Blood Glucose Control by a Model Predictive Control Algorithm with Variable Sampling Rate Versus a Routine Glucose Management Protocol in Cardiac Surgery Patients: A Randomized Controlled Trial

Abstract

Abstract Context: Elevated blood glucose levels occur frequently in the critically ill. Tight glucose control by intensive insulin treatment markedly improves clinical outcome. Objective and Design: This is a randomized controlled trial comparing blood glucose control by a laptop-based model predictive control algorithm with a variable sampling rate [enhanced model predictive control (eMPC); version 1.04.03] against a routine glucose management protocol (RMP) during the peri- and postoperative periods. Setting: The study was performed at the Department of Cardiac Surgery, University Hospital. Patients: A total of 60 elective cardiac surgery patients were included in the study. Interventions: Elective cardiac surgery and treatment with continuous insulin infusion (eMPC) or continuous insulin infusion combined with iv insulin boluses (RMP) to maintain euglycemia (target range 4.4–6.1 mmol/liter) were performed. There were 30 patients randomized for eMPC and 30 for RMP treatment. Blood glucose was measured in 1- to 4-h intervals as requested by each algorithm during surgery and postoperatively over 24 h. Main Outcome Measures: Mean blood glucose, percentage of time in target range, and hypoglycemia events were used. Results: Mean blood glucose was 6.2 ± 1.1 mmol/liter in the eMPC vs. 7.2 ± 1.1 mmol/liter in the RMP group (P < 0.05); percentage of time in the target range was 60.4 ± 22.8% for the eMPC vs. 27.5 ± 16.2% for the RMP group (P < 0.05). No severe hypoglycemia (blood glucose < 2.9 mmol/liter) occurred during the study. Mean insulin infusion rate was 4.7 ± 3.3 IU/h in the eMPC vs. 2.6 ± 1.7 IU/h in the RMP group (P < 0.05). Mean sampling interval was 1.5 ± 0.3 h in the eMPC vs. 2.1 ± 0.2 h in the RMP group (P < 0.05). Conclusions: Compared with RMP, the eMPC algorithm was more effective and comparably safe in maintaining euglycemia in cardiac surgery patients.