Bowel preparation practices have been traditionally practiced before colon surgery for many years. However, meta-analyses published recently have shown that bowel cleansing before colon surgery does not prevent anastomotic leaks, on the contrary, it significantly increases this risk and causes serious fluid electrolyte imbalances, especially in elderly patients. Therefore, bowel cleansing should not be performed except in patients scheduled for intraoperative colonoscopy. Further studies are needed to determine the optimum routine for very low rectal anastomosis. However, if a diverting ostomy is to be created to protect the anastomosis, the distal bowel should be cleaned. Bowel cleansing is contraindicated in major surgeries other than colon surgery.

The practice of stopping the patient's oral solid and liquid food intake starting at midnight before elective surgery (Nil Per Os) was initiated and has been applied until recently in order to reduce the possibility of pulmonary aspiration. However, in recent years, numerous studies have been published proving that this practice causes a decrease in well-being and some metabolic adverse effects, especially postoperative insulin resistance. In addition, a Cochrane review evaluating 22 randomized controlled trials provides solid evidence that reducing the preoperative fasting period for liquids to 2 hours does not increase complications. In light of these studies, preoperative fasting has officially been discontinued in many Northern European countries and the United States. In many countries, anesthesia specialist associations now recommend allowing fluid intake for up to 2 hours before the initiation of anesthesia, as well as a 6-hour fast for solid foods. The current practice is to allow solid foods up to six hours before surgery and clear liquid foods up to two hours before surgery. Patients who will undergo surgery should be given 800 ml of carbohydrate-rich liquid food until midnight before surgery to ensure metabolic satiety, and 400 ml of carbohydrate-rich liquid food 2–3 hours before surgery. This practice has been shown to increase postoperative well-being, reduce insulin resistance, and significantly shorten the length of hospital stay. This practice is at the forefront of what should be done to reduce metabolic stress during the surgical process.

 

Table. Preoperative fasting recommendations of the ‘‘American Society of Anesthesiologists’’

Food	Minimum fasting duration (hours)
Clear liquids(1)	2
Breast milk	4
Baby formula	6
Animal milk	6
Light foods(2)	6

(1): Water, fruit juice without pulp, light tea, coffee without additives
(2): Toast (fat free) and tea, water, coffee

The nutritional status of every patient who will undergo elective major surgery must be evaluated. Although many different methods can be used in this evaluation, the most recommended ones are the subjective global assessment (SGA) and NRS-2002. Body mass index can also provide information about nutritional status. Preoperative nutritional support planning should be made for patients with SGA-C or NRS-2002 scores above 3. This planning should be organized by teams working on clinical nutrition and the surgery should be postponed for a certain period of time (usually 7-10 days is sufficient).

Many developments have been made in preoperative cardiopulmonary preparation in the last 30 years and as a result, mortality rates have been reduced. However, the same success has not been achieved in complication rates due to reasons such as obesity, diabetes, modern lifestyle, hypertension and old age. In order to achieve success in this sense, all patients who will undergo major surgery should undergo surgery after their general condition has been brought to the highest level. In recent years, the concept of postoperative rehabilitation has been replaced by preoperative prehabilitation. The patient should undergo surgery after preparations that include quitting smoking and alcohol 8 weeks before the surgery, exercise programs, reducing the risk of comorbidities by making necessary consultations and many other similar issues.

Side effects of long-acting premedications such as opioids, long-acting sedatives and hypnotics prevent recovery by causing a prolongation of hospital stay. In contrast, short-acting anxiolytics do not prolong recovery or hospital stay. Therefore, unnecessary premedication should be avoided before anesthesia. Only patients who have previously used such medications can continue their medications with psychiatric consultation.

