Intravenous regional anesthesia
|Intravenous regional anesthesia|
Intravenous regional anesthesia (IVRA) using older tourniquet equipment. Modern electronic instruments include more safety features specifically for IVRA.
Intravenous regional anesthesia (IVRA) or Bier block anesthesia is a common anesthetic technique for surgical procedures on the body's extremities where a local anesthetic is injected intravenously. The technique usually involves exsanguination, which forces blood out of the extremity, followed by the application of pneumatic tourniquets to safely stop blood flow. The anesthetic agent is introduced into the limb and allowed to set in while tourniquets retain the agent within the desired area. After some time, the tourniquet is depressurized to restore circulation.
The use of tourniquets and injected agents to induce localized anesthesia was first introduced by August Bier in 1908. He used an Esmarch bandage to exsanguinate the arm and injected procaine between two tourniquets to quickly produce anesthetic and analgesic effects in the site. Though it proved effective, IVRA remained relatively unpopular until C. McK. Holmes reintroduced it in 1963. Today, the technique is common due to its economy, rapid recovery, reliability, and simplicity.
Protocols vary depending on local standard procedures and the extremity being operated on. A vast majority of practitioners begin by exsanguinating the limb as Bier did with an elastic bandage, squeezing blood proximally toward the heart. Pneumatic tourniquets are then applied to the limb and inflated to occlude all blood vessels. The local anesthetic, typically lidocaine or prilocaine, is slowly injected as distally as possible into the exsanguinated limb. The anesthetic sets in after approximately 20 minutes, at which point the tourniquets can be deflated and the surgery may begin. The wait time is important for avoiding toxic levels of anesthetics in the systemic bloodstream. Alternatively, the tourniquets may remain inflated to maintain a bloodless field.
The safety and effectiveness of IVRA is well established in clinical literature. It is often preferred for shorter procedures on the distal limb, especially on the forearm, except when the patient was advised against tourniquet use. A systematic review of IVRA-related complications found 64 cases reported between 1964 and 2005, which compares favorably against other techniques. The type of anesthetic agent, improper equipment, and technical error are prominent factors in most instances of morbidity related to IVRA. Modern practice now includes various safeguards for improving safety.
Reports from anesthesiologists and surgeons cite proper selection, inspection, and maintenance of equipment as important safety measures. The safest tourniquet equipment should have IVRA-specific features such as independent limb occlusion pressure measurements for each channel, as well as dual-bladder tourniquet cuffs combined with dedicated safety lockouts that reduce human error. Additionally, IVRA protocols should include procedures for regular preventative maintenance of the equipment and performance testing, whether manual or automated, prior to surgery.
Adjuvants improve the safety of IVRA by promoting anesthetic action and minimizing side effects. For example, benzodiazepine and fentanyl are often added to prevent seizures and to improve nerve blockage, respectively.
Improved protocols, including adherence to standardized practice, may also help ameliorate the chance and the effect of complications. For example, limb protection padding and a snug tourniquet application prevents tissue damage, while sufficient but not excessive tourniquet pressure ensures that anesthetics remain within the limb without risking injury. Should complications occur, constant physiological monitoring and ready access to resuscitative drugs and equipment facilitates a speedy response.
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- Holmes, C. McK. (1969). "The history and development of intravenous regional anaesthesia". Acta Anaesthesiologica Scandinavica (Wiley). Supplementum XXXVI: 11–18. doi:10.1111/j.1399-6576.1969.tb00473.x.
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- McEwen, James (21 June 2011). "Tourniquet Safety and Intravenous Regional Anesthesia (IVRA, also called Bier Block Anesthesia): What’s New and Why?". Retrieved 22 September 2011.