Transitions in Care. Howard A. Wolpert

to have the best glucose control possible. The challenge is how you achieve good control and how you balance the day-to-day demands of diabetes with the other demands (and pleasures!) of life. In this section, we will explore this difficult balancing act between diabetes and the rest of your life. In addition, we will outline a roadmap, which may help you get and stay on track with your diabetes.

UNDERSTANDING INSULIN REPLACEMENT

      Before we get to the principles about how to achieve good blood glucose control, we’re going to present a brief review of how insulin regulates glucose metabolism in the body. As you probably know, insulin is a hormone produced by the beta-cells in the pancreas. There are two different components to the insulin in circulation (see Figure 1):

      

Background insulin (also commonly referred to as basal insulin) controls the blood glucose levels in between meals and overnight. During these periods, the liver (which acts like the body’s glucose reservoir) is continuously releasing glucose into the bloodstream to provide energy for basic functions in the body. Insulin helps control this process. Without basal insulin, there would be an excessive release of glucose by the liver, and glucose levels in the blood would rise. In addition, in the absence of basal insulin, the liver starts producing ketone bodies, and these can accumulate in the blood, leading to a dangerous condition known as diabetic ketoacidosis.

      

Insulin surges at mealtimes (also commonly referred to as insulin boluses) cause the tissues of the body to take up glucose from the bloodstream. The amount of insulin produced in these mealtime surges is precisely controlled to ensure that there is just enough to take care of the carbohydrates being eaten. Eat a bit more, and more insulin is produced; eat a bit less, and less insulin is produced.

FIGURE 1 A 24-hour insulin and glucose profile in a person without diabetes.

      In type 1 diabetes, the immune system (which is normally involved in combating infections) misguidedly attacks and destroys the beta-cells in the pancreas. The end result is that the body can no longer produce insulin. The fundamental challenge in treating type 1 diabetes is in replacing the insulin your body is no longer making and taking just enough insulin to match your body’s needs. Too much insulin leads to low blood glucose levels and too little leads to high blood glucose. Trying to avoid large ups and downs in your glucose numbers is another challenge in treating type 1 diabetes; dramatic variations in your numbers can be particularly unpleasant.

APPROACHES TO INSULIN TREATMENT

      The insulin profile shown in Figure 2 may be familiar to you. In this traditional approach to insulin replacement, there are two injections of rapid-acting insulin (Apidra, Humalog, Novolog, or regular) at breakfast and dinner and two injections of a longer-acting insulin (NPH) to provide your body with basal insulin. Typically, the rapid-acting and longer-acting insulins are either premixed in one vial or one pen, or you can mix the two insulins into one syringe, so that you administer two injections per day, with two different insulins in each injection. The rapid-acting insulin injections take care of the carbohydrates eaten at breakfast and dinner, while the morning injection of NPH covers lunch and the evening injection of NPH controls the sugar that the liver releases into the bloodstream overnight. Striving for good glucose control using this type of insulin program can be challenging. These are some of the constraints:

      

If lunch is delayed, the morning injection of NPH will kick in and hypoglycemia (low blood glucose reaction) could result.

      

Snacks will often need to be eaten between meals (especially mid-morning and bedtime) to prevent the long-acting insulin from causing hypoglycemia.

      

Lunch and snacks will need to have a consistent carbohydrate content. If you eat too many carbohydrates, there may be insufficient insulin in the system and the blood glucose level will end up rising. If you eat too few carbohydrates, there may be more insulin in your body than you need to cover your food, and your blood glucose level may fall.

      

Waking times in the morning need to be consistent from one day to the next. If you get up later in the morning, the longer-acting insulin taken the evening before (to control the production of glucose by the liver overnight) may be running out, and the end result will be an increased glucose level.

      

Hypoglycemia in the middle of the night can occur if a bedtime snack is not consumed.

FIGURE 2 Injection therapy using Humalog/Novolog and NPH/lente. In this approach, there are two injections of rapid-acting insulin at breakfast and dinner and two injections of NPH/lente insulin to provide the basal insulin. B, breakfast; L, lunch; SN, snack; SUP, supper.

      As with most choices in our lives, there is a tradeoff with these insulin programs. There is no need for a lunchtime injection, which can be an important consideration for someone who would find this extra injection inconvenient or impractical at school. But if you want to keep your glucose levels within any targeted range, you need to follow a fairly regimented and consistent routine and meal plan. This means that meals and snacks need to be eaten at specific times, and the carbohydrate content of meals needs to be consistent from one day to the next. To address the risk of hypoglycemia in the middle of the night, some people will administer the rapid-acting insulin at dinner and the longer-acting insulin at bedtime. That way, the NPH is not peaking at 2:00 a.m. when you are asleep. This choice of an insulin regimen means administering three injections per day.

      The development of peakless long-acting insulins and insulin pumps has presented new options for insulin replacement. With these tools, we can be closer to mimicking the way the beta-cells of the pancreas release insulin into the body.

      This approach to insulin replacement (shown in Figure 3)—also known as basal/bolus therapy—allows more flexibility in a person’s schedule and eating. Insulin can be matched to cover the amount of food eaten, and there’s no need to eat on schedule. In addition, because the longer-acting insulin does not peak, there is no need to eat snacks between meals to prevent hypoglycemia. This can be quite helpful with weight control (see page 32). But this type of insulin program generally requires more injections per day or the use of an insulin pump.

DECIDING WHICH INSULIN PROGRAM IS RIGHT FOR YOU

      Some individuals will need a different insulin program for each phase of their life. For example, during the school years, when taking a lunchtime injection in the cafeteria can be impractical, the NPH-based insulin program may work best. Later during the college years, the extra flexibility provided by the basal/bolus program may be a real advantage. There are a couple of considerations in weighing the decision about whether to use injections or a pump for basal/bolus insulin replacement. Some find that it can be a hassle to take an extra injection every time they want to snack or have eaten more than planned, and with a pump, it is easy to take a bolus of insulin whenever there is a need. However, before you decide on the pump, there are two key questions you should ask yourself. First, “How comfortable will I be with wearing a pump and having an outward sign of diabetes?”