I read with interest the recent article on preoperative fasting for patients undergoing surgery with anesthesia. As a practicing anesthesiologist, this is a topic of great concern. I was surprised the author didn't explicitly mention that pulmonary aspiration can be fatal, even when the aspirated material is only a liquid of high acidity.
Accordingly, an anesthesiologist's first duty is to prevent this dreaded complication, even if the patient may be uncomfortable while fasting after midnight. Gastric emptying times may be short in normal patients, but many conditions may delay such emptying. For patients who must wait until the afternoon for their surgery, an IV infusion may be started. Patients scheduled for surgery later in the day may have a light breakfast.
The American Society of Anesthesiologists (ASA) recommendations on the issue of fasting before surgery, which are not labeled standards, are interesting but don't necessarily represent the standard of care. Also, to my knowledge, well-conducted randomized, double-blind studies haven't been undertaken to evaluate the incidence of aspiration in patients who followed NPO-after-midnight instructions versus those who were allowed to eat and drink near the time of surgery.
Finally, I have doubts about the author's statement that it's a myth that clear liquids ingested up to two hours before surgery increase the risk of aspiration. Why bet a patient's life on it?
Author Jeannette T. Crenshaw responds: Based on expert opinion and the results of multiple studies (including randomized controlled trials and meta-analyses of these), the ASA recommended a minimum fast of two hours from clear liquids for healthy patients of all ages receiving general, regional, or monitored anesthesia care for elective procedures.1, 2 The ASA specified when the guidelines may need to be modified or may not apply. Although practice guidelines may not represent local standards of care, they are strong recommendations based on carefully evaluated evidence and expert consensus. Adhering to them may reduce clinical variation from the best available evidence, improve quality of care, and reduce malpractice liability.3
Although certain conditions may delay gastric emptying of solids (obesity, diabetes with gastroparesis, use of narcotics), there are no data suggesting that patients with these conditions are at greater risk for pulmonary aspiration when clear liquids are consumed up to two hours before surgery. In fact, patients who consume clear liquids up to two to four hours prior to surgery have been found to have lower gastric volumes and similar or higher pH values compared with healthy patients who fast more than four hours.4–9
What puzzles me is why we're still debating preoperative fasting and the consumption of clear liquids. In addition to recommending clear liquids until a few hours before surgery, international practice guidelines recommend the routine use of oral carbohydrate-rich clear beverages two to three hours before surgery in most patients.10, 11 Referred to as carbohydrate loading, this can reduce the patient's discomfort, including preoperative thirst and anxiety and postoperative nausea and vomiting. It also reduces several of the potentially dangerous results of preoperative fasting, such as postoperative insulin resistance and diminished immune response.
The reference list for this letter can be found at http://links.lww.com/AJN/A31.
For more letters from AJN readers, go to http://links.lww.com/AJN/A32.
Mitchel B. Sosis, MD, PhD
Lafayette Hill, PA