Bier's breakthrough in spinal anaesthesia was made in 1898 when he performed the first planned spinal anaesthetic on a series of 6 patients for lower extremity surgery. Each of them received a spinal dose of cocaine and did well except for having nausea, vomiting and headache afterwards. After this series, Dr. Bier was to receive a spinal anesthetic administered by his assistant, one Dr. Hildebrandt. Unfortunately, although the spinal needle was placed correctly, with spinal fluid flowing freely from it, the syringe was only then discovered to not fit the needle. As a result, Dr Bier gained first-hand knowledge of the unpleasant post-spinal headache. Dr Hildebrandt instead became the recipient of the spinal anaesthetic which was achieved using cocaine. After the injection, Dr Hildebrandt's legs became numb and the two celebrated their success with wine and cigars. The profound analgesia of his legs was demonstrated with repeated kicks to his shins, which however, soon regained their sensation.
In 1908 he pioneered the use of intravenous procaine analgesia. Anesthesiologists still use the term Bier block for intravenous regional anaesthesia, where a local anaesthetic, usually Lidocaine, is injected into a vein in a limb below a tourniquet which is at a high enough pressure to trap the anaesthetic.
Bier's well-known quote is: "Medical scientists are nice people, but you should not let them treat you!"