Diabetes mellitus consists of hyperglycemia which is caused by insulin deficiency, impairment of insulin action, or both. Majority of the patients have type 1 diabetes.
1. Classification of diabetes mellitus
Diabetes mellitus is classified into two types:
Type 1 diabetes
Type 1 diabetes is caused by absolute insulin deficiency. Most cases among children and adolescents (95%) result from autoimmune destruction of the beta cells of the pancreas.
The peak age at diagnosis is 12 years, and 75-80% of individuals develop type 1 diabetes before age 30.
Type 2 diabetes is caused by insulin resistance and relative insulin deficiency. Most type 2 diabetics do not require insulin injections and are obese.
2. Management of diabetic ketoacidosis
DKA can be seen at the time of diagnosis of type 1 diabetes or in the patient who has established disease if diabetes management is inadequate.
DKA is caused by insulin deficiency, which leads to hyperglycemia and ketogenesis.
Symptoms include polyuria, polydipsia, hyperpnea with shortness of breath, vomiting, and abdominal pain. Hyperosmolar dehydration and acid/base and electrolyte disturbances occur.
Immediate evaluation should assess the degree of dehydration by determining capillary refill, skin temperature, and postural heart rate and blood pressure.
DKA is associated with total body potassium depletion. This deficit should be replaced by infusing potassium chloride after completion of the normal saline fluid resuscitation.
Lowering the glucose level
Regular insulin should be initiated as an intravenous infusion of 0.1 U/kg per hour. The goal of therapy is to lower the glucose level by 50 to 100 mg/dL per hour.
Once the glucose level is in the range of 250 to 350 mg/dL, 5% glucose should be initiated; when the glucose level is between 180 to 240 mg/dL, the infusate can be changed to 10% glucose.
Alkali therapy is usually not necessary to correct the acidosis associated with DKA. If acidosis is severe, with a pH less than 7.1, sodium bicarbonate can be infused slowly at a rate of 1 to 3 mEq/kg per 12 hours and discontinued when the pH exceeds 7.2.
3. Long-term diabetes management
Intensive management of diabetes results in a significant reduction in the development of diabetic complications.
Starting dose of insulin
: Most newly diagnosed patients with type 1 diabetes can be started on 0.2 to 0.4 units of insulin per kg. Adolescents often need more. The dose can be adjusted upward every few days based upon symptoms and blood glucose measurements.
: Insulin should be provided in two ways– as a basal supplement with an intermediate- to long-acting preparation and as pre-meal bolus doses of short-acting insulin (to cover the extra requirements after food is absorbed).
Insulin lispro (Humalog) has an onset of action within 5 to 15 minutes, peak action at 30 to 90 minutes, and a duration of action of 2 to 4 hours. Insulin lispro is the preferred insulin preparation for pre-meal bolus doses.
Insulin aspart (Novolog)is another monomeric insulin. It is a rapid-acting insulin analog with an onset of action within 10 to 20 minutes. Insulin aspart, like insulin lispro, can be injected immediately before meals, and has a shorter duration of action than regular insulin. Insulin aspart has a slightly slower onset and longer duration of action than insulin lispro.
If the goal is relief from hyperglycemic symptoms with a regimen that is simple, then twice-daily NPH insulin will be effective in many patients. Injection of regular plus NPH insulin before breakfast and before dinner results in four peaks of insulin action, covering the morning, afternoon, evening, and overnight, but the peaks tend to merge.
Insulin glargine (Lantus)
The NPH insulin is the insulin most commonly given at bedtime, insulin glargine may be equally effective for reducing HbA1c values and cause lesshypoglycemia.
Insulin regimens for intensive therapy of diabetes mellitus
Multiple daily injections
: The most commonly used multiple-dose regimen consists of twice-daily injections of regular and intermediate-acting insulin (NPH).
Although a twice-daily regimen improves glycemic control in most patients, the morning dose of intermediate-acting insulin may not be sufficient to prevent a post-lunch time rise in blood glucose concentrations.
The intermediate-acting insulin administered before the evening meal may not be sufficient to induce normoglycemia the next morning unless a larger dose is given, which increases the risk of hypoglycemia during the night. If necessary, the twice-daily regimen can be converted into a three- or four-injection program.
Monomeric insulins, insulin lispro and insulin aspart, may be most useful in patients in whom high postprandial blood glucose concentrations and unexpected high blood glucose values at other times are problems.
Inhaled insulin may become an alternative to monomeric insulins in the future. It causes a very rapid rise in serum insulin concentrations. Typical premeal doses consists of 1.5 units per kg taken five minutes before a meal.
Blood glucose monitoring
: Children and adolescents should test their blood glucose levels at least four times a day, before meals and at bedtime. Quarterly measurement of hemoglobin A1c (HbA1c) assesses glycemic control and reflects the average blood glucose over the last 120 days.