BACKGROUND: Nerve blocks involve the injection of a local anesthetic into or near a peripheral nerve or local pain-sensitive trigger point. Nerve blocks relieve pain by interrupting the body's pain sensory pathways and preventing chemical signals indicating pain from reaching the brain. They are a convenient way to numb targeted areas of the body for specific surgeries, and are thus the ideal anesthetic for surgeries on extremities such as the legs and arms.
HOW IT WORKS: Using ultrasound, doctors can identify the location of the nerves. Once the anesthetic is injected around the nerves, the limb becomes progressively number. They can be given in a single injection, a continuous infusion, or used to completely destroy the nerve for more permanent pain relief. A single injection can last several hours or up to one day. Unlike general anesthesia, patients receiving a nerve block can breathe on their own with no additional support. Patients do not experience nausea, vomiting, or sore throat. Patients recover more quickly and require less pain medication after surgery. Nerve blocks also provide effective anesthesia and pain relief for joint replacement surgery, major orthopedic trauma, severe burns, hernia repair, breast surgery, removal of kidney stones, and vascular surgery.
CAVEATS: Nerve blocks can provide temporary pain control but they are just one component of a pain management program. There can be side effects, such as allergic reactions to the local anesthetics. If steroids are used with the anesthetics to reduce inflammation, they can cause fluid retention, fluctuations in blood pressure and blood sugar, and mood swings. If nervous tissue is destroyed, a patient can experience partial loss of motor or sensory functions in the affected area. And patients who are taking anticoagulants such as heparin should not have a nerve block as the medications used can increase the risk of bleeding.
HOW ULTRASOUND WORKS: Ultrasound is a medical imaging technique that uses high-frequency sound waves and their echoes. It is similar to how bats navigate in the dark, and the SONAR used by submarines underwater. The machine transmits high-frequency sound pulses into the body using a probe. The sound waves travel through the body and bounce off any boundaries, such as between fluid and soft tissue, tissue and bone. Some of the sound waves are reflected back to the probe, while others travel further through until they bounce off another boundary. All the reflected waves are recorded by the machine, which then calculates the distance each sound wave traveled based on how long it took the sound wave's echo to return. This data is used to form a two-dimensional image based on the distances and intensities of those echoes.