Graduation Year

2012

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Nursing

Major Professor

Theresa M. Beckie

Keywords

Cardiac Surgery, Hyperglycemia, Postoperative Wound Infection, Surgical Site Infection

Abstract

The purpose of this study was to investigate the effects of three different glycemic control conditions (tight, conventional, and standard) in the intraoperative period on: 1) postoperative surgical site infections, and 2) postoperative procalcitonin, and C-reactive protein levels in patients undergoing open-heart surgery. Secondary aims of the study were to investigate the effects of the three glycemic treatment conditions on: 1) intraoperative blood glucose; 2) intraoperative glycemic stability; and 3) intensive care unit length of stay, in patients undergoing open-heart surgery.

An experimental design with a multilevel, single factor, within-subjects design was utilized. Patients were nested within anesthesia provider teams. The design was counterbalanced by means of a Latin square, where each of three anesthesia provider teams dispensed each of three glycemic control conditions once. Thirty-seven participants were randomized to either tight glycemic control (n =15), which maintained blood glucose 110-149 mg/dl via continuous intravenous insulin infusion, conventional glycemic control (n = 11), which maintained blood glucose 150-180 mg/dl via continuous intravenous insulin infusion, or standard glycemic control (n =11) which maintain blood glucose 150-180 mg/dl via intravenous bolus injections of insulin.

The main findings of this study were that there were no significant differences between the three glycemic interventional treatment groups in 1) thirty-day surgical site infections, 2) postoperative C-reactive protein or procalcitonin concentrations 3) intensive care unit length of stay, 4) intraoperative blood glucose levels, or 5) glycemic stability. An association between intraoperative peak blood glucose and surgical site infection was established. Participants that experienced higher peak blood glucose levels intraoperatively exhibited increased surgical site infections. Procalcitonin levels were significantly elevated in participants that experienced a surgical site infection, but C-reactive protein showed no significant difference between participants with or without a surgical site infection. Coronary artery bypass graft surgery concomitant with valve replacement surgery was associated with a higher rate of surgical site infections compared coronary artery bypass graft surgery or valve surgery independently.

In conclusion, an association was found between higher peak intraoperative blood glucose levels and increased surgical site infections, therefore maintaining intraoperative blood glucose levels below 180 mg/dl via a continuous intravenous infusion of insulin, may reduce postoperative surgical site infections in the open-heart patient. The use of tight glycemic control during the intraoperative period can be achieved safely, with the use of judicious protocols, but its benefits remain unproven. Inflammatory biomarker procalcitonin was predictive of infection, where C-reactive protein was not. The addition of procalcitonin to routine postoperative blood work, in open-heart patients, may benefit providers in the diagnosis and early treatment of surgical site infections. This study was underpowered. Further studies with appropriate sample size, may be able to determine if tight glycemic control, compared to moderate glycemic control, in the intraoperative period is of benefit to patients undergoing open-heart surgery.

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