Effectiveness of tight glycaemic control on mortality and morbidity in patients undergoing cardiac surgery in hospital: a systematic review

Abstract

Background: Hyperglycaemia is a well-documented and common response to critical illness and metabolic stress during the perioperative period of cardiac surgery; however, there remains considerable controversy regarding the role of tight glycaemic control during and/or after cardiac surgery. The objective of this review was to identify the effectiveness of tight glycaemic control compared to conventional glycaemic control on the mortality and morbidity in diabetic and nondiabetic patients undergoing cardiac surgery. Methods: A three-step search strategy was employed that aimed to locate both published and unpublished studies in the English language between 1990 until March 2014. An initial search in PubMed and CINAHL was followed by a second search using all identified keywords and index terms across multiple databases and grey literature sites. Critical appraisal was undertaken by two independent reviewers using the standard critical appraisal instrument from the Joanna Briggs Institute Meta- Analysis of Statistical Assessment and Review Instrument (JBI-MAStARI). Results from randomized controlled trials were pooled in statistical meta-analysis using RevMan V 5.3 software where appropriate. Effect sizes were calculated using a fixed effects model. Where the findings could not be pooled using meta-analysis, results are presented in a narrative form. Results: Twelve studies including 2713 participants were identified that met the inclusion criteria and were considered to be of adequate methodological quality. The included randomised controlled trials were generally of good quality with a clear description of study design and statistical analysis methods employed. Meta-analysis was conducted on comparisons between very tight glycaemic control (80- 150mg/dl), tight glycaemic control (100-200mg/dl) and conventional glycaemic control (160-250mg/dl). For all patients (both diabetic and/or nondiabetic) undergoing cardiac surgery, very tight glycaemic control as compared to conventional glycaemic control significantly reduced all-cause mortality (odds ratio [OR] 0.59, 95% confidence interval [CI] of 0.37 to 0.96), length of stay in hospital (mean difference [MD] -0.21,95% CI of -0.28 to -0.14); and tight glycaemic control compared to conventional glycaemic control significantly reduced all-cause mortality (OR 0.25, 95% CI of 0.09 to 0.68), length of stay in intensive care units (MD -0.65, 95% CI of -0.68 to -0.62), length of stay in hospital (MD -2.70, 95% CI of -2.77 to 2.63), atrial fibrillation (OR 0.42, 95% CI 0.26 to 0.66) and renal failure (OR 0.09, 95% CI 0.02 to 0.51). In diabetic patients undergoing cardiac surgery, very tight glycaemic control in comparison with conventional glycaemic control showed significant reduction in length of stay in hospital (MD -0.21, 95% CI -0.28 to -0.14), and tight glycaemic control compared to conventional glycaemic control showed significant reduction in length of stay in hospital (MD -2.71, 95% CI -2.78 to -2.63), length of stay in ICU ( MD -0.65, 95% CI -0.68 to -0.62) and atrial fibrillation (OR 0.36, 95% CI 0.22 to 0.59). Conclusions: The findings of this review indicate that very tight and/or tight glycaemic control compared to conventional glycaemic control during the periopertive period in patients undergoing cardiac surgery may have some positive effects in reducing mortality and morbidity following surgery.