EDITORIAL

Metabolic control, does it matter? Correspondence O. Rooyackers, Department of Anesthesiology and Intensive Care, Clintec, Karolinska Institutet and Karolinska University Hospital, Huddinge, Sweden E-mail: [email protected] Conflicts of interest The authors declare that they have no conflict of interest. Funding None. doi: 10.1111/aas.12531

It is well known that severe metabolic stress, as following surgery or during critical illness, impairs insulin sensitivity. In particular, the insulin resistance occurring after surgery is well described with a clear relation between the severity of surgical stress and impairment of the insulin sensitivity.1 This post-surgical insulin resistance can be reduced by decreasing surgical stress, by for instance, epidural blocks, avoiding preoperative fasting using preoperative glucose loading or peri-operative glucose control.1,2 Postoperative insulin resistance and morbidity are statistically related, but whether there is a causal relation needs to be further explored. Indeed, it could be that more severely ill patients both have a more impaired insulin action and also more complications postoperatively. Thus, it is not until we interfere with the insulin resistance, improve it and at the same time decrease morbidity that we can evaluate causality. Insulin is best known for its effects on glucose homeostasis, but it is also proven to be an anabolic hormone. It has been shown that postsurgical insulin resistance on glucose metabolism is correlated with impaired insulin effects on protein metabolism.3 Furthermore, the same study found that postoperative insulin resistance was decreased by preoperative glucose loading, and this improved both glucose and protein metabolism, as measured by a less negative whole body protein balance. In the current issue of Acta Anesthesiologica Scandinavica, Matteo Nafi and collaborators demonstrate a relationship between insulin resistance on glucose metabolism and protein metabolism in critically

ill patients following cardiac surgery.4 The authors demonstrate that patients with a better insulin sensitivity on glucose display a positive nitrogen balance (a surrogate measure for protein balance) despite being critically ill. They also show that when the insulin resistance is treated by intensive insulin administration to achieve normoglycemia (in this case, basically an extended insulin clamp), nitrogen balance improves from negative to positive in the insulin resistant patients. This study supports two important clinically relevant facts; (1) that insulin resistance occurring after metabolic stress affects both glucose and protein metabolism (2) that improving insulin sensitivity also affects other surrogate measures for a better outcome such as nitrogen balance which may extend to reduce postoperative morbidity and maybe lower mortality. These new findings generate the hypothesis that treating insulin resistance may open up the possibility to more effectively reduce protein loss, and to better preserve lean body mass in the critically ill. The rationale for protein feeding during critical illness is to preserve lean body mass or at least attenuate the loss of lean body. So far, literature is not very convincing on this point.5 This present study implies that nutrition alone is not sufficient, but insulin resistance needs to be treated in parallel. Future studies addressing this important hypothesis are needed and we look forward to upcoming data from such studies with great expectations. References 1. Ljungqvist O, Jonathan E. Rhoads lecture 2011: insulin resistance and enhanced recovery after surgery. JPEN J Parenter Enteral Nutr 2012; 36: 389– 98. 2. Blixt C, Ahlstedt C, Ljungqvist O, Isaksson B, Kalman S, Rooyackers O. The effect of perioperative glucose control on postoperative insulin resistance. Clin Nutr 2012; 31: 676–81. 3. Svanfeldt M, Thorell A, Hausel J, Soop M, Rooyackers O, Nygren J, Ljungqvist O. Randomized clinical trial of the effect of preoperative oral carbohydrate treatment on postoperative whole-body protein and glucose kinetics. Br J Surg 2007; 94: 1342–50.

Acta Anaesthesiologica Scandinavica 59 (2015) 683–684 ª 2015 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd

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4. Nafi M, Donatelli F, Carli F, Lorini L, Mirabile C, Macchitelli V. Twenty-four hours hyperinsulinemiceuglycemic clamp improves postoperative nitrogen balance only in low insulin sensitive patients following cardiac surgery. Acta Anaesthesiol Scand 2015. 5. Hoffer LJ, Bistrian BR. Appropriate protein provision in critical illness: a systematic and narrative review. Am J Clin Nutr 2012; 96: 591–600.

J. Nygren1,2 and O. Rooyackers3,4 Department of Clinical Sciences, Danderyds Hospital, Karolinska Institutet, Stockholm, Sweden 2 Department of Surgery, Ersta Hospital, Stockholm, Sweden 3 Department of Anesthesiology and Intensive Care, Clintec, Karolinska Institutet, Huddinge, Sweden 4 Karolinska University Hospital, Huddinge, Sweden 1

Acta Anaesthesiologica Scandinavica 59 (2015) 683–684

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ª 2015 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd

Metabolic control, does it matter?

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