The goal of this clinical trial is to investigate the effect of preoperative oral carbohydrate on insulin resistance in adult cardiac surgery patients with a cardiopulmonary bypass machine. Insulin resistance is when the body does not respond well to insulin, which can raise blood sugar and slow recovery.

The main question this study aims to answer is:

Does drinking a carbohydrate drink 2 hours before surgery lower insulin resistance compared to drinking only water after on pump cardiac surgery?

Researchers will compare two groups:

One group will drink 400 milliliters of a maltodextrin (carbohydrate) drink (CL group). The other group will drink 400 milliliters of water (PL group).

Participants will:

1. Be randomly assigned to one of the two groups.
2. Have blood samples taken to measure insulin and glucose before and after surgery (at hour-0, and hour-24 after ICU admission).
3. Be monitored in the intensive care unit for 24 hours after surgery.

This prospective, randomized controlled trial is designed to evaluate whether preoperative oral carbohydrate loading reduces perioperative insulin resistance in adults undergoing elective cardiac surgery at Dr. Sardjito Hospital, Yogyakarta, Indonesia. Fifty participants aged 20-60 years with American Society of Anesthesiologists (ASA) physical status II-III will be randomly assigned to one of two groups:

1. Intervention group (Carbohydrate Loading, CL): participants will receive 400 milliliters of a maltodextrin-based carbohydrate drink 2 hours before anesthesia.
2. Control group (Placebo Loading, PL): participants will receive 400 milliliters of plain water 2 hours before anesthesia.

All participants will follow standard preoperative fasting guidelines. Blood samples for glucose and insulin will be taken immediately after induction of anesthesia, upon ICU admission (hour 0), and at hour 24 in the ICU. The main outcome is the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Secondary outcomes include perioperative glucose levels and postoperative insulin requirements.

Randomization is computer-generated, with allocation concealed until assignment. Surgeons, anesthesiologists, ICU staff, outcome assessors, and data analysts will be blinded to group allocation. The sample size of 50 participants (25 per group) was calculated based on prior effect sizes, with 80% power and a two-sided alpha of 0.05.

Data will be analyzed using descriptive statistics and appropriate tests for continuous and categorical variables. Between-group comparisons will use Student's t-test or Mann-Whitney U test as appropriate. Normality will be assessed by Shapiro-Wilk test. Repeated measures will be analyzed with paired tests or ANCOVA models. A p-value <0.05 will be considered statistically significant.

This study is expected to provide new evidence on whether preoperative carbohydrate loading can reduce insulin resistance in the specific context of cardiac surgery, and potentially improve perioperative management and patient recovery.

Inclusion criteria:

• Age 20 to 60 years
• ASA physical status II or III
• Good tolerance to enteral fluid administration

Exclusion criteria:

• History of diabetes mellitus
• Thyroid insufficiency
• Adrenal insufficiency
• Gastroesophageal reflux disease
• Emergency cardiac surgery

Dropout criteria:

• Participant withdraws consent
• Cardiac surgery duration exceeds 4 hours

De-identified individual participant data (IPD) will be made available upon reasonable request to the corresponding investigator after publication of study results.

This study is double-blind. Participants, care providers (surgeons, anesthesiologists, ICU staff), investigators, outcome assessors, data collectors, and analysts were blinded to group allocation. Only the designated study staff who handled randomization and intervention preparation had access to allocation information.