Insulin Therapy in the Management of Type 1 and Type 2 Diabetes
Insulin Therapy in the Management of Type 1 and Type 2 Diabetes
Maureen Wallymahmed. Nursing Standard. Harrow-on-the-Hill: Oct 18-Oct 24, 2006. Vol. 21, Iss. 6; pg. 50, 7 pgs
This article describes the role of insulin therapy in the management of patients with type 1 and type 2 diabetes. It outlines the different types of insulin available, insulin regimens and the key role of nurses in patient education.
Aims and intended learning outcomes
This article provides an overview of the role of insulin therapy in the management of patients with type 1 and type 2 diabetes. It focuses on the different types of insulin available, insulin regimens and the importance of parieur education. After reading this article you should be able to:
* List the different types of insulin.
* Discuss the advantages and disadvantages of different insulin regimens.
* Identify the indications for insulin therapy in type 2 diabetes.
* Outline the management of hypuglycaemia and hyperplycaemia.
* Discuss important aspects of patient education.
Diabetes mellitus is a common, lifelong condition. In developed countries one person in 30 may be affected and it is likely that by 2025 there will he 300 million people with diabetes worldwide (Zimmet et al 2001). This is mainly the result of more sedentary lifestyles and increased obesity. In the UK it is estimated that there are more than two million people with diagnosed diabetes and up to one million who are undiagnosed (Diabetes UK 2006).
Poorly controlled diabetes causes distressing symptoms and in the long term is responsible for considerable morbidity. Complications that result in damage to small vessels (microvascular) and large vessels (macro vascular lean severely impair an individual’s quality of life and lead to early death. However, evidence confirms that improving diabetic control can significantly reduce microvascular complications in type 1 and type 2 diabetes ((Diabetes Control and Complications Trial (DCCT) Research Group 1993, United Kingdom Prospective Diabetes Study (UKPDS) Group 1998). Therefore management should be aimed at optimising glycaemic control while minimising the risk of hypoglycaemia.
Type 1 diabetes Type 1 diabetes is a common cause of chronic disease in young people and accounts for approximately 10 per cent of diabetes worldwide (Zimmet et al 2001). It results from autoimmune beta (ß) cell destruction causing insulin deficiency and must be treated with insulin injections to maintain life. Life expectancy is reduced with acute complications, such as diabetic ketoacidosis which is the biggest cause of death under the age of 30 years (Laing et al 1999). Excess mortality due to cardiovascular and cerebrovascular disease compared with the general population has been reported in people with type 1 diabetes of all ages (Laing et al 2003, Soedamah-Muthu et al 2006). Before the discovery of insulin in 1922 a diagnosis of type 1 diabetes would lead to death, usually due to diabetic ketoacidosis, within a few months.
Type 2 diabetes Type 2 diabetes accounts for the majority of diabetes worldwide and is caused either by insufficient production of insulin or by the body becoming resistant to the effects of insulin [insulin resistance). It is a progressive condition leading to a gradual loss of islet (ß cell) function and increasing hyperglycaemia. Initial management is aimed at lifestyle interventions (healthy eating and regular physical activity), however, as the condition progresses most patients require multiple oral hypoglycaemic agents-metformin, sulphonylureas and glitazones (National Institute for Clinical Excellence (NICE) 2002, Lowey 2005). It is estimated that up to 50 per cent of patients with type 2 diabetes will eventually need insulin injections to maintain good glycaemic control (Winocour 2002). As in type 1 diabetes life expectancy is reduced with cardiovascular disease being the main cause of mortality (Morrish et al 2001).
Regulation of blood glucose
In healthy individuals blood glucose levels are maintained within relatively narrow limits at about 4-7mmol/L. Insulin and glucagon, produced by the pancreas, are largely responsible for the regulation of blood glucose. Insulin is synthesised in and secreted from the ß cells within the islet sot Langerhans in response to high blood glucose levels, for example, after meals. It is inhibited by low glucose levels. Glucagon is secreted by the alpha (α) cells in response to low blood glucose levels and inhibited by high blood glucose levels.
Insulin replacement therapy
Insulin replacement therapy, using subcutaneous injections of short and long-acting insulin, is used to mimic the body’s normal insulin secreting pattern in patients with type 1 and type 2 diabetes.
