Transcript Boluses, basals and corrections – Getting the doses right

Boluses, basals and corrections –
Getting the doses right
Stephen W. Ponder MD, FAAP, CDE
Scott & White Clinic
Temple, Round Rock and College Station
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”?
Perfection
(not possible)
-
Reality
(what IS possible)
=
The
diabetes
care
“Gap”
Ponder’s Pumping Principles
I.
An insulin pump is no better or
worse than the human being
attached to it
VII. Quality diabetes self-care is
more about the PROCESS
than it is about OUTCOMES
II.
Master carb counting well
BEFORE pumping
VIII.Technology changes; people
don’t
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
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
Why should I care about
after meal blood sugar
levels?
Postmeal Blood sugars, A1c and CV Risk
Vascular system
220
glucose
HbA1c
180
8%
140
7%
100
6%
5%
Pre-meal
95
2 hr
?
Pre-meal
115
Goal: improve post-meal
control: BG < 180 mg/dl
Before meal sugar
After meal sugar
5 cardinal concepts to understand
1)
2)
3)
4)
5)
Target (range)
Basal rate(s)
Insulin:CHO ratio(s)
Correction factor(s)
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 Action
Or…UNDERSTAND YOUR TARGETS
High GI
Med GI
Low GI
0 hrs
1 hr
2 hrs
3 hrs
4 hrs
• 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
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?
½ TDD/24 = basal rate
Insulin on Board (IOB)
(2-8 hours)
500/TDD = carb ratio
Total
Daily
Dose
(TDD)
TARGET BG
1800/TDD = correction
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)
Basal-Bolus: Example
Calculations
30 units as glargine
Give dose at bedtime
TDD
60 units
~ 30 units divided as boluses
10 – 10 – 10 + snacks
OR…
60 units
500 rule
8.3 ~ 10
Insulin to
carbohydrate ratio
60 units
1800 rule
30
Correction factor
(aka sensitivity factor)
Adjust The TDD For A High Avg. BG or A1C
Example: someone with a TDD of 35 units and few lows.
A1c = 9%, so more insulin is needed: about 3.2 units.
worksheet
J.F.
8/7/89
7/6/01
8.0
49.7
7H
14N
5H
9 Lantus
35
35
26
13
35
26.25
13
1.08
1.0
Novolog
26
69.2
26
19
100-150
100-150
75
1:20
100-150
100-150
7/7/01
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
Starting a basal
rate
Example:
Pre-pump TDD = 48 units
75% of 48 units = 36 units
50% of 36 units = 18 units
18 divided into 24 hours = 0.75
U/hr
0.75 U/hr
B A S A L
time
Basal
rates
3 AM
Midnight
6 AM
Programmed for
the “typical”
day
1.0 U/hr
0.75U/hr
B A S A L
time
0.5 U/hr
25
21
22
20
16
15
15
%
10
10
9
5
3
2
1
1
0
1
2
3
4
5
6
7
8
9
Survey: number of basal rates
used
www.insulinN = 816
pumpers.org
10 >
Breakfast
6 – 9 AM
2 - 4 AM
Snack
Supper
Snack
Lunch
Snack
Breakfast
~2AM - 4AM is the physiologic nadir for insulin
~ 40% of hypoglycemia occurs during sleep! Often asymptomatic!
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
120 mg/dl
140
Set your BG range
reasonable
100-200
80-180
70-150
individualized
Two week pumper log sheet
(complete the open spots)
Influenced
by basal
Checks
overnight
basal(s)
Influenced
by boluses
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”
“Correction”
dose
250
2
hours
.
mg/dl
. .
.
.
.
5
.
110
mg/dl
180
mg/dl
.
.
bolu
s
gluco
se
..
.
Example: 1 to
25
Actual – target /
25
250 – 125 / 25 = 55
80
mg/dl
“Acceptable” = “target” +/- 30
mg/dl
0.75 U/hr
B A S A L
time
I N S U L I N
What defines a meal dose?
Tight coverage by insulin for
changes in blood sugar in
non-diabetic people
• “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
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
CH
O
I
G
Blood sugar level
Example: 1 to
10
60 grams CHO / 10
Insulin to Carb [I : CHO]
ratio
CH
O
60 / 10 = 66
.
. .
2
hours
.
125
mg/dl
6
bolu
s
gluco
se
..
.
0.75 U/hr
180
mg/dl
B A S A L
time
150mg/
dl
.
.
.
.
.
80
mg/dl
“Acceptable” = “target” +/- 30
mg/dl
I N S U L I N
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


Extended or square wave
bolus


Bolus taken immediately – most
meals
Bolus extended over time –
gastroparesis, pizza
Combo or dual wave bolus

Some now, some later – bean
burritos, al dente pastas and
pizzas, Symlin
Unused
insulin
“Stacking
6
Units
effect”
7
Units
6
Units
4-6 hours
0.75 U/hr
B A S A L
time
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)
“Thinking like a pancreas” example
220 mg/dl
2 units
1 to 50
T = 120
75 gm
5 units
7 units
1 to15
Does blood sugar (yes or no)
Correction or sensitivity factor, includes
target 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)
Bolus Size (Relative To Wt) Affects The DIA
Measured as units per kg(2.2 lb)
How long a bolus will lower the BG:
4 hrs
•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
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
Duration < 5 yrs
Thin
Physically active
High carb/low fat diet
~ 50% Basal
> 50% Basal
Most people
Duration > 5 yrs
Puberty
Less active
Insulin resistant
Low carb diet
Stop Lows First
Better 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 highs
Higher stress hormone release
makes glucose rise for 6-10 hrs
Excess carb intake leads to highs
Boluses may be reduced/skipped
More insulin than usual needed
To stop lows, lower the TDD!!!
Benefits Of Frequent checking
400 (22)
300 (17)
1 test versus 7 tests a day
200 (11)
100 (5.6)
Breakfast
Lunch
Dinner
Bed
Actual A1c Versus Testing Frequency
Data From 378 People On Pumps
12
Atlanta Diabetes Associates study:
378 patients sorted from a database of 591
Pumps=MM 511 or earlier
BG Target=100
C peptide <0.1
11
HbA1c
10
9
ADA:
< 7%%
8
7
HbA1c=5.99+5.32 / (BGpd+1.39)
AACE:
< 6.5%
6
5
4
0
2
4
6
8
10
SMBG Frequency (BG per day)
12
14
P. Davidson et al: Diabetes 53 (suppl 2): abstract 430-P, 2004
Questions?