Practice Guidelines for Preoperative Fasting: Reply

We thank Dr. Gupta for his letter to the editor¹  advocating for the need to update the American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting.^2,3 

The 2023 modular update of these guidelines had a limited focus, specific goals, and did not address specific procedures or named solutions, such as colonoscopy bowel preparation protocols or solutions.²  The Task Force was keen on presenting the available evidence in terms of principles and broad terms (e.g., carbohydrate-containing clear liquids) allowing clinicians’ judgments and individualization of care. In the same vein, the recommendations apply only to normal healthy patients undergoing elective procedures, because there is very limited research in patients that are at higher risk of aspiration of gastric contents.^2,3  We support clinicians’ judgments, individualization of care to the patient at hand for a specific procedure, with consideration of the content and quantity of consumed food or fluids preoperatively in light of the guidance provided by the guidelines.

As Dr. Gupta alluded to his letter, having an excellent quality of the bowel preparation so that the colonoscopy is successful is a major concern for endoscopists, as well as patients who are undergoing colonoscopy procedures.⁴  It is believed that the quality of the bowel preparation is primarily determined by the timing of ingestion of the solution.⁵  Use of split preparation with colonoscopy 2 to 6 h after ingestion of the solution generally leads to better colonoscopy conditions.^5,6  Different hospitals and endoscopy centers serve different patient populations and varying morbidities and use a large variety of different bowel preparation protocols and solutions. Hence, there is considerable variability in locally applied fasting practices as Dr. Gupta described.¹ 

There are a few points for anesthesiologists to consider when they make their medical judgment decisions:

1. While aspiration of gastric contents has been reported during colonoscopy,⁷  closed claims studies suggest that most serious aspirations occur in the presence of gastric or bowel obstruction or an acute abdominal process that causes ileus, not during routine colonoscopy.⁸ 

2. There are many kinds of bowel preparation solutions (some are clear, and some may contain particulate matter). Investigations are still ongoing to determine which solution and which protocol, especially the quantity and timing aspects of administration, will produce the best results. Some commonly used bowel preparation solutions (e.g., polyethylene glycol), contain additives such as different electrolytes.^9,10 

3. Large volumes (2 to 4 L) of administered polyethylene glycol solutions have a higher frequency of causing nausea, vomiting, and bloating, but are associated with a lower risk of dizziness and electrolyte abnormalities compared to sodium phosphate bowel preparation solution.¹⁰ 

4. Emerging evidence suggests that in patients who had their split bowel preparation with a portion administered in the morning of the procedure (that proved to yield a higher quality colonoscopy), their gastric residual volume and pH did not differ compared to those who received their preparation solution the night before the procedure.¹¹ 

Additional details concerning colonoscopy preparation solutions are well summarized in an editorial by Bhavani and Abdelmalak.¹² 

In conclusion, we recommend that the anesthesiologists use judgment in assessing whether the ASA guidelines pertain to each individual patient, consideration of patient comorbidities, and consideration of the type and content or characteristics, timing, and volume of the bowel preparation consumed before colonoscopy, because one size does not fit all.

The authors declare no competing interests.