Introduction The basic principle of enteral nutrition - if the gut is in use, use it. The small amounts of nutrients and water in the intestinal lumen can prevent intestinal mucosal atrophy, whereby the permeability of the intestinal barrier. This prevents bacterial translocation and endotoxemia, which may be the initiator of multisectoral organ failure. All of these underlying reasons for enteral feeding include cardiac surgery patient, hemodynamically stable with a functioning gastrointestinal tract. It is advisable to start enteral nutrition administration within 48h after surgical procedure. Objective The aim of the study is to determine the effect of sedation on constipation in postoperative cardiac surgical patients in the intensive care unit. This is also examined in the study the risk of diarrhea as a result of providing early enteral nutrition compared to late enteral nutrition in a postoperative cardiac surgical patient. The objective of this study is to compare the different enteral nutrition formulas - Fresubin energy drink and Nepro HP, which may reduce diarrhea in the postoperative cardiac surgical patient. Patients and methods A retrospective cohort study was conducted on 24 (18 men and 6 women) postoperative cardiac surgical patients initiated on enteral nutrition support during their stay in the Intensive Care Unit /University Hospital Rijeka/, from January 1st to December 31st, 2017. Inclusion criteria for participation in the study were cardiovascular patients requiring cardiac surgery cardiovascular disease. The electronic database of the integrated hospital information system (IBIS) was used in all the patients involved in the study. Results The results of the study show that sedated cardiac surgical patients do not have more constipation than untreated cardiac surgical patients. Cardiac surgical patients with early enteral nutrition do not have more frequent diarrhea than those with late enteral nutrition. Cardiac surgical patients with Fresubin energy drink enteral nutrition have rarely diarrhea than those with enteral nutrition on the Nepro HP. Conclusions Based on the results obtained, this study found that sedated cardiac surgical patients have no more constipation than untreated cardiac surgical patients. Patients with early enteral nutrition do not have more frequent diarrhea than those with late enteral nutrition. Cardiac surgical patients with Fresubin energy drink enteral nutrition are less likely to have diarrhea than patients who are fed with Nepro HP, but in hyperosmolar preparations, it is possible that diarrhea is a side effect. Due to the small sample, and the time constraints, the statistical views do not have the desired strength.