CREATING SLIDING SCALES    

 

TAKE HOME MESSAGES:

1.  THERE IS ABSOLUTELY NO EVIDENCE SUPPORTING THE BENEFITS OF INSULIN SLIDING SCALES

2.  In patients with type 1 diabetes, sliding scales should NEVER be used in the absence of SCHEDULED doses of insulin

3.  If using a scale, make sure you ADJUST it on a daily basis

4.  Most patients don’t eat meals qhs.  So do not use the same ‘scale’ at hs as you would for meal times

 

Sliding scales are commonly used orders that have absolutely NO EVIDENCE to support their use.  If anything, they increase the frequency of HYPERGLYCEMIA and HYPOGLYCEMIA when used alone and should never be used as the sole way to control blood sugars.  If you feel a patient will require insulin, order scheduled doses of insulin but a CORRECTIVE SLIDING SCALE can be used as a supplement to correct for high BG (e.g. > 15 mmol/L) to prevent against dehydration and metabolic compromise. 

 

To determine how much to use, it is useful to think about how much insulin is required to lower glucose by a certain amount.  This is called an INSULIN SENSITIVITY FACTOR (ISF).  It is dependent on how INSULIN RESISTANT a patient is.  A patient who is more resistant will require more insulin to lower glucose than a patient who is less resistant. 

 

How to create a starting corrective [sliding] scale that makes sense:

 

1.  If a patient is already taking OAHA’s or insulin, CONTINUE THEM if clinically indicated.

 

2.  Calculate insulin sensitivity factor (ISF) or CORRECTION FACTOR = expected in BG (in mmol/L) in response to 1 unit of insulin:

 

                        ISF =                 100                       

                                   total daily dose of insulin 

 

       For example, an ISF of 3 estimates that 1 unit of insulin will decrease glucose by 3 mmol/L

 

       In patients taking OAHA’s, use a more conservative ISF (e.g. 3) or NOT USE ONE AT ALL!

 

3. Option 1 - Create a “get me through the night” scale:  Remember, the goal of a corrective scale is to prevent high BG from becoming higher.  A scale has NO HOPE of fixing someone’s blood BG on its own.  This suggestion is conservative and used for the sole purpose of making sure things don’t get worse, but will not cause hypoglycemia.  IT MUST BE ADJUSTED AT LEAST EVERY 24 HOURS.

a.  Continue the patient’s usual treatment for diabetes (if  indicated)

b.  Select a BG for which you would be concerned that could result in dehydration or metabolic compromise (e.g. BG > 15 mmol/L)

c.  Order:  if BG < 15, give no additional insulin.  If 15-18 : give 4 units of lispro or aspart.  If > 18-20, give 5 units. If > 20: give 6 units & call MD.

d. ADJUST THIS SCALE based on its effects (e.g. if 5 units did nothing for a BG of 18, increase that amount for that tier)

 

4.   Option 2 - Create a precise “scale”:

a.  Select your target BG range. For most patients this will be between 4-8 or 4-10 mmol/L.  For this target range, you  would write that no additional insulin is needed (but remember the patient will still be getting their scheduled doses of OAHA’s or insulin)

b.  Set your increments for BG : ‘tiers’ for your scale can be whatever you calculated for ISF.   

c.  For example: patient who is on glargine 20 units qhs and lispro 10 units ac meals

 

                        Answer:  Total daily dose = (20 + 10x3) units

                                                                 = 50 units

 

                                         ISF = 100/50 = 2

                                               

Your orders would then appear as:

1   1.  Glargine 20 U qhs + lispro 10 U with meals

     2.  Sliding scale (as an adjunct to the schedule insulin above) would therefore appear as follows:

 

If blood  glucose

Give x units additional Humalog at mealtimes

<4.0

0, give juice + call MD

4.0 – 8.0

0

8.1 – 10.0

1

10.1 – 12.0

2

12.1 – 14.0

3

14.1 – 16.0

4

16.1 – 18.0

5

18.1 – 20.0

6

> 20.0

7 + call MD

 

 

Ex 2: Create sliding scale for patient who is only on metformin 1000 mg bid.

 

Answer

Although we do not know the patient’s precise insulin sensitivity factor, it is likely safe to use an ISF of 3.0

Sliding scale could therefore appear as follows (or consider not using a scale at all!):

 

If blood  glucose

Give x units Humalog at mealtimes

<4.0

0, give juice + call MD

4.0 – 10.0

0

10.1 – 13.0

1

13.1 – 16.0

2

16.1 – 19.0

3

19.1 – 22.0

4

> 22.0

5 + call MD

 

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