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Jai Ganesh

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Registered: 2005-06-28

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Local Anesthesia

Local Anesthesia

Gist

Local anaesthetics stop the nerves in a part of your body sending signals to your brain. You won't be able to feel any pain after having a local anaesthetic, although you may still feel some pressure or movement. It normally only takes a few minutes to lose feeling in the area where a local anaesthetic is given.

Summary

Local anaesthesia involves numbing an area of the body using a type of medicine called a local anaesthetic.

These medicines can be used to treat painful conditions, prevent pain during a procedure or operation, or relieve pain after surgery.

Unlike general anaesthetics, local anaesthetics don't cause you to lose consciousness.

This means they're generally safer, don't normally require any special preparation before they're used, and you can recover from them more quickly.

How local anaesthetics work
Local anaesthetics stop the nerves in a part of your body sending signals to your brain.

You won't be able to feel any pain after having a local anaesthetic, although you may still feel some pressure or movement.

It normally only takes a few minutes to lose feeling in the area where a local anaesthetic is given.

Full sensation should return when the medicine has worn off a few hours later.

How local anaesthetics are used

Local anaesthetics are usually given by dentists, surgeons, anaesthetists, GPs and other doctors.

Some medicines containing mild local anaesthetic are also available on prescription or over the counter from pharmacies.

Depending on what they're being used for, local anaesthetics can be given as injections, creams, gels, sprays or ointments.

Some of the main uses of local anaesthetics are outlined on this page.

Treating pain

Slightly painful conditions, such as mouth ulcers and sore throats, can sometimes be treated with over-the-counter gels and sprays that contain a local anaesthetic.

Injections of a local anaesthetic and steroid medicine may be used to treat more severe conditions, such as long-term joint pain.

Preventing pain during and after surgery

A local anaesthetic, usually given by injection, may be used along with a sedative medicine to keep you relaxed while an operation or procedure is carried out.

Local anaesthetics are mainly used for relatively minor procedures, such as:

* a filling or wisdom tooth removal
* a minor skin operation, such as the removal of moles, warts and verrucas
* some types of eye surgery, such as cataract removal
* a biopsy (where a sample of tissue is removed for closer examination under a microscope)

A local anaesthetic may occasionally be used for more major surgery when it's important for you to be awake, such as during certain types of brain surgery, or to prevent pain after a major operation that's been carried out under a general anaesthetic.

Epidural and spinal anaesthetics

An epidural anaesthetic, often referred to as an epidural, is where a local anaesthetic is continually injected through a tube into an area of the lower back called the epidural space.

A spinal anaesthetic is a single injection into a similar space in the back.

Both types of anaesthetic can be used to numb large areas of the body by stopping pain signals travelling along the nerves in the spine.

They're often used during childbirth to ease the pain of labour or if a caesarean section is needed.

They can also be used to reduce the amount of general anaesthesia needed during some operations and can provide pain relief afterwards.

In some types of surgery, such as knee and hip replacements, they can be used in place of a general anaesthetic.

Peripheral nerve blocks

A nerve block is an injection of a local anaesthetic to numb the nerves supplying a particular part of the body, such as the hand, arm or leg.

It may be used so an operation can be carried out without needing a general anaesthetic, or to prevent pain afterwards.

An ultrasound scan is often used to pinpoint the correct nerve.

The injection shouldn't be painful and usually takes about 30 minutes to become fully effective.

When peripheral nerve blocks and epidural or spinal anaesthetics are used in place of general anaesthetics, they're often combined with sedation to make you feel drowsy and more relaxed.

Details

A local anesthetic (LA) is a medication that causes absence of all sensation (including pain) in a specific body part without loss of consciousness, providing local anesthesia, as opposed to a general anesthetic, which eliminates all sensation in the entire body and causes unconsciousness. Local anesthetics are most commonly used to eliminate pain during or after surgery. When it is used on specific nerve pathways (local anesthetic nerve block), paralysis (loss of muscle function) also can be induced.

Classification

* LAs are of 2 types:

** Clinical LAs:
amino amide LAs
amino ester LAs
** Synthetic LAs

Cocaine derivatives

Synthetic cocaine-derived LAs differ from cocaine because they have a much lower abuse potential and do not cause hypertension vasoconstriction (with few exceptions).

The suffix "-caine" at the ends of these medication names is derived from the word "cocaine", because cocaine was formerly used as a local anesthetic.

Examples

* Short Duration of Action and Low Potency

** Benzocaine
** Procaine
** Chloroprocaine

* Medium Duration of Action and Medium Potency

** Lidocaine
** Prilocaine

* High Duration and High Potency

* Tetracaine
* Bupivacaine
* Cinchocaine
* Ropivacaine

Medical uses

Local anesthetics may be used to prevent and/or treat acute pain, to treat chronic pain, and as a supplement to general anesthesia.

They are used in various techniques of local anesthesia such as:

* Topical anesthesia (surface anesthesia)
* Topical administration of cream, gel, ointment, liquid, or spray of anesthetic dissolved in DMSO or other solvents/carriers for deeper absorption
* Infiltration
* Brachial plexus block
* Epidural block (extradural)
* Spinal anesthesia (subarachnoid block)
* Iontophoresis
* Diagnostic purposes (e.g. dibucaine)
* Anti-arrhythmic agents (e.g. lidocaine).

Acute pain

Even though acute pain can be managed using analgesics, 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. LA drugs are also often combined with other agents such as opioids for synergistic analgesic action. Low doses of LA drugs can be sufficient so that muscle weakness does not occur and patients may be mobilized.

Additional Information

Untreated dental problems can result in serious complications. When a tooth becomes infected, failure to visit a dentist can cause the bacteria to spread. Failure to attend to cavities can weaken teeth, which leads to breakage, cracks, and chips. As per studies published in the US national library of medicine, up to 30% of patients experience anxiety when they visit a dentist.

Some patients may find that dental local anesthesia is the ideal solution for them. This type of anesthetics is different from sedation dentistry. It is generally used in cases where the patient does not have severe anxiety. The area where the procedure is performed will be numbed with the local anesthetic.

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