the inferior roots of the plexus. for supraclavicular block, nerve stimulation with a minimal threshold of 0.9 ma can offer a dependable block. although ultrasound-guided supraclavicular block has been shown to be a safe alternative to the peripheral nerve stimulator guided technique, there is little evidence to support that ultrasound guidance provides a better block, or is associated with fewer complications. there is some evidence to suggest that the use of ultrasound guidance in combination with nerve stimulation can shorten the performance time of supraclavicular block. for axillary block, success rates are greatly improved with multiple injection techniques whether using nerve stimulation or ultrasound guidance. special situations the duration of a "single-shot" brachial plexus block is highly variable, commonly lasting anywhere from 45 minutes to 24 hours. the block can be extended by placing an indwelling catheter, which may be connected to a mechanical or electronic infusion pump for continuous administration of local anesthetic solution. a catheter may be inserted at the interscalene, supraclavicular, infraclavicular or axillary location, depending on the desired location of nerve block. specific branches of the brachial plexus can also be blocked individually, for example the suprascapular nerve. the infusion of local anesthetic can be programmed to be a continuous flow or patient-controlled analgesia. in some cases, people can maintain the catheters and infusions at home after release from the facility where the surgery was performed. complications as with any procedure involving disruption of the integrity of the skin, brachial plexus block can be associated with infection or bleeding. in people who are using anticoagulant agents, there is a greater risk of complications related to bleeding. complications associated with brachial plexus block include intra-arterial or intravenous injection, which can lead to local anesthetic toxicity. this may be characterized by serious central nervous system problems such as epileptic seizure, central nervous system depression, and coma. cardiovascular effects of local anesthetic toxicity include slowing of the heart rate and impairment of its ability to pump blood through the circulatory system, which may lead to circulatory collapse. in severe cases, cardiac dysrhythmia, cardiac arrest and death may occur. other rare but serious complications from brachial plexus block include pneumothorax and persistent paresis of the phrenic nerve. complications associated with interscalene and supraclavicular blocks include inadvertent subarachnoid or epidural injection of local anesthetic, which can result in respiratory failure. because of the close proximity of the lung to the brachial plexus at the level of the clavicle, the complication most often associated with this block is pneumothorax — with a risk as high as 6.1%. further complications of supraclavicular block include subclavian artery puncture, and spread of local anesthetic to cause paresis of the stellate ganglion, the phrenic nerve and recurrent laryngeal nerve. alternatives depending on the circumstances, alternatives to brachial plexus block may include general anesthesia, monitored anesthesia care, bier block, or local anesthesia. history in 1855, friedrich gaedcke (1828–1890) became the first to chemically isolate cocaine, the most potent alkaloid of the coca plant. gaedcke named the compound "erythroxyline". in 1884, austrian ophthalmologist karl koller (1857–1944) instilled a 2% solution of cocaine into his own eye and tested its effectiveness as a local anesthetic by pricking the eye with needles. his findings were presented a few weeks later at annual conference of the heidelberg ophthalmological society. the following year, william halsted (1852–1922) performed the first brachial plexus block. using a surgical approach in the neck, halsted applied cocaine to the brachial plexus. in january 1900, harvey cushing (1869–1939) — who was at that time one of halsted's surgical residents — applied cocaine to the brachial plexus prior to dividing it, during a forequarter amputation for sarcoma. the first percutaneous supraclavicular block was performed in 1911 by german surgeon diedrich kulenkampff (1880–1967). just as his older colleague august bier (1861–1949) had done with spinal anesthesia in 1898, kulenkampff subjected himself to the supraclavicular block. later that year, georg hirschel (1875–1963) described a percutaneous approach to the brachial plexus from the axilla. in 1928, kulenkampff and persky published their experiences with a thousand blocks without apparent major complications. they described their technique with the patient in the sitting position or in the supine position with a pillow between the shoulders. the needle was inserted above the midpoint of the clavicle where the pulse of the subclavian artery could be felt and it was directed medially toward the second or third thoracic spinous process. by the late 1940s, clinical experience with brachial plexus block in both peacetime and wartime surgery was extensive, and new approaches to this technique began to be described. for example, in 1946, f. paul ansbro was the first to describe a continuous brachial plexus block technique. he secured a needle in the supraclavicular fossa and attached tubing connected to a syringe through which he could inject incremental doses of local anesthetic. the subclavian perivascular block was first described by winnie and collins in 1964. this approach became popular due to its lower risk of pneumothorax compared to the traditional kulenkampff approach. the infraclavicular approach was first developed by raj. in 1977, selander described a technique for continuous brachial plexus block using an intravenous catheter secured in the axilla.