1998 clinical practice guidelines for the management of diabetes in Canada

Supplement to CMAJ 1998;159 (8 Suppl)

© 1998 Canadian Medical Association

The primary goal of therapy is to maintain the person's health in the broad sense of the word. Clearly, avoidance of acute and long-term complications is a major concern. In addition, the person's quality of life and overall sense of well-being are an integral part of management. Because virtually every aspect of daily life may be affected by management, it must always be remembered that the person with diabetes is the key member of the DHC team. For most people with diabetes, improving metabolic control will prevent the onset or delay the progression of long-term complications. Depending on the type of diabetes and the therapy required, this objective may be more or less difficult to achieve without acute adverse effects. The metabolic goals of treatment must, therefore, be tailored to the individual person and include consideration of the family and other psychosocial factors.

Examination and assessment

At the first visit of a person with newly or previously diagnosed diabetes, the primary care physician should conduct a comprehensive medical interview, focusing on the nature and extent of diabetes symptoms. A complete medical history should be obtained with special emphasis on potential risk factors for chronic disease. The information outlined in Table 6, Table 7, Table 8, Table 9 and Table 10 may have to be obtained in stages, but it is essential for comprehensive diabetes management. If diabetes has been diagnosed previously, information should be sought on a number of items, as indicated in Table 7.

A comprehensive physical examination should be performed, with special attention to systems affected by diabetes. Laboratory investigations, in addition to glycated hemoglobin and plasma glucose levels (to verify the accuracy of self-monitoring and assess immediate glycemic status), should be carried out (Tables 9 and 10). This information forms the basis for a long-term care plan.

Diabetes is a chronic disease, and those with diabetes require regular medical assessment and laboratory testing to ensure optimal health. Some newly diagnosed people with diabetes may require daily visits, whereas others could require weekly or monthly visits until target goals for metabolic control are achieved. Thereafter, all people with diabetes should be followed every 2 to 4 months, although more frequent visits should be scheduled if indicated.

Targets for metabolic control

There is strong evidence that decreasing blood glucose levels toward the normal range reduces the frequency of microvascular complications^76,77 and that improving lipid levels reduces the frequency of CAD.⁷⁸ Nevertheless, the levels required to maximize these benefits, while keeping side effects to a minimum, remain subject to debate.

Glucose levels

The target glucose levels defined in Table 11 apply to most adults and adolescents with diabetes mellitus. "Ideal levels" are levels within the normal range for people without diabetes. This level of glucose control may be attainable early after diabetes onset in those managed with diet therapy but rarely in those requiring pharmacologic therapy (attained in less than 5% of the intensive therapy group of the Diabetes Control and Complications Trial [DCCT]⁷⁷).

"Optimal levels" are those that approach the normal range and are associated with a low risk of developing chronic complications of diabetes. However, these levels may be impossible to attain in some people without severe side effects (e.g., hypoglycemia, decreased quality of life) and difficult to obtain in many (in the DCCT, they were attained in fewer than 50% of people in the intensive therapy group⁷⁷).

"Suboptimal glucose levels" attainable in the majority of people with diabetes (90% of subjects in the intensive therapy group in the DCCT⁷⁷), range between 7.1 and 10 mmol/L before a meal and between 11.1 and 14 mmol/L after a meal. However, most people with diabetes should strive to lower glucose levels further toward optimal levels. For certain people (e.g., those under age 5, those with hypoglycemic unawareness or those with a short life expectancy), this "suboptimal" level of glucose control may be the best that is safely attainable.

"Inadequate glucose levels" are associated with acute symptoms of hyperglycemia and a markedly increased risk of chronic complications and require reassessment and readjustment of therapy.

Lipid levels

The relation between lipid levels and CAD is discussed in the complications section. Target lipid levels for the prevention of CAD in people with diabetes are similar to those for people without diabetes. Table 12 shows these targets and also acknowledges the fact that diabetes itself is a potent risk factor for CAD in both men and women after age 30. Thus, a 35-year-old man with diabetes already has 2 key risk factors and an associated 10-year risk of CAD of 10% to 20%.⁷⁹

Monitoring blood glucose control

The ability of people with diabetes to monitor daily changes in blood glucose has markedly improved the ability to control glucose levels. It permits recognition of low levels of blood sugars before major problems occur^80,81 and allows people to assess the effects of diet, exercise and changes in treatment regimens. The person with diabetes, in consultation with health professionals, should decide on the frequency of blood glucose measurements, taking into account the benefits of monitoring and the cost and pain associated with the procedure.⁸² Many people treated through diet or with oral agents benefit from the assessment of fasting and postmeal testing. People with type 1 diabetes often use premeal and bedtime tests, as well as intermittent postmeal testing to adjust their insulin doses.

