General Anesthesia Explained: What Really Happens When You're ‘Put Under’

Over the years, I've heard people describe general anesthesia as being knocked out or put to sleep. While these expressions make for good drama, they're not always grounded in fact. So, let’s clear the air about general anesthesia—what it really is, how it works, and what the risks are.

What Is General Anesthesia?

According to the American Society of Anesthesiologists (ASA), general anesthesia is:

"A drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired." [1]

This means that under general anesthesia, you're completely unconscious and unaware. Your body may need help to breathe and keep blood pressure stable, which is why an anesthesia team monitors you closely. Anesthesiologists are trained to "rescue" patients if complications arise.

Types of General Anesthesia

There isn't just one way to perform general anesthesia. Depending on the surgery, patient characteristics, and local practices, the anesthesiologist may choose one of several techniques and from an array of medications. No matter the method, you’ll usually have an IV line placed and be connected to monitors that check your blood pressure, heart rate, oxygen levels, airway gases (like CO2), and temperature.

Here are three common approaches:

• TIVA (Total Intravenous Anesthesia): Both induction and maintenance of anesthesia are done using intravenous drugs.

• Balanced General Anesthesia: Anesthesia is induced with IV drugs, then maintained with inhaled gases like sevoflurane or desflurane.

• Inhalatory Anesthesia: This technique uses inhaled gases for both induction and maintenance. It's almost exclusively used in paediatric cases, where placing an IV line might be tricky at first.

Assessing Risk: It’s Complicated

There’s no one-size-fits-all formula to determine your anesthesia risk. It depends on many factors, such as your medical history, how your airway looks, the type and length of surgery, and even the surgeon's experience. It's also a highly subjective process, relying on the clinical judgment of the anesthesiology team.

To help with decision-making and safety, several tools and scoring systems have been developed. Here is some common risk scores used in day-to-day practice:

• ASA Physical Status Classification (mandatory in most settings and included in the WHO surgical safety checklist)

• The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) risk calculator

• Physiological and Operative Severity Score for enUmeration of Mortality and Morbidity (POSSUM)

These scores help estimate the likelihood of complications and guide discussions with patients and between doctors.

What Are the Real Risks?

Let’s bust a big myth: the risk of dying from anesthesia alone is extremely low (approximately 8.2/1 000 000 hospital discharges) [2]. In fact, it's lower than the odds of a commercial airplane crash. Anesthesia today is safer than ever, thanks to advancements in technology, training, and medications.

Of course, like any medical procedure, general anesthesia carries some risks. These may include nausea, sore throat, confusion (especially in older adults), allergic reactions, or more serious complications in very rare cases. That’s why the pre-anesthesia evaluation is so important.

It’s Not as Scary as You Think

General anesthesia can sound intimidating, but it doesn’t have to be. Anesthesiologists are highly trained medical professionals whose job is to keep you safe and comfortable. If you have concerns, talk to your anesthesiologist. They can walk you through the plan, address your fears, and help you feel more at ease.

So, the next time someone tells you you're being "put under," you can smile knowing there's a whole science (and a team) dedicated to making sure you wake up safely and comfortably on the other side.

References

[1] Statement on Continuum of Depth of Sedation: Definition of General Anesthesia and Levels of Sedation/Analgesia. https://www.asahq.org/standards-and-practice-parameters/statement-on-continuum-of-depth-of-sedation-definition-of-general-anesthesia-and-levels-of-sedation-analgesia

[2] Li G, Warner M, Lang BH, Huang L, Sun LS. Epidemiology of anesthesia-related mortality in the United States, 1999-2005. Anesthesiology. 2009;110:759–765. doi: 10.1097/aln.0b013e31819b5bdc.

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