EXPERTS contacted by New 杏吧原创 say that most mainstream anaesthetics or nerve agents could never be used to end a siege involving hostages.
The only true anaesthetic gas is nitrous oxide, better known as laughing gas. To knock people out, troops would have had to surreptitiously pump a huge volume of nitrous oxide into the Moscow theatre, enough to displace almost two-thirds of the air inside it. 鈥淭he concept of suddenly replacing all that air is a non-starter,鈥� says Peter Hutton, president of Britain鈥檚 Royal College of Anaesthetists.
Nor would mainstream surgical anaesthetics such as halothane, isoflurane, desflurane and sevoflurane have worked, even though they have an effect at far lower concentrations 鈥� around 4 or 5 per cent. All are liquids that have to be vaporised and added to air during anaesthesia but they all smell and take time to get people even partially asleep, says Hutton.
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A further problem is that such anaesthetics bind only temporarily to nerve receptors and need to be continually replenished to keep a patient unconscious.
Neither do nerve agents such as sarin appear up to the job. German chemists discovered the first nerve agent, called tabun, in 1936 while developing organophosphorus pesticides. Later versions include soman, VX and sarin, the gas used in 1995 by the Japanese Aum Shinrikyo sect to poison commuters on the Tokyo subway.
All these chemicals interfere with the nervous system by blocking acetyl cholinesterase, an enzyme that recycles the neurotransmitter acetylcholine. As a result, acetylcholine overstimulates receptors on muscle cells, which can ultimately cause people to stop breathing. Some of the fatalities and casualties among the theatre victims certainly appeared to be suffocating, says Hutton. But it can take tens of minutes to absorb nerve agents through the lungs or skin, too slow to have had the immediate effect seen in Moscow this week.
One widely touted knockout gas is a derivative of BZ, the 鈥渟uperhallucinogen鈥� developed in the 1950s by the US military. BZ, which has the chemical name 3-quinuclidinyl benzilate, acts both on the central nervous system and through the parasympathetic nervous system, which means it affects organs such as the eyes, heart, lungs, skin, gut and bladder. Like atropine, to which it is chemically related, it sets the heart racing and blocks sweating and salivating. It also produces a dreamlike delirium, and stuns people by painfully dilating the pupils of the eyes. As little as 0.05 milligrams of BZ can cause these effects, but it takes around an hour to work and like atropine it can kill.
One compound capable of incapacitating within seconds is trimethyl fentanyl, a fast-acting anaesthetic that is injected or given orally in medical emergencies. The US Navy is funding the development of fentanyl compounds at Pennsylvania State University, says Christopher Holstege, assistant professor of emergency medicine at the University of Virginia鈥檚 Blue Ridge Poison Center. The chemical acts in a similar way to heroin, blocking opioid receptors and instantly slowing the heartbeat. Patients become confused, then rapidly fall asleep. An aerosol form could work as fast as aerosolised Valium, which can knock people out within 18 seconds (Epilepsy, vol 35, p 356). Without the antidote, called naloxone, people eventually go into a coma, stop breathing and die. In contrast, says Holstege, BZ would produce confused, hallucinating survivors.