Diabetes and the Use of Insulin Pumps
- Is the Patient a Candidate for Insulin Pump Therapy?
- How does an insulin pump work?
- Starting a Patient on Pump Therapy
Discontinuing Pump Therapy
- Managing Patients with Type 1 Diabetes on an Insulin Pump
- Special Situations
Is the Patient a Candidate for Insulin Pump Therapy?
Based on a large body of evidence that supports the reduction in the number of microvascular, macrovascular and neuropathic complications with successful intensive diabetes management, the American Diabetes Association (ADA) recommends target A1c levels of <7.0% in adults. The International Society of Pediatric and Adolescent Diabetes (ISPAD) recommends target A1c levels of <7.5% in children.
Currently, the ADA recommends intensive insulin therapy through either continuous subcutaneous insulin infusion (CSII) or multiple (3+) daily injections of insulin (multiple daily injection, MDI) to obtain optimal glycemic control. Between these two modalities, the benefits of CSII with respect to lowering A1c, reducing severe hypoglycemia, and improving quality of life make the use of CSII well worth any additional costs. Insulin pumps have been used in the United States for more than 30 years, with an estimated 20%-30% of type 1 diabetes patients using them and <1% of type 2 diabetes patients utilizing them.
Adult Candidates for Insulin Pump Therapy
General adult candidates are patients searching for a more flexible treatment plan who are unable to achieve optimal control with injection regimens, either related to unpredictable and varying schedules and activity levels or who have noted limitations in control when using multiple daily injections.
Specific candidates are patients who, despite frequent blood sugar monitoring and consistent and appropriate insulin administration, may:
Have type 1 DM or absolute insulin deficient type 2 DM
Have hemoglobin A1c levels >7.0%
Suffer from frequent episodes of hypoglycemia (including possible severe hypoglycemia and hypoglycemic unawareness).
Experience erratic glucose extremes including episodes of diabetic ketoacidosis (DKA)
Feel that insulin management with multiple daily injections is limiting to daily living and overarching life goals
Suffer from extremes of insulin action including severe sensitivity or severe resistance
Have pronounced "dawn phenomenon"
Special situations such as before and during pregnancy, with children, competitive athletes and adolescents with eating disorders.
Pediatric Candidates for Insulin Pump Therapy
It is as important to evaluate the family/support unit for the child as it is to evaluate the child for appropriateness for CSII. Indications in pediatrics are similar to those in adults:
Elevated A1c levels on injection therapy
Recurrent, severe hypoglycemic episodes
Very young children
Wide fluctuations in glucose levels, regardless of A1c
Current treatment is not compatible with lifestyle needs
Presence of microvascular complications and/or risk factors for these complications
May be of benefit in specific populations: athletes, patients with pronounced dawn effect, patients with pronounced needle phobia, ketosis-prone patients and pregnant teens (when care is delivered by OB/Diabetes team with expertise in use of CSII in pregnancy)
The Appropriate Candidate/Caregiver Will Demonstrate the Following:
Reasonable expectations of pump therapy, including that it requires as much time as, if not more than, MDI
Motivation to achieve improved glycemic control
Checks blood sugar a minimum of 4 times daily (but optimally 6+ times per day)
Competency with carbohydrate counting
Good working knowledge of basic diabetes education- including how to test and treat hypoglycemia, how to follow up on hyperglycemia, sick day guidelines, and when to call the provider
Interest in technology and desire to undergo pump training
Willingness to continuously wear a pager sized device on their person attached via tubing or a tubeless pod that attaches directly to the skin
The manual dexterity to insert insulin pump sites and press buttons on the pump
The visual acuity to properly insert pump sites and read pump screen
Expectations of frequent follow-up with diabetes provider(s)
Does not have current untreated anxiety, depression or other cognitive issues that may interfere with ability to appropriately manage insulin pump therapy (including co-morbid medical conditions that can affect cognition, such as renal failure, medication sedation or post-chemotherapy).
An insulin pump is NOT the answer for patients who demonstrate limited diabetes education and/or poor self-management or for patients who expect the pump to "take over" diabetes care.
How does an insulin pump work?
Current models of insulin pumps are the size of small cell phones or pagers, are powered by AA or AAA batteries or can be recharged through a micro-USB (T-slim pump). Pumps use only rapid-acting insulin (aspart, lispro, or glulisine) or U-500 regular insulin. For most rapid-acting insulin, most insulin activity occurs within the first 3 hours after injection.
