Using sleeping gas on Seth makes sense when you realize overdosing on anesthetic is just as lethal as poison and the tube wasn't properly sealed, and thus a lethal dose might have become a survivable one.
Last screen appearance of Hoyt Axton (1938-1999)
Pat Morita goes up against a giant Cobra, he previously fought against a Karate dojo that was called Cobra Kai in the Karate Kid franchise.
The snake's name could be a reference to the Egyptian God, Seth, who was associated with the Serpent. His primary color that he was known for was the color Red, like the cobra in this film.