INSULIN ADMINISTRATION DEVICES
INSULIN PUMP THERAPY:
"Insulin pump therapy consists of a programmable infusion device that allows for basal infusion 24hrs daily as well as bolus administration before meals and snacks".
- Regular or rapid acting insulin is delivered from a reservoir either by infusion set tubing or through a small canula.
- Most infusion pumps are set in the abdomen, arm or other infusion sites by a small needle.
- Most patients prefer insertion in the abdominal tissue because this site provides optimal insulin absorption.
- Infusion sets should be changed every 2-3 days to reduce the possibility of infection.
Determination of Insulin Units:
- Patients use carbohydrate-to-insulin ratio to determine how many units of insulin are required.
- More specifically, an individual's ratio is calculated to determine how many units of the specific insulin being used in the pump "covers" for a certain amount of carbohydrates to be ingested at a particular level.
1. The 450 Rule (for Regular Insulin) or the 500 rule(for Rapid acting Insulin) are the most commonly used.
The 500 Rule:
- To calculate the ratio using 500 rules; the patient would divide 500 by his or her total daily dose of insulin.
- Eg; If a patient were using 25 units of insulin daily, his/her carbohydrate-to-insulin ratio could be 500:25 or 20:1.
This ratio theoretically means that 1 unit of rapid acting insulin should cover 20g of carbohydrates.
- If the blood glucose levels are below or above the desired blood glucose target, the amount of insulin can be adjusted.
- Once this ratio is determined, patients can eat more or fewer carbohydrates at a given meal and adjust the bolus dose accordingly.
Correction Doses:
In addition to meantime boluses, Correction doses based on premeal readings are also used.
- The amount of additional insulin for the correction is based on either the 1500 rule for regular insulin or the 1800 rule for rapid-acting insulin.
- For eg; if using the rapid acting insulin, divide 1800 by the patients total daily insulin dose. The resulting value will represent the reduction in glucose (mg/dL) produced by one unit of Insulin.
The 1800 rule:
- Using the 1800 rule; we find that 1800 is divided by 60 which gives 30. Thus, 1 unit of rapid acting insulin would be added for every 30mg/dL the patients' glucose is above the premeal glucose levels as a correction factor.
The correction dose would be given in addition to the bolus dose needed based on the patient's carbohydrate-to-insulin ratio and the amount of carbohydrates present in the meal he/she is about to consume.
USES OF INSULIN PUMP THERAPY
Insulin pump therapy may be used to
- lower blood glucose level in any level of DM
- Patients of T1DM are most likely candidates to use these devices.
- Use of an insulin pump may improve blood glucose control, reduce wide fluctuations in blood glucose levels, and allow individuals to have more flexibility in timing and content of meals and exercise schedules.
DRAWBACKS
- Insulin pump therapy is not for everyone, and the complexity associated with its use, cost, increased need for blood glucose monitoring and the psychological factors may prevent individuals from using this technology optimally.
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