Original Articles
Continuous intravenous insulin infusion reduces the incidence of deep sternal wound infection in diabetic patients after cardiac surgical procedures

Presented at the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.
https://doi.org/10.1016/S0003-4975(99)00014-4Get rights and content

Abstract

Background. Diabetes mellitus is a risk factor for deep sternal wound infection after open heart surgical procedures. We previously showed that elevated postoperative blood glucose levels are a predictor of deep sternal wound infection in diabetic patients. Therefore, we hypothesized that aggressive intravenous pharmacologic control of postoperative blood glucose levels would reduce the incidence of deep sternal wound infection.

Methods. In a prospective study of 2,467 consecutive diabetic patients who underwent open heart surgical procedures between 1987 and 1997, perioperative blood glucose levels were recorded every 1 to 2 hours. Patients were classified into two sequential groups: the control group included 968 patients treated with sliding-scale–guided intermittent subcutaneous insulin injections (SQI); the study group included 1,499 patients treated with a continuous intravenous insulin infusion in an attempt to maintain a blood glucose level of less than 200 mg/dL. There were no differences between these groups with respect to age, sex, procedure, bypass time, antibiotic prophylaxis, or skin preparation methods.

Results. Compared with subcutaneous insulin injections, continuous intravenous insulin infusion induced a significant reduction in perioperative blood glucose levels, which led to a significant reduction in the incidence of deep sternal wound infection in the continuous intravenous insulin infusion group (0.8% [12 of 1,499]) versus the intermittent subcutaneous insulin injection group (2.0% [19 of 968], p = 0.01 by the χ2 test). Multivariate logistic regression revealed that continuous intravenous insulin infusion induced a significant decrease in the risk of deep sternal wound infection (p = 0.005; relative risk, 0.34), whereas obesity (p < 0.03; relative risk, 1.06) and use of an internal thoracic artery pedicle (p = 0.1; relative risk, 2.0) increased the risk of deep sternal wound infection.

Conclusions. Use of perioperative continuous intravenous insulin infusion in diabetic patients undergoing open heart surgical procedures significantly reduces major infectious morbidity and its associated socioeconomic costs.

Section snippets

Patients

All known diabetic patients consecutively admitted to Portland St Vincent Medical Center for open heart surgical procedures between January 1987 and November 1997 were entered into the study (n = 2,467). Historical, demographic, and surgical variables that might possibly be associated with infectious complications were collected in a common database. These variables included age, sex, height, weight, race, type of preoperative diabetic control (insulin, oral, diet, or none), steroid use,

Demographics

Between January 1987 and November 1997, 14,468 patients underwent open heart surgical procedures through median sternotomy at St Vincent Medical Center. Seventeen percent of these patients (n = 2,467) were classified as diabetic at the time of admission, and all were enrolled in the study. Mean age was 65 ± 10 years, and 62% of patients were men. The cardiac procedures performed in this diabetic cohort included coronary artery bypass grafting in 2,117 patients, valve replacements in 158,

Comment

The present study reconfirms our previous finding [6] that hyperglycemia in the first 2 PODs is significantly associated with, and is an independent predictor of, DSWI (Table 4). These data indicate that hyperglycemia after cardiac operation in the diabetic patient may actually be a causal factor in that infectious process as well. When postoperative hyperglycemia was manipulated through an aggressive intravenous insulin infusion aimed at maintaining glucose levels in the 150 to 200-mg/dL

Acknowledgements

We extend our sincere appreciation to Steven Bookin, MD, endocrinologist, for writing a continuous intravenous insulin protocol that could be safely and effectively implemented by the nursing staff. Appreciation is extended to Patti Luckerath, Chris Pollack, and Elissa Walsh for assistance with data collection. We also thank Cindy Fessler and Natasha Lodahl for their tireless assistance in the preparation of the manuscript, figures, and slides.

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