If you’re feeling anxious about having surgery with anesthesia, consider the alternative. If you were having the same surgery 200 years ago, your only option for dealing with the pain would have been to down some whisky and grit your teeth.

Now, every day about 60,000 patients undergo all types of surgery and other medical procedures with the help of these pain-relieving drugs, according to the National Institutes of Health. There’s no doubt that anesthesia — whether inhaled as a gas or injected into your bloodstream by a highly trained doctor, dentist, or nurse anesthetist — has enabled millions of people to receive medical treatments that lead to longer and healthier lives. That said, there are some things about anesthesia that may surprise you.

1. People Who Smoke May Need More Anesthesia Than Nonsmokers

Anesthesiologists have long noticed that smokers often need extra anesthesia. And now experts are starting to confirm this: Preliminary research presented at the 2015 European Society of Anaesthesiology meeting in Berlin found that women who smoked needed 33 percent more anesthesia during their operation than female nonsmokers and those exposed to secondhand smoke needed 20 percent more. Another finding? Both of the smoking groups needed more painkiller medication after the surgery.

Smokers have irritated airways, explains John Reynolds, MD, an associate professor of anesthesiology at Wake Forest School of Medicine in Winston-Salem, North Carolina. As a result, they may need higher doses of pain medication to improve their tolerance with the breathing tubes, he says.

Interestingly, people who smoke or ingest marijuana (cannabis) on a daily or weekly basis may need more than twice the usual level of anesthesia for routine procedures, such as endoscopies, a study published in May 2019 in The Journal of the American Osteopathic Association found.

If you know ahead of time that you’re going to be undergoing surgery, quitting smoking even just a few days beforehand can help reduce your risk of complications and help you heal, according to a review published in the journal Anesthesiology.

2. Anesthesia Doesn’t Always Put You to Sleep

According to the Cleveland Clinic:

Local anesthesia only numbs a small area of the body to prevent pain during a procedure like having a tooth pulled, getting stitches for a deep cut, or having a mole removed.
Regional anesthesia suppresses pain and movement in a larger area of the body, but leaves you fully conscious and able to talk and answer questions. An epidural given during childbirth is one example.
General anesthesia affects the whole body, making you unconscious and unable to move. It's typically used for major and time-consuming operations. In smaller doses, general anesthesia medication can be used to induce something called “twilight sleep,” a less powerful type of anesthesia that sedates you so that you are sleepy, relaxed, and unlikely to move or know what’s going on.

3. It’s Possible to Wake Up During Surgery

But it’s also extremely rare, occurring in only 1 or 2 of every 1,000 medical procedures involving general anesthesia, according to the American Society of Anesthesiologists (ASA). This condition, called “anesthesia awareness,” occurs when a patient becomes aware of their surroundings and of events occurring during the surgery. Such awakenings are usually brief and patients usually do not feel pain. Anesthesia awareness can be more common in high-risk patients who have multiple medical conditions, or those who are being treated for an emergency, in which the usual dose of anesthesia cannot be safely given.

4. Being Heavy Can Increase Your Risk of Complications

It’s harder for anesthesiologists to provide the best dose of medication and deliver that medication intravenously to patients who are significantly overweight, according to the ASA. In addition, obesity increases the risk of sleep apnea, a condition that causes frequent pauses in breathing. This can make ensuring you get enough oxygen and airflow, especially during general anesthesia, more difficult. Losing weight before surgery can decrease the risk of complications.

5. Doctors Are Finding Different Ways That Anesthesia Can Work

Back when anesthetics had just become part of routine surgery, doctors who administered them knew very little about how they worked, according to the National Institute of General Medical Sciences (NIGMS). Today, it’s believed that anesthetics disrupt nerve signals by targeting specific protein molecules inside nerve cell membranes. As scientists continue to learn more about anesthesia, these drugs will only become more effective, says the NIGMS.

6. Redheads Don’t Need More Anesthesia Than Anyone Else

This is “a widely spread urban myth in the anesthetic community,” says Timothy Harwood, MD, the section head of outpatient anesthesia at Wake Forest Baptist Health. What prompted the idea is that people with red hair are likely to have a gene called melanocortin-1 receptor (MC1R), which was thought to decrease a person’s sensitivity to anesthetics, Dr. Harwood explains. But that idea didn’t hold up under further scrutiny: A study published in the journal Anaesthesia and Intensive Care found no difference in how much general anesthesia was required, the speed of recovery, or the amount of postoperative pain between patients with red hair or darker hair.

7. You Might Want to Try Aromatherapy When You Wake Up

Certain scents haves been shown to help quell the nausea and vomiting that often occurs after anesthesia. One study, published in the February 2019 in the journal Complementary Therapies in Medicine, found that inhaling ginger or lavender essential oils for five minutes lessened the severity of those symptoms better than a placebo. Similarly, an earlier study published in the journal Anesthesia & Analgesia concluded that patients who took three deep breaths while covering their nose with a gauze pad saturated with ginger essential oil, or a combination of ginger, spearmint, peppermint, and cardamom essential oils, felt less queasy after their procedure and requested fewer drugs to treat their nausea.

8. Anesthesia May Affect Your Memory

General anesthesia may cause memory loss that can last for days, even months, according to a University of Toronto Faculty of Medicine study published in November 2014 in the Journal of Clinical Investigation. As the researchers explain, about 37 percent of young adults, and 41 percent of elderly patients, report having postoperative memory problems upon discharge from the hospital. Some of this memory loss may be due to factors other than anesthesia, such as inflammation or stress triggered by the surgery. But some is likely due to anesthesia’s effect of memory-loss receptors in the brain.

What’s more, a more recent Mayo Clinic study, published in the August 2018 issue of the British Journal of Anesthesia, suggested that exposure to anesthesia can trigger enough of a decline in brain function to unmask hidden preexisting memory problems in patients over age 70.

Bottom line: Whatever your age, write down your doctor’s instructions after having general anesthesia, or bring a close friend or family member with you who can vouch for the accuracy of what you heard.

8 Surprising Facts About Anesthesia