Most models use a large syringe- like cartridge or reservoir to hold several days' worth of insulin
The cartridge/reservoir is attached to a length of tubing (18-42 inches) that then attaches to a small (6-17 mm) Teflon or steel needle catheter (entire unit is called the infusion set)
Teflon/steel needle catheter is inserted into the subcutaneous tissue (most commonly buttocks, abdomen or upper leg/hip) and secured with an adhesive patch that is part of the infusion set
Teflon catheter should be changed every 3 days and it is recommended that steel needle sets be changed every 2 days
Currently an alternative model, called a "patch" pump is also available: insulin and mechanics to deliver it are all encased in a small, disposable pod that is directly attached to the skin - insulin is dosed via wireless link with a hand-held device that is manipulated by the patient
All pumps deliver insulin in 2 ways: basal and bolus delivery
The majority of pumps are NOT fully automatic; basal insulin will be delivered automatically, but bolus insulin (approximately 50% of daily needs) MUST be programmed by wearer.
In late 2016, the FDA approved the first hybrid closed loop system, the Medtronic 670g with Guardian Sensor 3 glucose sensor and Guardian Link 3 transmitter. The Medtronic 670g system which is expected to be commercially available in 2017, uses the hybrid closed loop algorithm which is integrated into the pump itself. The pump features both a “manual mode,” and “auto mode” feature. When used in manual mode the pump functions similarly to pumps that are commercially available with pre-set basal rates, correction factors and insulin sensitivity factors and requires that the user input all carbohydrates consumed and blood sugars into the pump. When auto mode feature is employed, the pump receives blood sugar data from the sensor every five minutes and decides, through use of the algorithm, whether or not insulin is required, and if so, how much. In auto mode the pump is using a target blood glucose of 120 (or 150 if the user changes into an exercise mode.) In auto mode, basal rate settings are no longer used as the algorithm is determining background insulin use. Users must announce a meal, meaning they must enter carbohydrate amounts intended to be consumed into the pump before they eat. This is to address the fact that even with the fastest insulins we have available, these systems cannot adequately cover the glycemic excursion that occurs after a meal if a carbohydrate bolus is not given. For this reason, this system is call a “hybrid system.” The Medtronic 670g with Guardian 3 does not fully replace blood finger stick testing. At least two finger stick calibrations need to occur daily and the system may ask for additional blood glucose tests as part of a sensor integrity check that is built into this system for safety and accuracy. If the user enters a blood glucose test over 150 mg/dl as part of a calibration or blood glucose check, auto mode may recommend a correction bolus.
The infusion site for this pump needs to be changed every three days and the sensor site needs to be changed every seven days. The user initially needs to wear the pump and sensor in a manual mode for 72 hours before automode can be turned on when first starting on the system. The automode feature will not be available when the sensor is warming up between site changes, this may last for up to two hours.
A new pump was released by Medtronic in 2016 called the Minimed 630g. This was an updated version of the Medtronic 530g released in 2013 which was the first pump of its kind to suspend insulin use for two hours when worn with the Enlite continuous glucose sensor. The feature is called "threshold suspend" and automatically discontinues basal insulin when blood sugar reaches a pre-set low threshold and the individual does not respond to the low alarm. In studies it was shown that this pump was able to reduce the frequency and severity of hypoglycaemia and did not cause any increase in hyperglycemia. The ASPIRE (Automation to Simulate Pancreatic Insulin Response) study compared sensor augmented pump therapy and low glucose suspend and found that the low glucose suspend feature reduced hypoglycaemia by thirty percent and did not cause a change in overall glucose control. The Medtronic Minimed 630g continues to offer the same features of the 530g but offers a newly redesigned pump and a different menu platform that is very similar to the Medtronic Minimed 670g pump.
The Minimed 630g pump can be worn and used as a regular insulin pump as well but the threshold suspend feature will not be available if the patient is not also wearing the Enlite sensor system.
The threshold suspend range can be set between 60-90 mg/dl; during the suspend period no insulin boluses can be administered.
A new pump was released by Animas in 2015 and received a pediatric indication in 2016, the Animas Vibe offers integration of the Dexcom G4, now users can view Dexcom G4 sensor data on the screen of their Animas Vibe pump. This pump is approved down to the age of 2 years.
A new pump was released by Tandem, the T:slim, G-4, which incorporates Dexcom G4 data on the home screen. Tandem has also released the T:slim X2 which is compatible with the “Tandem Device Updater,” the first FDA-cleared use was to provide t:slim Pumps purchased before April 2015 an update to the latest software, but it has the potential to enable users to add new features in the future, independent of their insurance company’s pump replacement cycle.
Basal Insulin Delivery
Designed to keep blood glucose levels steady during overnight and between meals.
Regulates the rate of hepatic glucose production during fasting. It is NOT designed to cover food-related insulin needs.
