Pre- and postoperative accuracy and safety of a real-time continuous glucose monitoring system in cardiac surgical patients: a randomized pilot study

Diabetes Technol Ther. 2009 Jan;11(1):31-7. doi: 10.1089/dia.2008.0028.


Background: Our objective was to evaluate the accuracy and safety of a real-time (RT) continuous glucose monitoring system (CGMS) in patients before and after cardiothoracic surgery and to investigate whether activation of the alarm function of the RT-CGMS had an effect on glucose control.

Methods: Patients scheduled for elective cardiothoracic procedures, without a history of insulin-requiring diabetes, were perioperatively monitored with RT-CGMS for 72 h and were randomized into two groups: with or without the alarm function (set at 4 and 10 mmol/L) of the device activated. Sensor values were compared with capillary, arterial, and venous blood glucose values. Percentages of time spent in various glucose ranges were compared between groups.

Results: There were no adverse effects of the RT-CGMS. Of the 1,001 sensor value comparisons with capillary or arterial measurements, 96.6% fell within Clarke Error Grid zones A and B, with relative absolute differences ranging from 15% (preoperative period) to 12% (intensive care unit period) to 14% (postoperative period on the ward). Seventeen (7.9%) arterial and 16 (2.0%) capillary comparisons fell within zone D or E. Whether or not the alarm function, as used in this pilot study, was activated did not affect time spent in different glucose ranges.

Conclusions: Although the RT-CGMS is safe and accurate according to accepted standards, there are still small aberrations, which in our opinion preclude unlimited use in its present form in a clinical setting. The effect of the alarm function at different glucose levels remains to be investigated.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Biosensing Techniques
  • Blood Glucose / metabolism*
  • Cardiac Surgical Procedures*
  • Diabetes Mellitus, Type 2 / blood
  • Diabetic Angiopathies / surgery*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Monitoring, Ambulatory / standards
  • Monitoring, Physiologic / methods
  • Monitoring, Physiologic / standards
  • Pilot Projects
  • Postoperative Care*
  • Preoperative Care*


  • Blood Glucose