Related Clues:

• Operating room substance, once
• A real knockout?
• Anesthetic of yore
• Knockout stuff
• Rarefied air
• Early anesthesia
• Certain anesthetic
• Flammable anesthetic
• Old knockout cause
• Preoperative anesthetic of old
• Chloroform kin
• Kin of chloroform
• Knockout gas
• Early surgery aid
• Standard anesthetic, once