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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.

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Boluses, basals and corrections – Getting the doses right

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  1. Boluses, basals and corrections – Getting the doses right Stephen W. Ponder MD, FAAP, CDE Scott & White Clinic Temple, Round Rock and College Station

  2. 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”? The diabetes care “Gap” Perfection (not possible) Reality (what IS possible) - =

  3. Ponder’s Pumping Principles • An insulin pump is no better or worse than the human being attached to it • Master carb counting well BEFORE pumping • Age is not a limiting factor for a pump • Garbage in, garbage out: beware of the “pump and dump” phenomenon • The best pump doctor acts as a coach • Simple is a good place to start, but pumping skills MUST advance over time • Quality diabetes self-care is more about the PROCESS than it is about OUTCOMES • Technology changes; people don’t • Self-consistency is a virtue • Everyone’s blood sugar fluxes; seek out patterns in the chaos • Success is always a relative thing • Don’t ever be afraid to start over

  4. Why should I care about after meal blood sugar levels?

  5. Postmeal Blood sugars, A1c and CV Risk chronic inflammation Vascular system 220 glucose HbA1c 180 8% 140 7% 100 6% 5% Pre-meal 2 hr Pre-meal Goal: improve post-meal control: BG < 180 mg/dl 95 ? 115

  6. Before meal sugar After meal sugar

  7. 5 cardinal concepts to understand • 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)

  8. Diabetes is best approached 1 day at a time

  9. 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

  10. 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

  11. 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)

  12. D-teens count carbs POORLY 23%

  13. 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

  14. Why is the TDD so important? ½ TDD/24 = basal rate Total Daily Dose (TDD) TARGET BG Insulin on Board (IOB) (2-8 hours) 1800/TDD = correction 500/TDD = carb ratio

  15. 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)

  16. Basal-Bolus: Example Calculations 30 units as glargine Give dose at bedtime TDD 60 units 10 – 10 – 10 + snacks ~ 30 units divided as boluses OR… Insulin to carbohydrate ratio 60 units 8.3 ~ 10 500 rule Correction factor (aka sensitivity factor) 60 units 30 1800 rule

  17. 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.

  18. worksheet

  19. J.F. 7/6/01 8/7/89 8.0 7H 14N 49.7 5H 9 Lantus 35 35 35 26.25 26 13 13 1.0 1.08 Novolog 26 75 69.2 26 1:20 19 100-150 100-150 100-150 100-150 7/7/01

  20. 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

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

  22. 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

  23. 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 time

  24. Basal rates 3 AM Midnight 6 AM Programmed for the “typical” day 1.0 U/hr 0.75U/hr B A S A L 0.5 U/hr time time

  25. Survey: number of basal rates used % www.insulin-pumpers.org N = 816

  26. bolus bolus bolus Snack Lunch Snack Breakfast 6 – 9 AM Snack Supper Breakfast 2 - 4 AM ~2AM - 4AM is the physiologic nadir for insulin ~ 40% of hypoglycemia occurs during sleep! Often asymptomatic!

  27. 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

  28. “Practice approaches perfect”

  29. Selecting a blood sugar target • Upper and lower limits (range) • A specific number • Individualized • Achievable • Adjustable 100 mg/dl 120 mg/dl 140 mg/dl 130 mg/dl

  30. Set your BG range reasonable individualized 100-200 80-180 70-150 at least 75% of the time

  31. Two week pumper log sheet (complete the open spots) Influenced by basal Checks overnight basal(s) Influenced by boluses

  32. 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”

  33. “Correction” dose Example: 1 to 25 Actual – target / 25 2 hours 250 – 125 / 25 = 5 5 250 mg/dl . 180 mg/dl . . . . . . . . . glucose . 5 . 110 mg/dl 80 mg/dl bolus “Acceptable” = “target” +/- 30 mg/dl 0.75 U/hr B A S A L I N S U L I N time time

  34. 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

  35. 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

  36. Insulin to Carb [I : CHO] ratio Example: 1 to 10 60 grams CHO / 10 60 / 10 = 6 6 CHO . 180 mg/dl 2 hours . . . . . . . . . 150mg/dl 125 mg/dl glucose . . 6 80 mg/dl bolus “Acceptable” = “target” +/- 30 mg/dl 0.75 U/hr B A S A L I N S U L I N time time

  37. 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!

  38. 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 #

  39. 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

  40. 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

  41. Unused insulin 6 Units “Stacking effect” 7 Units 6 Units 4-6 hours 0.75 U/hr B A S A L time time

  42. 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)

  43. “Thinking like a pancreas” example Does blood sugar (yes or no) 220 mg/dl Correction or sensitivity factor, includes target blood sugar (yes or no) 1 to 50 2 units T = 120 Carbs to be eaten (limited by ability to count carbs effectively) (counts, guesses, or doesn’t count at all) 75 gm Insulin to carb ratio (uses or doesn’t use) 5 units 1 to15 7 units Insulin dose (given by doc, guessed, or calculated)

  44. 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 How long a bolus will lower the BG: 4 hrs Becker et al. Diabetes. 2005; 54 (Suppl. 1): 1367P

  45. 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

  46. Basal/Bolus Balance

  47. Stop Lows FirstBetter control and more stability 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 • 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 To stop lows, lower the TDD!!!

  48. Benefits Of Frequent checking 400 (22) 300 (17) 1 test versus 7 tests a day 200 (11) 100 (5.6) Breakfast Lunch Dinner Bed

  49. Actual A1c Versus Testing FrequencyData From 378 People On Pumps Atlanta Diabetes Associates study: 378 patients sorted from a database of 591 Pumps=MM 511 or earlier BG Target=100 C peptide <0.1 HbA1c=5.99+5.32 / (BGpd+1.39) ADA: < 7%% AACE: < 6.5% P. Davidson et al: Diabetes 53 (suppl 2): abstract 430-P, 2004

  50. Questions?

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