Insulin infusions in the neonatal unit: Delivery variation due to adsorption

Objective: To assess the extent of the variability in insulin delivery over time, under conditions used in Australian neonatal units, studying the fol lowing variables: diluent, preconditioning, flushing, sequential preconditi oning and flushing, insulin concentration, flow rate, catheter type, and ad dition of albumin. Methodology: A range of simulated insulin infusions was studied. Infusions were run over 22 h, with aliquots of infusate collected at baseline and aft er 15 min, 30 min, 1 h, 2 h, 6 h and 22 h. Insulin concentration was assaye d using a radioimmunoassay. Results: An infusion of 50 mU insulin/mL at 1 mL/h gave negligible insulin delivery until 22 h. However, after preconditioning and flushing the tubing , consistent insulin delivery was attained by 6 h. An infusion of 200 mU in sulin/mL at 1 mL/h did not provide consistent delivery until 6 h. At this c oncentration and rate, consistent insulin delivery was attained within 30 m in of the start of the infusion either by preconditioning and flushing the tubing, or by addition of albumin to the infusate. Conclusion: Clinically significant variation in intravenous insulin deliver y will occur in the neonatal setting unless counter-measures are taken, suc h as sequential preconditioning and flushing of the delivery system or the addition of albumin to the infusate.