Making Colonoscopies More Effective and Comfortable At The Same Time

Stanford R. Plavin, MD
Coalition Board
Vice Chairperson

Colorectal cancer is the third most commonly diagnosed cancer in the United States, resulting in the second highest rate of cancer-related mortality.1 Routine screening of asymptomatic adults has been shown to significantly reduce the number of colorectal cancer related deaths, with early-stage detection associated with a 5-year survival rate of 90%.

Bowel preparation is a major deterrent for patients undergoing screening colonoscopy.2 Poor bowel preparation compromises diagnostic accuracy of colonoscopy by reducing the visibility of the mucosa, resulting in increased procedural risks and the potential for missed diagnoses.

In an effort to establish best practices to enhance the quality of bowel preparations, the revised guidelines from the American College of Gastroenterology (ACG) recommend splitting the dose of the purgative by administering one dose the evening before colonoscopy and one dose the morning of the procedure (PM/AM split-dose).3 This regimen not only improves the efficacy of bowel preparation compared with the conventional regimen of administering the entire purgative the evening before colonoscopy, but it is also more tolerable for patients.4,5

One concern to the PM/AM split-dosing regimen is the result of a misunderstanding among many anesthesiologists that patients undergoing anesthesia should not eat or consume liquids (nothing by mouth) after midnight the day before their procedure. Specifically, anesthesiologists are concerned that the second purgative dose of a split-dose regimen violates the American Society of Anesthesiologists (ASA) guidelines.6 General anesthesia and deeper levels of sedation tend to suppress the protective airway and cough reflexes, thus anesthesiologists are concerned about the risk of aspiration of gastric contents into the respiratory tract during colonoscopy. Patients with disorders that cause delayed emptying of the esophagus or stomach may require longer periods of fasting as these patients may have an increased risk of aspiration. For patients without these disorders, the risk of aspiration during anesthesia is extremely rare. A study demonstrated the rate of aspiration in anesthetized patients as approximately 1 in 8671.6 Furthermore, ASA guidelines support a minimum fasting period of 2 hours for clear liquids and 6 hours for light meals prior to sedation, which allows patients to remain well hydrated.7

A PM/AM split-dosing regimen will not breach these guidelines if the second dose is completed no less than 2 hours before colonoscopy.8 Preoperative dehydration is a greater safety concern than drinking clear liquids before sedation, especially in patients who have undergone bowel preparation. In conclusion, PM/AM split dosing does not violate the ASA NPO guidelines for patients undergoing sedation and does not increase the risk of aspiration during colonoscopy. Also, following the PM/AM dosing guidelines will result in substantially improved visualization of the bowel mucosa by the physician performing the colonoscopy.

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