Preoperative carbohydrate load to reduce perioperative glycemic variability and improve surgical outcomes: A scoping review

Abstract

The detrimental effects of both diabetes mellitus (DM) and hyperglycemia in the perioperative period are well established and have driven extensive efforts to control blood glucose concentration (BGC) in a variety of clinical settings. It is now appreciated that acute BGC spikes, hypoglycemia, and high glycemic variability (GV) lead to more endothelial dysfunction and oxidative stress than uncomplicated, chronically elevated BGC. In the perioperative setting, fasting is the primary approach to reducing the risk for pulmonary aspiration; however, prolonged fasting drives the body into a catabolic state and therefore may increase GV. Elevated GV in the perioperative period is associated with an increased risk for postoperative complications, including morbidity and mortality. These challenges pose a conundrum for the management of patients typically instructed to fast for at least 8 h before surgery. Preliminary evidence suggests that the administration of an oral preoperative carbohydrate load (PCL) to stimulate endogenous insulin production and reduce GV in the perioperative period may attenuate BGC spikes and ultimately decrease postoperative morbidity, without significantly increasing the risk of pulmonary aspiration. The aim of this scoping review is to summarize the available evidence on the impact of PCL on perioperative GV and surgical outcomes, with an emphasis on evidence pertaining to patients with DM. The clinical relevance of GV will be summarized, the relationship between GV and postoperative course will be explored, and the impact of PCL on GV and surgical outcomes will be presented. A total of 13 articles, presented in three sections, were chosen for inclusion. This scoping review concludes that the benefits of a PCL outweigh the risks in most patients, even in those with well controlled type 2 DM. The administration of a PCL might effectively minimize metabolic derangements such as GV and ultimately result in reduced postoperative morbidity and mortality, but this remains to be proven. Future efforts to standardize the content and timing of a PCL are needed. Ultimately, a rigorous data-driven consensus opinion regarding PCL administration that identifies optimal carbohydrate content, volume, and timing of ingestion should be established.

Keywords: Preoperative carbohydrate load, Glycemic variability, Surgical outcomes, Glucose variability, Blood glucose concentration

Core Tip: Preoperative fasting reduces the risk for aspiration perioperatively; however, it may contribute to intraoperative insulin resistance and glycemic variability (GV). High GV is associated with an increased risk for postoperative complications, including mortality. The administration of a preoperative carbohydrate load (PCL) may reduce perioperative GV and lower the risk for postoperative complications. In this scoping review, we establish the clear negative impact of GV in patients with and without diabetes mellitus in a wide range of clinical settings. However, we are unable to determine from the current body of literature whether a PCL reduces GV intraoperatively and improves surgical outcomes. Future efforts to standardize the content and timing of the carbohydrate load are needed, as well as prospective studies that are designed to evaluate the carbohydrate load effect on GV indices.