Basal rates are programmed in units/hr, but hourly totals are divided into mini-pulses every few minutes. (Thus, the pump must be worn at nearly all times).
Most pumps have the ability to program multiple rates throughout the day to account for circadian variation in insulin needs.
Most pumps can save multiple different basal patterns (patient must toggle back and forth between patterns) - which is useful for patients with widely varying daily schedules - such as shift workers, weekend athletes or adolescents who sleep late on the weekends.
Bolus Insulin Delivery
Immediate burst of insulin manually entered by the wearer to be delivered "in the moment" for meals and/or to correct hyperglycemia
2 types of boluses: meal and correction
Ideally delivered 15-20 minutes before eating meal/snack to minimize post-prandial rise in BG
Delivery may also be done during or after meal if situation warrants such as with a picky eater, a new type of food, or pre-meal
Covers carbohydrate content of a meal or snack
Most pumps have meal bolus calculators, other pumps require patients to enter insulin dose to be delivered
Meal Bolus Calculator:
Pump is pre-programmed with an Insulin-to-carbohydrate ratio (ICR or the # grams of carbohydrate that 1 unit of insulin will cover), which is determined by the pump prescriber
Patient enters total number of carbohydrates from the meal or snack into the bolus calculator, which will determine a recommended dose of insulin based on the ICR
Patient must confirm result from bolus calculator and may adjust amount based on current circumstances
Designed to return glucose levels to the established target range
Most pumps have correction bolus calculator; others require patients to enter insulin dose to be delivered
Correction bolus calculator
Pump is pre-programmed with an Insulin Sensitivity Factor (ISF) or Correction Factor (the number of BG points that 1 unit of insulin drops the BG) and a target blood glucose range, which acts as the goal for the mathematical determination of the correction bolus
Wearer enters current BG value into pump (some pump models come with BG monitor which wirelessly pre-populates pump with current BG value)
Most current pump models allow for correction of a BG value that is either above or below target: for values above target - an additional insulin dose is calculated to bring down BG; for values below target - insulin is subtracted from meal bolus to raise BG
Most pumps have a feature that prevents wearers from taking too many boluses too close together - this feature can be set to "lock-out" patients from taking full boluses for a period of time, generally 2-6 hours after a previous bolus (see Managing Insulin Pumps Section for a discussion of stacking)
Additional Features of Insulin Pumps
Allow for temporary increase/decrease to basal rates without having to change saved settings
Useful in dealing with unexpected events such as during or after exercise (decrease in current rate), illness (increase in rate), stress (increase in rate), or prolonged hypoglycemia (decrease in rate) or hyperglycemia (increase in rate)
Programmed for a set duration of time (0.5-72 hours depending on pump model) and either in units/hr or more commonly as a percentage of the current rates (e.g., "doubling the basal rate" is programmed either as 200% or +100% depending on the pump model)
Pump will automatically resume normal basal rates at end of set time
Can easily be cancelled before pre-set time expires if user desires to do so
The Medtronic Minimed 670g hybrid closed loop system does not offer the function of temporary basal rates when in auto mode.
Custom Bolus Functions
There are alternate delivery options which can change the way a meal bolus is delivered
Extends the delivery of the meal bolus over a specific length of time
Wearer determines the length of time over which the bolus should be delivered, generally 30 minutes - 6 hours
Works well with foods that are low on the glycemic index or are full of fiber or for situations where eating is done over a prolonged period such as with a holiday meal or buffet
Combines normal bolus with extended bolus to allow some of the insulin bolus to be delivered immediately and the rest to be delivered over a prolonged period
Wearer must determine amount of insulin to be delivered "up front" and the length of time over which to deliver the remaining amount
Often programmed as a percentage split (e.g., 50% now and 50% over X hours)
Works well with high-fat foods or meals where the fat content of the food can significantly slow the absorption of the carbohydrate content
May be useful for patients with Gastroparesis; start with 50% upfront and remaining 50% over 2-4 hours and titrate based on BG results
The Medtronic Minimed 670g hybrid closed loop system does not offer the use of extended boluses when in auto mode.
Continuous Glucose Monitoring (CGM)
It is only relatively recently that CGM devices have become commercially available. Currently Medtronic, Animas and the Tandem T:slim offer an insulin pump model available in which the pump acts as the receiver for the CGM data. In addition, the Dexcom G5 CGM system can use an iphone as the receiver if the user downloads the Dexcom G5 mobile app. With this app, the user is able to review all CGM data on their phone and receive the same alerts they would get on a receiver. In addition, up to 5 individuals can be asked to follow the user through an app on their personal phone. This offers the option of remote monitoring for individuals, something that can be especially helpful in pediatrics.
