|Dr. J. R. Conway, Diabetes Clinic, Smiths Falls, K7A 2H6
17 April 2003 Note: Numbers in parentheses refer to slide numbers of this presentation (click here to download the presentation)
The objective of this presentation (2) is to optimize Type 2 Diabetes management by assisting in initiating insulin in the Family Physician’s office. One of the biggest challenges in management of Type 2 Diabetes for both patients & physicians comes when we run out of options for oral therapy (3) and have to make the paradigm shift to insulin.
We as Family Physicians (4) are usually the Primary Care providers for Type 2 Diabetics whereas most Type 1 Diabetics are followed by Endocrinologists or Diabetes Treatment Centers. The burden of Diabetes in our office practice is often more than we realize and is growing annually (5). Furthermore Diabetics have high risk for Cardiovascular disease, early death (6) and complications (7).
In order to treat Diabetes effectively we need to understand the pathophysiology (8) so that we can understand where the patient is in the progression of the disease and thus what the primary defect is that needs to be addressed first. In the early stages of the disease we are primarily treating insulin resistance while later the main defect is insulin deficiency. The UKPDS has shown us (9) that Diabetes is a progressive disease and that irrespective of treatment, A1c values continue to rise with time (though evidence on the Glitazones indicates that we may be able to preserve pancreatic function). The reason for the progressive increase in A1c is a progressive decrease (10) in beta cell functioning which leads to increasing insulin deficiency. (11) In Type 2 Diabetes we have both impaired beta cell functioning leading to insulin deficiency as well as impaired insulin action due to insulin resistance, these combine to give hyperglycemia (12) which leads to endothelial dysfunction (13) which in turn leads to the micro- and macro-vascular complications of Diabetes. We know from clinical trials (14) that decreasing levels of glycemia decrease complications and that insulin therapy is safe and does not increase complications. Small decreases in A1c (15) can lead to major decreases in complications. In order to minimize complications (16) we need to diagnose early and treat aggressively to target of A1c <7% (17). When we can no longer achieve Glycemic control with oral agents (18), we need to add bedtime insulin (19), then adjust the dose and add daytime insulin if needed.
In summary (20); indications for starting insulin are sub optimal glycemia (A1c >7%) despite maximum therapeutic or tolerated doses of oral hypoglycemic agents or the presence of complications.
Why add insulin to oral agents, why not go to insulin alone? (21) We still have the multiple factors of insulin resistance and glucose overproduction so we are better to deal with these issues using specific oral medications. The advantage of insulin (22) is that it improves control, overcomes glucose toxicity and it is easy & safe to use. The disadvantages are (23) hypoglycemia, possible weight gain and having to learn a new treatment paradigm with injections. Our aim is to bring glucose values (24) into the normal range (25).
We usually start with bedtime insulin (25) with a small initial dose, not to affect glucose disposal but to decrease hepatic glucose production. Because of the small doses and mechanism of action the risk of hypoglycemia is low and we aim for self adjustment of insulin dose until Glycemic goals are achieved. We use NPH insulin at bedtime (27) which has a peak action of 7 hours which coincides with greatest insulin needs due to the Dawn Phenomenon of highest growth hormone secretion around 6 AM. The advantage of bed time insulin (28) is that it is safe and unlikely to cause hypoglycemia, there is minimal weight gain, it is simple and teaches patients not to afraid of insulin and to do their own insulin adjustments. With today’s injection devices (29) it is easy & painless to administer. The patient who will benefit from bedtime insulin (30) can no longer be controlled on oral agents, has relative insulin deficiency, is monitoring and has the ability & motivation to handle injections. We start at a low insulin dose (31), not trying to achieve fasting glucose control but to avoid hypoglycemia and allow the patient to become accustomed to injections. You may teach the patient injection technique in the office and then observe the first injection although some physicians like to defer this to a Diabetes Education Center. Whichever is the case, it is important at some stage to actually see the injection being given in order to see that the technique is appropriate. Keep it simple!, we should not make a big deal out of insulin injections. I usually give the patient a 3cc disposable pen with NPH in the office, get them to give a daily dose of 10u then review in 4 weeks time. The disposable pen contains 300u insulin so 28 days later there should be 20u left in the pen. At the next visit when I review technique & insulin use, if there are no problems, we may then change to another injection device such as a re-usable pen or the INNOVO if the patients drug plan will not pay for the disposable pen. At this point we also start self adjustment of insulin dose, (32). Start with a nominal insulin dose, usually 10u, (less in the thin patient), then progressively increase the dose 1 or 2 units at a time after 3 successive days with fasting glucose >7 mmol/L. I think it is important to set the upper limit of acceptable glucose at the CDA goal level so that the patient quickly learns that levels higher than this are not acceptable. I set a ceiling dose above which the patient should not go without further discussion (usually 30u), so that the insulin resistant patient or the patient with a Somogyi reaction will not go on indefinitely increasing the dose. About 20% of patients will not respond to common dosage schemes because of profound insulin resistance Our goal is to achieve Fasting glucose levels of <7 mmol/L (33). Once we achieve this goal we look for the next highest glucose level and treat this. If glucose is highest in the evening after supper we can consider a pre-mix such as 30/70, Novomix 30 or Humalog mix 25 at suppertime instead of the bedtime insulin. If glucose levels remain high throughout the day then full insulin support will be needed (34) and at that point we can discontinue oral insulin secretagogues such as Glyburide or Gluconorm. Start a short acting analogue (bolus dose) of (aspart or lispro) with meals and as basal insulin either use an intermediate acing insulin such as NPH twice a day or a long acting analogue (glargine or detemir) once a day.