Tight Blood Glucose Control in the ICU: Response

Abstract

Strict blood glucose control targeting normoglycemia is being implemented in ICUs, based on results of the two randomized controlled trials1Vanhorebeek I Langouche L Van den Berghe G Tight blood glucose control with insulin in the ICU: facts and controversies.Chest. 2007; 132: 268-278Abstract Full Text Full Text PDF PubMed Scopus (138) Google Scholar2Van den Berghe G Wouters P Weekers F et al.Intensive insulin therapy in critically ill patients.N Engl J Med. 2001; 345: 1359-1367Crossref PubMed Scopus (8200) Google Scholar3Van den Berghe G Wilmer A Hermans G et al.Intensive insulin therapy in medical intensive care patients.N Engl J Med. 2006; 354: 449-461Crossref PubMed Scopus (2959) Google Scholar4Van den Berghe G Wilmer A Milants I et al.Intensive insulin therapy in mixed medical/surgical ICU: benefit vs harm.Diabetes. 2006; 55: 3151-3159Crossref PubMed Scopus (481) Google Scholar in Leuven, Belgium, and three implementation studies.5Furnary AP Gao G Grunkemeier GL et al.Continuous insulin infusion reduces mortality in patients with diabetes undergoing coronary artery bypass grafting.J Thorac Cardiovasc Surg. 2003; 125: 1007-1021Abstract Full Text Full Text PDF PubMed Scopus (945) Google Scholar6Krinsley JS Effect of an intensive glucose management protocol on the mortality of critically ill adult patients.Mayo Clin Proc. 2004; 79: 992-1000Abstract Full Text Full Text PDF PubMed Scopus (1020) Google Scholar7Reed CC Stewart RM Sherman M et al.Intensive insulin protocol improves glucose control and is associated with a reduction in ICUs mortality.J Am Coll Surg. 2007; 204: 1048-1054Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar The Leuven studies1Vanhorebeek I Langouche L Van den Berghe G Tight blood glucose control with insulin in the ICU: facts and controversies.Chest. 2007; 132: 268-278Abstract Full Text Full Text PDF PubMed Scopus (138) Google Scholar2Van den Berghe G Wouters P Weekers F et al.Intensive insulin therapy in critically ill patients.N Engl J Med. 2001; 345: 1359-1367Crossref PubMed Scopus (8200) Google Scholar3Van den Berghe G Wilmer A Hermans G et al.Intensive insulin therapy in medical intensive care patients.N Engl J Med. 2006; 354: 449-461Crossref PubMed Scopus (2959) Google Scholar4Van den Berghe G Wilmer A Milants I et al.Intensive insulin therapy in mixed medical/surgical ICU: benefit vs harm.Diabetes. 2006; 55: 3151-3159Crossref PubMed Scopus (481) Google Scholar advocated insulin infusion targeting a blood glucose level between 80 and 110 mg/dL, within the monitoring and feeding environment of these ICUs. In these two ICUs, and in many centers worldwide that attempt to implement this metabolic intervention, nurses and physicians use intermittent blood glucose readings to titrate the insulin dose. The adequacy of the readings is being evaluated by computing the mean morning blood glucose levels, obtained from the entire group or on a per-patient basis, by averaging, for example, all of the available glucose values per patient, the minimum/maximum blood glucose values, the time needed to reach normoglycemia, and the number of hypoglycemic events. As pointed out by Dr. Soo Hoo,8Soo Hoo GW Tight blood glucose control in the ICU [letter].Chest. 2008; 133: 316-317Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar such single measurements indeed do not capture the dynamics of blood glucose control, and average values can be biased. The sources of bias include different sampling frequencies, and the concomitant presence of hypoglycemic and hyperglycemic events that may result in “normal” calculated averages, whereas the levels of blood glucose are extremely abnormal. The hyperglycemic index, defined as the area under the glucose curve above the upper limit of the target range, divided by the length of ICU stay, also is prone to bias. Ideally, to capture the dynamics of glucose control in an ICU patient, nearly continuous monitoring with an accurate glucose sensor is required, although it remains unclear which aspect of the dynamics (ie, the time spent within the target range, the variance of the blood glucose reading, or the avoidance of hypoglycemia or overcorrection with hyperglycemia following the hypoglycemia) is important to achieve the full benefit of the intervention. We entirely agree with Dr. Soo Hoo that these aspects remain to be elucidated, and the development of continuous glucose sensors is a prerequisite before these questions can be answered.