Tourniquet Safety and Intravenous Regional Anesthesia (IVRA, also called Bier Block Anesthesia): What’s New and Why?
Many tourniquet systems are used for intravenous regional anesthesia (IVRA), also known as Bier block anesthesia. IVRA is a tourniquet-related alternative to general anesthesia for limb surgery that is inexpensive and widely used with adult and pediatric patients, with the frequency varying by type of surgery and patterns of practice .
In IVRA, blood is first exsanguinated from the limb, usually by wrapping it with an elastic bandage, beginning distally and squeezing and wrapping toward the heart. A dual-bladder tourniquet cuff is then applied proximal to the operative site and pressurized. The elastic bandage is removed and a local anesthetic agent is injected into the limb through an intravenous cannula. The local anesthetic remains in the limb as long as the tourniquet is inflated. About 20 minutes after infusion, most of the anesthetic agent has been absorbed into the limb tissues and deflation of the tourniquet will not result in systemic release of the agent in high concentration. IVRA may be performed by anaesthesiologists, anesthetists, nurse-anesthetists, surgeons, or occasionally others.
Surgical tourniquet systems, including tourniquet cuffs and instruments, play a vital role in the safety and success of IVRA.  Safe and successful IVRA typically requires the use of tourniquet instruments and cuff having advanced capabilities, including: two independent pneumatic channels, additional IVRA hazard suppression features, and special-purpose dual-bladder tourniquet cuffs (although special single-channel cuffs may occasionally be used). [3-4] Thorough testing of tourniquet instruments and cuffs prior to use, with results documented and checked, is also necessary to prevent hazards. [5-6]
IVRA has proven to be very simple, safe and effective over many years and large numbers of patients, when performed properly according to established protocols with safe, accurate and reliable tourniquet instruments and cuffs that have been thoroughly tested prior to use. [3-6] However, IVRA is not without risk. [1-2] Risks may be associated with inherent safety limitations of tourniquet instruments and tourniquet cuffs not specifically designed for IVRA, with failures of tourniquet instruments and cuffs during use, and with incomplete testing of instruments and cuffs prior to use. Those risks increase with non-standard protocols and with staff having limited training and experience with IVRA.  Some reports of IVRA-related injuries, hazards and their causes are given in the reference and citations below [1-7].
In the past, injuries associated with IVRA have been reported, eg . The deaths involved a combination of an agent no longer recommended for IVRA, failure of tourniquet instruments and cuffs and human error. Hazards associated with IVRA can include failure to establish limb anesthesia, complete or partial loss of limb anesthesia, the sudden release of a bolus of anesthetic agent into systemic circulation, venous congestion and the loss of a clear surgical field.
Safe IVRA requires the use of advanced tourniquet systems, including both tourniquet cuffs and instruments, which are reliable, accurate, safe and effective [3, 4, 6]. Some notable and unique improvements which have added considerable value and safety to modern tourniquet instruments and cuffs for IVRA include:
Tourniquet instruments having two completely independent channels for independent, accurate and reliable control of the tourniquet pressure in each bladder of a tourniquet cuff used for IVRA. This is especially important when individual bladders are being selectively depressurized, pressurized and regulated during IVRA.
Variable-contour dual-bladder tourniquet cuffs, in which the cuff shape matches patient-specific limb shapes from proximal edge to distal edge beneath each of the dual bladders, improving the uniform and reliable application of tourniquet pressure from each bladder to the underlying limb. Such cuffs include additional features to improve safety in IVRA, such as dual independent fasteners to help prevent sudden cuff detachment and release, positive locking connectors and improved gas passageways within the cuffs.
Automatic measurement of Limb Occlusion Pressure (LOP) embedded in some tourniquet instruments, so that patient-specific tourniquet pressures can be accurately determined or checked (for each bladder of a dual-bladder cuff), for each surgical procedure, limb location, limb shape, and technique of cuff application.
IVRA safety lockout embedded in some tourniquet instruments, to help prevent staff from inadvertently and unintentionally deflating both bladders of a dual-bladder cuff during a procedure, thereby helping prevent the hazard of a sudden and unanticipated loss of IVRA.
Automatic cuff testing capability embedded in some tourniquet instruments, to allow staff to quickly, automatically and thoroughly test tourniquet cuffs, according to recommended practices, prior to use in IVRA and especially after any cleaning or reprocessing. 
Automatic cuff leak detection embedded in some tourniquet instruments, to detect leaking cuffs, connectors and tubing during use and to identify them to users after each procedure, thereby helping to prevent their hazardous use in subsequent IVRA procedures.
References and Citations
 ECRI, Pneumatic Tourniquets Used for Regional Anesthesia: Hazard. Health Devices Dec 1982;12(2):48-9 www.mdsr.ecri.org/summary/detail.aspx?doc_id=8080
 www.tourniquets.org – McEwen JA, Educational website focused on surgical tourniquets, and related tourniquets for military and emergency applications, including tourniquet safety and usage.
 http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/search.cfm – MAUDE – Manufacturer and User Facility Device Experience, US Food and Drug Administration
 http://www.aorn.org/PracticeResources/AORNStandardsAndRecommendedPractices/EDocuments/ AORN, Recommended Practices for the Use of the Pneumatic Tourniquet, 2009.