How Does Anesthesia Work?

Anesthesia is a modern miracle with a very long history. Aside from the convenience of not having to feel pain, it allows doctors to perform life-saving surgeries. If you’ve ever had surgery, you may recall being asked to count down from 10 and not being able to get past five or six. That unique mix of drugs administered by a doctor was anesthesia. It not only induces unconsciousness but also prevents movement. Imagine a heart surgeon trying to tinker with your arteries while you were twitching. It’s a recipe for disaster. But how exactly does this medicine work? It’s time to talk about one of the most familiar yet least understood elements of modern medicine.

Advertisement

A Little History

Anesthetics are as old as civilization itself. Documents from ancient cultures mention local anesthetics such as opium poppy and alcohol. While not as sophisticated as modern methods, getting drunk will reduce pain in a pinch. A large portion of the history of anesthetics involves accidents. People would use a drug for one purpose and discover that it reduced pain in the process. Take alcohol, for instance; people noticed that they felt less pain while drunk, so they would get drunk before having to undergo something painful.

We also have more modern examples. Ether was a common anesthetic for hundreds of years, but it was first used as a recreational drug. Doctors noticed that people wouldn’t notice some injuries while under the influence of ether and began using it to numb pain. Cocaine also has a long history as an anesthetic and was discovered to have numbing properties when a scientist accidentally got some on his tongue.

As you may have noticed, these examples feature fairly dangerous substances: opium, alcohol, and cocaine. Anesthesiologists (doctors who administer anesthesia) no longer use these substances. Instead, compounds were created that have the same properties without all the negative effects. The process of discovering and refining technology is a key piece of anesthesia’s success story.

The Basics

Your body transmits pain signals via the nervous system. Without nerves carrying electrical signals through your body, you wouldn’t even know what pain was. Understandably enough, anesthesia works by interfering with your body’s ability to transmit pain signals, but it can also do much more.

There are three basic types of anesthesia: local, inhalation, and intravenous. Local anesthetics block signals from your body’s nervous system in a single place. When local anesthetics are in use, you likely aren’t having major surgery. That’s because major surgery requires doctors to do some things that otherwise would be exceptionally painful. In these cases, they need you not only unable to feel anything in a particular area but also unable to move. Inhalation or intravenous anesthesia accomplishes that.

Both inhalation and intravenous anesthetics are whole-body anesthetics. In other words, they prevent your brain from processing pain from any part of your body rather than from a single area. Inhalation anesthesia is inhaled, and intravenous anesthesia is injected into the bloodstream. Anesthesiologists usually combine multiple types of anesthesia to get the mixture just right. They have to tailor the mixture of drugs so that you lose consciousness, don’t move, and feel no pain, all without causing other problems such as your heart slowing down too much or your brain being unable to process more basic signals.

The Science Behind It All

Given all of that, how does it work? Your brain is made up of a network of cells called neurons. These neurons are separated from each other by little gaps called synapses. Anesthesia works by getting into neurons and synapses and preventing chemical signals from taking the correct path.

Different drugs accomplish this by blocking different chemicals at different points. Some anesthetics bind to proteins in the cell membranes of neurons, which allows a lot of negatively charged particles to enter. A huge part of successful transmission is keeping the right balance of positive and negative chemicals, which are called ions. Letting a lot of one type of ion or another will prevent neurons from successfully communicating with one another, thus preventing pain from registering.

New research from scientists at the Okinawa Institute of Science and Technology Graduate University has demonstrated how general anesthetics (the most commonly used kind for putting people to sleep during surgery) work. They studied the effects of a drug called isoflurane. What they found helped researchers understand just how anesthesia allows doctors to induce an immobile, unconscious state free from pain without stopping more basic bodily functions.

They discovered that the drug hinders brain signals in two ways. First, it interrupts the flow of ions in cells, which is critical to the transmission of brain signals. When enough ions build up in a neuron, it releases a batch of chemicals called neurotransmitters into a synapse. Neighboring neurons detect these chemicals and release their own into the next synapses. This chain reaction is how information travels throughout the brain. By hampering the flow of ions, not enough of them build up to cause a release of neurotransmitters.

The second way that isoflurane impedes signal transmission is by traveling into the synapse itself. Here, the chemical binds to areas where the packet of neurotransmitters would normally release. Have you ever seen a cartoon firehose that comically bulges near the spout right before it shoots out a flood of water? Something similar happens to the parts of neurons that are about to release neurotransmitters. Scientists discovered that, as the surface area increases, isoflurane can bind to more and more areas and thus prevent the firehose from ever releasing, so to speak.

These two mechanisms combined are enough to create all the side effects of anesthesia, but without negative consequences. Because isoflurane affects very active processes, ones that cause lots of ions to enter the cell or cause lots of neurotransmitters to be released, more inactive processes are relatively unaffected. In other words, things your body doesn’t need much brainpower to do (such as cause your heart to beat or your lungs to inflate) are not stopped by the anesthetic. It gives us the best of both worlds.

Wrapping It Up

Without the balance between activity and inactivity, anesthesia would be useless. Thankfully, experts can strike that balance quite well. Operating on patients who can’t move and don’t feel pain has allowed doctors to create new and better surgeries for hundreds of years. Incisions have gotten smaller, and outcomes have gotten better because doctors didn’t have to worry about patients kicking and screaming while they were trying to operate. If you like all that modern medicine has to offer, you can thank anesthetics. Without them, we’d all face a lot more pain.