“Why do I have to stop eating and drinking prior to surgery?” This is a common question I hear from my patients—they’re puzzled by the connection between going to sleep and avoiding eating after midnight the day prior to surgery.
It’s vital that your stomach is empty prior to elective surgery and anesthesia. Once you’re anesthetized, your cough reflex and gag reflex are abolished. These reflexes prevent food or liquids from entering your windpipe or your lungs, and are life-protecting reflexes in awake, healthy humans.
Under anesthesia these reflexes are absent. If you vomit or regurgitate stomach contents into your mouth, the material can descend into your windpipe or lungs. The complication of stomach contents entering your lungs is a dire event. The medical term for this occurrence is aspiration pneumonia. Aspiration refers to inhaling, and pneumonia refers to an inflammation of the lung tissue. In severe aspiration pneumonia, the lungs fail to exchange oxygen from the airways into the bloodstream, and brain and heart oxygen levels can drop to life-threatening lows.
The American Society of Anesthesiologists guidelines for fasting prior to elective surgery requiring general anesthesia, regional anesthesia, or conscious sedation/analgesia are as follows:
Fried or fatty foods 8 hours
A light meal (toast and clear liquids) 6 hours
Non-human milk 6 hours
Breast milk 4 hours
Infant formula 4 hours
Clear liquids 2 hours
Clear liquids may be consumed up to 2 hours prior to anesthesia. Clear liquids include water, fruit juices without pulp, soda beverages, Gatorade, black coffee or clear tea. Milk and thick juices with pulp are not clear liquids.
These fasting guidelines do not apply to surgical procedures under local anesthesia, or to those with no anesthesia. You don’t have to fast for a dentist office visit, for example. The guidelines do apply for colonoscopies or upper gastrointestinal endoscopy procedures. The intravenous sedation drugs used for endoscopy procedures may sedate you to a deep enough level such that your gag and cough reflexes are absent.
In certain conditions, the stomach will be considered to be full even if the patient has not eaten or consumed fluids for eight hours. Acute pain syndromes such as appendicitis, a gall bladder attack, a broken bone, or a febrile illness are known to diminish the stomach’s emptying, and anesthesiologists treat these patients as if they had a full stomach whether they’ve fasted or not. Pregnant women and morbidly obese patients are also treated as having full stomachs for any surgery, because of delayed stomach emptying due to increased intra-abdominal pressure.
If a patient presents for emergency surgery, the anesthesiologist must proceed without waiting for the recommended fasting times. On induction of general anesthesia, the physician anesthesiologist will have a second individual (a nurse or a physician) apply downward pressure on the cricoid cartilage of the patient’s neck immediately upon loss of consciousness. The science of this is as follows: the circumferential ring of the cricoid cartilage encircles the windpipe.
Pushing downward on this ring compresses the esophagus below, to prevent passive regurgitation or vomiting of stomach contents. This pressing-down maneuver is called “giving cricoid pressure” or “the Sellick Maneuver,” named after Dr. Brian Arthur Sellick, the anesthesiologist who first described the maneuver in 1961. Inducing anesthesia using the Sellick maneuver is referred to as a Rapid Sequence Induction (RSI) of general anesthesia. In a RSI the anesthesiologist administers into the patient’s intravenous line: 1) a hypnotic drug such as propofol, followed by 2) a rapid paralyzing drug such as succinylcholine. The endotracheal breathing tube can then be placed in the windpipe within about 30 seconds after the loss of consciousness. The Sellick maneuver is held throughout those 30 seconds until medical confirmation that the tube is in the windpipe.
If stomach contents enter the upper airway at any time during an induction of anesthesia, the anesthesiologist will see vomitus in the patient’s mouth or inside the clear plastic facemask. The anesthesiologist may also detect evidence of inadequate oxygen exchange—i.e. the patient’s pulse oximeter readings will decline to less than the safe level of 90%. The anesthesiologist will then suction the upper airway and place a breathing tube into the windpipe as soon as possible. This tube is called an endotracheal tube, and it has a balloon near its tip. When inflated, the balloon protects stomach contents from descending into the lungs.
The anesthesiologist will then suction out the lungs through the inside the breathing tube. Suction catheters of varying length and diameters exist for this purpose. The surgery will likely be cancelled if it has not yet started. If the aspiration of stomach contents occurs in the middle of surgery, it’s likely the surgery will be aborted or shortened.
As I have written in multiple posts on this website, all critical care medicine resuscitation follows the A-B-C mantra of Airway—Breathing—Circulation. The regurgitation of stomach contents interferes with both A and B by blocking the airway and interfering with breathing.
The medical term for fasting prior to surgery is NPO, which stands for “nil per os,” a Latin phrase for nothing per mouth. If you hear your doctor or nurse say, “Is she NPO?” they’re asking the important question of whether you have fasted as required. Being NPO may seem inconvenient and unnecessary, but it’s critical to assure your health and well being during anesthesia.
Reference: Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures An Updated Report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters, 2011; Anesthesiology, Vol 14(3), 495-511.
Introducing …, THE DOCTOR AND MR. DYLAN, Dr. Novak’s debut novel, a legal mystery. Publication date September 9, 2014 by Pegasus Books.
On October 2, 2014 THE DOCTOR AND MR. DYLAN became the world’s #1 bestselling anesthesia Kindle book on Amazon.com.
The first four chapters are available for free at Amazon. Read them and you’ll be hooked! To reach the Amazon webpage, click on the book image below:
In this debut thriller, tragedies strike an anesthesiologist as he tries to start a new life with his son.
Dr. Nico Antone, an anesthesiologist at Stanford University, is married to Alexandra, a high-powered real estate agent obsessed with money. Their son, Johnny, an 11th-grader with immense potential, struggles to get the grades he’ll need to attend an Ivy League college. After a screaming match with Alexandra, Nico moves himself and Johnny from Palo Alto, California, to his frozen childhood home of Hibbing, Minnesota. The move should help Johnny improve his grades and thus seem more attractive to universities, but Nico loves the freedom from his wife, too. Hibbing also happens to be the hometown of music icon Bob Dylan. Joining the hospital staff, Nico runs afoul of a grouchy nurse anesthetist calling himself Bobby Dylan, who plays Dylan songs twice a week in a bar called Heaven’s Door. As Nico and Johnny settle in, their lives turn around; they even start dating the gorgeous mother/daughter pair of Lena and Echo Johnson. However, when Johnny accidentally impregnates Echo, the lives of the Hibbing transplants start to implode. In true page-turner fashion, first-time novelist Novak gets started by killing soulless Alexandra, which accelerates the downfall of his underdog protagonist now accused of murder. Dialogue is pitch-perfect, and the insults hurled between Nico and his wife are as hilarious as they are hurtful: “Are you my husband, Nico? Or my dependent?” The author’s medical expertise proves central to the plot, and there are a few grisly moments, as when “dark blood percolated” from a patient’s nostrils “like coffee grounds.” Bob Dylan details add quirkiness to what might otherwise be a chilly revenge tale; we’re told, for instance, that Dylan taught “every singer with a less-than-perfect voice…how to sneer and twist off syllables.” Courtroom scenes toward the end crackle with energy, though one scene involving a snowmobile ties up a certain plot thread too neatly. By the end, Nico has rolled with a great many punches.
Nuanced characterization and crafty details help this debut soar.