Optimal use of blood glucose self-monitoring requires a periodic (at least annually) verification of accuracy. The level measured in capillary blood using a meter should differ by less than 15% from a simultaneous laboratory measurement of a fasting venous blood sample.⁸³ Testing for glycated hemoglobin should be performed periodically to assess overall glucose control, as it reflects glucose control over the preceding 2 to 4 months. If discordance in the assessment of the glucose control is apparent between self-monitoring of blood glucose at home and the HbA_1c measurement, despite verified accuracy of the meter, the use of memory-equipped meters should be considered. Supplemental checking of urine for ketones and more frequent monitoring of glucose level may be required in certain situations, such as during pregnancy and in people with type 1 diabetes during intercurrent illness or when the blood glucose level is consistently over 15 mmol/L.⁸²

Recommendations

19. Glycated hemoglobin should be measured every 3 to 4 months in all patients taking insulin and at least every 6 months in people on nutrition therapy or oral hypoglycemic agents. [Grade D, consensus]
20. Self-monitoring of blood glucose level is an essential component of the therapeutic plan of
    • all people with type 1 diabetes [Grade B, Level 2⁸⁴]
    • all pregnant women with pre-existing diabetes or GDM [Grade B, Level 1⁸⁵]
    • all insulin-treated people with type 2 diabetes. [Grade D, consensus]
21. Self-monitoring of blood glucose level is an integral component of the therapeutic plan for the majority of people with type 2 diabetes treated with oral hypoglycemic agents. It may be useful for people with type 2 diabetes controlled by diet therapy alone. [Grade D, consensus]
22. To ensure optimal self-monitoring of blood glucose level, the person with diabetes must be educated on the use of the glucose meter [Grade A, Level 1⁸⁶], interpretation of the results and (where possible) how to modify treatment according to blood glucose levels. [Grade D, Level 5⁸⁷]

Metabolic therapy for type 1 and type 2 diabetes

In people with type 1 diabetes, glucose control will depend on coordination of insulin doses, food intake and physical activity. In those with type 2 diabetes, deterioration of control over the disease over time is common and is associated with progressive deterioration of beta-cell function that occurs independently of the initial therapeutic approach chosen.^88,89 Therefore, it can be expected that therapy for people with diabetes will have to be progressively augmented over time. If the individually determined target levels for people with type 2 diabetes have not been attained within 2 to 4 months, the next level of therapy should be introduced, as indicated in the stepwise approach outlined in Figure 1.

Nutritional approaches

Nutrition is often said to be the cornerstone of diabetes care, but it is a controversial and complex topic. The following is not intended to be a complete discussion of the many issues involved, but merely to highlight some of the general principles and recommendations of the CDA. A detailed review of the nutritional management of diabetes is being prepared by CDA's National Nutrition Committee.

Everyone with diabetes should receive individual advice on nutrition and, whenever and wherever possible, they should be referred to registered dietitians who will assess their current intake and individual nutritional needs. In nutrition counselling, a number of factors must be considered to empower people with diabetes to achieve treatment goals. These factors are type of diabetes, lifestyle, socioeconomic issues, presence of obesity, progression of beta-cell dysfunction, type of treatment, personal preferences and the nature of any complications.

The dietitian, in cooperation with the DHC team, will provide education and development of skills to promote healthy eating habits, as well as continuing support as necessary through follow-up appointments. Nutrition counselling should be an ongoing process, with a stepwise increase in the complexity of the information given to the patient. Other members of the DHC team should discuss and reinforce dietary strategies with the person with diabetes.

In type 2 diabetes, nutritional approaches are oriented toward improving glucose and lipid levels through diet modification and weight loss when appropriate.⁹⁰ If weight reduction is needed, it should be attempted gradually (0.25 to 1.0 kg/wk). In type 1 diabetes, the major efforts are directed toward coordination of food intake (particularly carbohydrates) and insulin dosages to improve glycemic control.

