Anesthesia is a treatment that prevents patients from feeling pain during procedures like surgery, medical tests, and dental work. Anesthesiologists are doctors who have been specifically trained to give medicines used for anesthesia, which are called anesthetics.

Depending on the procedure they’re having, patients receive different types of anesthesia:

If you’ve ever had a surgery or even a minor procedure, you’ve probably benefited from the medical marvel of anesthesia—the treatment that doctors, called anesthesiologists, give to keep you from feeling pain. And it’s come a long way since the discovery of diethyl ether. Here we dive into the different types, its history, and the way it works.

NIGMS and Scholastic bring you Pathways: The Anesthesia Issue, which explores pain and the science behind anesthesia—the medical treatment that prevents patients from feeling pain during surgery and other procedures. Without anesthesia, many life-saving medical procedures would be impossible.

Pathways, designed for students in grades 6 through 12, aims to build awareness of basic biomedical science and its importance to health, while inspiring careers in research. All materials in the collection are available online and are free for parents, educators, and students nationwide.

How do you measure pain? A patient’s furrowed brow, a child’s cries or tears—all are signs of pain. But what if the patient suffers from severe dementia and can’t describe what she is feeling or is a young child who can’t yet talk? Caregivers can help read the signs of pain, but their interpretations may differ greatly from patient to patient, because people have different ways of showing discomfort. And when the patient is unconscious, such as during surgery or while in intensive care, the caregiving team has even fewer ways to measure pain.

Assessing pain is an inexact science. It includes both subjective and objective measures. A patient might be asked during a subjective assessment (performed, perhaps, with a caregiver showing a pain-rating scale such as the one in the figure), “How much pain are you feeling today?” That feedback is coupled with biological markers such as an increased heart rate, dilated pupils, sweating, and inflammation as well as blood tests to monitor high levels of the stress hormone cortisol. Combined, these measurements can give doctors a fairly clear picture of how much pain a patient feels.

But imagine if members of the surgical or caregiving team could actually “see” how the patient is feeling? Such insight would let them select better drugs to use during and after surgery, tailoring care to each patient. That tool could be put into service in the operating room and by the bedside in intensive care, giving nonstop reports of pain as the patient experiences it.

An objective measure of pain also has uses beyond the operating room and intensive care unit. Given the high risk for opioid misuse, such a measure could take the guesswork out of pain management and give doctors a more accurate indication of pain levels to prevent over-prescribing opioid pain relievers.

When Margaret Sedensky, now of Seattle Children’s Research Institute, started as an anesthesiology resident, she wasn’t entirely clear on how anesthetics worked. “I didn’t know, but I figured someone did,” she says. “I asked the senior resident. I asked the attending. I asked the chair. Nobody knew.” For many years, doctors called general anesthetics a “modern mystery.” Even though they safely administered anesthetics to millions of Americans, they didn’t know exactly how the drugs produced the different states of general anesthesia. These states include unconsciousness, immobility, analgesia (lack of pain) and amnesia (lack of memory). Understanding anesthetics has been challenging for a number of reasons. Unlike many drugs that act on a limited number of proteins in the body, anesthetics interact with seemingly countless proteins and other molecules. Additionally, some anesthesiologists believe that anesthetics may work through a number of different molecular pathways. This means no single molecular target may be required for an anesthetic to work, or no single molecular target can do the job without the help of others. “It’s like a symphony,” says Roderic Eckenhoff of the University of Pennsylvania Perelman School of Medicine, who has studied anesthesia for decades. “Each molecular target is an instrument, and you need all of them to produce Beethoven’s 5th.”

If you’re a fan of the reality TV show Shark Tank, you tune in to watch aspiring entrepreneurs present their ideas and try to get one of the investors to help develop and market the products. Afterward, you might start to think about what you could invent. Maureen L. Mulvihill has never watched the show, but she lives it every day. She is co-founder, president and CEO of Actuated Medical, Inc. (AMI), a Pennsylvania-based company that develops specialized medical devices. The devices include a system for unclogging feeding tubes, motors that assist MRI-related procedures and needles that gently draw blood. AMI’s products rely on the same motion-control technologies that allow a quartz watch to keep time, a microphone to project sound and even a telescope to focus on a distant object in a sky. In general, the devices are portable, affordable and unobtrusive, making them appealing to doctors and patients. Mulvihill, who’s trained in an area of engineering called materials science, says, “I’m really focused on how to translate technologies into ways that help people.”

Anesthetic drugs are vital to modern medicine, allowing patients to undergo even the longest and most invasive surgeries without consciousness or pain. Unfortunately, studies have raised the concern that exposing patients, particularly children and the elderly, to some anesthetics may increase risk of long-term cognitive and behavioral issues.

A scientific team led by Hugh Hemmings of Weill Cornell Medical College and Shelley Halpain of the University of California, San Diego, examined the effects of anesthesia on neurons isolated from juvenile rats. Given at doses and durations frequently used during surgery, the commonly administered general anesthetic isoflurane did in fact reduce the number and size of important structures within neurons called dendritic spines. Dendritic spines help pass information from neuron to neuron, and disruption of these structures can be associated with dysfunction in thinking and behavior.

Promisingly, the shrinkage observed by the researchers appeared to be temporary: After the researchers washed the anesthetic out of the cell cultures, the dendritic spines grew back. But because neurons in culture do not reproduce all aspects of intact neuronal networks, the scientists explain that the findings should be verified in more complex models. Other molecular mechanisms may also potentially contribute to late effects of anesthesia exposure.

This work also was funded by NIH’s National Institute of Mental Health.

Learn more:
University of California, San Diego News Release
Understanding Anesthesia from Inside Life Science