Six hundred and thirteen (99.5%) and 605 (98.2%) patients had postoperative glucose values less than 200 mg/dl on POD 1 and 2, respectively, and this was not significant between the three groups either on POD 1 (P=0.06) or POD 2 (P=0.18). To analyze whether DSWI rates for patients in the PGC group were a function of postoperative glucose control, models were fitted to the data from the subgroup where A1C was greater than 8.5% that included mean BG values from POD 1 and 2, both on the original scale and after a log transformation. The tests of fit of these variables were not significant. Higher A1C percentage was associated with an increased incidence of DSWI (hazard ratio=1.38, P=0.009) for each unit increase in A1C (Fig. 4).
In this study of patients with known DM, a higher preoperative A1C level was associated with a proportional increase in DSWI rates (a 38% increase in DSWI for each unit increase in A1C). Because the confounding effects of postoperative BG were well controlled, the preoperative BG association to outcomes is especially valid and is this study’s major strength. In the last decade, several trials have well characterized the association between postoperative BG levels and poor outcomes 12,31,32; therefore, the findings of this study add yet another dimension to glucose control and surgical complications.
Insulin resistance during surgery is evaluated in cardiac, colorectal, and gall bladder procedures 36–39. The association between intraoperative insulin resistance, preoperative glycemic control, and adverse events after cardiac surgery was investigated by Sato et al. 37 who found insulin resistance during surgery rather than a known diagnosis of DM, increased the risk of complications. In several studies, a high BMI was associated with DSWI but in our study this relationship did not attain statistical significance probably because of the smaller study size which was a subset of the DM population.
As with other retrospective analyses, our study is limited by multiple factors. A large number of patients did not meet inclusion criteria because of missing preoperative A1C data which could result in selection bias. As A1C testing occurred before surgery, the impact of this exclusion should be minimal. The 616 patients who were included could have preoperative medical care and comorbidities potentially confounding the association of A1C and DSWI; therefore, an expansive list of baseline demographic characteristics were analyzed. There also were a relatively small number of DSWIs which could weaken the statistical power to estimate risks after multivariable correction for confounders. For the same reason, all confounders could not be adjusted for in the same model.
Clinical limitations were a change in the antimicrobial prophylaxis administered following cardiothoracic surgeries from vancomycin to the addition of cefuroxime for postoperative prophylaxis. Although preoperative antibiotic prophylaxis or antibiotic washes administered before and during sternotomy were not evaluated, the practices were stable during the study period. The severity of disease before surgery was not recorded, and was assumed to be similar for the entire population.
The strengths of this study are the use of a well-collected and prospective data for all cardiac surgery procedures. To overcome the statistical limitations, we also evaluated baseline characteristics of the large excluded group that did not have a preoperative A1C recorded. Statistically significant differences were lower BMIs, less hypertension and chronic lung diseases, less use of insulin, and better BG control on POD 1 and 2, all characteristics suggesting a lower risk group. The major strength of this study was that postoperative BG management was stringent and used standardized insulin protocols; therefore, no statistically significant differences between BG control were found between patients with and without DSWI (P=0.07). DSWI cases were identified and classified with the assistance of a hospital infection control team using the CDC criteria which complement those defined by The Society of Thoracic Surgeons 40.
The results of this study suggest that DM patients at highest risk of infections can be identified by preoperative A1C levels. Interventions to improve BG before surgery may impact outcomes, even though postoperative BG is controlled to appropriate goals. Therefore optimizing A1C in the available time before cardiac surgery may help improve patient outcomes.
In patients with DM undergoing cardiac surgery, higher A1C levels demonstrated an increased incidence in DSWI. The association of preoperative BG control and postoperative complications in this, and other surgical cohorts needs to be evaluated by prospective clinical trials.
This work utilized the Biostatistics Core of the Michigan Diabetes Research and Training Center funded by DK020572 from the National Institute of Diabetes and Digestive and Kidney Diseases.
Dr Roma Y. Gianchandani is on the Speaker’s Bureau of Sanofi. For the remaining authors there are no conflicts of interest.
