Inpatient Insulin Basics
How to Safely Transition Between IV Insulin and SubQ Insulin
By Hannah Day, MSN, FNP-C, BC-ADM, CDCES
Safe insulin therapy in the inpatient setting is a key concern for hospital clinicians given it is indicated to treat patients on every floor of the hospital who are being treated for a variety of disease states. Knowing how to properly initiate and titrate intravenous (IV) and basal bolus subcutaneous (SubQ) insulin is crucial to maintaining patient safety. Transitions between IV and SubQ are a critical time for patients and require a thoughtful, deliberate approach to avoid glycemic excursions.
In this resource, we’ll cover inpatient insulin basics that help answer some common questions about transitioning patients from IV to SubQ insulin.
- How should providers calculate an IV insulin infusion rate?
- What is IV insulin’s half-life?
- How should providers transition patients from an IV insulin infusion to SubQ basal bolus insulin regimen?
- When should you stop an IV insulin infusion without transitioning to SubQ insulin?
- How should providers calculate the SubQ insulin dose?
- What do I need to know about NPO and insulin administration?
How should providers calculate an initial IV insulin infusion rate?
To calculate an initial IV insulin infusion rate, the American Diabetes Association (ADA) recommends providers use written or computerized protocols that guide insulin infusion rate adjustments, account for glycemic fluctuations and achieve low rates of hypoglycemia.1
IV insulin infusion rates depend on the specific details of a patient’s clinical situation, as well as their individual sensitivity to insulin. We recommend an IV insulin administration protocol that is guided by Glucommander, Glytec’s insulin dosing decision support module. Unlike paper protocols, Glytec’s eGlycemic Management System (eGMS) uses an evidence-based, FDA-cleared algorithm that leverages key patient data points, as well as current and historical blood glucose values, to learn how a patient is responding to insulin and to anticipate their future insulin needs.
Glucommander recommends an insulin infusion rate that brings the individual safely into target range without dropping blood glucose too quickly or risking adverse drug effects like hypoglycemia.2 Providers select the appropriate population-based order set, and Glucommander provides titration recommendations that are managed by clinicians at the point-of-care.
How should providers calculate an initial IV insulin infusion rate for diabetic ketoacidosis (DKA) patients?
The American Diabetes Association (ADA) also recommends providers use written or computerized protocols to calculate IV insulin infusion rates for DKA patients.1 Order sets for DKA should also include orders for fluid and electrolyte treatment.
Once blood glucose reaches an approximate threshold of less than 250 mg/dL, fluids containing dextrose are needed to allow for continuation of the insulin infusion until the acidosis has resolved while preventing hypoglycemia.
Glucommander supports the care of DKA patients by providing a reminder to the nurse to check orders for dextrose-containing fluids once information is entered that blood glucose is less than 250 mg/dL. In addition, eGMS will alert nurses to high anion gaps to prevent premature discontinuation of the insulin infusion before resolution of DKA.
eGMS also includes a glucose velocity warning which alerts nurses about sudden drops in patient blood glucose levels and prompts a blood glucose recheck sooner to ensure that patients reach the prescribed target range safely. This feature is designed to prevent hypoglycemia and side effects like cerebral edema that are caused by a rapid decrease in blood glucose.
What is IV insulin’s half-life?
When administered as intravenous, regular insulin’s half-life is 5-7 minutes, so infusion rates and blood glucose should be monitored hourly.
The short half-life of IV insulin allows for frequent rate adjustments as a patient’s clinical status changes. Therefore, IV insulin infusion is the preferred treatment for critically ill patients who experience changes in insulin requirements as their clinical condition changes.
How should providers transition patients from an IV insulin infusion to a SubQ basal bolus insulin regimen?
To maintain optimal glycemic control during the time IV insulin is discontinued and SubQ insulin treatment begins, a standard approach to transitioning is vital.
Because IV insulin has a short half-life and basal SubQ insulin has an onset delay of two to four hours, a basal bolus insulin protocol requires a bridging process when transitioning from IV insulin; this helps prevent rebound hyperglycemia and the need to restart the insulin infusion, which could delay transfer out of the ICU or critical care unit.
The transition process can be challenging and necessitates a careful approach, so first consider the following:
- The medical readiness of the patient to transition to SubQ insulin
- Potential changes in clinical status that may impact future insulin requirements
- Institutionally scheduled basal administration times
- Workflow challenges and potential patient risks which can result from timing the insulin to the scheduled basal administration times while avoiding basal stacking or gaps in basal coverage
Before you stop an IV insulin infusion and transition to SubQ insulin, consider the risks of transitioning, which include:
- Rebound hyperglycemia if there is no 2-4 hour overlap or bridge with basal insulin, which may require restarting IV insulin
- Hypoglycemia as a result of stacking basal insulin given at the time of transition and again at the standard administration time
- Severe hyperglycemia, including iatrogenic DKA, (a never event), due to gaps in basal insulin coverage which can result if basal insulin is given at the time of transition then not again until more than 24 hours later, such as when striving to achieve a standard basal administration time.
eGMS supports the transition from IV to SubQ insulin with workflows that guide the process and safety guardrails that help prevent dangerous errors.
