Intravenous Regional Blocks

Intravenous regional blocks were first described by a German surgeon, August Bier, in 1908.^[34] Early methods involved two tourniquets and the first synthetic local anesthetic, procaine. The technique lost popularity as reliable methods of blocking the brachial plexus evolved.

Clinical Applications

The Bier block has multiple advantages, including ease of administration, rapidity of recovery, rapid onset, muscular relaxation, and controllable extent of anesthesia. It is an excellent technique for short (<90 minutes) open surgical procedures and for closed reductions of bony fractures.

Technique

An intravenous cannula is placed in the upper extremity to be blocked as distally as possible; the patient should also have an intravenous cannula in the nonoperative upper extremity for administration of fluids and other drugs. Traditionally, a double tourniquet is placed on the operative side; both cuffs should have secure closures and reliable pressure gauges. After exsanguination of the arm, the proximal cuff is inflated to approximately 150 mm Hg more than the systolic pressure, and absence of a radial pulse confirms adequate tourniquet pressure. The total dose of local anesthetic is based on the patient's weight, and it is injected slowly (3 mg/kg of 0.5% prilocaine or lidocaine, without epinephrine). The onset of anesthesia is usually within 5 minutes. When the patient complains of tourniquet pain, the distal tourniquet, which overlies anesthetized skin, is inflated, and the proximal tourniquet is released. Data suggest that the use of a single wide cuff allows use of lower inflation pressures during intravenous regional anesthesia. The postulated advantage is that the lower pressures will decrease the incidence of neurologic complications related to high inflation pressures with the narrow double cuffs.^[35] The tourniquet may be safely released after 25 minutes, but the patient should be closely observed for local anesthetic toxicity for several minutes after the tourniquet release. Slow injection of local anesthetic solutions at a distal site has been shown to lower the risk of toxicity.^[36]

Side Effects and Complications

Technical problems with this block include tourniquet discomfort, rapidity of recovery leading to postoperative pain, difficulty in providing a bloodless field, and the necessity of exsanguination in the case of a painful injury. Accidental or early deflation of the tourniquet or use of excessive doses of local anesthetics can result in toxic reactions. Injection of the drug as distally as possible at a slow rate has been shown to decrease blood levels and theoretically may increase safety.^[36] The use of bupivacaine for intravenous regional anesthesia has been associated with local anesthetic toxicity and death ^[37] and is not recommended. Cyclic deflation of the tourniquet at 10-second intervals has been shown to increase the time to peak arterial lidocaine levels that may decrease potential toxicity.^[38] Other rare complications associated with this technique include phlebitis (with 2-chloroprocaine), development of compartment syndrome, and loss of a limb.