Recommendations

23. All people with diabetes should receive individual advice on nutrition from a registered dietitian. [Grade D, consensus]
24. In obese people with type 2 diabetes, diet therapy as well as lifestyle changes incorporating increased physical activity should be the initial therapy, as this can result in improved metabolic control and weight loss. [Grade B, Level 1⁹¹]
25. Nutritional recommendations for people with diabetes are the same as those of Health and Welfare Canada for the general population. This includes choosing a variety of foods from the 4 food groups (grain products, vegetables and fruits, milk products and meat and alternatives), attaining a healthy body weight, decreasing saturated fat intake to less than 10% of calories and having an adequate intake of carbohydrate, protein, vitamins and minerals. The distribution of nutrients may be tailored to the individual patient depending on needs and personal preferences. Meal-planning, using approximately 55% carbohydrate and 30% fat content often serves as a starting point in the development of specific recommendations. [Grade D, consensus]
26. Sucrose and sucrose-containing foods can be substituted for other carbohydrates as part of mixed meals, up to a maximum of 10% of calories, provided adequate control of blood glucose and lipids is maintained.⁹² [Grade B, Level 2⁹³]

Physical activity and exercise

An active lifestyle promotes cardiovascular fitness and well-being,⁹⁴ increased insulin sensitivity, lower blood pressure and a healthy lipoprotein profile in all people with diabetes. A consistent, stepwise increase in physical activity may also improve glycemic control and reduce the need for medications in people with type 2 diabetes.⁹⁵

Knowledge of the acute effects of exercise is mandatory for any person treated with insulin. Unless considerable hyperglycemia (i.e., >15 mmol/L) is present, low to moderate intensity exercise lowers glucose levels both during and after the activity, increasing the risk of a hypoglycemic episode. Conversely, intense exercise systematically raises glucose levels, both during the activity and for variable durations afterward, and can lead to progressive hyperglycemia (and even ketosis in people with type 1 diabetes), particularly in those who are hyperglycemic before exercising.

These effects on glucose levels can be moderated by altering diet, insulin and the type and timing of exercise. Systematic self-monitoring of glucose level before, during and especially for many hours after exercise is, therefore, important for establishing the patient's response to exercise and guiding the appropriate management of exercise. In patients with type 1 diabetes, the use of intensive diabetes management regimens with either multiple daily injections or continuous subcutaneous insulin infusion (CSII) provides additional flexibility in appropriately modifying the insulin dose for exercise.^96,97

Finally, the advantages of increased activity levels must be balanced against the risks.⁹⁸ For example, patients with macroangiopathy are susceptible to cardiac or other ischemic events and to cardiac arrhythmias; patients with proliferative retinopathy are at risk for vitreous hemorrhage; and patients with neuropathy are susceptible to lower extremity (particularly foot) injuries.

Recommendations

27. A stepwise increase in physical activity that is integrated into the person's lifestyle should be part of the therapeutic plan for everyone with type 2 diabetes who is able to increase activity. It should be prescribed with specific modifications for people with known occlusive vascular disease (or at high risk of subclinical disease), significant sensory polyneuropathy or advanced microvascular complications. [Grade D, consensus]
28. In anyone treated with insulin, recommendations regarding alterations of diet, insulin regimen, injection sites and self-monitoring should be appropriate for the general level of physical activity or specific types of exercise undertaken. Oral agent doses may need to be decreased. [Grade D, consensus]
29. The initiation of a vigorous exercise program requires an appropriate, detailed history and physical examination and specific laboratory investigations (e.g., exercise-stress cardiography in those over 35 years of age). [Grade D, consensus]
30. General advice regarding physical activity for everyone with diabetes includes:
    • use proper footwear, inspect both feet daily and after each exercise session, if indicated, and use adequate protective devices
    • avoid exercising during any period of poor metabolic control
    • ingest rapidly absorbed carbohydrate if pre-exercise glucose level is under 5 mmol/L
    • avoid exercise in extreme hot or cold conditions.
    • administer insulin into a site away from the most actively exercising extremities. [Grade D, consensus]