Type 1 diabetes is an autoimmune dis-ease characterised by autoimmune

destruction of the pancreatic islet cellsthat produce insulin. Insulin is essentialfor the incorporation of glucose intomuscle cells and for the storage of car-bohydrates in the liver. A lack of this hor-mone results in rising blood glucose.Most patients with type 1 diabetes takeat least four injections of insulin a day,a combination of short-acting analogueinsulin with meals, and a long-actinganalogue to provide a basal insulin – iemultiple daily injections (MDI). Control of diabetes is monitored by

measuring glycosylated haemoglobin(HbA1c). We know that achieving optimalcontrol of diabetes reduces the develop-ment of diabetes-related complicationsthat can include long-term complicationssuch as renal failure and blindness.Optimal control is difficult to achieve andalthough some people will manage thiswith MDI, others will not, and insulinpump therapy may present an alterna-tive option.1

MDI therapy is associated with somephysical limitations such as number ofinjections, but also there are physiologi-cal disadvantages. Once injected the

long-acting insulin sits as a depot sub-cutaneously and is released over 12 to24 hours irrespective of insulin require-ments, which can lead to problems suchas those arising at the time of exercise.It provides a flat profile, which physiolog-ically is at odds with the rise in bloodsugar in the early hours of the morning(dawn phenomenon). It is only practicalto inject short-acting insulin as a singlebolus with meals, which may not beappropriate for meals that are slowlyabsorbed or have a high fat content.That is not to say that insulin pump ther-apy is an easy alternative or perfect foreveryone.Insulin pump therapy, or continuous

subcutaneous insulin infusion (CSII), isa method of insulin delivery that moreclosely resembles physiological insulindelivery.2 It is an increasingly utilised

PRESCRIBING IN PRACTICE n

Prescriber 5 March 2015 z 11prescriber.co.uk

An introduction to insulinpump therapy Adam Nicholls BM, MRCP and Helen Partridge BSc, MRCP

Insulin pump therapy cur-rently seems to be reservedfor the few, yet many moretype 1 diabetes patientscould benefit from this delivery system. This reviewoutlines the evidence forinsulin pumps includingpatient selection and sug-gests more could be done toinitiate their use.

Figure 1. Insulin pump therapy is a method of administration that more closely resemblesphysiological insulin delivery and is increasingly utilised treatment for selected patients withtype 1 diabetes as a means of achieving improved glycaemic control

SPL

treatment for selected patients withtype 1 diabetes as a means of achievingimproved glycaemic control.3 It is notrecommended for patients with type 2diabetes.NICE advises that insulin pump ther-

apy should be started by a specialisthospital team with an interest in insulinpump therapy including a diabetologist,specialist nurse and dietician.

The mechanics of insulin pumptherapyAn insulin pump is a mechanical devicethat delivers a constant small infusionof insulin that can vary hour by hour tomeet individualised physiological needs.This is delivered via the pump through acannula inserted subcutaneously. Thecannula remains in situ for up to 72hours and must then be changed. Patients who go on to insulin pumps

are trained in the calculation of insulindoses using carbohydrate counting. Thisis the process where a patient ‘counts’how much carbohydrate is contained inthe food they are eating, and calculatesthe insulin required for this meal. Allfoods containing carbohydrates willhave an effect on blood sugar so needto be covered with the additional insulindose, known as the bolus dose. At everymeal the carbohydrate count is enteredinto the pump to give an additional doseof insulin. All of the commercially available

pumps are ‘smart pumps’ so they contain an on-board calculator that willcalculate the amount of insulin requiredfor any given carbohydrate value andalso suggest a correction dose to restorethe blood glucose back to the normalrange if it is outside of this prior to eating. When a patient checks their fin-ger-prick blood glucose this informationis transmitted via bluetooth to thepump. Smart calculators reduce thecomplexity for patients and allow morefine adjustment of insulin for a givencarbohydrate load.2

