Laughing gas users risk spinal damage

By MARTIN JOHNSTON health reporter

Heavy users of laughing gas risk damaging their spinal cords, doctors warn, after they found it was commonly inhaled by Auckland University students.

Dentists and doctors give laughing gas - nitrous oxide - as an anaesthetic, but it also has a long history of recreational inhalation and is used to whip cream and make cars faster.

Middlemore Hospital registrar Dr Jennifer Ng and colleagues surveyed first-year university students and found 12 per cent had used the drug "recreationally". Three per cent inhaled it at least monthly.

The figures, published in the Lancet British medical journal, are based on questionnaires completed by 1360 students last year.

The students bought the gas from hardware shops and supermarkets - in the form of small metal "bulbs" that release their gas into canisters to whip cream - and at a "nitrous club" on the campus.

The usual amount inhaled in a session was two to five bulbs, but regular users inhaled more than 10.

A kitchenware shop yesterday quoted $12.50 for a packet of 10 bulbs. Recreational users apparently release a bulb into a canister or similar container, squirting small amounts into a balloon from which they inhale.

The gas produces a momentary giddy euphoria, but can cause hallucinations and disorientation. Some people use it with other drugs such as cannabis.

Dr Ng said regular, heavy users of the gas risked permanent damage to the spinal cord, especially if they were vegetarians, although the problem was easily treated if detected early.

Nitrous oxide deactivates vitamin B12, which is vital for making the sheath that protects the spinal cord. A shortage of the vitamin, more likely in vegetarians, can lead to cord disease.

Dr Ng said Auckland Hospital treated two heavy users last year. One had been inhaling daily for 20 years, using 50 bulbs a day in the six months before seeking help.

He told doctors it was called "nanging" because of the sound distortions heard after inhaling the drug.

The man had tingling in his hands and feet, unsteadiness in walking, constipation and urinary incontinence.

Both patients recovered after treatment with vitamin B12 injections and oral supplements of folate.

Dr Ng said it would be impossible to ban nitrous oxide from sale, but urged limiting the number of bulbs that could be bought at one time to 10, and suggested warnings on the packets.

The Health Ministry said a sales limit would probably be unworkable. The law already banned sales where retailers suspected recreational use.

A staffer on the university student magazine Craccum, who requested anonymity, admitted he had used nitrous oxide occasionally.

"It tends to be quite popular amongst people who get stoned [on cannabis] to mix the nitrous with that," said the 25-year-old.

"I never have, but apparently it's quite interesting. Apparently it lasts longer and has more of an effect."

He was unaware of the vitamin B12 risk, reflecting the survey finding that 63 per cent of users thought inhaling nitrous oxide was safe.

The researchers said their findings should alert doctors to watch young people for problems caused by the gas.


Gas effects

* Death: Several overseas from suffocation.

* Nausea and vomiting.

* Heavy users risk damage to bone marrow and nervous system.

* Depletion of vitamin B12, which can cause impaired memory and mental function, physical instability, constipation, incontinence. Some symptoms can be permanent if not treated quickly.

* Frostbite and tissue damage from low temperatures if gas inhaled directly from canister.