CGM devices are comprised of a transcutaneous probe that generates an electrical current depending on the concentration of glucose in the interstitial fluid. The probe is connected to a transmitter that sits on the skin surface and wirelessly transmits the current data to a nearby receiver that converts the electrical current data into glucose concentrations. CGM devices provide glucose levels every few minutes as well as information regarding glucose trends both "in the moment" and over 1-24 hour periods (see chapter on Diabetes and Continuous Glucose Monitoring).
Current CGM systems are designed to "fill in the gap" between fingerstick glucose checks and in December 2016 the FDA approved the Dexcom G5 to replace some fingersticks in individuals down to age 2. BG testing still needs to be performed to calibrate the system at least once every 12 hours and users are cautioned to continue to perform a fingerstick in situations of hypoglycemia and/or hyperglycemia or if they feel that the sensor data is not accurate.
The FDA cautions that Acetaminophen use with the Dexcom can give false sensor glucose readings and should not be used if possible. If the user does use an acetaminophen containing product while on the Dexcom, they should not use the data to make any decisions regarding diabetes management and should instead revert back to using only fingerstick BG values for management decisions.
Inherent "lag time" between interstitial glucose levels and blood glucose levels
This lag can become more pronounced during times of acute BG changes
Data from CGM may be used to alter insulin doses in real-time and retrospectively
Requires additional intensive education of pump wearer/caregiver on how best to utilize the sensor data
Promise of Future Closed Loop System or "Artificial Pancreas"
Many current upcoming and ongoing clinical trials for a variety of systems using differing pumps/sensors and algorithms. As mentioned above the Medtronic Minimed 670g hybrid closed loop system is currently approved, and will be commercially available in 2017. (See above section on How Do Insulin Pumps work.)
Closed loop systems involve continues glucose sensors, insulin pumps, and an algorithm run off an implantable chip in the pump itself, tablet, or android device to regulate glucose levels.
Patients wear the pump and sensor. The sensor sends blood sugar readings as well as trend data to the operating system on a minute-to-minute basis. Then the computer algorithm tells the pump when and how much insulin to give.
At this time, it is still necessary to calibrate the system with accurate blood sugar values taken from fingersticks or intravenous blood samples.
When systems are available clinically, patients should be able to go about their normal day and expect that the system will keep their blood sugars under tight control and reduce large variations in blood sugars. The Minimed 530g pump (mentioned above) and now 630g were the first commercially available initial step to a closed loop-type system. The Medtronic Minimed 670g system will take this another large step forward and automate all insulin delivery with the exception of meal boluses. Leaving the user to still need to enter into the pump all carbohydrates consumed.
Starting a Patient on Pump Therapy
Clinical Systems for Success
Successful implementation of pump therapy requires not only a motivated and educated patient, but also a diabetes care team with comfort and expertise in the start-up and management of patients on insulin pumps. Ideally, the diabetes care team is comprised of many disciplines including diabetologists/endocrinologists, advanced practice providers (NP/PA), Certified Diabetes Educators (CDE), pump trainers, and nutritionists.
Insurance Issues and Ordering Process
Ensure that the patient has medical insurance and/or the financial means to allow both purchase of the pump and continued coverage of the associated medical supplies. Without insurance, the pump itself can cost up to $6,000, and supply costs are estimated at $200-$400 per month (in addition to the usual insulin and blood glucose strip costs). Typically, the pump is covered by durable medical and at least partially covered by most major insurance companies. Additionally The Medicare Insulin Pump Coverage Act of 1999 states that Medicare will pay for an insulin pump if the patient is type 1 and meets particular criteria, including the presence of islet cell antibodies or low c-peptide levels.
Once a pump model is decided upon (see section below) the ordering process is typically initiated by the medical provider. The pump manufacturer will then reach out to the patient's insurance and to the patient themselves to clarify how the costs of the pump will be covered and to arrange payment of co-pays or deductibles. The insulin pump is typically shipped to the patient's home, unless otherwise specified. Training typically takes place next. Training procedures can vary from practice to practice.
Choosing an Insulin Pump Model
There are many different types of insulin pumps available from a variety of manufacturers.
Clinician comfort and expertise with a particular model: this should be one of the primary considerations when choosing a pump. The prescribing clinician is the professional resource with regard to pump adjustments and functions, and should thus be very comfortable with the functions of the pump
Size of reservoir/cartridge: does the patient have a large total daily dose requirement?
Small basal/bolus capability: does patient have low insulin needs and require a basal rate of 0.025-0.05 unit?
