insulin pumps

Mealtime bolus applications in patients using CSII
with delayed stomach emptying

As the use of CSII to manage diabetes continues to grow, strategies are needed to address the issues related to delayed digestion and gastroparesis common in those with longstanding diabetes. With new evidence that tightening postprandial glucose values can benefit long-term complications, practical applications are needed to assist those using CSII to gain the full benefits of the technology. In addition, the use of CGM in evaluating the effects of the meal on glucose levels can provide the confidence needed to make regimen changes. This article will assist the practitioner in establishing and evaluating the application of meal bolus strategies.

Background.- Many individuals with longstanding diabetes report discomfort during and after the mealtime phase. These symptoms may include a lack of appetite, an early sense of satiety during a meal, nausea and vomiting. In addition, early meal phase hypoglycemia and later hyperglycemia are common. In the early stages of delayed stomach emptying, the first meal of the day is more effectively digested than those meals eaten later in the day. Strategies to look at diurnal variations in insulin delivery also assist in mealtime management.

Management of the meal bolus is complex. Education by the health tare professional has focused on helping the individual quantify the carbohydrate content of a meal, test and apply the individual carbohydrate ratio. Reinforcement of postprandial glucose testing, evaluation of the effects of fiber fat and meal composition are also main themes in education around the meal bolus. Out of target postprandial glucose values are often attributed to improper carbohydrate counting, or unknown meal composition /content. The most common approach in this case is to vary the carbohydrate ratios for all meals and snacks throughout the day.

CSII and Bolus Options.- CSII offers several unique options for the delivery of the meal bolus as comported to multiple daily injections. The bolus can be a normal (all bolus delivered at once) dual wave (a portion of a normal bolus, and the remainder delivered over a duration of time) or square (extended over a period of time). If needed, meals can be delayed or skipped without compromising overall health or glucose control. Using alternate bolus methods can assist in matching the prandial needs of the patient and provide safety from early meal phase hypoglycemia.

Timing.- New clinical guidelines indicate the need for control of post-prandial glucose to prevent excursions that can affect A1c and complication risk. These values however, are only applicable to the evaluation of each meal, if the pre-prandial value was in target. For example, someone who has a pre-meal glucose value of 12mmol and a 2-hour post meal value of 5.6mmol, like1y will encounter hypoglycemia prior to their next meal. Using CGM has added a new element of understanding of the post-prandial phase and has been used to clarify the subjective experience of delayed digestion.

Breakfast.- People with longstanding diabetes often have a deficit of counter-regulatory hormones which are responsible for the "dawn phenomenon". They report a flat basal) profile in the pre-dawn hours, but as upon waking, their glucose risas without food. This "delayed dawn phenomenon" is present in 15-25% of pump users. Also at breakfast time, the stomach is empty and "primed" for absorption of carbohydrates. Stimulants such as caffeine, or nicotine if taken before eating, can raise glucose levels independent of any food. Adding to this, the types of foods offered for this meal are usually highly refined.

In managing breakfast, it is important to test the overnight through mid-morning basal rate. If the basal rate is stable between 3 am and 8 or 9 am without any food or stimulants taken in, it is correctly set. People with delayed digestion are often the same individuals who have a delayed dawn phenomenon. It is therefore important to establish the presented of delayed dawn phenomenon in order to address the true carbohydrate effects at breakfast vs. the delayed effect of counter-regulatory hormones. Usually, a "normal" bolus taken at or prior to breakfast will meet the post-prandial needs for that meal.

All other meals.- Dietary interventions to address delayed digestion revoke around meal composition (mainly fat, fibra and protein) portion sine and frequency. Since carbohydrates account for 90% of the mealtime insulin requirements, it's their absorption rate that can cause early meal phase hypoglycemia and late meal phase hypergIycernia. If nausea or vomiting in the early meal phase occurs, the modified meal bolus should be taken 1/2 hour after the meal has been ingested. A dual wave delivery of a "normal" up-front bolus and a square or extended wave bolus is the optima) choice because the extended portion can be cancelled at anytime if later vomiting occurs.

There is no one approach that will effectively eliminate the need for evaluation of meal bolus timing, however; a successful starting point is to set the normal or "up front" portion at 70% of the total bolus and the remaining 30% delivered as the square or extended portion over 2 hours. In this scenario, testing at 2, 3 and 4 hours post meal will reveal) whether the total bolus needs to increase, the extended dose prolonged or increased. The priority in setting up an approach to bolus methods is to prevent early meal phase hypoglycemia. The normal or up front portion the bolus should be decreased until target one and two hour post meal glucosas occur. Alternatively, with normal 1 and 2 hour post meal glucose levels but rising 3 and 4 hour glucose levels, the square portion of the bolus may be extended to 3-4 hours and increased in total dose if needed.

When applying CGM to diabetes management, the opportunity to view the effects of specific foods is available. More importantly, identifying the trends over each meal can make optimization of insulin to carbohydrate ratio and characteristics of the post meal phase easier than two-hour post meal testing alone. Watching the immediate effects using CGM, the presence of trend arrows can be an early indicator of overall matching. With a change in glucose of more than 2mmol/L at 2 hours post meal as indicated by two arrows up and glucose already at 10mmol/L, it is unlikely that the meal bolus will accurately match the absorption profile. Using CGM can also prevent early meal phase hypoglycemia using analysis of the trending arrows. If the glucose is less than 6mmol at anytime up to 2 hours post meal and there are any downward trending arrows, hypoglycemia is a possibility. Using downloading software, the post meal phase can be evaluated and fine-tuned.

Addressing the post meal phase requires a methodical and individualized approach. Using tools such as CGM can enhance awareness of the post meal phase, which a 2-hour PC alone can miss especially in those who have delayed meal digestion.
Jill Milliken RN CDE
Diabetes Nurse Specialist - Canada
insulin pumps > mealtime bolus applications in patients using CSII with delayed stomach emptying