Regional Anesthesia: Definition and Examples
What Is Regional Anesthesia?
While general anesthesia is used most often for surgery, there are some surgeries that can be done with, or supplemented with, regional anesthesia. As an anesthesiologist, having the option to use nerve blocks in certain surgeries is very helpful, but requires vigilance and proper training and experience.
Regional anesthesia refers to numbing a region of the body, rather than the whole body by inducing unconsciousness with general anesthesia.
Regional anesthesia includes peripheral nerve blocks and neuraxial anesthesia. A special type of block called an IV (intravenous) regional anesthetic may also be included in this category. This is traditionally called a Bier block and is mostly used for upper extremity procedures lasting less than one hour.
Neuraxial anesthesia refers to spinal and epidural blocks that numb the lower half (or a bit more) of the body. Peripheral nerve blocks numb an area of the body supplied by a nerve or group of nerves. Bier blocks (IV regional) involve the use of a tourniquet applied to an arm after the blood has been squeezed and drained from it. Local anesthetic is placed into a vein in the hand, and the arm is anesthetized until the tourniquet is released or the anesthetic is metabolized.
Consult Your Doctor
The decision to use or not use regional vs. other types of anesthesia must be decided on a case-by-case basis. There are many factors influencing the decision that need to be discussed with your anesthesiologist and surgeon. This article is not meant to suggest that these techniques can or should be used in any particular case.
When Is Regional Anesthesia Used?
Regional anesthesia can be used, obviously, only when the surgery is contained within an area that is amenable to numbing.
Some lower abdominal surgeries can be done with epidurals and spinals. The most common surgery done with neuraxial regional anesthesia is cesarean section. Other times, special circumstances may lead to the use of spinals or epidurals for abdominal surgeries.
Peripheral nerve blocks also provide regional anesthesia. A nerve or bundle of nerves can be anesthetized to numb the area of the body that they supply.
When Can't Regional Anesthesia Be Used?
There are many times that regional anesthesia cannot be used. These limitations may be related to the patient, surgeon, surgery type or anesthesiologist.
- Regional anesthesia requires cooperation from the patient. If a patient is unable or unwilling to maintain a proper position for placement of regional anesthesia, then it cannot be safely done.
- Because regional anesthesia for surgery means that unconsciousness with general anesthesia is not needed, the patient will be awake, or only partially sedated. Anyone who cannot comfortably (physically or mentally) lie on the operating bed in a specified position for the length of the surgery is not a good candidate for regional anesthesia.
- Regional anesthesia is administered by injection. Anytime a needle is used, there is a risk of bleeding. Patients who take blood thinners or have disease that limits normal clotting should not usually have regional anesthesia, except in very special cases.
- Likewise, infection can be spread by needles. A patient who has an infection near the injection site, or in the blood stream should not get a regional anesthetic.
- Finally, any patient who does not want a nerve block or neuraxial anesthesia is always able to refuse.
- Some surgeons are not comfortable doing surgery on a patient who is awake and just numb in a region of their body. Patients can often still move the rest of their body and even a little movement can make the surgery more difficult.
- Likewise, some anesthesiologists are not as skilled or comfortable doing regional anesthesia as others. Experience is a factor in the success of blocks, so this is an important considerations. If you are not offered a regional anesthetic, the truth is that the doctor may not be comfortable providing the type you need.
- Not all surgical sites can be covered by regional anesthetics, at least not practically.
- Lower abdominal or pelvic surgery can be done under spinal or epidural anesthesia. BUT, if the surgery is being done by a laparoscopic technique, then this usually isn't possible or desirable. First, the abdomen is inflated with gas to create a dome in which the surgeon can work. This insufflation of gas causes pain above the area that can be safely covered by the regional anesthesia. Also, the gas makes it harder to breathe adequately, as can spinal or epidural anesthesia. This combination makes a general anesthesia a better choice since breathing can be assisted and unconsciousness removes the discomfort.
- Regional anesthetics are not good for surgeries lasting longer than a couple hours. Blocks that are done by single injection may not last long enough. Even when techniques are used (such as placing catheters) to allow for repeated or continuous drug administration, it is difficult for patients to be comfortable, even when sedated, for that period of time.
