Background Prior to the development of effective local anaesthesia, even minor surgical procedures involved the significant risks of inhalational general anaesthesia. In the early 20th century, local anaesthetic techniques were unreliable, not widely known and restricted to limited small nerve blocks. In 1908, German surgeon August Bier described a method of producing whole limb anaesthesia through vascular isolation and intravenous administration of local anaesthetic – a technique now known as intravenous regional anaesthesia (IVRA). Technique Informed by his pioneering work in spinal anaesthesia in 1898, Bier’s block involves the exsanguination of a limb, application of a tourniquet, and intravenous injection of local anaesthetic, originally a dilute cocaine solution, into the isolated vascular compartment. Anaesthesia is rapid, dense, and reversible, resolving predictably with tourniquet release. It provides theoretically indefinite anaesthesia as there is no drug metabolism or washout as long as the tourniquet remains applied – however, functionally the onset of tourniquet pain limits the procedure to approximately 20-40 minutes. Historical and clinical significance In a time when both general and local anaesthesia had significant risks, Bier’s innovative technique provided a simple, effect and low-risk anaesthesia for extremity surgery. It did not demand additional expertise beyond establishing intravenous access, and maintained relevance despite the nerve blocks in the early 1900s, which remained limited by issues of neurovascular injury and need for a high level of operator skill. Until the widespread implementation of ultrasound guidance in the early 2000s, Bier’s block remained an effective and accessible option, especially in resource- or expertise-poor settings. Conclusion More than a century after its introduction, Bier’s block endures as both a practical technique and a historical marker of cross-disciplinary innovation beyond the surgical skillset.