Boluses, basals and corrections – Getting the doses right

Stephen W. Ponder MD, FAAP, CDEScott & White Clinic

Temple, Round Rock and College Station

Perfection(not possible)

Reality(what IS possible)

- = The diabetes

care “Gap”

Generally speaking, diabetes self care is the result of the “perfect” minus the “reality”. We can (at best) only control our “reality”. Perfection in

diabetes self care is not possible. Therefore, we must try to accept the size of the gap. Gaps shrink

and expand. So…by this thinking… are you OK with the current size of your “gap”?

Ponder’s Pumping PrinciplesVII. Quality diabetes self-care

is more about the PROCESS than it is about OUTCOMES

VIII. Technology changes; people don’t

IX. Self-consistency is a virtue

X. Everyone’s blood sugar fluxes; seek out patterns in the chaos

XI. Success is always a relative thing

XII. Don’t ever be afraid to start over

I. An insulin pump is no better or worse than the human being attached to it

II. Master carb counting well BEFORE pumping

III. Age is not a limiting factor for a pump

IV. Garbage in, garbage out: beware of the “pump and dump” phenomenon

V. The best pump doctor acts as a coach

VI. Simple is a good place to start, but pumping skills MUST advance over time

Why should I care about after meal blood

sugar levels?

180

100

Pre-meal 2 hr

glucose

140

220

Pre-meal

7%

5%

6%

8%HbA1c

Vascular system

95 115?

Postmeal Blood sugars, A1c and CV Risk

Goal: improve post-meal control: BG <

180 mg/dl

Before meal sugar After meal sugar

5 cardinal concepts to understand

1) Target (range)2) Basal rate(s)3) Insulin:CHO ratio(s)4) Correction factor(s)5) Insulin on board (IOB)

• A number or range• Start with 1 rate• Start with 1 I:CHO• Start with 1 CF• 3.5 to 5 hours (4)

Diabetes is best approached 1 day at a time

Diabetes care is a process, not an action

• It has purpose, meaning or direction

• It has a logical structure or order

• Steps are mostly measureable

• It has a goal, outcome or result

Duration Of Carb ActionOr…UNDERSTAND YOUR TARGETS

• Most carbs have most of their affect within 1 to 2.5 hours

• But complex carbs are slowed down by their protein and fat content

0 hrs 1 hr 2 hrs 3 hrs 4 hrs

High GIMed GILow GI

Carb Counting• Accounts for half the day’s control• Accuracy allows boluses to

match carbs for post-meal control and a significantly lower A1c

• Made easier with automatic carb bolus calculations by pump

• Always make an effort to estimate (if not count carbs)

D-teens count carbs POORLY

23%

TIP: A standing insulin dose (or regimen) is ALWAYS CHANGED LAST

• When troubleshooting a type 1 diabetes blood sugar problem

• First consider…– Food– Timing– Equipment

• BEFORE changing an insulin regimen

Why is the TDD so important?

TotalDailyDose(TDD)

1800/TDD = correction500/TDD = carb ratio

TARGET BGInsulin on Board (IOB)(2-8 hours)

½ TDD/24 = basal rate

Average TDD insulin ranges by age and weight

0.6-0.8 U/kg/d (toddler)

0.8-1.0 U/kg/d (child)

1.0-1.2 U/kg/d (teen)

60 units~ 30 units divided as boluses

30 units as glargine

60 units 1800 rule 30

60 units 500 rule 8.3 ~ 10Insulin to carbohydrate ratio

TDD

Correction factor (aka sensitivity factor)

Basal-Bolus: Example Calculations

Give dose at bedtime

10 – 10 – 10 + snacks

OR…

Adjust The TDD For A High Avg. BG or A1CExample: someone with a TDD of 35 units and few lows.

A1c = 9%, so more insulin is needed: about 3.2 units.

worksheet

J.F. 7/6/018/7/89

8.049.7

7H 14N

5H9 Lantus35

3535 26.25

26 1313 1.08 1.0

26

26 19

69.2 75

1:20

100-150100-150

100-150100-150

7/7/01

Novolog

What is basal insulin?

