Paediatrics: Type 1 diabetes mellitus: insulin therapy

Type 1 diabetes mellitus: insulin therapy

Table 12.1 describes the various insulin analogue preparations (created by minor amino acid substitutions to the ‘native’ human insulin molecule).

The daily requirement for insulin varies with age:

·  at diagnosis, 0.5U/kg/day;

·  childhood/prepubertal, 0.5–1.0U/kg/day;

·  puberty, 1.2–2.0U/kg/day;

·  post-puberty, 0.7–1.2U/kg/day.

Insulin is administered SC, usually as a bolus injection. A number of patients receive insulin in the form of a continuous SC insulin infusion (CSII) deliv-ered by a pump device. Insulin injection sites include the SC tissues of the upper arm, the anterior and lateral thigh, the abdomen, and buttocks.

There is a variety of different daily insulin injection therapy regimens. The choice of regime is a compromise between achieving optimal therapy and minimizing psychosocial development. The patient and family must have input into the choice.

Insulin regimens

Two dose regimen

The simplest regimen. Two injections per day. Each injection is a mix of short/rapid-acting insulin plus an intermediate-acting insulin. Traditionally 2/3 of the total daily dose is given at breakfast and 1/3 given before/at the evening meal.

Disadvantages

·  Need to mix insulins.

·  Peak action of insulin does not correspond with timing of main meals.

·  Increased frequency of between meal and nocturnal hypoglycaemia.

·  Between meal snacks required to minimize hypoglycaemia.

Note: Less hypoglycaemia with rapid analogue insulin use.

Three-dose regimen 

Improvement and intensification of the two-dose regimen:

·At breakfast: mix of short or rapid acting insulin plus an intermediate-acting insulin.

·Before/at evening meal: short- or rapid-acting insulin only.

·At bedtime: intermediate-acting insulin only.

Advantages 

Delayed evening intermediate-acting insulin results in reduced frequency of nocturnal hypoglycaemia.

Basal bolus regimen 

This regimen attempts to mimic physiological secre-tion. Low level, background, basal insulin provides for fasting and between meal insulin requirements and larger acute doses of fast-acting insulin are given to provide for prandial requirements.

·Basal insulin: once a day intermediate- or long-acting insulin (traditionally at bedtime).

·Fast-acting insulin: At meal times (i.e. 3 per day) and with between meal snacks.

Advantages

·Increased flexibility with meal times/exercise planning.

·Insulin dose adjustment— carbohydrate (CHO) counting.

Disadvantages

·Need for more injections.

·Need more frequent blood glucose monitoring.

CSII 

Current insulin infusion pumps are reliable and portable. CSII therapy can be used in children of all ages. Short/rapid-acting insulin is adminis-tered as a continuous insulin infusion. Meal time boluses and ‘blood glu-cose correction’ boluses are administered when required.

Advantages

·No bolus injections/reduced injection frequency.

·Increased flexibility meal times/exercise planning.

·Insulin dose adjustment—CHO counting.

·Reduced frequency hypoglycaemia.

Disadvantages

·No long-acting insulin. Infusion interruption: risk of rapid DKA.

·Need more frequent blood glucose monitoring.

·Greater management expertise required.

Insulin requirements and dose adjustment 

Insulin doses are adjusted based on home blood glucose monitoring. Generally it is best not to alter the basic insulin regimen every time the blood glucose levels are outside the target range (4–10mmol/L). Rather, recorded blood glucose levels should be reviewed and insulin adjustments should be made to correct recurrent profiles that are either too low or high. Insulin doses are adjusted by 5–10% at a time.

CHO counting: insulin dose adjustment system 

Applies the principle that the amounts of fasting/rapid acting insulin given at mealtimes are adjusted and matched according to the amount of CHO consumed.