The solution provides a total daily dose (TDD) recommendation based on insulin requirements at the time of transition, supports the 2-4 hour bridging process with basal insulin, and supports workflows to achieve a scheduled basal administration time, avoiding basal stacking and gaps.
When should you stop an IV insulin infusion without transitioning to SubQ insulin?
There may be certain situations where IV insulin can be discontinued without a transition to SubQ insulin, like when a patient’s stress hyperglycemia has resolved and they have no history or evidence of diabetes.
Glucommander helps clinicians manage the safe discontinuation of IV insulin infusions by guiding them in best practice. The software will provide a warning if a clinician begins to discontinue IV insulin if the blood glucose is still elevated more than 180 mg/dL as well as if the anion gap is still elevated.
How should providers calculate the SubQ insulin dose?
When you’re ready to calculate the basal insulin dose for transition, the first step is to determine whether your patient will require SubQ insulin at transition. For instance, a patient with T1D will definitely require continued insulin, whereas a patient with stress hyperglycemia, normal A1c and minimal IV insulin needs (<1-2 units/hr) may not require insulin at transition.
The next step would be to determine your patient’s insulin requirements at transition. This can be done in several ways. The first method is to determine your patient’s recent insulin needs. Glucommander will do this automatically for you at the time of transition - the transition module will guide the user through the process.
If you’re using a manual protocol, a clinician would need to look at the last 4-6 hours of IV insulin and estimate a patient’s transitional insulin needs using a manual calculation. For instance, if a patient was on 2 units/hr on average for the past 6 hours, that patient would need about 48 units over a 24 hour period. In general, 70-80% of that 24-hour need would be estimated to be the TDD (total daily dose) a patient requires. In this case, the TDD would be about 38 units. Additionally, a weight-based approach can be used; dosing may range from 0.3 units/kg/day for insulin-sensitive patients to 0.5 to 0.7 units/kg/day for insulin-resistant patients. Most importantly, the estimated TDD can be compared to a home regimen, if the patient was on insulin at home.
The TDD includes the total basal and bolus insulin needed for a 24-hour period. Generally, 50% of the TDD can be used to calculate the basal insulin dose needed at the time of transition and ongoing, while the remaining 50% can be used to calculate the bolus insulin doses needed at mealtimes.
Calculating the correct basal dose is critical. Because basal insulin remains in the patient’s system for up to 24 hours, an incorrect dose will necessitate a lot of correction throughout the day. Glucommander’s SubQ module guides clinicians to easily manage basal bolus insulin regimens and includes safety guardrails designed to help prevent errors or alert clinicians to patient harm situations that need their immediate attention.
Clinicians must consider a patient’s medical readiness and clinical condition at the time of transition. Medical readiness criteria include:
- resolution of critical illness
- off vasopressors
- minimal variation in the insulin drip rate
- lower insulin drip rates (ie <2-3 units/hr) at the time of transition
The potential changes in clinical factors that could affect insulin requirements include nutritional changes, steroids, renal function and continued improvement in critical conditions. This may require adjusting the TDD and, subsequently, the basal insulin dose.
To determine the total daily insulin needs for patients on a home insulin regimen, you should adjust the TDD for the inpatient setting based on acute factors related to the patient’s current clinical situation. No matter what, monitor the patient’s response to insulin doses and adjust accordingly to prevent hyperglycemia and hypoglycemia.
Glucommander’s SubQ insulin module helps providers easily calculate SubQ insulin doses based on a variety of factors and adjust dosing based on how the patient is responding. With options for basal/bolus+correction, basal+correction and basal/insulin:carb ratio+correction, the Glucommander SubQ module provides personalized dosing recommendations that improve patient safety and help providers achieve the standard of care.3
What do I need to know about NPO SubQ insulin administration?
Patients who are nil per os (NPO), meaning they’re not eating or drinking, can be treated with basal insulin plus correction insulin. The meal bolus insulin component is held.
The weight-based approach may be used to determine total daily insulin needs when calculating the TDD requirement of SubQ insulin for NPO patients. Half the TDD can be used to calculate the basal insulin dose needed; the remaining 50% that would be used to calculate the meal bolus needs is held until the patient is eating again.
Glucommander’s SubQ insulin module includes order set options for treating patients who are eating (with basal, meal bolus, plus correction insulin) or patients who are NPO (with basal plus correction insulin).
- 15. Diabetes Care in the Hospital: Standards of Medical Care in Diabetes—2020. American Diabetes Association. Diabetes Care Jan 2020, 43 (Supplement 1) S193-S202; DOI: 10.2337/dc20-S015
- Dudley D, Gaines M. Use of Technology Reduces Incidence of Hypoglycemia-Related Adverse Drug Events Among Patients Re- quiring Insulin Therapy While Hospitalized. DTS Virtual Poster Meeting. June 18, 2020.
- Newsom R, Patty C, Camarena E, Gray T, Sawyer R, Brown B, McFarland R. Safely Converting From Sliding Scale to Basal Bolus Insulin Across an Entire Medical Center via Implementation of the eGlycemic Management System. American Diabetes Associa- tion Scientific Sessions. June 2017.
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