Which of the hallucinogens has never been used as a medical anesthetic?

LSD. The real danger of hallucinogens is not their toxicity but their unpredictability. People have had such varied reactions to these substances, especially to LSD, that it is virtually impossible to predict the effect a hallucinogen will have on any given individual. Effects depend upon the person's mood, surroundings, personality, and expectations when taking the drug.