What happens if you eat just before surgery?


Eating before surgery is a controversial topic. Many doctors instruct patients not to eat or drink anything for 8-12 hours before surgery. However, current research shows the rules around eating before surgery may be more flexible than once thought. Here’s an overview of the concerns around eating before surgery and what the research shows about how long you need to fast for before different types of surgeries.

Why Doctors Recommend Fasting Before Surgery

Doctors typically recommend not eating or drinking anything, including water, for 6-8 hours before surgery. This fasting period is referred to as “NPO guidelines” which stands for nil per os or nothing by mouth.

Here are the main reasons why fasting is recommended before surgery:

Avoid Aspiration

When you eat or drink before surgery, food and liquid can remain in your stomach during the procedure. General anesthesia used for surgery causes the muscles that move food through your digestive tract to relax. This includes the muscles that prevent food and stomach acid from coming back up your esophagus.

As a result, when under anesthesia, you are at risk of pulmonary aspiration. This is when stomach contents leak up from the stomach and into the lungs. Aspiration can cause serious complications like:

– Pneumonia
– Respiratory failure
– Acute lung injury
– Death (in rare cases)

By fasting before surgery, your stomach is empty and the risk of pulmonary aspiration is practically zero.

Reduce Vomiting Risk

Along with anesthesia, pain medications given during and after surgery can also slow digestion. This makes vomiting more likely.

Vomiting while under anesthesia is extremely dangerous because stomach contents could get inhaled into the lungs. Fasting helps reduce the urge to vomit during and after surgery.

Help Absorb Anesthesia

Eating before surgery can also interfere with absorbing anesthesia during surgery. Anesthetics are most effective when they can be absorbed directly into the bloodstream. Food in the stomach can prevent proper absorption of anesthesia.

This could lead to you waking up during surgery or the anesthesia wearing off too soon after surgery. Proper fasting helps anesthesia be absorbed efficiently so you stay fully unconscious during the operation.

Potential to Relax Fasting Rules Before Surgery

While the risks of pulmonary aspiration and issues with anesthesia absorption are real, some research suggests the guidelines around fasting before surgery may be longer than necessary.

The traditional NPO guidelines instruct patients not to eat or drink anything, including water, for 8 to 12 hours before surgery. However, several studies have found that certain types of fluids and light foods may be safely consumed up to 2 to 4 hours before surgery.

Water & Clear Fluids May Be Allowed Before Surgery

Water and clear fluids like black coffee or apple juice move through the stomach very quickly. Unlike a heavy meal, these clear liquids are emptied from the stomach within minutes.

Several studies have tested allowing patients to drink water up to 2 hours before surgery compared with traditional fasting from midnight. They found no increase in complications like aspiration pneumonia in the group who drank water before surgery.

Based on this research, the American Society of Anesthesiologists changed their preoperative fasting guidelines in 2017. They now say:

– It’s okay to drink clear liquids up to 2 hours before surgery
– No need to restrict water or clear fluids after midnight unless specifically instructed by your doctor

However, not all surgeons follow these updated guidelines yet. Many still require no water or other fluids starting at midnight before surgery.

Small Snacks May Be Allowed in Some Cases

There’s also some research showing certain types of light, easily digested foods may be safely eaten up to 4-6 hours before surgery.

In one study, patients who ate a light breakfast including toast and clear fluid 4-6 hours before surgery had faster recovery times and fewer complications compared to patients who fasted from midnight.

Another study found that patients who ate a small snack like a granola bar 5 hours before surgery did not have an increased risk of aspiration or issues with anesthesia.

However, most surgeons still recommend avoiding any solid foods for 6-8 hours before surgery. But this research provides hope that the guidelines around eating before surgery may continue to evolve to allow small snacks or light meals in the future.

How Long to Fast Before Specific Surgeries

Here is an overview of the typical fasting recommendations based on your specific surgery type:

Minor Surgery

For minor surgeries like cyst removal or dental procedures:

– No solid foods for 6-8 hours before surgery
– Clear liquids often allowed up to 2-3 hours before surgery

Abdominal, Hernia & Bowel Surgery

For surgeries involving the abdomen, intestines or bowels:

– No solid foods or liquids starting at midnight (12+ hour fast)
– Additional bowel prep may be required like laxatives or enemas

Longer fasting times of up to 24 hours may be recommended to empty the digestive tract and prevent complications like leaks from bowel surgery sites.

