Does Continuous Insulin Therapy Reduce Postoperative Supraventricular Tachycardia Incidence After Coronary Artery Bypass Operations in Diabetic Patients?

Objective: To compare continuous insulin infusion (CII) and intermittent subcutaneous insulin therapy for preventing supraventricular tachycardia. The authors propose that continuous insulin therapy is more effective to reduce supraventricular tachycardias.

Design: A prospective randomized study.

Setting: This study was performed in 2 different centers between April 2005 and February 2007: Gülhane Military Medical Academy and University of Süleyman Demirel.

Participants: Two hundred diabetic patients were included in this prospective randomized study. Patients were divided into 2 groups according to their insulin therapy in 2 different centers.

Interventions: Group 1 included 100 diabetes mellitus (DM) patients, and CIIs were administrated. These patients received a CII infusion titrated per protocol in the perioperative period (Portland protocol). Group 2 also included 100 DM patients, and subcutaneous insulin was injected every 4 hours in a directed attempt to maintain blood glucose levels below 200 mg/dL. Sliding scale dosage of insulin was titrated to each patient's glycemic response during the prior 4 hours.

Measurements and Main Results: There were 5 hospital mortalities in the intermittent insulin group. The causes of death were pump failure in 3 patients and ventricular fibrillation in 2 patients. There were 2 hospital mortalities in the CII group (p = 0.044). Thirty-six patients in the intermittent insulin group and 21 patients in the CII group required positive inotropic drugs after cardiopulmonary bypass (p = 0.028). Low cardiac output developed in 28 and 16 patients in the intermittent and CII groups, respectively (p = 0.045). Univariate analysis identified positive inotropic drug requirement (p = 0.011, odds ratio [OR] = 3.41), ejection fraction (EF) (p = 0.001, OR = 0.92), cross-clamp time (p = 0.046, OR = 0.97), left internal mammary artery (p = 0.023, OR = 0.49), chronic obstructive pulmonary disease (COPD) (forced expiratory volume in 1 second <75% of predicted value (p = 0.009, OR = 2.02), intra-aortic balloon pump (p = 0.045, OR = 1.23), body mass index (p = 0.035 OR = 5.60), and CII (p < 0.001, OR = 0.36) as predictors of SVT. Stepwise multivariate analysis confirmed the significance of some of the previously mentioned variables as predictors of SVT. The value of −2 log likelihood of multivariate analyses was 421.504. These were EF (p < 0.001, OR = 0.91), positive inotropic drug requirement (p < 0.001, OR = 3.94), COPD (p = 0.036, OR = 2.11), and CII (p < 0.001, OR = 0.19).

Conclusion: Continuous insulin therapy in the perioperative period reduces infectious complications, such as sternal wound infection and mediastinitis, cardiac mortality caused by pump failure, and the risk of development of supraventricular tachycardias.

Key words: insulin therapy, supraventricular tachycardia, coronary artery bypass surgery