The adverse effects of overnight fasting before surgery have been well-documented in the contemporary literature. Still, due to the possibility of pulmonary aspiration of gastric contents, many clinicians worldwide still employ this practice. On the other hand, the benefits of preoperative oral carbohydrate loading (OCHL) have been shown in various patient groups. Studies examining the usefulness of preoperative OCHL in aortic surgery are lacking. In particular, no randomized control trials have specifically examined the impact of preoperative OCHL on the postoperative course in patients undergoing open abdominal aortic surgery.

The aims of the study are: 1) to assess the effect of preoperative OCHL on the postoperative course in terms of length of ICU stay, the incidence of surgical and non-surgical complications, postoperative local wound infections, and short-term (30-days) mortality rate; 2) to evaluate the impact of preoperative OCHL on glucose homeostasis, insulin resistance, and patients' subjective well-being; 3) to compare the differences between preoperative OCHL and a conventional fasting protocol.

A prospective, single-center randomized control trial will include approximately 50 consecutive patients undergoing elective open repair due to abdominal aortic aneurysm or Leriche Syndrome. All patients will be operated on under the conditions of general anesthesia during the period from April to October 2024 at the investigators' Institution.

Basic demographic, anthropometric, and clinical data of interest (data on current disease, comorbidities, smoking status, preoperative chronic therapy, previous operations, and basic laboratory and coagulation parameters) will be collected through patient interviews and obtained from medical records. Data regarding intraoperative and postoperative course (including length of ICU stay, postoperative complications, and intrahospital mortality) will be extracted from medical records and database included in daily practice. Data regarding short-term (30 days) morbidity and mortality will be obtained through telephone interviews or personally - on the postoperative control examinations.

Glucose and insulin values will be assessed from the peripheral venous or arterial blood samples (from the arterial cannula postoperatively), taken at T1, 9-11 p.m. in the evening before the surgery (before high-carbohydrate beverage in OCHL group), T2 90 min after high-carbohydrate beverage ingestion in OCHL group, i.e., at 06 a.m. in the control group, on the day of the surgery, T3 six hours following the surgery, and T4 06 a.m. on the first postoperative day. Other parameters of insulin resistance (Homeostatic Model Assessment for Insulin Resistance, HOMA-IR; insulin sensitivity index, HOMA-ISI; and homeostasis model assessment of β-cell function, HOMA-β) will be calculated based on the following equations: HOMA-IR = [fasting insulin (μU/mL) × fasting glucose (mmol/L)]/22.5; HOMA-ISI = 1/log/[fasting glucose (mmol/L) + fasting insulin (μU/mL)], HOMA-β = (20 × fasting plasma insulin [µU/ml])/(fasting plasma glucose [mmol/L] - 3.5), for each of four-time points. No intravenous fluid administration will be given preoperatively, while intraoperatively, no glucose-containing fluids nor insulin will be administered. Also, patients will not receive intravenous or oral glucose solutions six hours before the postoperative morning blood sampling (from midnight to 06 h). Subjective well-being will be assessed using the visual analog scale (VAS) for the six following aspects: anxiety, hunger, thirst, tiredness, pain, and headache. The patients will be instructed to mark a vertical line on a 100 mm horizontal scale, which will be marked with "no symptom" at its left end (score of zero) and with "the worst possible symptom" (score of 10) at its right end. The distance from the left end to the patient's mark will represent the score of the perceived symptom. The variables of subjective well-being will be evaluated at several time points: in the morning before the surgery, 6-12 hours after the surgery, and 24 hours after the surgery. Local wound infection will be defined as redness, pain, and/or drainage on the surgical site, along with an increase in infectious parameters, with or without fever > 38°C.

A median stay of three days with a standard deviation of one day was noted by analyzing the ICU length of stay in a historical cohort of patients who underwent open elective aortic surgery. A power calculation showed that a total sample size of 32 patients is sufficient to have an 80% chance of detecting, as significant at the 5% level, a decrease in the ICU length of stay from 3 in the control group to 2 days in the experimental group. To allow for dropout, the investigators will recruit 50 patients.

Inclusion Criteria:

• Consecutive patients admitted due to elective surgical treatment of abdominal aortic aneurism or Leriche Syndrome.
• Patients scheduled to be operated on first on a given day, that is, patients whose surgery will be performed first in the morning.
• Personally signed informed consent.

Exclusion Criteria:

• Patients with diabetes or fasting glucose level above seven mmol/L;
• Patients with disorders that prolong gastric emptying (gastroesophageal reflux disease, history of gastrointestinal surgery, hiatus hernia or intestinal obstruction);
• Patients with conditions that could potentially prolong the postoperative recovery (severe physical disability, cognitive impairment, autoimmune diseases, severe infection, significant liver and renal failure, or severe psychiatric/mental disorders);
• Patients with alcohol/drug abuse
• Obese patients with obesity class 3 (BMI ≥ 40 kg/m2);
• Patients undergoing emergent surgery;
• Patients treated with immunosuppressants and/or steroids in the past three months before surgery;
• Patients in whom difficult airway is anticipated.