cells is called infiltrate.-Classification:...
- Plexus block
- Epidural (extradural) blockEpiduralThe term epidural is often short for epidural analgesia, a form of regional analgesia involving injection of drugs through a catheter placed into the epidural space...
- Spinal anesthesiaSpinal anaesthesiaSpinal anaesthesia , also called spinal analgesia or sub-arachnoid block , is a form of regional anaesthesia involving injection of a local anaesthetic into the subarachnoid space, generally through a fine needle, usually 9 cm long...
(subarachnoid block)
Adverse effects depend on the local anesthetic
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...
agent, method, and site of administration and is discussed in depth in the local anesthetic
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...
sub-article, but overall, adverse effects can be:
- localized prolonged anesthesiaAnesthesiaAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
or paresthesiaParesthesiaParesthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...
due to infection, hematomaHematomaA hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...
, excessive fluid pressure in a confined cavity, and severing of nerves & support tissue during injection, - systemic reactions such as depressed CNSCentral nervous systemThe central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
syndrome, allergic reaction, vasovagal episode, and cyanosisCyanosisCyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
due to local anesthetic toxicityLocal anesthetic toxicityWhile generally safe, local anesthetic agents can be toxic if used in excessive doses or administered improperly. Even when administered properly, patients may still experience unintended reactions to local anesthetics....
. - lack of anesthetic effect due to infectious pus such as an abscessAbscessAn abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...
.
Non-medical local anesthetic techniques
Local pain managementPain management
Pain management is a branch of medicine employing an interdisciplinary approach for easing the suffering and improving the quality of life of those living with pain. The typical pain management team includes medical practitioners, clinical psychologists, physiotherapists, occupational therapists,...
that uses other techniques than analgesic
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....
medication include:
- Transcutaneous electrical nerve stimulationTranscutaneous electrical nerve stimulationTranscutaneous electrical nerve stimulation is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes...
, which has been found to be ineffective for lower back pain, however, it might help with diabetic neuropathyDiabetic neuropathyDiabetic neuropathies are neuropathic disorders that are associated with diabetes mellitus. These conditions are thought to result from diabetic microvascular injury involving small blood vessels that supply nerves in addition to macrovascular conditions that can culminate in diabetic neuropathy...
. - Pulsed radiofrequencyPulsed radiofrequencyPulsed radiofrequency is the technique where by radio frequency oscillations are gated at a rate of pulses per second . Radio frequency energies occupy 1.0 X 104Hz to 3.0 X 1011HZ of the electromagnetic spectrum...
, neuromodulationNeuromodulationIn Neuromodulation several classes of neurotransmitters regulate diverse populations of central nervous system neurons...
, direct introduction of medication and nerve ablationAblationAblation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
may be used to target either the tissue structures and organ/systems responsible for persistent nociceptionNociceptionNociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...
or the nociceptors from the structures implicated as the source of chronic pain.
Citations
External links
- New York School of Regional Anesthesia
- Anesthesia Books
- General information and tutorials in peripheral regional anesthesia
- http://www.worldanaesthesia.org Free online manual of regional anaesthesia- John Hyndman
- Clinical Use of Peripheral Nerve Stimulators and The Neuromuscular Junction