Meta-analyses have shown that subcutaneous low-dose unfractionated heparin regimens are effective in reducing deep vein thrombosis, pulmonary embolism, and mortality in patients undergoing colorectal surgery. Meta-analyses comparing low molecular weight heparin (LMWH) with unfractionated heparin have found no difference in efficacy or bleeding risk. LMWH is preferred because of its once-daily dosage and lower risk of heparin-induced thrombocytopenia. Antiplatelet drugs and intravenous dextran are less effective for prophylaxis of deep vein thrombosis, but may be effective in preventing pulmonary embolism. Due to their side effect profiles, they can only be recommended for high-risk patients in whom LMWH and unfractionated heparin are contraindicated. There is insufficient evidence on the safety of continuous epidural analgesia in patients receiving LMWH. Prophylactic doses of LMWH should be given before ion of an epidural catheter and within 12 hours after its removal. Although the concomitant use of NSAIDs and LMWH is considered safe, a potential risk of epidural hematoma has been mentioned. Attention should be paid to other factors affecting coagulation and, where necessary, alternative methods of thromboprophylaxis (antithromboembolism stockings, etc.) should be used.

Antibiotic prophylaxis should be administered in accordance with local and universal guidelines and before skin incision. Although a single dose is sufficient, it is recommended to repeat intraoperatively in surgeries lasting longer than 3 hours. New generations of antibiotics should not be used for prophylaxis and should be reserved for infectious complications.

Although there is no definitive information on the most appropriate anesthesia method for the surgical procedure to be performed, the use of short-acting agents seems rational. It is logical to use short-acting agents (propofol, remifentanil hydrochloride) instead of long-acting intravenous opioids (morphine sulfate, morphine hydrochloride, fentanyl citrate), thus allowing proactive recovery to begin immediately after surgery. Midthoracic epidural anesthesia, which is strongly recommended in colon surgeries, will have two benefits. The first is to provide adequate analgesia with lower postoperative morbidity. The second is that midthoracic epidural blockade will also block the adrenal glands, thus reducing the metabolic endocrine response to trauma. Thus, the release of stress hormones will be reduced, the duration of postoperative ileus will be shortened, and postoperative insulin resistance will decrease. As a result, the severity of metabolic trauma experienced by the patient will be reduced, their well-being will be increased, and the duration of hospital stay will be reduced. Although the risk of hematoma, abscess, or neurologic damage due to epidural anesthesia is between 0.01% and 0.6%, this possibility should definitely be considered. The optimal T elevation for colon surgery is between 6 and 11% to provide ideal anesthesia and analgesia. The catheter should be placed while the patient is awake to avoid neurologic complications. Intraoperative blockade can be achieved by continuous infusion of local anesthetic (e.g., 0.1% to 0.25% bupivacaine hydrochloride, or 0.2% ropivacaine hydrochloride) and an additional low opiate dose (e.g., 2.0-μg/mL fentanyl citrate or 0.5 to 1.0-μg/mL sufentanil citrate) at 4 to 10 mL/h. Small doses of epidural opioids act synergistically with epidural local anesthetics in providing analgesia. Addition of epinephrine (1.5 - 2.0μg/mL) to thoracic epidural infusion increases analgesia. In conclusion, the recommended protocol is to perform the surgery with midthoracic epidural blockade and short-acting anesthetics, and to provide analgesia via midthoracic epidural catheter in the postoperative period.

There are studies reporting that transverse or curved incisions used in abdominal surgery are more advantageous than longitudinal incisions in terms of postoperative pain and pulmonary dysfunction. However, many surgeons prefer longitudinal incisions due to their exploration advantages. According to ERAS protocols, although there is no binding element regarding the shape of the incision, the shortest possible incision should be used.

A meta-analysis conducted 22 years ago showed that routine nasogastric decompression should be avoided after colorectal surgery, as patients without a nasogastric tube had less fever, atelectasis, and pneumonia. A recent Cochrane meta-analysis of 33 studies including over 5000 patients confirmed this, and also emphasized that patients' bowel function returned earlier when nasogastric decompression was avoided. Having a nasogastric tube also delays oral feeding.

