Uses, types, and risks of local anesthesia
An anesthetic drug is applied to the part of the body that is to undergo surgery.
It may be used with sedation, which calms the patient and reduces stress levels. Together, they enable the surgeon to carry out the procedure without pain or distress.
Local anesthesia only lasts a short time, so it is mainly used for minor outpatient procedures, where the patient can leave on the same day.
Local anesthesia provides pain relief in dental surgery and other outpatient procedures.
Local anesthesia is used when:
- surgery is minor and does not require general or regional anesthesia
- the procedure can be done quickly and the patient does not need to stay overnight
- the operation does not need the muscles to be relaxed or for the patient to be unconscious
Examples include dental surgery, the removal of a verruca, a mole, or a cataract, and biopsies.
The type and dose of anesthesia will depend on many factors. These include the patients' age, weight, any allergies, the part of the body to be operated on, and any current medical condition.
Various drugs are used to block the pain. They can be applied as an injection or through applying a spray or an ointment.
The drug works by acting on certain nerve pathways to prevent the nerves in the area of application from sending signals to the brain.
It normally takes a few minutes for the drug to take effect, and it wears off after a few hours. A stronger and higher dose will last for longer.
Cocaine was the first anesthetic, but now it is rarely used. Lidocaine is now the most widely used local anesthetic, but different drugs are used for different purposes.
For longer procedures, bupivacaine is more suitable, but it can be more painful when first administered. An anesthetist may, therefore, use lidocaine first, then inject with bupivacaine later, if numbness is needed for a longer period.
Synthetic anesthetics are similar in structure to cocaine, but these drugs do not have the same abuse potential.
If a patient is going to have surgery that involves a local anesthetic, the doctor should explain beforehand how to prepare.
Patients must inform the doctor if they are using any medications, especially if these are blood thinning agents, such as aspirin or warfarin.
The doctor may give instructions not to eat anything a few hours before surgery. It is also important not to drink any alcohol for 24 hours before receiving the anesthetic.
In the doctor's office, the doctor will apply a local anesthetic agent to the relevant area of the body. It will begin to feel numb.
The doctor will not proceed if the patient does not feel the numbing effect.
The anesthetic will prevent any pain from being felt, but the patient may still feel pressure during the operation.
Depending on what the procedure is, and how anxious the patient feels, a sedative may also be given at the same time. This will help the patient to feel calm and less anxious.
The physician will monitor the amount of oxygen in the blood using a small device placed on the finger. In rare cases, a plastic nasal tube will be used to provide extra oxygen.
Risks and complications
Local anesthesia is generally considered very safe. For minor surgery, it is safer than general anesthesia.
There may be some tingling and pain when the drug is administered, and when it is wearing off, and there may be some bruising, but these are usually minor.
A person who has had a local anesthetic should be careful not to injure themselves while they cannot feel pain, for example, by biting their cheek after dental treatment.
Temporary adverse effects that affect some people include:
- blurred vision, dizziness, and vomiting
- muscle twitching
- continuing numbness, weakness, or tingling
Some people may have an allergic reaction. The patient could develop hives, itching, and breathing difficulties.
Cyanosis can occur, in which the skin becomes bluish due to poor circulation or inadequate oxygenation of the blood.
In very care cases, the person may experience a depressed CNS syndrome, in which the central nervous system slows down too much, leading to a decreased rate of breathing and heart rate. This can lead to cardiac arrest if the blood stops pumping to the heart.
An overdose of local anesthetic can lead to seizures. This can be life-threatening.
Local anesthesia can also be used in diagnosing some chronic conditions, and to relieve pain after an operation.
In 2010, findings from a rodent study in Turkey suggested that local anesthetics may ease some symptoms of inflammatory bowel disease (IBD).
Anyone administering any type of anesthetic must be appropriately trained and qualified.