Value of continuous glucose monitoring for minimizing severe hypoglycemia during tight glycemic control

Abstract

Objective: Tight glycemic control can potentially reduce morbidity and mortality in the intensive care unit but increases the risk of hypoglycemia. The most effective means to avoid hypoglycemia is to obtain frequent blood glucose samples, but this increases the burden to nursing staff. The objective of this study was to assess the ability of a real-time continuous glucose monitor to reduce hypoglycemia (blood glucose <60 mg/dL [3.3 mmol/L]) during standard care or tight glycemic control effected with a proportional integral derivative insulin titration algorithm.

Design: Real-time continuous glucose monitor profiles obtained from an ongoing prospective randomized trial of tight glycemic control were retrospectively analyzed to determine whether the continuous glucose measure had prevented instances of hypoglycemia.

Setting: Cardiac intensive care unit.

Patients: Children 3 yrs of age or younger undergoing cardiac surgery were studied.

Interventions: Intravenous insulin infusion and rescue glucose guided by the real-time continuous glucose monitor and the proportional integral derivative algorithm in the tight glycemic control arm (n = 155; target glucose 80-110 mg/dL [4.4-6.1 mmol/L]) and the real-time continuous glucose monitor in the standard care arm (n = 156).

Measurements and main results: No reduction in hypoglycemia was observed with real-time continuous glucose monitor alarms set at 60 mg/dL (3.3 mmol/L) (zero of 19 occurrences of blood glucose <60 mg/dL [3.3 mmol/L] detected); 18 of 40 subsequent incidences of hypoglycemia were detected after the alarm threshold was increased to 70 mg/dL (3.9 mmol/L). In the tight glycemic control arm, eight incidences were reduced in duration and an additional eight events were prevented with intravenous glucose. In the standard care arm, three of nine occurrences of hypoglycemia were detected with the duration reduced in all cases. On average, one to two false hypoglycemia alarms were observed in each patient.

Conclusions: The real-time continuous glucose monitor in combination with proportional integral derivative control can reduce hypoglycemia during tight glycemic control. The real-time continuous glucose monitor can also reduce hypoglycemia during standard care. However, false alarms increase the overall nursing workload.

Figures

Figure 1

a) Glucose profiles (mean±sem) obtained over the first 24 hours of tight glycemic control (TGC) and standard care (STD). b) Histogram of all glucose levels assessed individually from the start of continuous glucose monitoring, c) Time to target glucose assessed individually.

Figure 2

a) Example subject in which hypoglycemia was deemed to have been prevented by predictive hypoglycemic alarm (square symbol) and glucose rescue bolus (green bar). Grey bar indicates target glucose, yellow shading indicates mild hypoglycemia, and light red shading indicates severe hypoglycemia b) Insulin delivery recommendations made by the Proportional Integral Derivative (PID) algorithm.

Figure 3

Regression of sensor glucose (SG) versus arterial blood glucose (BG). Bias in regression slope and offset results in overestimation (yellow) of BG at low values and underestimation (blue) at high values of BG. Intersection of SG=BG and regression lines indicates the point at which the sensor is unbiased. Significant differences in STD and TGC regression lines were observed (p