Insulin Dilution and CRI (U-100)
Posted: Tuesday, January 4th, 2022 | Updated: Sunday, January 16th, 2023
Posted: Tuesday, January 4th, 2022 | Updated: Sunday, January 16th, 2023
General Information
In veterinary medicine, we'll sometimes see patients who require insulin therapy at very small doses. When you're unable to accurately deliver a desired quantity of regular insulin, you may choose to dilute it. The following dilution may be used for regular insulin requiring the use of U-100 syringes
The Dilution
U-100 syringes are made so that there's 100 units of insulin for every ml drawn up. Hence, they are labeled as 100 units/ml or U-100. This also equates to having every 1 unit be equal to 0.01 ml (100 units/ml x 0.01 ml = 1 unit). Say we need to administer 0.20 units of regular insulin. To most accurately dose that amount, the veterinarian asks you to dilute it prior to administration. One of the easiest ways to dilute insulin is by adding 10 units of regular insulin to 0.90 ml of 0.9% NaCl for a total volume of 1 ml. This concentration yields 10 units/ml. If you need 0.20 units of regular insulin, divide by your newly made concentration of 10 units/ml. You'll need 0.02 ml of this new solution (0.20 units / (10 units/ml) = 0.02 ml). Therefore, you may draw up the dose in a typical syringe at 0.02 ml or at 2 units in a U-100 insulin syringe (0.02 ml x 1 unit/0.01 ml = 2 units)
Other variations of this concentration are as follows:
10 units Regular Insulin (U-100) and 0.90 ml of 0.9% NaCl = 10 units/ml concentration
5 units Regular Insulin (U-100) and 0.45 ml of 0.9% NaCl = 10 units/ml concentration
1 unit Regular Insulin (U-100) and 0.09 ml of 0.9% NaCl = 10 units/ml concentration
Treating Diabetic Ketoacidosis (DKA) with an Insulin CRI
Occasionally, we may see patient that requires a CRI of insulin. These are typically our DKA patients. Many clinicians will create their own protocol for intravenous fluid therapy, but others may follow a pretty standard method used across veterinary medicine. Always clarify the doctor's orders and confirm insulin doses or calculations with another person. Remember to never flush an intravenous catheter with insulin in the line. Labeling the catheter used for insulin therapy may prevent others from mistakenly flushing the catheter. Insulin is very potent and care must be made to try and remove as much insulin from the t-port and catheter itself prior to flushing. The t-port itself may be replaced completely and the catheter may be aspirated in an attempt to draw the remaining insulin out. The following is a common method used to treat DKA in cats and dogs
Empty a 500 ml bag of 0.9% NaCl in an aseptic manner. Save 250 ml of the 0.9% NaCl and add it back to the empty bag. Some clinicians may only have you add 240 ml of 0.9% NaCl back to the bag. A few practices may have additional sizes of 0.9% NaCl and any will be okay to use so long as the end volume is 250 ml or 240 ml depending on clinician preference. The clinician will ask you to add a calculated dose of regular insulin to the bag. Generally, clinicians use a dose of 1.1 units/kg for a cat and 2.2 units/kg for a dog. Make sure to prime the intravenous fluid line by running at minimum 50 ml of the mixture through. Insulin tends to absorb to the plastic tubing. Adjust the insulin rate and fluid rate/type after checking a blood glucose. The following chart is used to determine adjustments. Always keep the total fluid volume the patient is receiving the same. Hence, if you go up 2 ml/hr on the insulin CRI, you must go down 2 ml/hr on the other intravenous fluid. Some clinicians will want the patient to stay on dextrose once started on it. Ask the clinician to clarify what they would like to do. Additionally, there are more variations of the chart below. Again, this will all be based on hospital protocols and/or clinician preference. Always clarify with your clinicians
In veterinary medicine, we'll sometimes see patients who require insulin therapy at very small doses. When you're unable to accurately deliver a desired quantity of regular insulin, you may choose to dilute it. The following dilution may be used for regular insulin requiring the use of U-100 syringes
The Dilution
