Fasting Before Surgery Often Overdone
Study finds many doctors ignore loosened guidelines
MONDAY, May 6, 2002 (HealthDayNews) -- Despite revised guidelines that say you don't have to fast for 12 hours before surgery, many doctors still tell their patients to go without food or drink for that long before an operation.
That's what a new study has discovered, and the researchers note that sticking with such a tough regimen may be more than unpleasant; it could also be unhealthy.
A report in the May issue of the American Journal of Nursing found that among 155 patients interviewed following surgery, almost half had been told to stop taking liquids for at least 12 hours before their surgery and three-quarters had not eaten food for 12 hours or more. In addition, one patient had nothing to drink for as long as 20 hours and two patients went without food for 37 hours.
However, under American Society of Anesthesiology guidelines published in 1999, such prolonged fasting is just not necessary.
The guidelines permit the intake of clear liquids, such as black coffee, tea, apple juice or carbonated beverages, up to two hours before elective surgery; a light breakfast six hours before the procedure; and a heavier meal if the surgery is eight hours away.
The reason doctors want patients to have empty stomachs before surgery is to lower the risk of a potentially serious complication called pulmonary aspiration.
Pulmonary aspiration is not pretty -- and it can in fact be deadly. According to Dr. Mark T. Warner, chairman of anesthesiology at the Mayo Clinic, something about being under general anesthesia can cause patients to regurgitate -- where the contents of the stomach go up into the esophagus and trachea.
Because the patient is under the general anesthesia, the contents of the stomach don't come out of the patient's mouth, but are drawn back down into the lungs.
"The patient's body can't respond to the regurgitation, they can't close their vocal chords to stop the contents from going back into their lungs," Warner explains. "This can cause severe damage to the lungs and complications such as pneumonia, and people can die from this."
For those who have to undergo emergency surgery with a potentially full stomach, the risk is a significant concern. However, Warner says in scheduled surgeries on healthy people, the risk is relatively low -- only about one in 3,500.
For years, hospitals used the so-called "NPO after midnight" policy (nil per os, Latin for "nothing by mouth"), to prevent pulmonary aspiration, but the new guidelines, drawn from the bulk of literature on risks, deemed that policy outdated three years ago.
Still, many doctors err on the side of caution.
However, having less stringent fasting policies isn't just a matter of comfort, says study author Jeannette Crenshaw, a family education coordinator at Presbyterian Hospital of Dallas.
In fact, clear fluids can reduce the amount of acid in the stomach, which is another concern with pulmonary aspiration, she says.
"The more acid that's in the stomach, the more damage it can do to the lungs if the patient aspirates," Crenshaw explains. "But without fluids, you have these acids just sitting in your stomach, and there's plenty of research showing that clear fluids lower that acid content by diluting it."
Furthermore, she says, fluids are typically gone from the stomach within 45 minutes, so even the two-hour policy is conservative.
Considering that looser fasting guidelines are possibly even safer than strict fasting, the issue of patient discomfort becomes an even more important factor, Crenshaw says.
"Some will say, 'So, they're a little hungry, but it's just one day,' but there are more adverse effects from prolonged fasting than just hunger and thirst," Crenshaw says. "Prolonged fasting is associated with headaches, irritability, hypoglycemia, dehydration and other problems."
Not everyone can follow the looser fasting rules, however. Patients with particular conditions that slow or prevent gastric emptying or who have other problematic conditions may require tighter fasting guidelines.
Yet, with safety issues for most other cases resolved with the revised guidelines, Crenshaw says fasting all night is unnecessary and unfair to most healthy patients.
"As a nurse, what's important to me is I don't want patients going through these discomforts unless I can tell them it's safer, and the research just doesn't support that it's safer," she says.
What To Do
You can read the ASA guidelines for a better understanding of Preoperative Fasting Procedures.
And you can learn much more about what awaits you during surgery with Anesthesia and You from the American Society of Anesthesiology.