Just one bottle can be deadly

When the central nervous system is heavily depressed from alcohol, breathing can stop, causing death. Photo / Herald on Sunday

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The reflex that makes many people vomit if they overdose on alcohol can be a lifesaver.

Those who don't have this safety mechanism are at risk of death, as a large overdose will quickly cause their blood-alcohol level to soar.

"After a large volume of alcohol is consumed, especially spirits, one of the most common scenarios is that it doesn't get past the stomach," toxicologist Dr Allan Stowell said yesterday.

"A high concentration of alcohol tends to irritate the stomach," said Dr Stowell, of the Institute of Environmental & Scientific Research.

"The stomach closes off and causes the person to vomit. It's a safety mechanism. Many people are alive today because of that safety mechanism."

Otherwise, a large volume of alcohol passes into the intestine, where most of it is absorbed.

From the intestine it rapidly starts being absorbed into the bloodstream, which sends it to all parts of the body, critically to the brain.

The main risks are through depression of the central nervous system. The person can become sleepy or might collapse into deep unconsciousness.

When the central nervous system is heavily depressed from alcohol, breathing can stop, causing death, because the nerves involved stop functioning adequately.

But more commonly the person vomits and inhales, causing asphyxiation, or chokes on their tongue.

Very rarely, alcohol overdose can cause a fatal abnormal heart rhythm.

Toxicologist Dr Michael Beasley, of the National Poisons Centre at Otago University, said drinking 400ml of pure alcohol could be enough to kill someone who didn't usually drink, although there was wide variability depending on a person's weight, age and gender.

A heavy drinker could tolerate more than a light drinker. One litre of vodka with 40 per cent alcohol content would contain 400ml.

In other drinks, the deadly dose would be in about 23 440ml cans of beer at 4 per cent or four bottles of 13 per cent strength wine.

The medical treatment for a heavy overdose usually involves protecting the airways. This entails putting a moderately unconscious patient on their side and observing them.

The deeply unconscious may need to have a breathing tube inserted down the windpipe and be connected to a breathing machine.

Dr Beasley said acidosis of the blood could occur and was usually managed with fluid replacement, glucose and thiamine. In severe cases haemodialysis was used, especially if the blood-alcohol level was very high.

The Alcohol Advisory Council says the way to treat someone who has drunk an overdose is to put them in the recovery position and make sure they are breathing and their mouth is empty. If they are not breathing, start CPR and call an ambulance.

Auckland City Hospital intensive care specialist, Dr Les Galler, said if someone seemed to be sleeping after an overdose, it was important to check they were not in a coma.

"I would call an ambulance if the patient was unconscious."

Lethal dose:

* 23 cans of beer

* Four bottles of wine

* One litre of neat vodka