Poster Presentation Australian Diabetes Society and the Australian Diabetes Educators Association Annual Scientific Meeting 2017

POSTER DISCUSSION: Circadian hormonal variation impacts the effects of insulin pump basal rate changes (#224)

Sybil A McAuley 1 2 , Glenn M Ward 2 3 , Jodie C Horsburgh 1 , Judith L Gooley 1 , Alicia J Jenkins 1 2 4 , Richard J MacIsaac 1 2 , David N O'Neal 1 2
  1. Department of Medicine, University of Melbourne, Melbourne
  2. Department of Endocrinology & Diabetes, St Vincent's Hospital Melbourne, Melbourne
  3. Department of Pathology, University of Melbourne, Melbourne
  4. NHMRC Clinical Trials Centre, University of Sydney, Sydney

Background: Insulin pumps provide flexibility of insulin delivery in type 1 diabetes. Circadian hormonal changes impacting insulin sensitivity most likely influence the effect of insulin therapy on glycaemia, though limited evidence guides basal insulin dosing adjustment in clinical practice.

Aim: To investigate the impact of minor insulin pump basal rate changes typical of clinical practice.

Methods: This two-stage study involved twelve adults with type 1 diabetes using Roche Accu-Chek pumps and insulin aspart. An insulin basal rate change of 0.2 unit/h (increase in first stage, reduction in second stage) was implemented at ~09:30 h, after a single overnight basal rate (without bolus insulin), while fasting participants rested. During the rate increase stage only, if baseline blood glucose was ≤10 mmol/L intravenous 5% dextrose was infused (100 mL/h) to minimise hypoglycaemia risk. Frequent venous samples for the assessment of plasma free insulin, glucose and cortisol were collected from 60 min before until 300 min after rate change.

Results: The 0.2-unit/h basal rate change represented a mean±SD alteration of 23±6%. During observation, plasma cortisol levels declined by 119±28 nmol/L and 116±20 nmol/L in the rate increase and reduction stages, respectively (P<0.01 vs baseline for each stage). After rate increase, plasma glucose fell from baseline by 3.9±3.4%, 3.3±3.5% and 25.7±4.8% at 60, 120 and 300 min, respectively (with no significant difference from baseline until 225 min). After rate reduction, plasma glucose paradoxically fell from baseline by 4.8±3.2%, 5.5±3.2% and 17.4±3.7% at 60, 120 and 300 min, respectively (with no significant difference from baseline until 255 min); the associated increase in fractional glucose disappearance correlated with the decrease in plasma cortisol (P=0.009).

Conclusions: Counter-regulatory hormone circadian variation may significantly influence glycaemia when implementing minor changes at low basal rates. The time of day warrants consideration when anticipating the clinical effects of basal rate changes.