Presenter: Katie Marrero MD, MA | Carle Foundation Hospital Background: The use of gastric acid suppressing medications after surgery for gastrointestinal cancers varies widely among surgical oncologists. Recent literature suggests that, in at least some patient populations, the use of these medications is associated with significant adverse effects, including an increase in soft tissue infections, colitis, pneumonia, acute kidney injury and malabsorption. However, gastrointestinal surgical oncology patients have never been specifically studied and the impact of post-operative acid suppression in this patient group is generally unknown. We compared the incidences of post-operative morbidity including infection and organ dysfunction in upper GI cancer patients who were prescribed acid suppressing medications versus those who were not. Methods: The records of all patients who underwent surgical oncologic intervention for gastric, liver, small bowel, biliary or pancreatic cancers over a 10-year period at a fully integrated, university affiliated, tertiary referral center were assessed. Using administrative data available through the hospital’s electronic health record, we stratified patients according to those who did and did not receive acid suppressing medication during their postoperative inpatient course. Outcome measures included post-operative fever, infection, AKI, pancreatitis, liver failure and pneumonia. Preoperative comorbidities were equal in both groups. However, the group receiving acid suppression did have a longer mean length of stay and were more frequently in the ICU. Results: Eighty-eight patients who underwent a gastric, liver, small bowel, biliary or pancreatic oncologic surgery between 2008 and 2018 were included. Of these 88 patients, 64 received acid suppressing medication during the postoperative period, while 24 patients did not receive any acid suppressing medication. We compared patients who were prescribed acid suppressing medication with those who were not prescribed these medications: 66% percent vs. 21 % experienced post-operative infections (p = 0.000) and 41% vs 13 % experienced acute kidney injury (p =0.012). The incidence of pancreatitis, liver failure, pneumonia and fever did not occur at significantly different rates in the two groups (Table 1). There was no statistically significant difference between groups in having a history of cardiovascular disease, chronic kidney disease, diabetes mellitus, liver disease, gastro-esophageal reflux disease, Barrett’s esophagus, H. pylori colonization, alcohol use or inflammatory bowel disease. Conclusion: While previous studies on acid suppressing agents’ effects on patients have been done, these studies have largely excluded a critical and vulnerable patient group- surgical oncology patients. We found that those patients receiving acid suppressing medications during the perioperative period had higher rates of all post-operative complications with statistically significant differences in infections and AKIs. This begs to wonder if these agents alter the patient’s ability to heal in this critical post-operative time period. While other patient factors may play a role in these outcomes, the effects of acid suppression cannot be overlooked as a mitigating factor in these events. Thus, it questions the necessity for acid suppressing agents in all surgical oncology patients. Having specific and strict criteria for which patient may benefit from these medications may help to eliminate some of the deleterious outcomes that are likely associated with these medications.