Banishing consciousness: How anaesthesia works

What is the purpose of anaesthesia in surgery?

When surgery used to be done without anaesthesia, the types of operations were limited, and pain was a big issue. The purpose of anaesthesia is to relieve pain and the only way out of this was using analgesics - a pain relief agent. Around 1844, general anaesthesia came into play using nitrous oxide, chloroform and ether. Chloroform and ether alter a patient’s consciousness and put them to sleep while nitrous oxide has pain-relieving properties.

How has the administration of anaesthesia changed over the years?

Today, we do what is called balanced anaesthesia. It has four components: sleep (hypnosis), pain relief (analgesic), muscle relaxing (key for surgeries in the chest area, abdomen or any long operation), and reflexes.  The amount or degree of the four components will depend with the surgery but the most important is pain relief.

What are the different types or techniques of anaesthesia?

General anaesthesia, where the patient falls asleep completely, is the most known. Spinal anaesthesia where the medicine is injected between specific vertebrae of the spine is used mostly in child delivery; it paralyses the body from the waist down. Epidural anaesthesia also works the same way but the medicine targets nerves. There is also regional anaesthesia where a specific area of the body is made numb through a nerve block.

Who or what dictates the type of anaesthesia to be used?

The type of procedure dictates this but again depending on the procedure, it can be the patient’s choice and the anaesthetist has to respect the patient’s choice which is done within the confines of informed consent. In each situation you have to tailor the medicine, you may have the same procedure on different patients but you use different techniques, to get a good outcome.

How does age influence administration of anaesthesia?

For older patients, you have to look at the geriatric component of the anaesthesia technique. Post-operation you have to monitor them closely as they tend to get more delirious. This population may have comorbidities like hypertension and diabetes so they are likely to be on other medications. If you find a patient on multiple medication, you have to adjust the medicine. Children are not small adults, at least in our world. That is why we have the paediatric field in anaesthesia. You might use the same medicine used in older patients, but the way they react is different. It is not all about titrating and deciding that since children weigh less, then they require less dosage. As a rule, we discuss with the parents and obtain consent on the technique to be used.

Does weighing more mean a higher dosage of anaesthesia?

Not necessarily, but it depends if the medicine is lipid soluble. Most anaesthesia we use target the muscles and prescription is per kilogramme but within ranges like 0 to 12 kg and so on.

Some of the medication used in anaesthesia are controlled substances. How do you handle a patient with history of drug use?

We have to get their history to know what adjustments to make like what drug, how long ago they used it and if they were put on drug addiction medication. Some of them may have been on methadone so they will have a challenge with pain relief.

 Is there specific information you seek from patients before the surgery?

 Since we use quite a number of drugs in anaesthesia, we have to ask the patients if:

·       They have any allergies and underlying conditions.

·       If they are on herbal medication. These can affect how the anaesthesia works and may cause more bleeding so we have to get the history of the patient and plan our anaesthesia appropriately.

·       For comorbidities, we inquire about the conditions and the medication they use. We can even consult a specialist on the specific disease to give insight on optimisation of anaesthesia.

 Which comorbidity is so challenging when administering anaesthesia?

Hypertension is a major challenge. An anaesthetist should ensure the patient’s blood pressure is stable before and throughout the procedure. If I have two patients both with 160/100 blood pressure –one on hypertensive treatment and the other without similar history – it is wise to operate on the one on treatment. The one not on treatment would have unstable blood pressure during the surgery, which is unfavourable.

There are also procedures that will require the anaesthesiologist to lower blood pressure or even body temperature to lower chances of complications.

How do you handle an emergency case, like accident, that requires lifesaving surgery and the patient cannot give a history of comorbidities or consent on the technique used?

The surgery will still be done but since there is no history, the anaesthetist has to monitor the patient’s vitals during the procedure and even after. If the sugar level change, medicine should be administered to stabilise same as the blood pressure.

What are the most critical moments in anaesthesia?

This is during induction and reversal. Complications usually arise during these two phases. There is a lot of time- keeping to be observed; like when to intubate (insert a tube in trachea) the patient, or extubate (remove the tube). For example, before you extubate, the patient needs to have regained muscle movement, or they may not be able to breath on their own. That is why though minimum safe oxygen saturation is 95 per cent, we boost the patients to 100 per cent during induction and reversal for safety.

How long should it take for a patient to wake up after the surgery? Does the length of the surgery dictate?

There is no time limit. Once you switch off the medicine (anaesthesia) the patient starts waking up.  As the surgeon is stitching, the anaesthetist is also titrating the anaesthesia down so that by the time the surgeon is done, the patient is almost awake. Unlike the past, today we have newer medicines where a patient can wake up minutes after the surgery. In the past, patients used to take long to regain consciousness because the medicines used were not so friendly and we had no control over that so it was normal for a surgery to end at 10 am and by 4pm the patient is still not awake. Today, a patient can wake up five to 10 minutes after the surgery.

Are there cases where patients delay waking up after surgery?

You can have delayed reversal where the patient takes longer to wake up. In such cases, troubleshooting is done to find out the cause. For example, if it was a neurosurgery procedure then maybe the patient might have bled inside the brain and a computerised tomography (CT) scan will be done to determine the cause.

Are anaesthetists only required during surgeries?

We have other responsibilities apart from theatre. We administer medicines for radiotherapy procedures, and are also involved in sedation and transport or management of patients in intensive care.