Insulin pumps also have ‘advancedfeatures’. When a meal contains a largecarbohydrate content or a mixture ofcarbohydrate, fat and protein, theabsorption of this carbohydrate load isslower than it would be if eaten alone or

in smaller quantities. An insulin pumpcan deliver a set bolus of insulin calcu-lated for this carbohydrate load over alonger defined period of time to mimicnormal physiology.2

Additionally, insulin pumps have multiple functions to offer advantages topatients who exercise. The basal ratecan be increased or decreased by a set percentage before, during or afterexercise. There have been a number of

advances in insulin pump therapies.Patch pumps or tubeless pumps consistof a patch (reservoir of insulin and tinypump) attached to the skin with thesmart calculator and glucose monitor asa separate handheld device communi-cating by bluetooth. This has the advan-tage of no long wires connecting thepump to the patient. The technologies toassist patients in managing their dia-betes are progressing rapidly with thepotential to end blood glucose monitor-ing, by using devices that measure theinterstitial glucose in a semi-continuousmanner and communicate directly withthe pump.4

Which patients benefit frominsulin pump therapy?It is important to remember that manypatients with type 1 diabetes will managevery well on MDI. Interventions that havebeen shown to improve glycaemic controlin patients with type 1 diabetes includeout-patient teaching programmes such asBERTIE (Beta cell Education Resourcesfor Training in Insulin and Eating) or

DAFNE (Dose Adjustment For NormalEating), which teach patients self-man-agement skills.8 All patients referred forassessment for insulin pump therapymust have had the opportunity to max-imise their diabetes control using MDIand input from a specialist team. In somesituations, however, progression to insulinpump may be appropriate. The pros andcons of insulin pump therapy are outlinedin Table 1.

Problematic hypoglycaemiaMany patients with type 1 diabetes willstruggle with persistently elevated HbA1clevels. Current guidelines recommendan HbA1c between 48 and 58mmol/mol.1 Aiming for tight glycaemic controlmay result in increased frequency ofhypoglycaemia. Severe hypoglycaemia(requiring third party assistance) mayoccur in up to 40 per cent of patientswith type 1 diabetes.9 Insulin pump ther-apy may allow reduced glucose variabil-ity, which can reduce the risk ofhypoglycaemia and, therefore, increaseconfidence to improve overall control.9

Continued disabling hypoglycaemiadespite best attempts with multiple dailyinjections is a recommended indicationfor insulin pump therapy.

Persistent suboptimal diabetes controlInitiation of insulin pump therapy onaverage leads to a reduction in HbA1c ofbetween 3.3 and 6.6mmol/mol. Thegreatest reduction in HbA1c is seen inthose patients with a higher HbA1c atbaseline.10 NICE advises insulin pump

n PRESCRIBING IN PRACTICE l Insulin pump therapy

12 z Prescriber 5 March 2015 prescriber.co.uk

Table 1. Pros and cons of insulin pump therapy5–7

Pros of insulin pump therapy Cons of insulin pump therapy

• Cost-effective in terms of quality- • Costs between £2000–3000adjusted life-years (QALYs) • Not all patient want to be attached to a

• Increased flexibility in lifestyle machine 24 hours a day• Increased freedom with food • Psychological body image barriers,• Reduced hypoglycaemia and glucose particularly with teenagersvariability • Concerns over pump failure

• Possible 30–40% insulin dose reduc- • Requires increased frequency of bloodtion on initiation may help weight loss glucose monitoring

• Assists in cases of severe needle • Not always easy to change the infusion phobia set

• Benefits those with lipohypertrophy • Perceived increased risk of diabetic or lipoatrophy ketoacidosis among some patients

therapy for patients with a HbA1c above69mmol/mol. This is the level at whichinsulin pump therapy is most cost-effec-tive in terms of improvement in quality-adjusted life-years.9,11

