Abstract
Good glycaemic control confers an outcome benefit in both diabetic and non-diabetic critically unwell patients. Critically unwell patients receiving intravenous insulin in the intensive care unit (ICU) require hourly glucose monitoring. This brief communication highlights the impact of the introduction of the FreeStyle Libre glucose monitor, a form of continuous glucose monitoring, on the frequency of glucose recordings in patients receiving intravenous insulin in the ICU at York Teaching Hospital NHS Foundation Trust.
Introduction
Hyperglycaemia is common in critically ill patients with the proportion of patients estimated to be as high as ninety percent. 1 Hyperglycaemia is thought to predispose patients to complications such as infection, polyneuropathy, multiple organ failure and death. 2 In 2001, Leuven demonstrated better patient outcomes in patients with tight glycaemic control (80–110 mg/decilitre). 2 This in combination with a second study from Leuven 3 led to considerable enthusiasm for tight glycaemic control in critically unwell patients in ICUs globally. However, this began to change when in 2009 the NICE-SUGAR trial 4 reported increased mortality and incidents of hypoglycaemia for patients receiving intensive glucose control regimes.
With the arrival of new technologies for monitoring glucose levels, there is the possibility that closed loop systems will lessen the risk of hypoglycaemia that is inherent in an intensive glucose control regime. In light of this, we performed a quality improvement project at York Teaching Hospital NHS Foundation Trust to look at whether the FreeStyle Libre could improve the frequency of monitoring of glucose levels in patients receiving intravenous insulin on ICU. Current guidelines for York Hospital ICU recommended that patients on intravenous insulin should have their glucose monitored hourly. 5
Methods
We conducted a retrospective analysis of the frequency of glucose measurements in two cohorts of patients who were admitted to York Hospital ICU between July 2018 and December 2018. Cohort one consisted of standard monitoring with capillary blood glucose or arterial blood glucose. Cohort two consisted of standard monitoring with the addition of the FreeStyle Libre. The FreeStyle Libre consists of a glucose sensor, which is attached to the patient’s arm, and measures glucose in interstitial fluid. We chose not to use the FreeStyle Libre alone for the second cohort of patients, as there were not any current safety trials of the efficacy of using the FreeStyle Libre in critically ill patients and this would have constituted clinical research. Nursing staff were unaware that frequency of measurements was being monitored and they were appropriately trained in how to use the FreeStyle Libre monitoring system. Nurses were asked to simply record the additional reading taken from the FreeStyle Libre on top of their routine blood glucose monitoring. Data were retrieved retrospectively from ICU observation charts.
Patients were included in the project if they fulfilled the following criteria: Required admission to the critical care unit. Patient required intravenous insulin infusion. Patient verbally consented for FreeStyle Libre.
Results
Where we had data on the method of glucose measurement (40 data points for capillary blood glucose and 33 for arterial blood glucose), we looked at the difference between these measurements and the FreeStyle Libre recording. Only in one incidence in each dataset did both capillary and arterial blood glucose measures were lower than the FreeStyle Libre measurement. On average, capillary blood glucose measurements were 2.02 mmol/L greater than FreeStyle Libre measurements (SD = 2.35 mmol/L), whilst arterial blood glucose measurements were 4.25 mmol/L greater than FreeStyle Libre measurements (SD = 3.31 mmol/L). This difference is unlikely to be a clinically significant difference, and the FreeStyle Libre reading lower than other measures may prevent more hypoglycaemias.
Discussion
Introducing the FreeStyle Libre device lead to an increase in the frequency of monitoring, which has implications for better patient outcomes by reducing instances of both hyper- and hypoglycaemia. However, one of the limitations of this quality improvement project was the variability between glucose measurements using standard capillary or arterial glucose monitoring and the FreeStyle Libre. We believe this may have led to reluctance from nursing staff to adopt the new technology as they lacked confidence in it. However, what it has highlighted is that further work is needed to establish if the FreeStyle Libre alone would be a safe alternative to standard practice in critically unwell patients. We are just starting to see studies testing this technology in noncritical care. 6
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