• Maintains balance• Minimizes drift/flux• +/- 30 mg/dl over time• Does not account for

disruptive effect of snacks, activity or stress

• May change over time • Usually 40-60% of TDD

What defines an effective basal insulin? (here’s a good visual)

Hints about basal insulin• 50% Rule: basals usually

make up 40 to 60% of an accurate Total Daily Dose

• Basal rates will be similar through the day, such as between 0.45 and 0.7, or between 1.0 and 1.4

• Adjust a basal rate in small steps – 0.05 to 0.1 u/hr

• Change basals 3 to 8 hours before need arises

0.75 U/hr

Starting a basal rate

B A S A L

Example:Pre-pump TDD = 48 units75% of 48 units = 36 units50% of 36 units = 18 units18 divided into 24 hours = 0.75 U/hr

timetime

0.75U/hr

Basal rates

0.5 U/hr

1.0 U/hr

Midnight

3 AM

6 AM

B A S A L

timetime

Programmed for the “typical” day

Survey: number of basal rates used

9

15

21 22

16

10

3 2 1 10

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 >

%

www.insulin-pumpers.orgN = 816

~2AM - 4AM is the physiologic nadir for insulin~ 40% of hypoglycemia occurs during sleep! Often asymptomatic!

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bolusbolus

bolus

2 - 4

AM

Bre

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– 9

AM

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Can’t “target practice” without a target!

• Targets are specific numbers

• May vary based on time of day or other considerations

• Are mathematical guides only

• Must be reasonably set

“Practice approaches perfect”

Selecting a blood sugar target Upper and lower

limits (range) A specific number Individualized Achievable Adjustable

100 mg/dl120 mg/dl130

mg/dl140 mg/dl

Set your BG range

100-200

80-18070-150

reasonable

individualized

Two week pumper log sheet (complete the open spots)

Influenced by basal

Influenced by boluses

Checks overnight basal(s)

What defines a correction?• Correction: to bring

something back into order or balance

• Diabetes: to lower (or raise) and out of range blood sugar level.

• Situational variables – Time– Quantity – Recent/impending

actions• Reproducibility?• Evolving nature?

Stock “correction”

5

time

0.75 U/hr

“Correction” dose

B A S A L I N S U L I N

. . ..

..

.

..

.

..

2 hours

time

180 mg/dl

80 mg/dl

250 mg/dl

110 mg/dl

Example: 1 to 25Actual – target / 25250 – 125 / 25 = 5

5

“Acceptable” = “target” +/- 30 mg/dl

gluc

ose

bol

us

What defines a meal dose?

• “Covers” the potential rise in sugar level after eating a meal.

• In non-D people, the 2 hour after meal BG is <140 mg/dl (by definition)

• Personal goals must be set by the patient/doc

Tight coverage by insulin for changes in blood sugar in

non-diabetic people

Insulin to carb ratio• Based on the “500

Rule”• 500 ÷ TDD =

grams of carbs covered by 1 unit insulin

• Example: 500 ÷ 60 = 8.3 = ~ 8

• Therefore: 1 unit for every 8 grams

• Easier: 1 unit for 7.5 gm or 2 for 15 grams

• 15 grams = 1 carbohydrate choice

CHO

I

G

Blood sugar level

6

time

0.75 U/hr

Insulin to Carb [I : CHO] ratio

B A S A L I N S U L I N

. . ..

..

.

..

.

..

2 hours

time

180 mg/dl

80 mg/dl

125 mg/dl

150mg/dl

Example: 1 to 1060 grams CHO /

10 60 / 10 = 6

6

“Acceptable” = “target” +/- 30 mg/dl

gluc

ose

bol

usCH O

Carb Ratio or Factor• Carb factor – how many grams of carb

are covered by 1 unit insulin• Carb bolus is based on:

• Your carb factor• How many grams of carbs you

plan to eat• Your BG allows a correction bolus determination • Amount of BOB (IOB) still active (ALSO determined from BG!)

