Effects of pre-operative oral carbohydrates on insulin resistance and postoperative recovery in diabetic patients undergoing coronary artery bypass grafting: study protocol for a prospective, single-blind, randomized controlled trial

Preoperative carbohydrates (CHO) supplement has been widely investigated in nondiabetic patients undergoing a variety of surgeries. It has been proved that preoperative CHO could alleviate postoperative insulin resistance (IR) and improve patients' well-being in nondiabetic patients. However, it remains controversial whether preoperative CHO could yield similar effects in diabetic patients. Till now, seldom has the administration of preoperative CHO been investigated in diabetic patients and there are limited studies reporting IR and postoperative recovery of diabetic patients undergoing cardiac surgery. We present a prospective, single-center, single-blind, randomized, no-treatment controlled trial of preoperative CHO on diabetic patients undergoing off-pump coronary artery bypass grafting (OPCAB). A total of 62 patients will be enrolled and randomized to either Group CHO or Group control (CTRL). Patients in Group CHO will consume CHO fluid containing 50 g carbohydrates orally the evening before surgery (20:00-24:00) while their counterparts in Group CTRL will be fasted after 20:00 the evening before surgery. The primary endpoint is postoperative IR assessed via homeostasis model assessment (HOMA). The secondary endpoints are postoperative levels of potential mediators relating to IR including inflammatory factors and stress reaction characterized by serum cortisol. Exploratory endpoints are in-hospital clinical endpoints. Continuous variables will be compared by Student's t-test or Mann-Whitney U test. Categorical variables will be compared with χ test or Fisher's exact test. All tests in the present study are two-tailed and P