Comfort with estimating carbohydrate content of foods: some pumps have food/carbohydrate content look-up functionality integrated into the pump itself
Remote control: some pump models have the ability to bolus from a remote (versus directly on the pump unit)
Closed loop technology capability
Display size/color: Color screens or larger displays may be beneficial to people with vision issues
Complete lack of tubing: there is currently only one model of "patch" pump that completely eliminates the need for any tubing
Waterproof vs water resistant: Waterproof pumps may be appropriate for people who work/play in a water environment
Other languages: is the patient's primary language something other than English?
Patient and/or caregiver should demonstrate competency in the following areas prior to initiating therapy:
Carbohydrate counting/accurate estimation
Ability and motivation to check BG levels at least 6 times daily
Basic principles of basal/bolus therapy; BG target levels, insulin action
Identification and management of hypo-/hyperglycemia
Sick day management with CSII
Exercise management with CSII
Identification and management of pump/infusion site failure
Mechanics of pump function, insertion and maintenance of infusion sites
Follow-up assessment and "refresher" educational activities should be completed following CSII initiation
Determining Initial Insulin Pump Settings
Calculate the patient's approximate total daily dose (TDD) of insulin.
In adults, multiply patient's current weight (in kilograms) by 0.7 (adolescents may require a calculation with 1.0 to account for increased insulin resistance whereas elderly patients should start with 0.5 unit/kg as they produce less endogenous glucose) OR
Average patient's total daily insulin use via injection over a 14-day period and then reduce this total by 10-20% to account for pharmacokinetic differences between CSII and MDI, especially if patient has A1c in target range and/or history of frequent hypoglycemia
Divide the TDD by 40%-50% and then divide this amount by 24 hours to derive initial basal rate settings
In adults the initial rates can be set at a flat rate and adjusted as necessary based on blood sugar readings (including a midnight and 3 am test) or 20% can be initially deducted from the starting rate for the 12 am rate to account for the fact that the majority of adults require approximately 20% less insulin between 1 am-3 am than between 5 am-7 am.
For patients with pronounced "dawn phenomenon", overnight basal rate can be increased by 10%-20% at 3 am .
Basal rates for young children may total 30%-50% of TDD and may have more circadian fluctuation than adults
Adolescents often need increased basal insulin 5-9 am and again in later afternoon
Young children often need increased basal insulin from 9 pm-12 midnight
Meal Bolus Settings
If patient already on basal bolus therapy with MDI, it is possible to use their current insulin-to-carbohydrate ratios
You can also determine a starting carbohydrate-to-insulin ratio by dividing 500 by the TDD
Adjustments can be made to original settings by monitoring blood sugars 2 hours after meals. Target 2 hour post-prandial BG as determined by the American Diabetes Association is a blood glucose < 180 mg/dL
If these numbers are out of target, the carbohydrate ratio should be made more aggressive by lowering the number, typically in increments of 2-3 grams of carbohydrate.
For example, if a patient had an insulin-to-carbohydrate ratio of 1:18 for breakfast but each 2-hour postprandial number was over 180, it would be advised to change the breakfast insulin-to-carbohydrate ratio to make it more aggressive (meaning more insulin will be given for breakfast meal). Changing it to 1:15 and re-evaluating would be a good place to start.
Correction Bolus and Blood Glucose Target Settings
If patient is currently on basal/bolus therapy you can use the current correction for pump settings
You can also derive it by dividing 1700-1800 by the TDD.
Adjustments can be made by analyzing if the patient comes back into target 2 hours after giving a correction for a high blood sugar (is easier to do if analyzing situations where a food bolus was not also involved)
Typically recommended correction target of 100 mg/dL for most pump wearers (may choose to use higher target overnight of 120 mg/dL)
Targets may be less aggressive for elderly, very young children or other individuals at risk for hypoglycemia
Initial Follow-up Recommendations
Daily initial follow-up with pump trainer and/or member of diabetes care team
Follow-up clinic visit with member of diabetes care team within 3-14 days after initiation of CSII
Education "consults" (phone, email, or face-to-face) at least every 1-2 weeks, progressing to PRN basis
Once successful transition is made to CSII, return to quarterly clinic visit schedule
"24-hour" access to CSII/diabetes specialist for urgent situations
Discontinuing Pump Therapy
Unfortunately, insulin pump therapy may not work for every patient started on a pump. Indications for discontinuing pump therapy either temporarily or permanently include:
Patient preference, after pros and cons of continuing CSII vs transition to other method of insulin delivery are discussed
Frequent infusion site infections
Repeated episodes of diabetic ketoacidosis (DKA) due to pump mis-management
Intentional mis-use of pump; missed boluses, inadequate BG testing, missed site changes
If it is determined that pump therapy is no longer an option, ideally the patient is switched to basal/bolus therapy using MDI.
