Postprocedural pain following colorectal EMR low versus high epinephrine in the submucosal injectate for non-pedunculated colorectal polyps sized 10-20 mm: a randomized controlled trial
This randomized controlled trial demonstrates that using a lower concentration of epinephrine (1:500,000) rather than a higher one (1:200,000) in the submucosal injectate significantly reduces postprocedural pain following endoscopic mucosal resection of 10–20 mm non-pedunculated colorectal polyps without compromising hemostatic efficacy or safety.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every year, doctors perform millions of minor surgical procedures inside the human colon to remove small growths called polyps. These growths are the precursors to colorectal cancer, and removing them is one of the most effective ways to prevent the disease from ever starting. The standard method for removing these polyps, known as endoscopic mucosal resection, involves a delicate balancing act. Before cutting the tissue, the doctor must inject a fluid underneath the polyp to lift it away from the deeper muscle layers of the intestinal wall. This creates a safety cushion that prevents the cutting tool from burning or piercing the colon. To help stop bleeding during the cut, doctors often mix a tiny amount of a powerful blood-vessel-tightening drug, called epinephrine, into that lifting fluid. However, this common practice has a hidden cost: the drug can cause cramping and significant pain for the patient after the procedure is over. For decades, the medical community has debated how much of this drug is actually necessary. Too little might not stop the bleeding, but too much might leave the patient in unnecessary discomfort.
A team of researchers at Shenzhen People's Hospital set out to solve this specific puzzle by testing two different strengths of the drug mixture. They focused on patients with non-pedunculated polyps, which are flat or slightly raised growths measuring between 10 and 20 millimeters in size. In a carefully controlled experiment, they divided patients into two groups. One group received the standard, higher concentration of the drug mixture, while the other received a version that was diluted five times more, making it much weaker. The study was designed so that neither the patients nor the doctors knew which mixture was being used until after the results were analyzed. The primary goal was simple: to see if using the weaker mixture could reduce the pain patients felt thirty and sixty minutes after the procedure, without letting the bleeding get out of control.
The results were clear and immediate. Patients who received the highly diluted mixture reported significantly less pain than those who received the standard mixture. Thirty minutes after the procedure, the group with the weaker drug had a median pain score of 3 on a scale of 0 to 100, while the standard group also had a median of 3, but the distribution of scores showed that the weaker group had far fewer people experiencing higher levels of pain. By the one-hour mark, the difference became even more distinct. The group with the weaker mixture had a median pain score of 1, whereas the standard group remained at 2. More importantly, a large portion of the patients in the weaker group reported feeling no pain at all after an hour, compared to very few in the standard group. This suggests that the stronger concentration of the drug was indeed the cause of the extra discomfort, likely because it constricted blood vessels so tightly that it temporarily reduced blood flow to the area, causing cramping.
Crucially, the researchers found that reducing the strength of the drug did not compromise the safety of the surgery. The rates of bleeding during the procedure were nearly identical between the two groups, with only a tiny, statistically insignificant difference. Similarly, the rates of bleeding that occurred after the procedure were exactly the same in both groups. The success of the surgery, measured by whether the polyps were removed completely and cleanly, was also the same for everyone. The study confirmed that the weaker mixture provided the same protection against bleeding as the stronger one, but without the painful side effects. Statistical analysis further revealed that the strength of the drug and the total volume of fluid injected were the main factors driving the pain, rather than the size of the polyp or how long the surgery took.
This finding offers a straightforward, cost-free improvement for a very common medical procedure. By simply diluting the drug mixture five times more than usual, doctors can significantly improve the comfort of their patients without increasing the risk of complications. The study was limited to polyps of a specific size and was conducted at a single center with experienced specialists, so the results may not apply to every single case, but for the typical 10 to 20 millimeter growth, the evidence is strong. The researchers concluded that using this lower concentration is a practical way to make the recovery from colon polyp removal much more pleasant, proving that sometimes, less is truly more when it comes to medical treatment.
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