The aims of insulin therapy are to:
* Alleviate symptoms, for example, thirst, polyuria, polydipsia and fungal infections.
* Minimise the risk of long-term microvascular complications, for example, retinopathy (eye damage), neuropathy (nerve damage) and nephropathy (kidney damage).
* Improve the patient’s quality of life.
In type 1 diabetes insulin is currently the only treatment option and is required to maintain life. In type 2 diabetes the main indication tor insulin is persistent poor glycaemic control (HbA^sub 1c^> 7.5%) despite maximum oral hypoglyacaemic therapy and lifestyle interventions. Insulin therapy is also indicated in women with type 2 diabetes who art-planning to become pregnant-this is because of contraindications to oral hypoglycaemic agents during pregnancy.
Other possible indications tor insulin in type 2 diabetes include: acute illness or surgery, foot ulceration and painful neuropathy. In some situations, for example, acute illness, insulin therapy may be short term with patients returning to oral hypoglycaemic agents when the acute illness is resolved. Insulin may also be indicated following myocardial infarction (MI). Malmberg et al (1995) suggest that intensive insulin therapy following MI may improve long-term survival.
Most patients now use human insulin although purified animal insulin (porcine and bovine) is still available. A wide variety of: insulin is available which, after subcutaneous injection, varies in onset and duration of action. There a re five main types of insulin preparations: rapidacting, short-acting, intermediate-acting, long-acting analogue and premixed insulin (Royal College of Nursing (RCN) 2004).
Rapid-acting insulin (also known as fast-acting analogue), such as NovoRapid®, Humalog® and Apidra®, can be injected immediately before or just after eating. After injection it begins to work in a very short time and lasts approximately three to four hours. It is usually used in combination with intermediate or long-acting insulin as part of a basal-bolus regimen (see insulin regimens). Rapid-acting insulin is clear and should not be used if it is discoloured or frosty.
Short-acting insulin (also known as soluble) such as Actrapid®, Humulin S®, Velosulin® and Hypurin® porcine neutral should be injected about 15-30 minutes before a meal, has a peak effect at about two to four hours and can List for up to eight hours. Short-acting insulin is usually combined with intermediate or long-acting insulin as part of a twice daily or basal-bolus regimen. Short-acting insulin shoukl always be clear and should not be used if it is cloudy or lumpy.
Intermediate-acting insulin such as Insulatard®, Humulin I® and Insuman Basal®, starts to work approximately one to two hours after injecting, has a peak effect ar about four to 12 hours and can last up to 24 hours. It can be used in combination with rapid or short-acting insulin or with oral hypoglycaemic agents in type 2 diabetes. Intermediate-acting insulin is cloudy and should not be used if clumping in the container is noted.
Long-acting analogue insulin such as Lantus® and Levemir® has a prolonged duration of action without a peak. Lantus® is usually given once daily and can he used along with rapid or short-acting insulin, or m combination with oral hypoglycaemic agents in type 2 diabetes. Levemir® can be given once or twice daily. Both of these insulins, although long-acting, are clear and it is important to make patients aware of this.
Premixed insulin (also known as biphasic) such as NovoMix30® and Humalog® Mix25 are prefixed mixtures of rapid-acting analogues and intermediate insulin. For example, NovoMix 30® consists of 30 per cent rapid-acting insulin and 70 per cent intermediate-acting insulin. These insulins can be injected immediately before or after eating, which is convenient for many patients. Mixtures of soluble and isophane insulin, for example, Mixtard® 30, Humulin M3® Insuman® Comb 25 should be injected about 30 minutes before eating and are therefore not as convenient as mixtures containing rapid-acting analogues. Premixed insulin is cloudy and needs to be inverted or the delivery device rotated about 20 times to mix the insulin before use.
Insulin can be kept at room temperature for up to 28 days. Spare pens, cartridges or vials should be kept in the fridge at 4-8°C. Patients should be reminded to always check the type of insulin and expiry date before use. For more information on different insulin preparations please refer to the British National Formulary (BNF) (2006).
