Our results showed that, for patients with type 2 diabetes undergoing elective gastrointestinal surgery, preoperative carbohydrate loading with supplemental insulin selectively did not promote the recovery of gastrointestinal function; however, it improved patients’ comfort and decreased intraoperative hypotension and PONV.
Return of gastrointestinal function is crucial for postoperative recovery after gastrointestinal surgery (Hedrick, et al., 2018). Time to first flatus/defecation are widely used variables indicating the return of gastrointestinal function (Short, et al., 2015). In the present study, the median time to first flatus and defecation were 40 and 93 hours in control group, which were consist with previous results (Dulskas, 2015; Liang, et al., 2011). It was reported that preoperative carbohydrate loading improved the recovery of gastrointestinal function in various surgeries (ÖZdemİR, et al., 2011; An, et al., 2008; Noblett, et al., 2006). However, up to now, sample sizes of available studies were small and conclusions couldn’t be drawn regarding gastrointestinal function. For the first time, we investigated the effect of preoperative carbohydrate loading on gastrointestinal function in diabetic patients but did not find any difference between the two groups.
As for secondary outcomes, we found that preoperative carbohydrate loading significantly reduced patients’ discomfort and the occurrence of PONV, which improved patients’ well-beings during the perioperative period. Our results were consistent with previous studies (Cakar, et al., 2017; Kaska, et al., 2010). In the present study, another interesting finding was that preoperative carbohydrate loading facilitated intraoperative volume and hemodynamic maintenance, evidenced by less intraoperative hypotension. We also found time to first ambulation tended to be earlier in patients with carbohydrate drinks. Other studies reported that preoperative carbohydrate loading was helpful in preserving muscle strength which might promote early ambulation after surgery (Liu, et al., 2018; Gava, et al., 2016; Lidder, et al., 2013).
We did not find any difference in the incidence of postoperative complications and length of stay in hospital after surgery, which were in line with results of recent meta-analyses (Smith, et al., 2014; Amer, et al., 2017). Two reasons might explain this. First, as an important predictor for length of hospital stay, time to return of gastrointestinal function did not differ between groups. Second, alleviating stress and promoting early recovery require multi-disciplinary and multi-module management interventions (Helander, et al., 2019), whereas preoperative carbohydrate loading is only a part of the Enhanced Recovery After Surgery (ERAS) bundles (Gustafsson, et al., 2019; Mortensen, et al., 2014). It is difficult to demonstrate the absolute benefit from a single intervention due to its limited value.
For many years, gastric emptying was thought to be decreased in diabetic patients and they were excluded from trials investigating preoperative carbohydrate loading for aspiration concerns. As a matter of fact, gastric emptying might be accelerated in diabetic patients (Gustafsson, et al., 2008; Mihai, et al., 2018). Studies reported that rapid gastric emptying occurred in those early type 2 diabetic patients (Schwartz, et al., 1996; Phillips, et al., 1992). Similar result was also found in patients with long diabetic course (Weytjens, et al., 1998). In accord with these, none of our patients in carbohydrate group developed aspiration. Another worry when administering carbohydrate loading in diabetic patients is hyperglycemia [9], which may worse perioperative outcomes (Kwon, et al., 2013). To avoid significant blood-glucose fluctuation, we designed a protocol of prescribing volume of carbohydrate drink and dose of insulin according to the individual situation of patients. Our results showed that, although carbohydrate drink increased blood-glucose level, the maximal blood-glucose fluctuation and the rate of hyperglycemia were similar between the two groups, indicating the feasibility of our carbohydrate loading regimen in diabetic patients.
Our study had several limitations. First, we did not measure the residual gastric volume before anesthesia induction, thus direct evidence of sufficient gastric emptying was lacking. Second, carbohydrate drink used in this trial has a high glycemic index. Intermittent blood-glucose monitoring might have missed some higher values. A continuous glucose monitoring device may be more helpful in the future. Thirdly, we did not detect insulin resistance on the first day after surgery.