Brief reportAdsorption of insulin onto infusion sets used in adult intensive care unit and neonatal care settings
Introduction
Tight glycaemic control in adult long-stay critically ill patients using intensive insulin therapy reduces absolute mortality [1], [2]. However, target glycaemia may be difficult to achieve in clinical practice [3]. A low infusion rate of insulin is used in neonatal hyperglycaemia if blood–glucose concentrations are persistently high, and in the management of neonatal diabetes [4].
Insulin adsorption onto infusion equipment may affect glucose control [5], possibly leading to hyperglycaemia [6], [7]. Adsorption may depend on infusion flow rate and concentration [7]. Over time, protein adsorption onto injecting equipment increases until binding regions reach saturation [8], with maximum adsorption occurring in the first 30–60 min [9]. The clinical significance of this in the adult ICU and neonatal settings is uncertain [8].
In this study, adsorption of insulin onto infusion sets used in the adult ICU and for neonatal insulin delivery at University College Hospital (UCH), London, at clinically relevant flow rates was analyzed. The effect of tubing composition and dimensions were also considered.
Section snippets
Methods
Soluble human insulin (Actrapid®, 100 U/ml, Novo Nordisk) was diluted to 1 U/ml in 0.9% NaCl, prepared from HPLC grade water (Fisher Scientific) and sodium chloride (Sigma–Aldrich).
The UV absorbance of insulin solutions passing through a continuous flow UV detector (Agilent Technologies 1200 Series) was measured at 210 nm. Insulin adsorption onto adult ICU infusion tubing (Cardinal Health, polyethylene (PE) 200 cm × 0.9 mm internal diameter, prime volume 1.6 ml) was determined at rates of 0.5 and 1 ml/h
Results
At a flow rate of 0.5 ml/h, insulin was adsorbed onto the PE ICU tubes, such that the concentration flowing from the tubing was 86.23% of that in the syringe after the first 30 min, and only achieved a steady state of 100% of initial concentration after approximately 600 min (Fig. 1). At 1 ml/h, the initial insulin concentration was 95.08% and took around 400 min to reach 100%. At 4 ml/h, the initial concentration was 99.06% and approximately 200 min were required to reach steady state.
For the PVC
Discussion
The relatively small loss of insulin on the syringe indicates that the majority of insulin loss observed in this study resulted from adsorption to tubing.
Maximum loss of insulin in tubing occurred at the beginning of infusion as previously described [9], with recovery of insulin increasing as adsorption sites are saturated [8]. The flow rate had a considerable effect on insulin loss. At low rates, there was greater opportunity for interaction with plastic surfaces. Comparing the two tubings at
Conflict of interest
The authors declare that they have no conflict of interest.
References (9)
- et al.
Intensive insulin therapy in critically ill patients
N. Eng. J. Med.
(2001) - et al.
Intensive insulin therapy in the medical ICU
N. Eng. J. Med.
(2006) - et al.
Tight glycaemic control: A prospective observational study of a computerised decision-supported intensive insulin therapy protocol
Crit. Care
(2007) - BNF for Children. Drugs used in diabetes. BMJ Publishing Group Ltd. and RPS Publishing, London, 2006, pp....