Intravenous regional anesthesia
Intravenous regional anesthesia (IVRA) or Bier block anesthesia is an 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.
|Intravenous regional anesthesia|
Intravenous regional anesthesia (IVRA) using older tourniquet equipment. Modern electronic instruments include more safety features specifically for IVRA.
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(Esmarch bandage), squeezing blood proximally toward the heart, then pneumatic tourniquets are applied to the limb and inflated 30mmHg above arterial pressure to occlude all blood vessels and then the elastic bandage is removed. The local anesthetic, typically lidocaine(DOC) or prilocaine without adrenaline, is slowly injected as distally as possible into the exsanguinated limb. The veins are filled with the anesthetic and sets in after approximately 6–8 minutes, after which the surgery may begin. Analgesic effect remains for up to two hours. The wait time is important for avoiding toxic levels of anesthetics in the systemic bloodstream which can lead to hypotension, convulsions and even death in extreme cases so, cardiotoxic LA like bupivacaine and etidocaine are strictly contraindicated.
The safety and effectiveness of IVRA is well established in clinical literature.Cardiotoxic LA like bupivacaine and etidocaine are contraindicated. It is often preferred for shorter procedures (for up to 2 hours) on the distal limb, especially on the forearm, except when the patient was advised against tourniquet use(like in sickle cell anaemia-risk of massive hemolysis due to low oxygen tension or hemolytic crisis due to slow blood flow) 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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- Clark, Natasha (2002). "Intravenous Regional Anaesthesia - Bier's Block". Retrieved 23 September 2011.
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- Goodman &Gilman 11th edition. p. 381.
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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.