2. . Standards of medical care in diabetes – 2011. Diabetes Care. 2011;34(Suppl 1):S11–S61
3. Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine R. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31:1–6
4. Lazar HL, McDonnell M, Chipkin SR, Furnary AP, Engelman RM, Sadhu AR, et al. The Society of Thoracic Surgeons practice guideline series: blood glucose management during adult cardiac surgery. Ann Thorac Surg. 2009;87:663–669
5. Furnary AP, Gao G, Grunkemeier GL, Wu Y, Zerr KJ, Bookin SO, et al. Continuous insulin infusion reduces mortality in patients with diabetes undergoing coronary artery bypass grafting. J Thoracic Cardiovasc Surg. 2003;125:1007–1021
6. Finney S, Zekveld C, Elia A, Evans T. Glucose control and mortality in critically ill patients. JAMA. 2003;290:2041–2047
7. Krinsley J. Association between hyperglycemia and increased hospital mortality in a heterogeneous population of critically ill patients. Mayo Clin Proc. 2003;78:1471–1478
8. Krinsley J. Effect of an intensive glucose management protocol on the mortality of critically ill adult patients. Mayo Clin Proc. 2004;79:992–1000
9. Clement S, Braithwaite SS, Magee MF, Ahmann A, Smith EP, Schafer RG, Hirsch IB. Management of diabetes and hyperglycemia in hospitals. Diabetes Care. 2004;27:553–591
10. Fish L, Weaver T, Moore A, Steel L. Value of postoperative blood glucose in predicting complications and length of stay after coronary artery bypass grafting. Am J Cardiol. 2003;92:74–76
11. Anderson R, Brismar K, Barr G, Ivert T. Effects of cardiopulmonary bypass on glucose homeostasis after coronary artery bypass surgery. Eur J Cardiothorac Surg. 2005;28:425–430
12. Zerr K, Furnary A, Grunkemeier G, Bookin S, Kanhere V, Starr A. Glucose control lowers the risk of wound infection in diabetics after open heart operations. Ann Thorac Surg. 1997;63:356–361
13. Hruska L, Smith J, Hendy M, Fritz V, McAdams S. Continuous insulin infusion reduces infectious complications in diabetics following coronary surgery. J Card Surg. 2005;20:403–407
14. Sjogren J, Malmsjo M, Gustafsson R, Ingemansson R. Poststernotomy mediastinitis: a review of conventional surgical treatments, vacuum-assisted closure therapy and presentation of the Lund university hospital mediastinitis algorithm. Eur J Cardiothorac Surg. 2006;30:898–905
15. Kramer R, Groom R, Weldner D, Gallant P, Heyl B, Knapp R, Arnold A. Glycemic control and reduction of deep sternal wound infection rates. Arch Surg. 2008;143:451–456
16. Borger MA, Rao V, Weisel RD, Ivanov J, Cohen G, Scully HE, David TE. Deep sternal wound infection: risk factors and outcomes. Ann Thorac Surg. 1998;65:1050–1056
17. Loop FD, Lytle BW, Cosgrove DM, Mahfood S, McHenry MC, Goormastic M, et al. Sternal wound complications after isolated coronary artery bypass grafting: early and late mortality, morbidity, and cost of care. Ann Thorac Surg. 1990;49:179–186
18. Crabtree T, Codd J, Fraser V, Bailey M, Olsen M, Damiano R. Multivariate analysis of risk factors for deep sternal infection after coronary artery bypass grafting at a tertiary care medical center. Semin Thorac Cardiovasc Surg. 2004;16:53–61
19. Furnary A, Zerr K, Grunkemeier G, Starr A. Continuous intravenous insulin infusion reduces the incidence of deep sternal wound infection in diabetic patients after cardiac surgical procedures. Ann Thorac Surg. 1999;67:352–360
20. Lu J, Grayson A, Jha P, Srinivasan A, Fabri B. Risk factors for sternal wound infection and mid-term survival following coronary artery bypass surgery. Eur J Cardiothorac Surg. 2003;23:943–949
