In this study, 1,122 patients admitted to the hospital with acute heart failure and without diabetes were divided into tertiles depending on their admission blood glucose levels. Diabetes was defined as an admission blood glucose greater than or equal to 200 mg/dl, a known diagnosis of diabetes recorded in the chart, or the presence of anti-diabetic medications on the patient’s medication list. Tertile #1 had an average admission blood glucose of 92 mg/dl (with a range of 54-102); tertile #2 had an average admission blood glucose of 113 mg/dl (with a range of 103-127); and tertile #3 had an average admission blood glucose of 147 mg/dl (with a range of 128-199). Mortality was evaluated according to tertile.
In this study, patients in tertile #3 had significantly higher inpatient mortality (7.2%) than patients in tertile #1 or #2 (3% and 4%, respectively). There was a significant association between hyperglycemia and mortality, even at 60 days follow-up, although not at six and 12 months follow-up. The association remained significant, even when patients with acute MI were excluded. Besides hyperglycemia, the authors noted that increasing age, increasing creatinine, a New York Heart Association (NYHA) functional class of III or IV, and a systolic blood pressure of lower than 115 were also significant, independent predictors of in-hospital mortality in this patient population.
For a hospitalist, the intriguing question is this: Is hyperglycemia just a marker of worse disease, or might it contribute to poorer outcomes? Clearly, hyperglycemia is associated with poorer outcomes in other types of patients, including post-surgical patients, critically ill patients, MI patients, and general medical patients.1 But is hyperglycemia just a marker of more severe illness? In heart failure, perhaps more severe decompensation results in a more profound activation of the sympathetic nervous system and a more vigorous release of stress hormones, such as cortisol and catecholamines. In that case, one might expect a sicker patient to have a higher blood glucose.
More recent studies, however, show that better control of hyperglycemia in some acutely ill patients actually results in improved outcomes, suggesting that the hyperglycemia itself might be contributing to the poorer outcomes in some cases.2-5 Hyperglycemia is known to alter human physiology in a variety of adverse ways.1 For example, hyperglycemia is known to inhibit nitric oxide production and to alter endothelial dysfunction. In a patient with acute heart failure, these alterations might be expected to have a significant effect on outcomes.
This study does not intend to answer these questions, but it does add to our understanding of the association of hyperglycemia and poor outcomes in acutely ill patients. More research is needed to examine whether or not heart failure patients, specifically, will benefit from better glycemic control in the acute setting. TH
References
- Clement S, Braithwaite SS, Magee MF, et al. Management of diabetes and hyperglycemia in hospitals. Diabetes Care. 2004 Feb;27(2):553-591.
- Van den Berghe G, Wouters P, Weekers F, et al. Intensive insulin therapy in the critically ill patients. N Engl J Med. 2001 Nov 8;345(19):1359-1367.
- Van den Berghe G, Wilmer A, Hermans G, et al. Intensive insulin therapy in the medical ICU. N Engl J Med. 2006 Feb 2;354(5):449-461.
- Furnary AP, Zerr KJ, Grunkemeier GL, et al. Continuous intravenous insulin infusion reduces the incidence of deep sternal wound infection in diabetic patients after cardiac surgical procedures. Ann Thorac Surg. 1999 Feb;67(2):352-362.
- Furnary 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 May;125(5):1007-1021.