Preoperative carbohydrate loading: a review of the current evidence
Authors: Shanley S. 
Published: May 2009

Background:  Surgery induces a stress response associated with injury resulting in insulin resistance (Thorell et al., 1999). Fasting is a common procedure presurgery and leads to reduced insulin sensitivity as a result of disturbances in glucose, protein and fat metabolism. Reduced insulin sensitivity has been associated with increased surgical outcome and enhanced patient recovery (van den Berghe et al., 2001). The purpose of this study was to review the current evidence relating to preoperative carbohydrate loading, particularly focusing on outcomes including post‐operative complications, patient well‐being and length of hospital stay.Methods:  A structured review was carried out in a systematic manner of randomised clinical trials published between 1998 and 2008 using four medical databases (Medline, CSA Illumni, Pubmed and ISI Web of Knowledge). The available literature published within the last 10 years that measured an objective clinical load was considered for inclusion. Initially, literature searches were commenced using the broad terms ‘preoperative’ and ‘carbohydrate’ (both terms present). This approach was then refined to improve specificity using the following terms in a variety of different combinations: preoperative carbohydrate load; oral carbohydrate; post‐operative period; hospital stay; preoperative nutrition; and treatment outcomes. Exclusion criteria included duplicate records, those not written in English language, animal studies, observational studies with and without controls, protocols, proposals, discussion papers and conference abstracts. The bibliographies of relevant literature were searched for further studies not found by the database searches.Results:  A total of 16 randomised control trials were identified from initial searches. Of the 16 that were assessed in full form, three were excluded. The remaining thirteen randomised trials all measured clinical outcomes after a preoperative carbohydrate load 2–3 h prior to elective surgery. The study intervention was similar in each study. The number of patients included in each study varied greatly, from 12 to 252, with seven studies having unequal sample sizes between comparison groups. Nine of the 13 studies had a placebo group, and six studies had a control group. The post‐operative regimen was similar in all thirteen studies and was standardised in studied groups. The clinical, metabolic and nutritional outcomes were reported in all of the studies. Results showed that a preoperative carbohydrate load could reduce post‐operative insulin resistance. Statistical significance was not reached for length of hospital stay, improved well‐being and reduced loss of lean tissue, although trends were seen. None of the trials noted any adverse affects as a result of preoperative carbohydrate load.Discussion:  The body of evidence surrounding reduced insulin resistance was of good quality and was consistent with a study by Nygren et al. (1995) where insulin resistance was shown to be reduced by 50% in the same population group. Statistically, individual studies did not provide significant evidence with regard to reduced length of stay, reduced loss of lean muscle mass and patient well‐being. Further research is warranted in all of the reported outcomes because a small sample size has resulted in trends, rather than conclusive evidence. A meta‐analysis may produce more conclusive results.Conclusions:  A preoperative oral carbohydrate was associated with several positive outcomes; however, statistical significance was not reached as a result of the small nature of the studies. No adverse affects were associated with a preoperative oral carbohydrate 2–3 h prior to surgery; therefore, overnight fasting guidelines in elective surgery should be questioned.References Nygren, J., Thorell, A., Jacobsson, H., Larsson, S., Schnell, P., Hylen, L. & Ljundqvist, O. (1995) Preoperative gastric emptying: effects of anxiety and oral carbohydrate administration. Ann. Surg.222, 728–734.Thorell, A. Nygren, J. & Ljundqvist, O. (1995) Insulin resistance – a marker of surgical stress. Curr. Opin. Clin. Nutr. Metab Care2, 69–79.Van den Berghe, G., Wouters, P. & Weekers, F. (2001) Intensive insulin therapy in critically ill patients. N. Engl. J. Med.345, 1359–1367.