Nerve block
Encyclopedia
Regional nerve blockade, or more commonly nerve block, is a general term used to refer to the injection of local anesthetic
onto or near nerve
s for temporary control of pain. It can also be used as a diagnostic tool to identify specific nerves as pain generators. Permanent nerve block can be produced by destruction of nerve tissue.
, neck pain, sciatica
(from a herniated disc), spinal stenosis
, reflex sympathetic dystrophy (a complex regional pain syndrome), shingles, cancer
, and painful peripheral vascular disease. It can also be used in the treatment of migraine
headaches.
(such as lidocaine
) with epinephrine
, a steroid
(corticosteroid
), and/or opioid
s. Epinephrine produces constriction of the blood vessels
which delays the diffusion of the anesthetic. Steroids can help to reduce inflammation. Opioids are painkillers. Injection nerve blocks can be either single treatments, multiple injections over a period of time, or continuous infusions. A continuous peripheral nerve block can be introduced into a limb undergoing surgery, for example, a femoral nerve block to prevent pain in knee replacement
.
Permanent nerve block can be effected using other drugs or methods including alcohol or phenol
to selectively destroy nerve tissue, cryoanalgesia to freeze nerves, and Radiofrequency ablation
to destroy nerve tissue using heat.
Nerve blocks are sterile procedures that are usually performed in an outpatient facility or hospital. The procedure can be performed with the help of ultrasound
, fluoroscopy
(a live X-ray) or CT
. Use of any one of these imaging modalities enables the physician to view the placement of the needle. A probe positioning system
can be used to hold the ultrasound transducer steady.
In addition, electrical stimulation can provide feedback on the proximity of the needle to the target nerve.
Complications include:
examinations in horses. A local anesthetic alone is injected perineurally to desensitize tissues beyond the site of injection. For example, the palmar digital nerves can be blocked to investigate pain arising from the sole and heel area of the hoof
. If pain is arising from this area, the horse will stop limping. If the source of lameness arises from higher up in the leg, the horse will continue to limp, and a nerve block can be performed higher up the leg. Because there are essentially no motor neuron
s in the lower limbs of horses, the risk of weakness or ataxia
is negligible.
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...
onto or near nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s for temporary control of pain. It can also be used as a diagnostic tool to identify specific nerves as pain generators. Permanent nerve block can be produced by destruction of nerve tissue.
Therapeutic uses
Nerve blocks can help patients who suffer from lower back painBack pain
Back pain is pain felt in the back that usually originates from the muscles, nerves, bones, joints or other structures in the spine.The pain can often be divided into neck pain, upper back pain, lower back pain or tailbone pain...
, neck pain, sciatica
Sciatica
Sciatica is a set of symptoms including pain that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve, or by compression or irritation of the left or right or both sciatic nerves. The pain is felt in the lower back, buttock, or...
(from a herniated disc), spinal stenosis
Spinal stenosis
Lumbar spinal stenosis is a medical condition in which the spinal canal narrows and compresses the spinal cord and nerves at the level of the lumbar vertebra. This is usually due to the common occurrence of spinal degeneration that occurs with aging. It can also sometimes be caused by spinal disc...
, reflex sympathetic dystrophy (a complex regional pain syndrome), shingles, cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, and painful peripheral vascular disease. It can also be used in the treatment of migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
headaches.
Methods
Temporary nerve blocks are achieved by combining a local anestheticLocal 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...
(such as lidocaine
Lidocaine
Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...
) with epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
, a steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
(corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
), and/or opioid
Opioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...
s. Epinephrine produces constriction of the blood vessels
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...
which delays the diffusion of the anesthetic. Steroids can help to reduce inflammation. Opioids are painkillers. Injection nerve blocks can be either single treatments, multiple injections over a period of time, or continuous infusions. A continuous peripheral nerve block can be introduced into a limb undergoing surgery, for example, a femoral nerve block to prevent pain in knee replacement
Knee replacement
Knee replacement, or knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve the pain and disability of osteoarthritis. It may be performed for other knee diseases such as rheumatoid arthritis and psoriatic arthritis...
.
Permanent nerve block can be effected using other drugs or methods including alcohol or phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
to selectively destroy nerve tissue, cryoanalgesia to freeze nerves, and Radiofrequency ablation
Radiofrequency ablation
Radio frequency ablation is a medical procedure where part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from the high frequency alternating current to treat a medical disorder...
to destroy nerve tissue using heat.
Nerve blocks are sterile procedures that are usually performed in an outpatient facility or hospital. The procedure can be performed with the help of ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
, fluoroscopy
Fluoroscopy
Fluoroscopy is an imaging technique commonly used by physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an X-ray source and fluorescent screen between which a patient is placed...
(a live X-ray) or CT
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
. Use of any one of these imaging modalities enables the physician to view the placement of the needle. A probe positioning system
Probe positioning system
A probe positioning system is a tool for the positioning of a measuring device, such as an ultrasound transducer in a fixed, predetermined place to the object, such as a patient...
can be used to hold the ultrasound transducer steady.
In addition, electrical stimulation can provide feedback on the proximity of the needle to the target nerve.
Digital nerve block
Digital nerve blocks involve infiltrating local anesthesia around the two nerves that supply a digit. Historically this has been done with a local anesthetic without epinephrine however the use of a solution with epinephrine appears to be safe.Complications
Nerve blocks, like other medical procedures, are not risk-free. There is a possibility of side effects and complications from the procedure, needle puncture, and medications used. The most critical factor in the efficacy of a nerve block is the proper location of the target nerve.Complications include:
- Infection
- Allergy reactions
- Increased pain
In other animals
Short-term nerve blocks are useful in regionalizing the source of pain during lamenessLameness (equine)
Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...
examinations in horses. A local anesthetic alone is injected perineurally to desensitize tissues beyond the site of injection. For example, the palmar digital nerves can be blocked to investigate pain arising from the sole and heel area of the hoof
Hoof
A hoof , plural hooves or hoofs , is the tip of a toe of an ungulate mammal, strengthened by a thick horny covering. The hoof consists of a hard or rubbery sole, and a hard wall formed by a thick nail rolled around the tip of the toe. The weight of the animal is normally borne by both the sole...
. If pain is arising from this area, the horse will stop limping. If the source of lameness arises from higher up in the leg, the horse will continue to limp, and a nerve block can be performed higher up the leg. Because there are essentially no motor neuron
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
s in the lower limbs of horses, the risk of weakness or ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
is negligible.