• A pump can determine the bolus needed for a meal when the carb count and the carb factor are accurate

• Visit your dietitian to learn!

Check Your Carb Boluses

• Does your carb factor work for LARGE meals? – half your weight (lbs) as grams of carb

• Are carb counts accurate?

• Are boluses given 20 min before meals when the glucose is normal?

For frequent lows after meals –> raise carb factor #For frequent highs after meals –> lower carb factor #

An Accurate Carb Ratio or Factor:

• Returns the blood sugar: to within 30 mg/dl (1.7 mmol) of

where it started by the time selected for your

duration of insulin action (DIA) with no lows within 5 hours after

carb bolus given

Carb Bolus Varieties

Normal carb bolus Bolus taken immediately –

most meals Extended or square wave

bolus Bolus extended over time –

gastroparesis, pizza

Combo or dual wave bolus Some now, some later – bean

burritos, al dente pastas and pizzas, Symlin

0.75 U/hr

Unused insulin

7 Units 6

Units

B A S A L

timetime

6 Units

4-6 hours

“Stacking effect”

Avoid Insulin Stacking• The goal is to help

patients prevent over-correcting

• Available scientific data says how much active insulin remains

• Current practices to avoid insulin “stacking” include:

• Crude formulas (ie. 25% per hour or 50% of usual)

• Crude strategies (ie. set a high Post-Prandial target BG)

Does blood sugar (yes or no)

Carbs to be eaten (limited by ability to count carbs effectively) (counts, guesses, or doesn’t count at all)

Insulin to carb ratio (uses or doesn’t use)

Insulin dose (given by doc, guessed, or calculated)

“Thinking like a pancreas” example

Correction or sensitivity factor, includes target blood sugar (yes or no)

220 mg/dl

1 to 50

75 gm

1 to15

T = 1202 units

5 units

7 units

Bolus Size (Relative To Wt) Affects The DIAMeasured as units per kg(2.2 lb)

•Larger boluses have a longer duration of action.

•For 50 kg (110 lb) person: –0.3 u/kg = 15 u–15 u/kg = 7.5 u–0.075 u/kg = 3.75 u

Becker et al. Diabetes. 2005; 54 (Suppl. 1): 1367P

4 hrs

How long a bolus will lower the BG:

Recommendations For DIA Times

• DIAs on current pumps can be set from 2 to 8 hours.

An inaccurate DIA can significantly impact control.

Mudaliar et al: Diabetes Care, 22: 1501, 1999

Basal/Bolus Balance

< 50% Basal ~ 50% Basal > 50% Basal

Duration < 5 yrs ThinPhysically activeHigh carb/low fat diet

Most people Duration > 5 yrsPubertyLess activeInsulin resistantLow carb diet

Stop Lows FirstBetter control and more stability

• Mild lows cause followup lows

• Small epinephrine release makes muscles sensitive to insulin

• Can lead to another low as much as 36 hours after the first

• More carbs than usual are needed

Severe lows cause highsHigher stress hormone release

makes glucose rise for 6-10 hrsExcess carb intake leads to highs Boluses may be reduced/skippedMore insulin than usual needed

To stop lows, lower the TDD!!!

Benefits Of Frequent checking

Breakfast

100 (5.6)

200 (11)

400 (22)

300 (17)

DinnerLunch Bed

1 test versus 7 tests a day

4

5

6

7

8

9

10

11

12

0 2 4 6 8 10 12 14SMBG Frequency (BG per day)

HbA

1c HbA1c=5.99+5.32 / (BGpd+1.39)

Atlanta Diabetes Associates study:378 patients sorted from a database of 591 Pumps=MM 511 or earlierBG Target=100C peptide <0.1

Actual A1c Versus Testing Frequency Data From 378 People On Pumps

ADA:< 7%% AACE:

< 6.5%

P. Davidson et al: Diabetes 53 (suppl 2): abstract 430-P, 2004

Questions?