Insulin delivery devices
Over the past decade considerable advances have been made m insulin delivery devices and most patients now use insulin pens to administer insulin rather than insulin syringes. However, some patients still prefer to use a syringe and personal choice should alwavs be considered. There are two main types of insulin pens: preloaded (disposable) and cartridge (reloadable) pens. Choice of device is usually down to the individual, however, the decision may he guided by the following factors: dexterity-some pens are heavier and the plunger is more difficult to push down; visual impairment – some pens have audible clicks and simplicity. Selection of the most appropriate insulin device-is impotant and can help to maintain a patient’s independence. It is important to remember that most insulin devices are insulin-specific so, in some cases, the choice of insulin is determined by the patient’s ability to manage the device.
Continuous subcutaneous infusion Insulin can also be delivered by a continuous subcutaneous insulin infusion using an insulin pump. Insulin (soluble or fast-acting analogue) is delivered at a set rate, on a continuous basis with premeal bolus doses. Although this method of insulin delivery has become more popular over recent years, patients need to he motivated and require considerable education.
Inhaled insulin Inhaled insulin (Exubera®) has nou been licensed for use in the UK. Inhaled insulin is fast-acting and can be used in combination with intermediate or long-acting insulin in type 1 diabetes, or in combination with oral hypoglycaemic agents in type 2 diabetes. Inhaled insulin is contraindicated in patients who smoke and those with severe asthma. NICE is currently considering the clinical indications for inhaled insulin. Preliminary recommendations suggest that it may be useful in patients with proven needle phobia (diagnosed by a psychologist or psychiatrist) and those with severe persistent injection site problems, for example, lipohypertrophy (fatty lumps) (NICE 2006). The final document is expected later this year.
The choice of insulin regimen and insulin type should be made on an individual patient basis taking into account social circumstances, lifestyle, osmotic symptoms and weight.
Insulin in combination with oral hypoglycaemic agents In obese patients with type 2 diabetes there is good evidence that combining once daily intermediate or long-acting insulin with metformin is more effective than insulin alone (Wulffele et al 2002, Kilo et al 2003). Advantages of combination therapy include less risk of weight gain and hypoglycaemia and simplicity of the regimen (RCN 2004). Insulin can also be used in combination with a sulphonylurea, for example, gliclazide or with metformin and a sulphonylurea. In some cases, once daily insulin is not enough to achieve good glycaemic control and twice daily insulin is needed.
Twice daily insulin Twice daily insulin, usually using premixed insulin, is a commonly used insulin regimen in type 1 and type 2 diabetes. Insulin is injected before break fast and the evening meal, and the combination of two different types of insulin provides insulin cover over the 24-hour period (Figure 1). This insulin regimen is suitable tor patients with a regular lifestyle who eat at a regular time each day. Patients with type 2 diabetes who are thin or of normal body weight, or who are symptomatic and losing weight due to poor glycaemic control, are best managed on twice daily insulin, rather than mice daily insulin in cnmbinarinn with oral hypoglvcaemic agents.
Basal-bolus regimen A basal-bolus insulin regimen (multiple injections) aims to mimic the natural pattern of insulin secretion. A basal injection of intermediate or long-act ing analogue insulin is given once a day, often at bedtime, to provide ‘background’ insulin. In addition a bolus dose of rapid or short-acting insulin is given at meal times to cover rises in blood glucose after eating. Because of their peak less action, long-acting insulin analogues (Lantus® or Levemir®) are useful as basal insulin with rapid-acting insulin analogues for meal time cover (Figure 2).
A basal-bol us insulin regimen allows greater flexibility over when and how much people want to eat and is suitable for those with irregular working patterns, for example, shift workers. However, it does require at least four injections per day which is not acceptable to some patients. In type 1 diabetes intensive insulin regimens such as this have been shown to lead to improvements in glycaemiccontrol and a reduction in the risk of complications (DCCT Research Group 1993, WritingTcam for the Diabetes Control and Complications Trial Kpidemiology of Diabetes Interventions and Complications Research Group 2002). Many patients now alter their own insulin on a meal-to-meal basisaccordingto carbohydrate intake. Such an approach has been shown to have beneficial effects on glycaemic control and patient satisfaction (DAFNK Study Group 2002. Shearer et al 2004).
Side effects of insulin therapy The main side effect of insulin therapy is hypoglycaemia, which is discussed in detail later. Lipohypertrophycan develop and is usually caused by injecting into the same site. Lipohypertrnphy is unsightly (Figure 3), can lead to erratic alisorptii m of insulin, poor glycaemic control and has been reported in nearly 50 per cent of patients (Wallymahmed et al 2004).