Hypothermia may increase bleeding by stimulating sympathetic discharge and metabolic endocrine response to trauma and by disrupting coagulation systems. Some studies have shown that maintaining normothermia using a warming blanket reduces wound infections, cardiac complications, bleeding, and transfusion requirements. Starting systemic warming preoperatively, continuing it during surgery, and extending it up to 2 hours postoperatively may provide additional benefits.

Postoperative nausea and vomiting should be prevented as they will also restrict the patient's oral intake in the early period. In addition to the use of antiemetics for this purpose, the use of agents that induce vomiting, especially during surgery, should be avoided. Risk factors for postoperative nausea and vomiting are being a woman, not smoking, a history of motion sickness (or postoperative nausea, vomiting anemia), and postoperative opioid administration. Patients at moderate risk (factor 2) should receive prophylaxis with dexamethasone sodium phosphate at the beginning or a serotonin receptor antagonist at the end of the operation. Patients at high risk (factor 3) should receive general anesthesia with propofol and remifentanil, supplemented with 4-8 mg dexamethasone sodium phosphate at the beginning of the operation, serotonin receptor antagonists or droperidol or 25-50 mg metoclopramide hydrochloride 30-60 minutes before the end of the operation.

With traditional perioperative intravenous fluid regimens in abdominal surgery, patients may receive 3.5 to 7 L of fluid on the day of surgery and more than 3 L for the following 3 to 4 days. This may result in a weight gain of 3 to 6 kg. These practices may delay the return of normal gastrointestinal function, impair wound and anastomosis healing, and affect tissue oxygenation. This results in a long hospital stay. Evidence from recent studies indicates that overloading and restricting fluid intake significantly reduce postoperative complications and shorten the length of hospital stay, and therefore should be recommended. In the modern understanding of fluid therapy, fluid infusion that does not leave the patient dehydrated is considered sufficient. The best way to limit postoperative intravenous fluid administration is to stop intravenous infusions early and start oral fluids immediately. The target here should be the first day after surgery. Accordingly, oral fluids should be given to the patient after 2 hours postoperatively and at least 800 ml should be taken on the day of surgery. As oral fluid intake increases, the amount of parenteral fluid should be reduced. Intraoperatively and in the early postoperative period, it is recommended to use vasopressor agents instead of fluids, especially in combating hypotension that may develop due to epidural blockade. Transesophageal Doppler ultrasonography may be an appropriate guide for measuring cardiac output and providing hydration in high-risk patients.

There is no current study showing the positive contribution of drain use to surgical outcomes in elective abdominal surgery. In addition, the presence of a drain reduces patient mobilization and it has been shown that drain use has no effect on anastomotic leaks. For these reasons, routine use of drains should be avoided. Guidelines for other system surgeries also include recommendations that limit the unnecessary use of drains.

Bladder catheters should be removed early due to their disadvantages such as urinary infection and restriction of mobilization. However, since the possibility of urinary retention increases as a result of epidural blockage, the catheter should be kept as long as the blockage continues. In surgeries with extensive pelvic dissection, suprapubic catheterization should be preferred over urinary catheters.

When ERAS protocols are applied, blood glucose levels can be managed more easily. Since both metabolic stress and postoperative insulin resistance are minimized with many elements, very few patients experience difficult-to-control hyperglycemia. Diabetic patients should be well prepared preoperatively and closely monitored postoperatively. As recommended in many guidelines, the goal should be to keep blood sugar levels around 140-180 mg/dL.

Prevention of postoperative ileus, which is the main reason for late discharge after abdominal surgery, is the main goal of ERAS protocols. Although no prokinetic agent is currently effective in reducing or treating postoperative ileus, many other interventions have been successful. Midthoracic epidural analgesia is highly effective in preventing postoperative motility disorders when compared to intravenous opioid analgesia. Fluid overload during and after surgery impairs gastrointestinal function and should be avoided. Stimulation of gastrointestinal motility in the early postoperative period and, perhaps more importantly, avoiding agents that may negatively affect motility are essential for early enteral feeding. For this purpose, epidural analgesia, avoidance of opiates and overhydration, and use of 2x1 g/day oral magnesium oxide are required. In addition, bowel function returns earlier and oral dietary intake is achieved more rapidly in laparoscopic surgeries compared to open surgery.