Children and type 1 diabetesIn paediatric care thresholds for insulinpump therapy are lower because manypaediatricians see multiple daily injec-tions of insulin as being impractical forchildren. This is supported by NICE forchildren under 12 years, although thoseover 12 should be treated with the sameguidelines as adults.11 Many paediatriccentres in the UK now use insulin pumptherapy as first-line treatment upon diag-nosis of type 1 diabetes.9,12

Pregnancy and insulin pump therapyTight glucose control is advised at thetime of conception and pregnancy toreduce pregnancy-related complica-tions. Insulin pump therapy in preg-nancy can help patients achieve optimalcontrol. Any reduction in HbA1c beforeand sustained during pregnancyincreases the chance of a successfulpregnancy. The risk of hypoglycaemiaduring pregnancy can be increasedbecause of the intensive regimen toimprove glycaemic control. Insulin pumptherapy can reduce these episodes inpregnant patients.13

There are other circumstances inwhich insulin pump therapy may beadvised, such as in patients with co-exist-ing coeliac disease and in patients withcomplications such as gastroparesis.

ConclusionInsulin pump therapy is an increasinglyused method for managing type 1 dia-betes. Evidence and guidelines supportthe use of insulin pump therapy, andhave demonstrated improvements inboth HbA1c and quality-of-life measures. Selection criteria for insulin pump

therapy suggested in guidelines are use-ful in determining those patients mostlikely to benefit. The benefits and down-sides to insulin pump therapy should beexplained to patients to allow each indi-vidual to make an informed decision witha team experienced at commencinginsulin pump therapy.

References1. NICE. Type 1 diabetes: Diagnosis and man-agement of type 1 diabetes in children, youngpeople, and adults. CG15. July 2004.2. Walsh J, Roberts R. Pumping insulin:Everything you need for success on a smartinsulin pump. Torey Pines Press, 2006.3. Pickup J, Keen H. Continuous subcutaneousinsulin infusion at 25 years: evidence base forthe expanding use of insulin pump therapy intype 1 diabetes. Diabetes Care 2002;25:593–8. 4. Cummins E, et al. Clinical effectiveness andcost-effectiveness of continuous subcutaneousinsulin infusion for diabetes: systematic reviewand economic evaluation. Health TechnolAssess 2010;14(11):iii–iv, xi–xvi, 1–181.5. Hanas R, Ludvigsson J. Hypoglycemia andketoacidosis with insulin pump therapy in chil-dren and adolescents. Paediatr Diabetes2006;7(Suppl 4):32–8.6. Maynard D. Pros and cons of pumping.Discussion of the many advantages and disad-vantages of insulin pump therapy. InsulinPumpers UK, June 2001. www.insulin-pumpers.org.uk/prosandcons. 7. DAFNE Study Group. Training in flexible, inten-sive insulin management to enable dietary free-dom in people with type 1 diabetes: doseadjustment for normal eating (DAFNE) ran-domised controlled trial. BMJ 2002;325:746.8. Pickup J. Insulin-pump therapy for type 1 dia-betes mellitus. NEJM 2012;366:1616–24.9. Retnakaran R, et al. Continuous subcuta-neous insulin infusion versus multiple dailyinjections: the impact of baseline A1c. DiabetesCare 2004;27:2590–6.10. NICE. Continuous subcutaneous insulininfusion for the treatment of diabetes mellitus.TA151. July 2008.11. Johnson S, et al. Long-term outcome ofinsulin pump therapy in children with type 1 dia-betes assessed in a large population-basedcase-control study. Diabetalogia 2013;56:2392–400.12. Castorino K, et al. Insulin Pumps inPregnancy: using technology to achieve normo-glycemia in women with diabetes. Curr Diab Rep2012;12:53–9.

Declaration of interestsNone to declare.

Dr Nicholls is a specialist registrar andDr Partridge is consultant in diabetesand endocrinology at BournemouthDiabetes and Endocrine Centre, RoyalBournemouth and ChristchurchHospitals Foundation Trust,Bournemouth.

n PRESCRIBING IN PRACTICE l Insulin pump therapy

14 z Prescriber 5 March 2015 prescriber.co.uk