Education of patients starting on insulin
For must patients a diagnosis of din betes means considerable lifestyle changes and for patients with type 1 diabetes, insulin injections can add to the stress. In type 2 diabetes it is important to talk about the progressive nature of the condition and to acknowledge that after several years of diabetes many patients need insulin injections. The positive aspects ofinsulin treatment such as an improvement in osmotic symptoms- for example, thirst, passing lots of urine-should be stressed. In type 2 diabetes where patients may be asymptomatic the benefits of improving diabetic control, for example, reducing the risk of complications, should be emphasised. Most patients feel anxious at the prospect of starting insulin injections. The greatest fear is self-injection and a practice ‘needle insertion’ can often allay the fear.
Initial education Education is a vital aspect of self-management in people with diabetes and features heavily in the National Service Framework for Diabetis: Standards document (Department of Health (DH) 2001).
Insulin injection technique Good injection technique is important in achieving glycaemic control and nurses have a mainrrole in educating patients. Important aspects of injection technique include:
* Teaching the patient how to use the injection device and discussing the type of insulin, dose, regimen and timing of. injections. Reassessing insulin injection technique on a regular basis.
* Insulin should be injected at a 90° angle into the subcutaneous far. It is not necessary to clean the injection site with an alcohol wipe because this can cause pain and make the skin hard.
* Rotation of injection sites is important because insulin absorption rate varies from site to site (abdomen fast absorption, buttocks slower absorption) and to prevent lipohypertrophy.
* Patients with type 2 diabetes should know which oral hypoglycaemic agents to continue with and which to stop.
* Pen needles come in a variety of lengths (5, 6, S and 12mm I, shorter needles are suitable for most patients. Needles should only be used once and should be disposed of safely (arrangements will vary locally).
Some patients will not be able to give their own insulin and will need support from the family, ind district nursing team.
Insulin is anabolic and can cause an increase in body weight All patients starling on insulin should be referred to a dietician because dietary advice ca n minimise weight gam. General dietary advice can, however, he given by nurses and should include a voiding sugary food and drinks and eating regular meals.
Home blood’glucose monitoring Most, but not all, patients starting on insulin should be taught home blood glucose monitoring (capillary blood glucose). There are a variety of meters available and frequency of monitoring will depend on the patient and the regimen. Patients who altcr their own insulin may monitor their blood glucose levels up to six tunes daily.
It is important to advise patients to calibrate and quality control blood glucose meters on a regular basis to ensure accuracy of results.
Hypoglycaemia occurs when the blood glucose level falls below 4mmol/L and is a common side effect of insulin therapy. Causes of hypoglycaetnia include missed or late meals, not eating enough, taking too much insulin, exercise and excessive alcohol. All patients starting on insulin injections should be given advice on the causes, avoidance, recognition and treatment of hypoglycaeniia. The following points should be discussed with .ill patients or their carers as appropriate:
* Common ma infestations of hypoglycaemia include sweating, shaking, palpitations, hunger and poor concentration.
* Hypoglycaemia should be treated with fast-actingcarhohydrate, for example, 3-6 glucose tablets, 15OmI fizzy drink or 50-100ml Lucozade®, and followed up with a longer-acting carbohydrate, tor example, biscuits or a sandwich.
* Glucose gels, for example, ClucoGcl® are useful to raise blood glucose levels.
* Blood glucose should be recorded five to ten minutes after treatment.
* Patients should be advised to carry identification (stating diabetes treatment) and easily accessible glucose, for example or Lucozadc®, Dextrasol®.
Severe hypoglycaemia If the patient is unable to take carbohydrate or is unconscious then glucagon 1mg may be given intramuscularly. Glucagon is available on prescription and relatives should be educated on its use. In hospital settings glucagon should be readily available; alternatively 50ml20% dextrose can he given intravenously (BNF 2006).
It is important to remember that bedside blood glucose meters are not always accurate at low reading and that hypoglycacmia slum Id Iv considered in patients with typical symptoms. Insulin injections should tint be omitted duetn a single hypoglycaemic episode, the hypoglycaemia should be treated and usual insulin dose given. However, if the patient is experiencing frequent hypoglycaemic episodes then his or her treatment sin mid be reviewed.
