The Japanese surgeon who performed the world's first general anesthesia in 1804

Health · Published 3 October 2026 Swipe more like this →

In short: Long before Western medicine mastered painless surgery, Hanaoka Seishū developed a potent herbal anesthetic called tsūsensan. In 1804, he successfully performed a mastectomy on a patient rendered unconscious by his concoction. Despite his revolutionary success, Japan's isolationist policies kept his pioneering work hidden from the global medical community for decades.

Hanaoka Seishū, a surgeon born in 1760 in Japan's Wakayama prefecture, spent years attempting to recreate a legendary anesthetic potion known as mafeisan, attributed to the 2nd-century Chinese surgeon Hua Tuo. Hanaoka’s research was deeply personal and perilous; his wife volunteered for his experiments, eventually losing her sight due to the toxic side effects of the developing formula. By 1785, he began his systematic quest to synthesize a compound that could induce deep unconsciousness and muscle paralysis.

The resulting formula, tsūsensan, was a complex mixture of botanical extracts, including Datura stramonium, Aconitum, and Angelica sinensis. When boiled and consumed, the drink rendered patients insensitive to pain for hours. On October 13, 1804, Hanaoka utilized this anesthetic to perform a partial mastectomy on Kan Aiya, a 60-year-old woman. This event is widely considered the first reliable documentation of a surgery performed under general anesthesia, predating similar Western advancements by nearly forty years.

Hanaoka’s influence extended beyond anesthesia; he was a prolific surgeon who treated conditions ranging from bladder stones to malignant tumors, performing over 150 breast cancer surgeries before his death in 1835. He trained numerous students and documented his cases in detailed, hand-copied manuscripts. However, because Japan was under the Sakoku isolation policy, his techniques remained largely unknown to the outside world until after 1854. By the time his work reached the West, modern anesthesia had already been independently developed, leaving Hanaoka’s legacy as a brilliant, isolated milestone in medical history.

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