The total daily basal dose is replaced with 1-2 injections of long-acting glargine or detemir insulin or 1 injection of ultra long-acting insulin degludec.
Both the ICR and ISF from the pump may be used to calculate doses for rapid-acting boluses.
If patient is resistant to the required 4+ injections of insulin needed for success with MDI, combinations of other insulins may need to be employed to provide the patient with the necessary 24-hour insulin coverage.
Because insulin absorption can be different between MDI and CSII, frequent BG testing (including overnight) should be done to assess the need for dose adjustments.
Managing Patients with Type 1 Diabetes on an Insulin Pump
This section is meant to provide general information and guidelines on the management of patients using insulin pumps and should not replace care from or consultation with diabetes care providers who are experts in insulin pump therapy. Ideally, the patient is managed by a diabetes care team and is seen regularly by members of that team.
Upon initiation of insulin pump therapy, it is recommended that patients have face-to-face follow-up with their diabetes care providers within the first 3-14 days after starting.
As with patients on MDI, insulin doses for patients on insulin pumps should be adjusted regularly. Adjustments are made whenever BG patterns indicate a need. Typically, a pattern is established over a period of several days before changes are made, thus minimizing the potential for "chasing" BG levels. Once a change is made, the effectiveness of this change should be determined over several more days. The need for constant adjustments to meet the needs of the growing child and adolescent is the hallmark of insulin treatment in pediatrics.
Adjusting Basal Rates
Change the basal rate that occurs 2-3 hours before the abnormal BG levels are seen
Adjustments typically made in 10% increments, rounding to nearest 0.1 unit or 0.05 unit, depending on pump model
Alternative adjustment strategy: Increments of 0.1 units for those whose hourly rate is >1 unit/hr, 0.05 unit for those whose hourly rate is 0.5-1 unit/hr, and 0.025 unit for those whose hourly rate is <0.05 unit/hr
Elevations in fasting BG levels are typically caused by inadequate basal insulin
Patient may need to test BG at 2-3 am for several nights to better determine which basal rate should be changed
Daytime can be more difficult to determine need to adjust basal vs. bolus insulin: typically start w/ basal adjustment if abnormal BG occurs more than 2-3 hours after a meal
Basal testing: technique to determine whether glucose levels remain in range when the patient skips a meal or eats a carbohydrate-free meal and BG is monitored every 2 hours until the next meal (May be difficult and/or unrealistic for some patients to complete this)
Adjusting Meal Boluses
Test the 2-hour postprandial (2-hr PP) BG level to eval/uate effectiveness of meal bolus
2 hours after meal target of <160-180 mg/dL
Consider accuracy in carb counting as one cause for bolus ineffectiveness
Increase ratio to decrease amount of insulin given with bolus (e.g., change in ratio from 1:15 grams to 1:18 grams)
Decrease ratio to increase the amount of insulin given with bolus (e.g., change in ratio from 1:15 grams to 1:12 grams)
Adjustments typically made in 10%-20% increments
Adjusting Correction Boluses
Test BG 2 hr after correction dose to determine effectiveness of correction bolus
When given as part of a meal bolus for correction of hyperglycemia, BG by next meal should be close to target range
BG should be close to target range programmed into the pump at the 2-hour mark
Increase ratio to decrease the amount of insulin given with bolus (e.g., change in ratio from 1:50 mg/dL to 1:65 mg/dL)
Decrease ratio to increase the amount of insulin given with bolus (e.g., change in ratio from 1:50 mg.dL to 1:35 mg/dL)
Adjustments typically made in 10%-20% increments.
Hypoglycemia is virtually unavoidable in the treatment of type 1 diabetes. However, pump therapy is associated with less hypoglycemia, specifically, fewer episodes of severe hypoglycemia. Hypoglycemia is defined as a BG <70 mg/dL, although some patients with a history of hypoglycemia unawareness, autonomic neuropathy or at extremes ends of the age spectrum may benefit from beginning treatment for hypoglycemia at a higher threshold.
Too much insulin/not enough food, unplanned exercise, delayed effects of afternoon exercise, or stacking boluses (see next section)
10-15 grams of fast-acting carbohydrates; 4 ounces juice or regular soda, 3-4 glucose tablets, 3-4 Starbursts
Treatment should not include any protein/fat as this will slow the absorption of the glucose
Additional carbohydrates that may be consumed over and above initial 10-15 grams should be followed by a meal bolus to prevent rebound hyperglycemia
Allow 20 minutes for treatment to work before re-testing BG, if remains below threshold at this time, repeat treatment until BG rises
If hypoglycemia occurs at mealtime
Treatment with fast-acting carbohydrates can be taken - but should NOT be included in meal bolus
For mild hypoglycemia, some patients may elect to forgo treatment with fast-acting carbohydrates and subtract 10-15 grams from meal total
Many pumps also offer a reverse correction feature where insulin is subtracted from a meal bolus when BG falls below the lower range of the target level
Stacking: Delivering repeated boluses of insulin (particularly correction boluses) too close together
Occurs when patients follow the "more is better" philosophy and give multiple correction boluses in too short a time frame, likely leading to hypoglycemia several hours later.
