IV regional: Pharmacology
Basic, Clinical Subspecialties
Intravenous regional anesthesia, or “Bier Block,” involves the delivery of intravenous local anesthetic while a tourniquet is applied. The technique is commonly used in distal upper extremity procedures as well as occasionally albeit less frequently in lower extremity procedures.
A variety of local anesthetics have been used for Bier Blocks, but the most popular local anesthetic in the United States is lidocaine (prilocaine is used frequently in Europe but is used less frequently in the U.S. due to its propensity to lead to methemoglobinemia). The maximum recommended dose of lidocaine is 3 mg/kg, and when an amount less than this is used, the procedure is considered safe. No significant differences have been found between different local anesthetics, although higher concentration/lower volume fluids have been associated with faster onset and delayed block regression.
NYSORA recommends 12-15 mL of 2% lidocaine or 30-40 mL of 0.5% lidocaine HCl for upper extremity blocks and doubling those amounts for lower extremity blocks to account for the larger extremity size. Onset of action is usually within 5 minutes, and sensory block can last up to an hour if a double-tourniquet system is used. Gradually, enough local anesthetic diffuses into the systemic circulation that it becomes safe to release the tourniquet without risk of LAST; opinions on the length of time for safe cuff deflation vary but generally the tourniquet should remain inflated for at least 20 minutes.
Numerous adjuncts have been described in the literature, including opioids, NSAIDs, dexmedetomidine, ketamine, corticosteroids, neostigmine, and muscle relaxants. Of these medications, NSAIDs and muscle relaxants were both shown to marginally improve analgesia and/or postoperative motor block. However, due to the added complexity, increased possibility of side effects, and increased risk of drug-related medical errors, most centers do not routinely use adjuncts.
Updated definition 2020:
Intravenous regional anesthesia was first described in the early 1900s by August Bier, and involve the delivery of local anesthetic intravenously while a tourniquet is applied.
Via his early efforts, Bier came to the conclusion that two mechanisms of anesthesia were associated with this technique. A peripheral infiltration block, from local anesthetic bathing bare nerve endings in the tissue, which occurred rapidly. As well as a conduction block, as local anesthetic is transported to the substance of the nerve via the vasa nervorum, much like other typical conduction block mechanisms.
This technique is commonly used in distal upper extremity procedures and uncommonly in distal lower extremity procedures. Its advantages are ease of administration, rapid onset, rapid recovery, and controllable level of anesthesia. It is a popular technique for short procedures.
Lidocaine is the most commonly used local anesthetic for IV regional anesthesia in the United States. Prilocaine has historically been the most commonly used local anesthetic in Europe but carries with it the increased risk of methemoglobinemia. The maximum recommended dose of lidocaine is 3mg/kg. NYSORA suggests 12-15mL of 2% lidocaine or 30-40ml of 0.5% lidocaine for upper extremity blocks and doubling those amounts for lower extremity blocks. The onset of anesthesia is typically within 5 minutes and the technique should provide appropriate surgical anesthesia for procedures up to 1 hour's duration.
For the most part, no significant differences have been found amongst the different local anesthetics in regards to surgical anesthesia, but higher concentration/lower volume blocks have been associated with faster onset, delayed block regression, and increased post-operative pain control.
In utilizing the technique, the tourniquet should not be deflated until at least 30 minutes has elapsed from the time of local anesthetic injection. Deflating prior to this risks significant local anesthetic release into the circulation and resultant systemic toxicity.
A variety of adjuncts have been described in the literature, including NSAIDs, opioids, alpha-2 agonists, ketamine, corticosteroids, and muscle relaxants. Of these, NSAIDs have shown the most clinical promise in regard to improving analgesia. However, most centers do not routinely utilize adjuncts given the increased risk of side effects and drug-related medical errors.