Orthopedic Surgery

For surgeries on bones, joints or muscles:

– No solid foods for 6-8 hours before surgery
– Clear liquids may be allowed up to 2 hours before surgery

Shorter fasting times are often allowed because aspiration risks are lower for orthopedic procedures not involving the digestive tract.

Cardiac Surgery

For surgeries on the heart like bypass, angioplasty or valve repair:

– No solid foods after midnight (12+ hours)
– Clear liquids may be allowed up to 3 hours before surgery

Longer fasting times are recommended because heart surgery requires complete anesthesia and has higher risks if aspiration occurs.

Brain Surgery

For neurosurgeries on the brain or spine:

– No solid foods or liquids after midnight (12+ hours)
– Additional bowel prep may be prescribed

Longer fasts are required because neurosurgery requires deeper anesthesia. Vomiting and aspiration risks are also higher because you may have difficulty swallowing after brain or spinal surgery.

Plastic Surgery

For elective cosmetic procedures:

– No solid foods for 6-8 hours before surgery
– Clear liquids are often allowed up to 2 hours before

The more superficial anesthesia used for cosmetic surgery means fasting requirements are often not as strict. But avoiding food and fluids is still important to prevent complications.

Cataract Surgery

For eye procedures like cataract removal:

– No solid foods for 2-4 hours prior
– Small sips of water are allowed up to 1 hour before

Very mild anesthesia is used for eye surgeries. Shorter fasts are recommended because fluids pass rapidly through the stomach.

What if You Eat Before Surgery?

Okay, but what if you accidentally eat something too close to your scheduled surgery? Will they cancel the operation if you break the fasting rules?

In most cases, your surgery will still be able to proceed. The anesthesiologist may recommend adjusting the timing or types of anesthesia given. But eating less than 6-8 hours before surgery does not often cause a need to postpone.

The main risks if you eat before surgery are:

– Increased likelihood of nausea and vomiting
– Higher risk of pulmonary aspiration if contents are still in stomach
– Anesthesia may not work as effectively or wear off sooner

To avoid cancellation, be honest with your doctors if you do eat or drink anything within 8-12 hours of surgery. This allows them to take precautions and adjust anesthesia dosage accordingly.

In some cases, your surgeon may recommend rescheduling if you eat a large, heavy meal too close to the procedure time. This is generally only necessary with intestinal surgeries where emptying the digestive tract is critical.

Tips to Remember Proper Fasting Times Before Surgery

Here are some tips to help make sure you don’t accidentally eat in the restricted time period before your procedure:

– Note the exact time your fasting period begins on your pre-op instructions. This is often midnight morning of surgery.
– Set an alarm on your phone for this fasting start time as a reminder.
– Stick a note on your door or kitchen cabinet with the fasting start time.
– Avoid scheduling early morning surgeries. Afternoon slots allow you to eat breakfast closer to the procedure time.
– Stock up on clear liquids like water, black coffee, and apple juice to drink up until your cutoff time.
– Chew gum during the fasting period to help distract your mind and appetite.
– Follow all instructions from your medical team carefully. Only drink approved fluids within the specified timeframe.
– If you do eat or drink by accident, notify your surgical team immediately before proceeding.

The Bottom Line

Traditionally, patients are instructed not to eat or drink anything after midnight on the night before surgery. However, research shows the guidelines on eating and drinking before surgery may be longer than necessary.

Certain clear fluids and light snacks do not appear to increase complication risks when consumed 2-6 hours before anesthesia. But most surgeons still recommend a 6-8 hour fast from any solid foods before a procedure.

The exact fasting duration required depends on your specific surgery type and the anesthesia methods used. Be sure to follow your doctor’s preoperative instructions exactly. Let your surgical team know immediately if you do accidentally eat or drink closer than advised to your procedure. With proper preparation and precautions, you can proceed safely even if you break the typical fasting rules.

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