ObjectivesFirstly, to evaluate the accuracy and reliability of continuous glucose monitoring (CGM) in patients undergoing cardiac surgery and, secondly, to assess the impact of preoperative liraglutide administration on perioperative glucose control as captured by CGM. DesignProspective, single-center, pre-specified analyses of the GLOBE trial, a randomized controlled trial comparing preoperative liraglutide treatment to placebo in patients undergoing cardiac surgery. SettingA single center academic hospital in the Netherlands. ParticipantsTwenty-five patients undergoing cardiac surgery, recruited from the hospital's cardiac surgery department. InterventionsParticipants received the Dexcom G5 CGM system from the day before surgery until discharge from the Intensive Care Unit after surgery. Additionally, participants were randomized to receive either preoperative liraglutide or placebo. Measurements and Main ResultsArterial blood gas (ABG) glucose measurements were collected as reference and matched to CGM readings to assess accuracy and reliability. In 240 paired CGM–ABG glucose measurements, the mean absolute relative difference (MARD) was 14.4±12.5%. Temporary sensor interruption occurred mainly intraoperatively (92% of patients). The median duration of intraoperative sensor interruption was 65 (48-95) minutes. Liraglutide increased glycemic time in range, 72% vs 47% in the control group (absolute difference 25%, 95% CI -41.4 to -8.9, p = .004). ConclusionsDespite intraoperative sensor interruption, CGM seems an accurate method to use as a semi-invasive, real-time assessment of blood glucose levels. CGM can provide a detailed observation of the pre- and postoperative glycemic trajectory, demonstrating increased time in range following perioperative liraglutide treatment compared to placebo.