21. Ridderstolpe L, Gill H, Granfeldt H, Ahlfeldt H, Rutberg H. Superficial and deep sternal wound complications: incidence, risk factors and mortality. Eur J Cardiothorac Surg. 2001;20:1168–1175
22. Stahle E, Tammelin A, Bergstrom R, Hambreus A, Nystrom S, Hansson H Eur J Cardiothorac Surg. 1997;11:1146–1153
23. Douville EC, Asaph JW, Dworkin RJ, Handy JR Jr, Canepa CS, Grunkemeier GL, Wu Y. Sternal preservation: a better way to treat most sternal wound complications after cardiac surgery. Ann Thorac Surg. 2005;78:1659–1664
24. Grossi EA, Culliford AT, Krieger KH, Kloth D, Press R, Baumann FG, Spencer FC. A survey of 77 major infectious complications of median sternotomy: a review of 7949 consecutive operative procedures. Ann Thorac Surg. 1985;40:214–223
25. Gordon S, Serkey J, Barr C, Cosgrove D, Potts W Infection Control and Hospital Epidemiology, Vol. 18, No. 5, Part 2. The Seventh Annual Meeting of SHEA, The Society for Hospital Epidemiology of America, April 27-29, 1997 (May, 1997), pp. P1-P64
26. Horan T, Andrus M, Dudeck M. CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting. Am J Infect Control. 2008;36:309–332
27. Garner J, Jarvis W, Emori T, Horan T, Hughes J. CDC definitions for nosocomial infections. Am J Infect Control. 1988;16:128–140
28. . The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329:977–986
29. . Effects of intensive glucose lowering in type 2 diabetes. N Engl J Med. 2008;358:2545–2559
30. . Intensive blood glucose control and vascular outcomes in patients with type 2 diabetes. N Engl J Med. 2008;358:2560–2572
31. Halkos ME, Puskas JD, Lattouf OM, Kilgo P, Kerendi F, Song HK, et al. Elevated preoperative hemoglobin A1C level is predictive of adverse events after coronary artery bypass surgery. J Thorac Cardiovasc Surg. 2008;136:631–640
32. McAlister FA, Man J, Bistritz L, Amad H, Tandon P. Diabetes and coronary artery bypass surgery: an examination of perioperative glycemic control and outcomes. Diabetes Care. 2003;26:1518–1524
33. Latham R, Lancaster A, Covington J, Pirolo J, Thomas C. The association of diabetes and glucose control with surgical-site infections among cardiothoracic surgery patients. Infect Control Hosp Epidemiol. 2001;22:607–612
34. Medhi M, Marshall MC Jr, Burke HB, Hasan R, Nayak D, Reed G, et al. HbA1c predicts length of stay in patients admitted for coronary artery bypass surgery. Heart Dis. 2001;3:77–79
35. Alserius T, Anderson R, Hammar N, Nordqvist T, Ivert T. Elevated glycated hemoglobin is a major risk marker in coronary artery bypass surgery. Scand Cardiovasc J. 2008;42:392–398
36. Knapik P, Ciesla D, Filipiak K, Knapick M, Zembala M. Prevalence and clinical significance of elevated preoperative glycosylated hemoglobin in diabetic patients scheduled for coronary artery surgery. Eur J Cardiothorac Surg. 2011;39:484–489
37. Sato H, Carvalho G, Sato T, Lattermann R, Matsukawa T, Schricker T. The association of preoperative glycemic control, intraoperative insulin sensitivity, and outcomes after cardiac surgery. J Clin Endocrinol Metab. 2010;95:4338–4344
38. Gustafsson U, Thorell A, Scoop M, Ljungqvist O, Nygren J. Hemoglobin A1c as a predictor of postoperative hyperglycemia and complications after major colorectal surgery. Br J Surg. 2009;96:1358–1364
39. Thorell A, Nygren J, Essén P, Gutniak M, Loftenius A, Andersson B, Ljungqvist O. The metabolic response to cholecystectomy: insulin resistance after open compared with laparoscopic operation. Eur J Surg. 1996;162:187–191