Neuraxial Regional Anesthesia: Epidurals and Spinals
As mentioned, spinal blocks and epidurals are often included in the regional anesthesia category. They are their own special category referred to as "neuraxial anesthesia" as described above.
Neuraxial means that the numbing medicine is placed close to the axis of the spinal cord.
For a spinal anesthesia, the numbing medicine is placed directly into the cerebrospinal fluid (CSF, spinal fluid). This results in numbing of approximately the lower half of the body, or from the level of the breast bone down, in some surgeries. Very little medicine is needed and the block is usually very dense, preventing both movement of the lower extremities and sensation below the desired area.
Epidurals are different, but similar. The epidural space is outside the lining covering the spinal cord and CSF. It is a very thin space where the nerves exit the lining over the cord. More medicine is needed to get the anesthetic to spread and penetrate the coverings of the nerves. Often, a catheter is placed in the epidural space so that the medicine can be adjusted as needed. A larger needle is used so that a catheter (thin tube) can be threaded through it and left behind as the needle is removed. Epidurals are technically more difficult and may have a higher risk profile.
Femoral Nerve Block
Peripheral Nerve Blocks: Examples
The most common nerve blocks (in my practice, at least) are femoral nerve blocks and interscalene nerve blocks.
Femoral nerve blocks are used for thigh (front) and knee surgery, most often knee replacement and ACL surgery. Medicine is injected at the point where the femoral nerve enters the upper leg near the groin, rather than at the knee itself. By injecting at this point distant from the site to be numbed, more of the nerve distribution to the knee is covered. As the nerve goes down the leg, it divides into branches, which would make several injections necessary to provide the same block. At the top of the leg, the nerve is still gathered into a bundle, so injection there provides more complete numbing. Thus, a region of the body is numbed by an injection into the area around a large peripheral nerve or nerve bundle.
Interscalene blocks are useful for shoulder surgery. Like femoral nerve blocks, they are usually used in conjunction with general anesthesia, rather than by themselves. They are most useful to decrease the amount of general anesthesia needed and to provide pain relief for the first six to 18 hours after surgery. The site of injection is in the side of the neck. This is where a structure called the "brachial plexus" is most accessible and bundled to allow a single injection for numbing the desired area. The brachial plexus, a complex collection of nerves, goes on to divide into nerves that supply the shoulder and upper arm.
Axillary blocks can be used for surgery on the lower arm. The injection is into the armpit and is useful for surgeries like AV fistula placement in the forearm for dialysis. Other nerve blocks (at least for me) are used less often. Ankle blocks are useful for foot surgery and are often employed to clean out foot wounds for diabetic patients who have infections on the toes or foot.
There are peripheral nerve blocks and regional anesthesia techniques for many areas of the body and so these are just a few examples.
Interscalene Nerve Blocks
Femoral Nerve Block
IV (Intravenous) Regional Anesthesia: Bier Block
Bier blocks are usually used on the upper extremity, but have been used in the legs as well. They are useful for surgery on the hand or lower arm that lasts less than about one hour.
The extremity to be anesthetized has a small intravenous line placed in the hand. The arm is raised and an elasticized wrap is tightly wound around the extremity to drain all the blood from the arm. A tourniquet to occlude the now compressed blood vessels is inflated in the upper arm (a double tourniquet can be used, as well, to improve safety and patient comfort).
Once there is confirmation that there is no circulation to or from the extremity, local anesthesia is injected into the IV that had been placed. It is important to prevent complications by ensuring that the local anesthetic doesn't leave the arm and enter the circulation. Full monitoring of vital signs and communication with the patient about abnormal signs or symptoms of local anesthesia toxicity are necessary to ensure safety, as well.
The local anesthetic numbs the hand and arm. The surgery can be completed during the duration of action of the anesthetic and as long as the patient can tolerate the tourniquet on the upper arm. The tourniquet can be released after about 30 minutes, but many of us think it is safer to leave it inflated as long as is tolerated.
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