Studies show that it can take 90-130 minutes to reach full peak effect from an insulin bolus.
Patients may check BG at 60-minute mark and see an inadequate improvement in level and deliver an additional bolus.
Prevention is key - ensure patient comprehends insulin action/effect, instruct patient to wait at least 2 hours before re-checking BG level, set insulin action/duration feature on insulin pump and instruct patient NOT to override pump
Hyperglycemia is virtually unavoidable in the treatment of type 1 diabetes. Pump therapy offers the ability to correct acute rises in glucose levels in a timely manner.
Too little insulin/too much food, sedentary lifestyle, stress, illness
Deliver correction bolus (if no other bolus has been delivered within the last 2 hours)
Allow at least 2 hours before repeating BG (to ensure that peak effect of insulin has occurred)
Consider use of temporary rate to increase basal rates, especially with stress or illness - start with 25%-50% increase over 3-4 hours and have patient evaluate effect
Review and re-educate regarding carbohydrate counting
Diabetic Ketoacidosis (DKA) Prevention
Insulin pump therapy is a known risk factor for DKA; therefore, special attention must be given to situations of acute, prolonged hyperglycemia. Interruption of insulin delivery will result in urinary and blood ketones in 4-6 hours. One of the most common causes of delivery interruption is failure of the subcutaneous catheter - either disconnection, dislodgement or kinking. Patients should rely on BG testing results and not presence/absence of pump alarms to indicate that there is an issue with insulin delivery.
Recommendations for the treatment of acute, prolonged hyperglycemia (2 consecutive BG levels >250 mg/dL, at least 2 hrs apart) include:
Check urinary/blood ketone levels
Administer correction dose of rapid acting insulin via SQ injection (determine dose using pump bolus calculator)
Change infusion site (regardless of when last change was done)
Evaluate pump function: confirm insulin delivery - disconnect tubing and program test bolus;
Consider contacting pump manufacturer customer service (number listed on back of pump) if pump appears not to function properly
If ketones present, consider temporary increase in basal rates:
Increase of 25%-50% for 2-3 hours for moderate ketones (>1.0-1.6 mmol/L)
Increase of 50%-100% for 2-3 hours for large ketones (1.6->= 3.0 mmol/L)
Encourage hydration with sugar-free fluids
Repeat BG in 2-3 hours
Remains >250 mg/dL
Instruct patient to contact diabetes specialist for further evaluation
Consider giving double correction via injection
Consider continuing temporary basal rate
BG <250 mg/dL
Continue to monitor ketones until clear
Continue close monitoring of BG for several hours until levels stabilize, and monitor for hypoglycemia
Patient should have back-up supplies, including: ketone strip, batteries, infusion sets, rapid and long-acting insulin vials and/or pens, syringes, or pen needles, and copy of current pump setting - these should always be available
If pump malfunctions, patient may need to return to MDI until pump can be replaced (contact pump manufacturer immediately to facilitate timely replacement)
Downloading Pump/Data Retrieval
Retrieving data from a pump can be a helpful and time-saving tool for the clinician and patient.
All pumps currently on the market can be uploaded through either use of a special cable and software downloaded on a specific computer or through a web-based interface that uses a USB to wirelessly upload the pump and associated meters (data can then be exported or printed if downloaded on specific device or viewed remotely if done with web-based software).
The specific pump company can provide the actual software and downloading tools as well as patient instruction on how to use the technology.
Providers may want to ask their pump patients to upload their pump the night before their visit and also bring reports for efficiency and efficacy.
Once the pump is uploaded, a variety of reports can be viewed, including; current device settings, logbook reports that show blood sugar numbers and carbohydrate amounts entered into the pump as well as the amount of insulin delivered (helpful to review when making dose adjustments). Reports will outline pump events such as suspensions, alarms, temporary basal rates, rewinding the pump, and cannula filling (helpful when assessing compliance). Statistical reports use a variety of modalities such as line charts, pie charts and graphs to display minimum/maximum and average blood sugars, boluses and basal information. These can often be broken down by time of day or meal for better assessment of control and need for changes.
Hospital care considerations
Contact diabetes care specialist as quickly as possible.
Do NOT discontinue pump unless diabetes specialist has directed its removal and an alternative source of insulin is available.
