Continuous subcutaneous insulin infusion

Continuous subcutaneous insulin infusion (CSII) uses an external battery-driven pump, containing an insulin reservoir. The pump continuously delivers rapid-acting insulin at a basal rate via a subcutaneous cannula, and the user initiates delivery of bolus doses immediately before meals. The number of patients using a CSII pump varies between centres, but uptake by children and adolescents has been considerable compared with adults.

Total daily doses of insulin given by CSII pump are roughly the same as those for a multiple daily injection (basal–bolus) insulin regimen, and the proportion infused at a basal rate is adjusted for each child. For most patients, the proportion of basal insulin is typically 40 to 50% of the total daily dose. Bolus doses of insulin are given before all food (ie main meals and all snacks, large or small). Supplemental (correction) doses of insulin are given to reduce high blood glucose concentrations to target; they are usually given when blood glucose concentrations before food are above the target (usually 6 mmol/L).

Bolus and supplemental doses of insulin are calculated by the CSII pump using preset insulin-to-carbohydrate ratios, which can be adjusted for different times of the day if required. For example, many children (especially peripubertal) need extra insulin at breakfast because of insulin resistance, and therefore have a lower insulin-to-carbohydrate ratio for breakfast bolus doses, resulting in a higher insulin dose for the same amount of carbohydrate.

For further information about use of CSII pumps, see Continuous subcutaneous insulin infusion for adults with type 1 diabetes.