History of anesthetics 1846 – Ether first demonstrated as a surgical anesthetic. CH 3 CH 2 OCH 2 CH 3
What does an anesthetic drug need to be able to do? Relieve pain (analgesia) Induce memory loss (amnesia) Relax muscles Reduce consciousness (if necessary)
What makes a good anesthetic? Chemical stability Minimal irritation upon inhaling (if gaseous) Rapid and pleasant onset of anesthesia (time to loss of consciousness) Speed and safety of emergence from anesthesia Rapid changes in depth of anesthesia Minimal metabolism Absence of toxic effects in normal doses, especially cardiovascular and respiratory and toxicity to the liver Wide margin of safety
Two types of modern anesthetics Intravenous (drugs used in anesthesia) – Hypnotics (e.g. Etomidate) – Opioids (e.g. Morphine) – Other (e.g. Ketamine) Inhalational (true anesthetics) – Desflurane – Enflurane – Halothane – Isoflurane – NITROUS OXIDE
Synthesis of nitrous oxide Nitrous oxide is commonly prepared by heating solid ammonium nitrate to make water vapor and gaseous nitrous oxide. (a)What type of reaction is this? (b)Write the balanced chemical equation for this reaction. +=
Pros and cons of nitrous oxide as an anesthetic PROS: nonflammable, nonirritating, powerful analgesic agent, rapid onset and recovery (due to low blood/gas solubility), little or no toxicity, not metabolized, ease in regulation of the depth of action CONS: N 2 O is not a strong enough anesthetic for the use in large operations. It is uncomfortable for people who have trouble breathing through their nose. It is also a greenhouse gas with potential to cause global warming when released into the environment (310 times the ability to trap heat in atmosphere than CO 2 ).