Intensive vs. conventional glycemic control in critically ill cardiac patients: a systematic review and meta-analysis of randomized controlled trials

Background Hyperglycemia is common during cardiac surgery and acute cardiac illness, but the balance between potential benefits and harms of lower glucose targets remains uncertain. Methods PubMed, Embase, the Cochrane Library, and Web of Science were searched through 21 December 2024. Eligible studies were randomized controlled trials comparing an intensive with a conventional glycemic-control protocol in adults undergoing cardiac surgery or experiencing an acute cardiac condition. Stroke and myocardial infarction were primary outcomes. Atrial fibrillation, 30-day mortality, infection, sepsis, acute renal dysfunction, intensive care unit (ICU) length of stay, and hospital length of stay were secondary outcomes. Risk ratios (RRs) or mean differences (MDs) with 95% confidence intervals (CIs) were pooled. Prespecified disease-based subgroup analyses and interaction tests were performed. Results Sixteen unique randomized trials representing 6,525 participants were included. Intensive glycemic control was associated with fewer strokes (RR 0.36, 95% CI 0.23–0.55; I 2 = 0%) but not fewer myocardial infarctions (RR 0.96, 95% CI 0.82–1.13; I 2 = 9%). It was associated with lower risks of infection (RR 0.50, 95% CI 0.37–0.67; I 2 = 0%) and acute renal dysfunction (RR 0.73, 95% CI 0.57–0.94), but not with 30-day mortality (RR 0.93, 95% CI 0.70–1.22), ICU stay (MD 3.03 h, 95% CI −0.84 to 6.89), or hospital stay (MD −0.02 days, 95% CI −0.50 to 0.46). Atrial fibrillation was lower after non-CABG cardiac surgery but not after CABG. Tests for interaction by cardiac condition were not significant. Conclusions Lower-target protocols may reduce selected complications, particularly stroke and infection, but the evidence is heterogeneous and does not support routine glucose targets below current critical-care recommendations. Treatment should prioritize avoidance of both marked hyperglycemia and hypoglycemia, protocolized monitoring, and individualized targets. Larger contemporary trials that report hypoglycemia and glycemic variability are required. Systematic Review Registration: PROSPERO CRD42023418963.