BOLUS Insulin : Options and types
Rate of glucose rise in response to a meal depends upon carbohydrate content but additional factors also influence rate of glucose rise. They determine the way bolus to be delivered, i.e., Bolus Type.
There are generally 3 types of Bolus options are available with Insulin pump.
These are - Normal, Dual and Square Bolus.
1. Normal Bolus: This type of bolus is given when food consumed is predominantly carbohydrate based. Here the whole of bolus dose is given in one go. For example if the bolus given is 8 units the whole of 8 units will be delivered in 36 seconds. Normal bolus is also used as correction bolus for high Glucose.
2. Dual Bolus: This is given when food is of mixed type i.e. it contains both carbohydrates and fat. Here, bolus is split in two parts. One part is given as normal bolus and second part is square for which duration is decided by pump user depending on type of meal. In general most Indian mixed meals are better covered with Dual bolus of 70% now and 30% over 2 hours. While a very fatty meal may require 30% now and 70 % over 4 hours.
3. Square Bolus: This is given for multi-course meals eaten over a long period of time, i.e. banquets, receptions, etc., or for a meal which contains more then 40 % of protein. This can also be used in case of Gastroparesis, where absorption of food is delayed. In this type of bolus, Insulin is pumped slowly over a period of defined hours, So for example if the bolus is 8 unit is set as square for 4 hours, then 2 unit per hour insulin will be delivered and 8 units will be delivered over 4 hours.
Deciding type of Bolus:
Following information about a meal helps in deciding type of bolus-
• Carb content of meal
• Glycemic index of meal
• Protein content if high then adjustment
• Fat content if high then adjustment
• Pre-meal Glucose value. If correction needs to be given then this will be as normal bolus only.
If a meal is balanced that is nearly 60% calories are from Carbohydrate,
10 - 20% from protein and less than 30% from fat then bolus quantity depends only on carb content of meal. But if more than 30% calories is from protein or more than 40% is from fat then consideration for these factors is also needed.
A high fat meal leads to delayed carbohydrate absorption leading to a late rise in glucose.
To manage this, a pump user can
• Take Dual Bolus 50% now and 50% in next 2 hours. If this leads to low in early hours and high in late hours than can take 30% now and 70% in next 2 hours.
• In addition a high temporary basal can be set for next 4 hours. This may be considered if glucose is high after 68 hour post high fat meal.
While a high protein meal (protein contributing to more than 40% of meal), leads to rise in glucose several hours later. The rise occurs due to conversion of protein to glucose by a process called Gluconeogenesis. To cover this delayed effect from high protein meals, half of the meal bolus can be taken with meal and remaining bolus 3 hrs later or a square bolus for 2 to 3 hrs may be considered. For only protein diet [almost no carb], calculate grams of protein in meal and this needs to be divided by 2. This number can be considered as carbs in gram to calculate bolus and this Insulin will be pumped as square bolus over 4 hours.