The adoption of enhanced recovery after surgery (ERAS) pathways stands as a paradigm shift in the approach to perioperative care, resulting in both substantial improvements in clinical outcomes and cost savings in colorectal surgery patients and beyond.1 ERAS pathways aim to minimize the physiologic derangements associated with surgery and emphasize patient and family engagement, optimal nutrition with avoidance of prolonged periods of fasting, early mobility, multimodal analgesia, and best evidence for preventable harms (Table 1). Although ERAS pathways are considered one of the most effective innovations in perioperative care in recent years, there is limited information on the individual impact of each bundle element on patient outcomes.
One of the strategies to optimize perioperative nutrition is to promote carbohydrate loading within a few hours before surgery using either sports drinks or specially formulated carbohydrate beverages such as Boost or ClearFast. Importantly, none of the ERAS guidelines specify how to address this practice in patients with diabetes.1,2 The widespread implementation of this practice is based on a theory that the insulin resistance and muscle catabolism induced by surgical stress can be dampened by preoperative carbohydrate loading. Proponents of carbohydrate loading suggest that preoperative treatment with oral carbohydrates increases insulin levels, which reduces postoperative insulin resistance, maintains glycogen reserves, decreases protein breakdown, and improves muscle strength.1,3 Although there are data showing insulin resistance is associated with poor perioperative outcomes, prospective studies analyzing perioperative glucose levels and clinical outcomes remain lacking4 and newer studies do not show preoperative carbohydrate drinks alter perioperative insulin resistance.5 The 2014 Cochrane Review of this subject concluded there had not been a rigorous study showing significant benefit or improved clinical outcomes with use of carbohydrate drinks.3 Although patients given carbohydrates before planned surgical procedures went home between 0.04 and 0.56 days sooner than those receiving a placebo drink or having nothing to eat or drink before surgery, the supplements had little or no effect on complication rates or on how people feel in-hospital during recovery from surgery.3 Since that review, newer randomized studies have not shown any significant benefits for use of the drinks.6,7 In addition, there are almost no data in certain populations such as those with prediabetes, impaired glucose tolerance and diabetes, and we are concerned that these drinks may potentially cause harm in these groups.
Patients With Either Unknown or Iatrogenic Insulin Resistance
Insulin resistance is common in the perioperative setting even in patients without a diagnosis of diabetes. Up to 25% of normal adults have a defect in insulin action similar to patients with either impaired glucose tolerance or type 2 diabetes.8 These individuals compensate for insulin resistance with chronic hyperinsulinemia. In addition, many patients receive dexamethasone perioperatively to reduce postoperative nausea and vomiting. Perioperative dexamethasone significantly increases whole body insulin resistance, potentially resulting in hyperglycemia in patients with and without diabetes. This increase in blood glucose is even greater in patients with obesity or poor glycemic control.9
Of importance, the largest randomized study on preoperative glucose drinks7 did not include patients with diabetes and dexamethasone administration was avoided. In this select population, the study did show that the use of an oral preoperative carbohydrate load resulted in fewer insulin doses needed in nondiabetic subjects for a blood glucose level >180 mg/dL, but there was no effect on the risk of postoperative infectious complications, length of stay, or any other measured outcome. Given the small effect shown in this study in those largely with normal glucose metabolism, the patient who has chronic hyperinsulinemia is unlikely to benefit from presurgical treatment with a carbohydrate drink. Similarly, the theoretical goal of preoperative carbohydrate drinks, reducing insulin resistance, is undermined if dexamethasone is administered, as the physiologic changes associated with dexamethasone would render any potential insulin sensitization of carbohydrate-loading inconsequential.
Patients With Diabetes
The impact of carbohydrate drinks in patients with diabetes is unknown. Most of the studies conducted to evaluate the impact of carbohydrate drinks on perioperative outcomes have excluded these patients. Current guidelines recommend that carbohydrate drinks (whether soda or juice) be eliminated from the diet in people with diabetes, as they result in hyperglycemia. Instead, liquid carbohydrate loads are used as treatment for hypoglycemia. One would expect that the effect of a preoperative carbohydrate drink should be similar and hence the consideration of potential benefit would ideally depend on rigorous investigation. In 1 study of preoperative carbohydrate drinks and bariatric surgery, patients with diabetes were included.6 Details on the glucose changes were not reported, but the authors reported no beneficial effects of the preoperative carbohydrate drinks on any measured outcomes for any patients. Anecdotally, we, and our colleagues around the United States, report some patients with diabetes having their procedures cancelled due to elevated glucoses after receiving these drinks. Despite lack of evidence of benefit and potential downsides, people with diabetes continue to receive carbohydrate beverages preoperatively.
Another complication is the not insignificant number of patients who are diagnosed with diabetes postoperatively. These patients are administered a significant carbohydrate load that may result in unmonitored and uncontrolled hyperglycemia. They may have worse outcomes than patients with previously diagnosed disease because the care team is not prepared to monitor their glucose levels.
Contrary to the theorized physiologic benefit, insulin resistance in patients with type 2 diabetes would not be expected to improve following the administration of additional carbohydrates, but rather worsen as a result of hyperglycemia and glucotoxicity. The preponderance of data examining perioperative outcomes in patients with diabetes, albeit mostly from retrospective studies, show a clear relationship between perioperative hyperglycemia and poor outcomes. Since the strongest demonstrated relationship is between the postoperative glucose and outcomes,10 it is imperative to at minimum demonstrate that preoperative hyperglycemia induced by carbohydrate drinks does not negatively impact postoperative glycemia.
We need to demonstrate both the benefit and the safety of preoperative carbohydrate loading in patients with diabetes before this practice can be considered the standard of care. Hospitals should consider excluding this process from ERAS pathways for this population until we understand (1) the effects on blood glucose levels across a wide spectrum groups of patients at risk for hyperglycemia and (2) the impacts of potential treatment of resulting hyperglycemia, including insulin-induced hypoglycemia.
In conclusion, the success of the ERAS programs has been marked by transdisciplinary collaboration between surgeons, anesthesia providers, and nurses. To fully realize the optimal surgical outcomes, these pathways can deliver similar collaboration should be fostered with other specialists such as endocrinologists when metabolic challenges are being considered. At this time, there are no data to support the use of preoperative carbohydrate loading in patients with underlying insulin resistance or with diabetes. In these patients, the drink will not reduce insulin resistance, but rather induce hyperglycemia and this could possibly be associated with adverse events. We suggest that patients with diabetes undergoing a procedure on an ERAS pathway should not be administered a carbohydrate drink before surgery. In addition, with the rapid adoption of ERAS in the United States, further study should be conducted on the role of the carbohydrate drink on surgical outcomes. In addition, in the future, when recommendations for metabolic modulation are contemplated, transdisciplinary opinions should be sought before widespread implementation.
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