Intercurrent illness, such as infection, can have an effect on glycaemic control causing blood sugars to rise and can lead to diabetic ketoacidosis. Patients should be advised to never stop taking insulin, monitor blood sugar frequently (sometimes every two hours), test urine tor kenmes (it positive,can be an indication of insulin insufficiency), drink plenty of fluids, increase insulin if Wood glucose is raised (increases of about 20 per cent are recommended) and seek advice early. If vomiting and diarrhoea are present dehydration can occur quickly and advice should be sought. Other causes of hyperglycaemia include: systemic corticosteroids, dietary factors, non-concordance with medication and stress.
Diabetic ketoacidosis (DKA) is a medical emergency and is a significant cause of morbidity and mortality in patients with type I diabetes. Precipitating causes include: intercurrent illness, infections, omission of insulin and newly diagnosed type I diabetes. Presenting features include: hyperglycaemia, ketonuria, thirst, polyuria and polydipsia. Acetone (which smells like pear drops) can often be detected on the patient’s breath. Vomiting can lead to severe dehydration and patients should be referred to the hospital emergency department immediately. Principles of treatment are rehydration, correction of electrolyte imbalance (mainly potassium depletion) and insulin treatment. dKA is potentially preventable. Patients and healthcare professionals should be educated on management of illness and when to seek advice. Although DK A predominantly occurs in type I diabetes, it can occur in patients with type 2 diabetes during severe intercurrent illness.
Monitoring glycaemic control
Glycated haemoglobin IHbA^sub 1c^) is the standard way of monitoring glycaemic control. This blood test measures the percentage of haemoglobin bound to glucose and is useful because it reflects about two to three months’ of blood sugar control. Target HbA^sub 1c^ levels are 6.5-7.5 percent depending on individual circumstances, for example, complications (NICE 2002, 2004). In addition, when monitoring control, the following should be taken into account: capillary blood glucuse monitoring (home or hospital), symptoms, frequency of hypoglycaemia and weight. Because acute illness can alter blood sugar control it is useful for all inpatients with diabetes to have an HhA^sub 1c^ blood test while in hospital.
Driving Patients treated with insulin must inform the Driver and Vehicle Licensing Agency (DVLA) and are usually issued a licence for one, two or three vehicle. They are not allowed to hold a large goods vehicle (LGV) or passenger carrying vehicle (PCV) licence and must undergo a medical assessment before applying for a Cl licence, which is required for vehicles weighting 3.5-7.5 tonnes. They must infurmtlie DVLA irrelevant complication s develop, for example, eye problems affecting visual acuity or inability to recognise hypoglycaemia. Patients must also inform car insurance companies that diabetes has been diagnosed and treated with insulin.
Employment Diabetes managed by diet or tablets poses leu restrictions to employment, provided that complications are not present. However, statutory medical standards may prevent patients on insulin from enter ing certain types of work because of the risk of hypoglycaemia. Occupations that may have such restrictions are: the armed forces, the police, the fire service, taxi driving (although this depends on the local authority worked for), airline pilot and jobs requiring a LGV or PCV licence, for example, bus or train driver. If diabetes is diagnosed in an individual already empluyed in some of the occupations mentioned, it is sometimes possible to continue. The charity Diabetes UK can be contacted for up-to-date information on employment rights and restrictions.
Ongoing education Education of people with diabetes is aimed at self-management and should be a lifelong process. Formal education should he patient-centred, structured and delivered by healthcare professionals trained in adult education techniques (DH 2005). However, opportunist informal opportunities for patient education present themselves on a day-to-day basis and nurses working with patients who have diabetes should endeavour to use such occasions. Many centres now developed care path ways tor patients starring on insulin (Cartwright et al 2006), which may include group education sessions.
Educating patients in groups can have many benefits because patients are able to meet others who are starting on insulin iind support each other. Discussion points are generated in the group and patients are able to learn from the experiences of others-this is particularly important when managing practical situations, such as eating out. However, not everyone is happy in
the group situation and most will benefit from a combination of individual and group-based sessions (Wailymahmed and MacFarlane 2005).
Insulin therapy is currently the only treatment option available for patients with type 1 diabetes. It also has a major role to play in type 2 diabetes because of the progressive nature of this condition. Many patients are initially reluctant to start on insulin injections mainly because of anxiety about self-inject inn. Education should be aimed at encouraging self-management skills. Nurses working with patients with diabetes should use every opportunity to promote diabetes education