U-100 syringes are made so that there's 100 units of insulin for every ml drawn up. Hence, they are labeled as 100 units/ml or U-100. This also equates to having every 1 unit be equal to 0.01 ml (100 units/ml x 0.01 ml = 1 unit). Say we need to administer 0.20 units of regular insulin. To most accurately dose that amount, the veterinarian asks you to dilute it prior to administration. One of the easiest ways to dilute insulin is by adding 10 units of regular insulin to 0.90 ml of 0.9% NaCl for a total volume of 1 ml. This concentration yields 10 units/ml. If you need 0.20 units of regular insulin, divide by your newly made concentration of 10 units/ml. You'll need 0.02 ml of this new solution (0.20 units / (10 units/ml) = 0.02 ml). Therefore, you may draw up the dose in a typical syringe at 0.02 ml or at 2 units in a U-100 insulin syringe (0.02 ml x 1 unit/0.01 ml = 2 units)
Other variations of this concentration are as follows:
10 units Regular Insulin (U-100) and 0.90 ml of 0.9% NaCl = 10 units/ml concentration
5 units Regular Insulin (U-100) and 0.45 ml of 0.9% NaCl = 10 units/ml concentration
1 unit Regular Insulin (U-100) and 0.09 ml of 0.9% NaCl = 10 units/ml concentration
Treating Diabetic Ketoacidosis (DKA) with an Insulin CRI
Occasionally, we may see patient that requires a CRI of insulin. These are typically our DKA patients. Many clinicians will create their own protocol for intravenous fluid therapy, but others may follow a pretty standard method used across veterinary medicine. Always clarify the doctor's orders and confirm insulin doses or calculations with another person. Remember to never flush an intravenous catheter with insulin in the line. Labeling the catheter used for insulin therapy may prevent others from mistakenly flushing the catheter. Insulin is very potent and care must be made to try and remove as much insulin from the t-port and catheter itself prior to flushing. The t-port itself may be replaced completely and the catheter may be aspirated in an attempt to draw the remaining insulin out. The following is a common method used to treat DKA in cats and dogs
Empty a 500 ml bag of 0.9% NaCl in an aseptic manner. Save 250 ml of the 0.9% NaCl and add it back to the empty bag. Some clinicians may only have you add 240 ml of 0.9% NaCl back to the bag. A few practices may have additional sizes of 0.9% NaCl and any will be okay to use so long as the end volume is 250 ml or 240 ml depending on clinician preference. The clinician will ask you to add a calculated dose of regular insulin to the bag. Generally, clinicians use a dose of 1.1 units/kg for a cat and 2.2 units/kg for a dog. Make sure to prime the intravenous fluid line by running at minimum 50 ml of the mixture through. Insulin tends to absorb to the plastic tubing. Adjust the insulin rate and fluid rate/type after checking a blood glucose. The following chart is used to determine adjustments. Always keep the total fluid volume the patient is receiving the same. Hence, if you go up 2 ml/hr on the insulin CRI, you must go down 2 ml/hr on the other intravenous fluid. Some clinicians will want the patient to stay on dextrose once started on it. Ask the clinician to clarify what they would like to do. Additionally, there are more variations of the chart below. Again, this will all be based on hospital protocols and/or clinician preference. Always clarify with your clinicians
Blood Glucose (mg/dL) |
Insulin CRI Rate (ml/hr) |
Maintenance IVF Additives (ml/hr) |
>250 mg/dL |
10 ml/hr |
No additives |
200 to 250 mg/dL |
7 ml/hr |
2.5% Dextrose |
150 to 199 mg/dL |
5 ml/hr |
2.5% Dextrose |
100 to 149 mg/dL |
5 ml/hr |
2.5% Dextrose |
<100 mg/dL |
Discontinue CRI |
5.0% Dextrose |
*Note Per Plumb's as of 01/16/23: "Regular insulin is reportedly physically incompatible when mixed with the following drugs/solutions: aminophylline, ampicillin, butorphanol, chlorothiazide, cytarabine, diazepam, dobutamine, famotidine, furosemide, gentamicin, glycopyrrolate, ketamine, pantoprazole, pentobarbital, phenobarbital, piperacillin/tazobactam, polymyxin B, propranolol, quinidine, and thiopental."
Sources:
Ford, Richard B., and Elisa M. Mazzaferro. Kirk and Bistner's Handbook of Veterinary Procedures and Emergency Treatment. 8th ed., Saunders Elsevier, 2006.
On The Job Training and Routine Practices
Plumb's Veterinary Drugs App accessed from Instinct on 01/16/23.
Ford, Richard B., and Elisa M. Mazzaferro. Kirk and Bistner's Handbook of Veterinary Procedures and Emergency Treatment. 8th ed., Saunders Elsevier, 2006.
On The Job Training and Routine Practices
Plumb's Veterinary Drugs App accessed from Instinct on 01/16/23.