Anaesthetics

What is anaesthesia?

The word 'anaesthesia' is derived from Greek, meaning 'lack of sensation'. This can be achieved using several methods.

A general anaesthetic renders you unconscious using a combination of drugs, and a local anaesthetic blocks painful sensations from specific areas of the body.

Methods range from:

• Using local anaesthetic cream to numb skin before an injection or blood test
• Injecting local anaesthetic into the area being operated on, blocking nerves that detect sensation from an area, such as a finger or an arm
• Injecting local anaesthetic close to the spinal cord to block large areas of the body, such as the legs or lower abdomen

These methods can also be combined to provide the safest anaesthetic, reduce side-effects and help the surgeons with their task.

Your anaesthetist

An anaesthetist is a doctor who has passed a series of specialist postgraduate exams to become a consultant or senior hospital doctor.

The anaesthetist's main role is to ensure the safety of patients undergoing operations, but you may come across them elsewhere in the hospital.

They run intensive care units, provide epidural pain relief during labour, help babies being delivered by caesareans and are involved in resuscitation in A&E and on wards. They also lead acute pain teams and run chronic pain clinics.

Your anaesthetist and you

Before you go into theatre for an operation, an anaesthetist will visit you and take a detailed medical history. This will help them to identify any risk factors and discuss the most appropriate method of anaesthesia and pain management for you.

They may also prescribe you drugs known as premedication ('premeds'). These can reduce any anxiety, fear, nausea or sickness, or may be more specific to the operation or medical condition you have.

Occasionally, the anaesthetist will have to decide if you're fit enough or suitable for the operation, or if there are any treatments or investigations that would make your procedure safer. For example they may request a chest X-ray, blood test or ECG before they are happy that you are not at greater risk from the anaesthetic or the operation.

After your operation, the anaesthetist's responsible for ensuring you receive adequate pain relief. They'll also treat any nausea and sickness, prescribe fluids and oxygen, and make sure you're stable before you go back to the ward.

How does anaesthesia work?

The ideal general anaesthetic causes a reversible loss of consciousness, keeps the patient still and reduces the body's normal responses to unpleasant stimulation, such as increased blood pressure and heart rate.

There are many different types of drugs that anaesthetists can use to achieve this, including gasses.

Research has shown, broadly speaking, where and how these drugs affect the brain to make a patient unconscious, but many questions remain unanswered.

However, the drugs used by anaesthetists are those with the most predictable, desirable effects and the least unpleasant side-effects.

In contrast, the way in which local anaesthetics block nerves to stop sensation or movement is well understood.

Safety issues

Over the past 30 years, advances in monitoring equipment, newer and safer drugs, and better training and supervision of anaesthetists have led to major improvements in patient safety.

It's difficult to exactly predict a person's risk of dying from an anaesthetic, but for young, fit people with no other medical diseases, between one in 100,000 and one in 500,000 will die from the anaesthetic itself.

Other factors can increase the risk. These include:

• The type of operation - those on the heart, lungs, brain and bowel all carry higher risks
• If the operation is being performed as an emergency
• If the patient has been injured before surgery
• Pre-existing illnesses (such as heart disease or cancer)
• The patient's age
• The anaesthetist will assess all these factors and advise on the most appropriate and safest anaesthetic for each patient

Other complications vary from the very common (affecting about one in ten patients) to rare (one in 10,000) or very rare (one in 1,000,000).

Common complications include:

• Feeling sick
• Shivering
• Sore throat

Less common complications include:

• Postoperative chest infection
• Damage to teeth or lips
• Abrasions to eyes
• Minor damage to nerves

Rare complications include:

• Serious drug reactions or anaphylaxis
• Serious nerve damage
• Being aware during an operation under general anaesthesia
• Awareness under general anaesthesia

Many patients worry that, despite a general anaesthetic, they'll be aware of what's happening during their operation and may even be able to feel pain.

Awareness while under anaesthetic can range from the recall of a conversation to the recognition of being paralysed or the experience of pain.

It can be caused by too little anaesthetic being given, due to poor technique by the anaesthetist or the patient being in an unstable condition. Occasionally, equipment administering the drug may malfunction or the patient may have some resistance to the anaesthetic.

The incidence of awareness is estimated at one in 1,000 general anaesthetics, while awareness with pain is estimated at one in 3,000.

These numbers are falling as advancements in technology mean anaesthetists can monitor the levels of drugs within patients and the effect these are having on their brain.

More information

The Royal College of Anaesthetists produces information for patients and relatives.

Most hospitals also provide patient information leaflets - just ask your doctor.

Dr Patrick Dobbs, a consultant neuroanaesthetist, who also anaesthetises patients for colorectal and gynaecological surgery wrote this article in March 2007.