Applying Continuous Glucose Monitoring to Assess how Preoperative Indicators of Long-term Glycaemic Control Relate to Glycaemia Associated Risk Metrics during the Perioperative Period

  • Kate Millar

Student thesis: Doctoral Thesis

Abstract

Abstract
Diabetes in surgical patients is associated with increased morbidity, mortality and length of stay. Preoperative glycated haemoglobin (HbA1c) is routinely measured and used as a marker of surgical risk although limitations of HbA1c include no insight into glycaemic variability which can be best measured using continuous glucose monitoring (CGM).
This was an exploratory pilot study utilising CGM before and after surgery to examine the relationship between preoperative HbA1c and glucose profile metrics which are associated with increased glycaemic risk. The patients recruited had type 2 diabetes undergoing elective orthopaedic joint replacement surgery, they wore CGM for a minimum of 7 days prior and 7 days post-surgery.
18 participants provided CGM data before and after surgery. In the preoperative period, there was a statistically significant association between preoperative HbA1c and preoperative mean glucose, time above range (TAR) defined as >10mmol/L and TAR defined as >15mmol/L and time below range (TBR) defined as <4mmol/L. There was no statistically significant association between preoperative HbA1c and preoperative coefficient of variation (CV) (R= -0.11, p=0.674), TBR defined as <3mmol/L (R= -0.41, p=0.092) and time in range (TIR) defined as 4-10mmol/L (R= -0.23, p=0.355).
In the postoperative period, there was a statistically significant association between preoperative HbA1c and postoperative mean glucose, TAR defined as >10mmol/L, and TAR defined as >15mmol/L, TIR, TBR defined as <4mmol/L, TBR defined as <3mmol/L and interquartile range (IQR). There was no statistically significant association between preoperative HbA1c and postoperative CV (R= -0.16, p=0.530).
Patients with TIR of 70% or higher post-operatively had a significantly lower median HbA1c (50 mmol/mol, IQR 45-55) than those with TIR lower than 70% (64 mmol/mol, IQR 57-78). Comparison of CGM glucose profile metrics between pre and postoperative periods found a statistically significant increase in the mean of Glucose IQR post-surgery in comparison to pre- surgery.
Preoperative HbA1c is an important and valuable assessment prior to surgery however CGM has helped us to understand more about its limitations and therefore more work is needed to help develop clinical guidelines about how to assess and manage glycaemic risk associated with surgery most effectively.
Date of Award15 May 2024
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorDavid Laight (Supervisor), Mike Cummings (Supervisor) & iain cranston (Supervisor)

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