Continuous subcutaneous insulin infusion (CSII)

Continuous subcutaneous insulin infusion (CSII) uses a small battery-powered syringe driver or insulin pump and a short-acting insulin (or insulin analogue). The pump is worn 24 hours a day and insulin is delivered via a subcutaneous needle sited in the abdominal wall or thigh.

The pump holds sufficient insulin for 2 to 3 days, after which the pump is refilled and the subcutaneous needle resited.

The pump can be programmed to infuse insulin continuously - the so-called 'basal rate'. In addition, the patient is able, by means of a button on the pump, to administer boluses of insulin whenever he or she takes a meal - 'boosting'. More expensive pumps can be programmed to change their basal rate automatically and are of use in people with brittle diabetes who are not controlled on a fixed basal rate.

CSII pumps have a number of advantages and disadvantages:

• advantages include:
  • flexibility with the timing and composition of meals.
  • with CSII, insulin delivery is more physiological than other regimens and in a few people with difficult-to-control diabetes CSII produces good glycaemic control
  • there is evidence that insulin pumps can reduce hypoglycaemia, insulin doses required and weight gain and improve metabolic control (1,2)
• disadvantages include:
  • regular blood glucose measurement is an essential part of CSII therapy and patients using it must be well motivated
  • an insulin pump can be an inconvenient; it must be removed for most sports and when bathing or showering

A review stated (3) that:

• CSII improves glycaemic control compared to other intensified insulin regimens, with a small decrease in HbA_1c and mean blood glucose, and a larger reduction in glucose fluctuation
• improved control is not associated with an increased risk of hypoglycaemia; also, CSII probably results in significantly lower rates of severe hypoglycaemia
• there is no evidence that those using CSII are at increased risk of diabetic ketoacidosis
• CSII is uniquely associated with a small risk of application site infection
• CSII has a positive impact on quality of life
• there is much less evidence concerning the benefits of CSII in reducing microvascular or macrovascular complication rates
  • small studies, mostly from the 1980s, show improvements in markers of early nephropathy, retinopathy progression and neuropathy, but the potential long-term impact of CSII has not been proven
• use of CSII in type 2 diabetes (4):
  • there may be improvements in blood glucose profiles, and there is a high degree of patient satisfaction with CSII, over 90% preferring it to multiple daily injections (MDI)
  • CSII therapy provided efficacy and safety comparable to MDI therapy for type 2 diabetes
  • the study authors concluded that patients with type 2 diabetes can be trained as outpatients to use CSII and prefer CSII to injections, indicating that pump therapy should be considered when initiating intensive insulin therapy for type 2 diabetes

NICE states that (5):

• CSII therapy is recommended as a treatment option for adults and children 12 years and older with type 1 diabetes mellitus provided that:
  • attempts to achieve target HbA_1c levels with MDIs result in the person experiencing disabling hypoglycaemia (for the purpose of this guidance, disabling hypoglycaemia is defined as the repeated and unpredictable occurrence of hypoglycaemia that results in persistent anxiety about recurrence and is associated with a significant adverse effect on quality of life) or
  • HbA_1c levels have remained high (that is, at 8.5% [69 mmol/mol] or above) on MDI therapy (including, if appropriate, the use of long-acting insulin analogues) despite a high level of care
• CSII therapy is recommended as a treatment option for children younger than 12 years with type 1 diabetes mellitus provided that:
  • MDI therapy is considered to be impractical or inappropriate, and
  • children on insulin pumps would be expected to undergo a trial of MDI therapy between the ages of 12 and 18 years
• CSII therapy is not recommended for the treatment of people with type 2 diabetes mellitus
• following initiation in adults and children 12 years and older, CSII therapy should only be continued if it results in a sustained improvement in glycaemic control, evidenced by a fall in HbA_1c levels, or a sustained decrease in the rate of hypoglycaemic episodes; appropriate targets for such improvements should be set by the responsible physician, in discussion with the person receiving the treatment or their carer

References:

1. Bode BW et al (1996). Reduction in severe hypoglycaemia with long-term continuous subcutaneous infusion in type 1 diabetes.Diabetes Care;19: 324-7.
2. Zinman B et al (1997). Insulin lispro in SCII: results of a double-blind cross-over study. Diabetes; 46: 440-3.
3. Br J Diabetes Vasc Dis 2004;4:104-08.
4. Raskin P, Bode BW, Marks JB et al. Continuous Subcutaneous Insulin Infusion and Multiple Daily Injection Therapy Are Equally Effective in Type Diabetes. Diabetes Care 2003;26:2598-603.
5. NICE (August 2015). Type 1 diabetes in adults: diagnosis and management.