Fasting before anesthesia: 4 myths, busted

If you’ve ever been under anesthesia or are expecting to receive anesthesia before surgery or another procedure, you may have been told not to eat or drink anything for a certain amount of time before your appointment. This fasting period is commonly called NPO, an abbreviation for the Latin phrase “nils per os” or “nothing by mouth.” 

This precaution is a safety measure used to ensure patients don’t aspirate – or inhale – stomach contents while they’re sedated. 

“When you’re awake and you get sick, you can sit up and turn your head to cough up stomach contents, but under anesthesia, you won’t be able to do that,” says Shannon Popovich, M.D., medical director of MD Anderson’s Perioperative Evaluation and Management Center.  

She breaks down the truth behind four myths about fasting before anesthesia and explains why it’s important for patients with cancer to stick to these guidelines for safe, effective treatment. 

Myth 1: You only need to fast if you’re having surgery.

Facts: When you think of anesthesia you may associate it with surgery, but other procedures may require sedation, and NPO. MRI, colonoscopy, bronchoscopy, and even some dental procedures are done under some type of anesthesia. 

“Any time a patient is receiving anesthesia, they’ll be asked to fast for a certain amount of time,” Popovich says. 

Guidelines from the American Society of Anesthesiology determine how long you’ll be asked to fast, depending on your procedure, medical history and your diagnosis.

Myth 2: You can’t have anything to drink before anesthesia.  

Facts: Despite the literal meaning, NPO doesn’t always mean you can’t eat or drink anything. In fact, patients are usually encouraged to drink clear liquids up to two hours before receiving anesthesia. 

“Clear liquids can help keep patients well-hydrated and stable enough to undergo necessary cancer treatments,” Popovich says.

These include water, black coffee or tea, pulp-free juices, certain energy drinks, gelatin and even clear broth like chicken or beef broth. It usually takes less than 2 hours for these items to leave your stomach and not be an aspiration risk.

“The rule of thumb is liquids you can read a newspaper through,” Popovich says, “Although, of course, alcohol is not included in this list.” 

She adds that patients should avoid any red food coloring ahead of a procedure, as these can linger in your digestive system and look like blood in an emergency. 

Myth 3: You should eat a big meal before your fast

Facts: Patients may worry that they’ll be hungry after fasting, but Popovich says it’s best not to load up on heavy foods right before your fasting period begins. 

Fried, fatty foods typically require at least eight hours to clear your stomach. 

Lighter meals are easier to digest – and easier on your stomach. Especially when you’re having surgery, you’ll want to eat something that will sit well and won’t make you uncomfortable later. 

“Eat something you normally would,” Popovich recommends. “Don’t overdo it for fear of being hungry later.” 

If you think it will be too hard not to eat something before treatment, you can ask your care team if IV fluids are an option to help your body retain electrolytes before anesthesia.

Most of the time, you’ll be able to start eating and drinking again slowly as soon as you’ve woken up from your procedure. 

Myth 4: My care team won’t notice if I have a small snack before my procedure

Facts: Before your appointment, you’ll be asked several times when you last had something to eat or drink. Even if you had a small latte to help you wake up or ate a few crackers to stave off nausea, it’s important that you’re honest with your care team. 

“NPO isn’t a punishment; it’s for your safety,” Popovich says. “Tell the truth if you weren’t able to stick to your fasting orders.” 

Depending on what you’ve had to eat or drink, your care team can delay or reschedule your appointment to make sure you have an empty stomach and can safely receive anesthesia.

Request an appointment at MD Anderson online or by calling 1-855-647-1974.