Meta-analyses have shown that optimal analgesia is achieved with opioids or continuous epidural local anesthetic for 2 to 3 days after surgery in both open and laparoscopic surgery. When given intravenously, opioids do not provide the same efficacy of analgesia and have a less beneficial effect on the surgical stress response compared to epidural local anesthetic techniques. After the application of epidural blockade, there are some changes in perfusion of the splanchnic area, cardiac output and mean arterial pressure. Therefore, vasopressors should be considered to balance blood pressure. In the case of heart failure, an adequate preload is required to improve colonic blood flow, for which positive inotropes are mandatory. Low-dose norepinephrine and dobutamine hydrochloride are not detrimental to perfusion of the splanchnic area. Continuous analgesic infusion via epidural catheter and additional paracetamol 4 mg/day should be used routinely for the first 2 days after surgery. If this protocol is inadequate, nonsteroidal anti-inflammatory drugs can be added in between. Nonsteroidal anti-inflammatory drugs should be started as routine analgesics in the period close to the removal of the epidural catheter and should be used as needed after discharge.

Randomized controlled trials comparing early enteral or oral feeding with conservative oral feeding conclude that there is no advantage to fasting patients after elective gastrointestinal resection. Early feeding reduced both the risk of infection and the length of hospital stay, and did not pose a high risk of anastomotic leakage. However, patients fed early had an increased risk of vomiting, and when multimodal motility therapy was not added, there were problems such as bloating, impaired pulmonary function, and delayed mobilization. Patients should be encouraged to take oral fluids at the second hour and solids at the fourth hour after surgery. Oral nutritional solutions should be provided until adequate oral nutrition is achieved. In patients who receive preoperative nutritional support due to nutritional deficiencies (especially in cancer patients), postoperative support should be continued for at least 8 weeks. In ERAS programs, oral nutritional supplements have been used successfully the day before surgery and for at least the first 4 days after surgery to achieve ideal energy and protein intake. When used in combination, preoperative oral carbohydrate loading, epidural analgesia, and early enteral feeding have been shown to provide appropriate nitrogen balance without causing hyperglycemia.

As bed rest after surgery is prolonged, insulin resistance increases, muscle weakness and loss of muscle mass develop. In addition, pulmonary function is impaired and the risk of thromboembolism increases. Epidural analgesia is important in many ways, as well as playing a key role in early mobilization. The goal should be to provide physical conditions where the patient's pain can be relieved and they can move. According to the ERAS protocol, the patient should be out of bed for 2 hours on the day of surgery and 6 hours per day until discharge on the following days.

The patient's discharge should be planned at the time of admission and explained to the patient in detail. The patient should be informed of possible causes and durations of disruptions in this plan as much as possible. According to the protocol, the following criteria should be met for hospital discharge:

• Adequate pain control,
• No need for intravenous fluids,
• The patient can mobilize on their own as much as they did before surgery,
• The patient is willing to return home.

Discharged patients should be called by phone after 24-48 hours to learn about their condition. If no problems occur, they should be invited for a wound check and stitch removal on the 7th-10th postoperative day. A pathology report is also prepared during this period and additional oncological treatment should be planned if necessary. It should be kept in mind that 1-3% of patients discharged home will develop an anastomotic leak or another major complication and every complaint should be carefully examined. The next interview can be done by phone on the 30th postoperative day.

Systematic audit is essential to determine clinical outcome and ensure successful implementation of the protocol. If results do not reach the desired quality standards, it is important to distinguish between unsuccessful implementation and failure to achieve the desired effect from the implemented protocol. Comparison with other centers using similar protocols and the same recording methods is necessary.