Evaluate BG and ketone status as early as possible.
Use caution when initiating glucose-containing intravenous fluids.
The American Diabetes Association supports the use of insulin pumps in patients who are able to provide their own diabetes self-management while admitted to a hospital: "Patients who use [CSII]...can be candidates for diabetes self-management in the hospital, provided they have the mental and physical capacity to do so."
Personnel with expertise in pump therapy should be available in all hospitals.
Nursing staff caring for patients on pumps should document basal and bolus insulin doses at least daily.
For stable patients, BG targets for hospital stay should be <140 mg/dL before meals and <180 mg/dL for random glucose tests. These targets may be tightened or loosened depending on individual needs.
ALL insulin pumps should be removed prior to patients undergoing any radiologic test.
If patient requires prolonged imaging and will need to be disconnected for longer than 1-2 hours, an alternate source of insulin (such as SQ injection) will need to be initiated.
Collaboration among anesthesiologists, surgeons, and diabetes specialists to determine perioperative diabetes management
For short/minor procedures (<1 hr), pump may be left on and basal rates continue to infuse
Secure infusion set with additional tape for added protection during surgery
If pump is discontinued, an alternate source of insulin MUST be used
Frequent BG monitoring should be cornerstone of perioperative diabetes management
Patients/caregivers should be in contact with diabetes specialists to determine preoperative diabetes management
Bring 2-3 times the amount of insulin pump supplies and insulin typically necessary for trip length
Bring back-up long-acting insulin and syringes or long-acting insulin pens and short-acting insulin pens
If traveling via plane, obtain a travel letter from diabetes team explaining necessity of carrying supplies on the person at all times
Pack all supplies in carry-on luggage
The pump should not go through airport x-ray machines (it is ok to pass through the metal detector)
If full-body scanner is being utilized at airport, notify authorities of use of medical device and seek alternate security evaluation
It is safe to wear pumps in full functioning mode during air travel
Exercise is associated with an increased risk of hypoglycemia secondary to enhanced insulin sensitivity. Consequently, to avoid hypoglycemia, adjustments in carbohydrate intake or insulin delivery must occur.
BG monitoring should occur before, during, and after activity.
Disconnecting or suspending basal rates may be useful, but caution should be taken to ensure hyperglycemia does not occur.
Insulin pumps can be removed for up to 2 hours before insulin deficiency begins to occur.
Myriad strategies are available to deal with exercise, depending on particular effect in patient. Some patients experience hypoglycemia during exercise, others immediately following and still others not until several hours later - patients can see an exercise effect 7-11 hours after completing exercise.
Suggested strategies include (but are not limited to): reducing meal bolus for meal preceding exercise session, lowering basal rates for 1-2 hours prior to activity, lowering overnight basal by 10%-20% following late afternoon/evening activity, consuming small snack (without meal bolus) just prior to exercise, hydrating with sugar containing fluid during activity.
Check with the particular pump company to see if the pump is waterproof.
Typically, patients disconnect for showers and swimming (the site itself can be immersed and exposed to water).
In the event that someone is ill and not eating, the body still requires insulin to counteract increases in glucose and ketone production by the liver due to increased secretion of stress hormones (cortisol, glucagon, growth hormone, epinephrine/norepinephrine).
Never suspend insulin delivery or disconnect a pump when a patient is ill.
Being ill can put patients at risk for developing DKA; therefore, it is very important to advise patients to check for ketones and monitor blood sugar every 2-4 hours around-the-clock, even if the blood sugar is in normal range.
If ketones are present, see section on DKA prevention.
If vomiting is present without ketones: avoid solid foods until vomiting subsides, gradually start liquids (sugar free if blood sugar >150, with sugar if <150); begin with 1 tablespoon every 10 minutes. Increase slowly as tolerated. Resume intake of bland solids after 1-2 hours with no vomiting.
Advise patients to call diabetes healthcare team urgently or seek emergency care with moderate or large ketones, persistent nausea, low blood sugar with nausea and/or vomiting and any signs or symptoms of DKA such as abdominal pain, chest pain, altered consciousness, deep breathing.
Drugs that Can Affect Blood Sugar and May Require Temporary or Permanent Dose Adjustments
Beta-adrenergic antagonists: May alter physiologic and subjective symptoms of hypoglycemia, can potentially decrease tissue sensitivity to insulin
Corticosteroids: Can raise blood sugars through increased gluconeogenesis; transient insulin resistance
Estrogen products (typically higher doses): Can possibly raise blood sugars
Ethanol: intrinsic hypoglycemic effect; impairs gluconeogenesis
Vitamin B3 (niacin): May increase blood sugar
Thiazide diuretics (high dose): May increase blood sugar
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