INTRAVENOUS REGIONAL ANESTHESIA (IVRA) of the extremities is one of the simplest and oldest regional anesthetic techniques available, but requires understanding of peripheral venous anatomy, local anesthetic pharmacology, and physiology to ensure safe and effective anesthesia. Introduced in 1908 by August Bier, the eponymous Bier block was initially a surgical technique that required exposure of the veins. Subsequent development of the intravenous cannula and pneumatic tourniquet enabled modern IVRA techniques, which for years were the mainstay of extremity regional anesthesia in many operating suites. The growth of ultrasound-guided regional anesthesia and peripheral nerve blocks has lessened the role of IVRA in contemporary anesthetic practice.

I. Anatomy

A. Venous plexi of the extremities. The peripheral nerves of the extremities are nourished by small arteries, the vasa nervorum. Metabolic by-products are cleared via venules, which flow
into the extremity’s venous plexus. Injection of sufficient volume of local anesthetic into the venous plexus leads to retrograde diffusion of drug into the nerve’s microcirculation and thereby produces anesthesia. Sufficient volume is attained by using a proximal pneumatic tourniquet to prevent egress of local anesthetic into the systemic circulation.

B. Mechanism of action. Surgical anesthesia is produced by several complimentary mechanisms. Diffusion of local anesthetic to small peripheral nerves throughout the extremity constitutes the initial effect of IVRA. The main anesthetic effect results from conduction blockade of larger nerves at more proximal sites. Tourniquet-induced ischemia and direct nerve compression further impede nerve conduction (1).

II. Drugs

A. Local anesthetics

1. Lidocaine is the most commonly used drug and has a long safety record. Because large volumes are necessary to distend the venous plexus, lidocaine 0.5% is used in volumes of 50 mL for the upper extremity or 100 mL for the lower extremity. These volumes can be reduced to 30 mL or 50 mL when forearm or calf tourniquets, respectively, are used. In children or small adults, volumes should be reduced on the basis of a dose of 3 mg/kg lidocaine. A separate priming dose of intravenous lidocaine 1 mg/kg administered minutes before IVRA institution reduces tourniquet pain (2).

2. Bupivacaine has been used for IVRA, but is not recommended because of significant concern for local anesthetic systemic toxicity (LAST) in the event of tourniquet failure or early release. Although ropivacaine has also been used (3), similar concerns remain for those patients at higher risk for LAST. Such patients include those at the extremes of age, with small muscle mass, or with cardiac disease (4).

3. Despite rapid clearance, 2-chloroprocaine has been associated with LAST and phlebitis (5).

B. Additives

1. Numerous studies have evaluated local anesthetic additives to improve IVRA anesthesia, analgesia, and tourniquet tolerance. Evidence supports nonsteroidal anti-inflammatory drugs (NSAIDs), clonidine, and dexmedetomidine. Other additives, including opioids, muscle relaxants, magnesium, neostigmine, dexamethasone, and tramadol, have relatively limited clinical benefit and/or are associated with unwanted side effects (6).

a. Presumably through a peripheral site mechanism of action, NSAIDs mixed with local anesthetic for IVRA improve block quality and tourniquet tolerance.

b. Ketorolac 20 mg added to lidocaine for upper extremity surgery reduces the need for rescue analgesics in the post-anesthesia recovery unit (6).

a. Clonidine 1 µg/kg improves postoperative analgesia and prolongs tourniquet tolerance (7).

b. Dexmedetomidine 0.5 µg/kg improves the quality of perioperative analgesia when added to lidocaine, with minimal side effects (8).

c. Both α₂-agonists are more expensive than ketorolac.

a. Nondepolarizing agents can provide muscle relaxation that can assist with fracture reduction, but may risk airway compromise in the case of tourniquet failure or residual systemic effects (6).

III. Technique

A. Indications

1. The primary advantages of IVRA are its simplicity and reliability. It is the easiest and most effective block of the distal upper extremity for simple, quick procedures, and it is therefore well suited for novices and for ambulatory surgery.

2. IVRA is suitable for many operations on the distal extremities when a proximal occlusive tourniquet can be applied safely.

a. The block is used primarily in the arm. An upper-arm single- or double-cuff pneumatic tourniquet is used commonly. A forearm tourniquet allows reduction of local anesthetic dose and is advocated for rescue when upper-arm tourniquet pain ensues.