Imagine you are an experienced and confident baseball shortstop. Your position on the field allows for lots of “in the moment” choices to be made during the game. You are continuously aware of the following: 1) the player at bat, 2) what you know about the batter’s hitting style and power, 3) the number of runners on base, their speed and quickness, 4) the game score at the moment, 5) number of outs, strikes and balls called, 6) the skills of the pitcher and your fellow players, 7) the playing conditions on the field and in the sky, 8) your unique abilities and experience, and perhaps even more.
A line drive ground ball streaks your way, slightly to your left. You quickly intercept it on the run. Next, your choice of where you throw the ball will be determined by several factors. Whether there is a runner on 3rd base, racing for home. Or…perhaps a double play if third base was empty and there is a runner already on 1st. These sorts of split-second decisions are prepared for and rehearsed in training.
The principles of dynamic decision making are similar between many sports and Sugar Surfing™. They only differ in their speed of execution. The Sugar Surfer has the added benefit of more time to choose her/his actions or omissions. Hopefully, Surfers choose wisely and use their results to gain experience for next time.
Fielders need choices
Ever since blood sugar meters came on the scene, rapid-acting insulin dosing for meals, snacks or out of range corrections has been approached as a basic math problem. First, someone provides a formula, ratio, or ‘sliding scale’. Next, the person plugs in ‘variables’ (blood sugar level and/or carbohydrate count) and voila the amount of rapid insulin to inject materializes.
Prior to blood sugar meters, a color chart was used to define the amount of sugar in a urine sample. That was all we had to estimate blood sugar levels. It was grossly indirect and backwards looking. It was also impossible to convert a color into a number which would be suitable for calculating an insulin dose in the moment. Therefore, we were assigned fixed daily insulin doses which were only changed by the doctor every few months.
Today, the blood sugar meter era is transitioning into the age of continuous glucose monitoring (CGM). With this revolution comes the need for a paradigm shift in our thinking about how to estimate a rapid acting insulin dose in response to a planned self-management situation (e.g., eating food), or in response to a sudden change in blood sugar conditions (e.g., “correct a high”).
Traditionally, rapid acting insulin dosing is based on a measured blood sugar level and/or an anticipated amount of food (usually but not always just the carbohydrate amount) to be eaten. Some people make dosing modifications for fat and protein. The data we input are one-dimensional (e.g., point in time glucose level, grams of carbs).
This contrasts with the dynamic nature of blood sugar ebb and flow as reflected in a CGM trendline. CGM users quickly discovered that old style insulin dosing management was like putting a mathematical square peg into a round hole. The equations into which these estimates are inserted were themselves rigid and unyielding. They do not consider changing (dynamic) conditions.
Anyone with type 1 diabetes who has worn a glucose sensor for a few days quickly realizes that blood sugars are in constant motion and can shift up and down capriciously. These shifting sugars may often defy your expectations based your understanding of how insulin and carbohydrates work within the body. Over time, you may start to question the value of the set of dosing equations you were assigned. These equations might have seemed to work at first. Yet, over time their effectiveness fell off.
As rigid ratio-based insulin dosing lost its luster, you might have started to question the static concept altogether. At first you might have concluded they were improperly assigned by the specialist at the last medical visit. Or, maybe you think you have just outgrown the last ratios given. Maybe the insulin itself is not working for some unknown reason. Maybe you miscounted the carbs. All of these are reasonable explanations for lack of expected outcomes, at least up to a point. Falling back on these possible reasons for unexpected glucose results might have led you to believe that poor results are based on someone’s errors: yours, your doctor’s, or both.
However, your faith in the certainty of a fixed insulin dosing ratio may not have been diminished. You think “I just need to keep working on finding the right set of ratios.” After weeks to months of this Quixotic, ‘Holy Grail’ style odyssey, you now have evolved into 5 separate fixed insulin to carb ratios through the day, 3 different BG correction dosing algorithms, 3 different glycemic targets and (if pumping) 8 different basal insulin settings. Yet…your blood sugar metrics are at best a few percentage points improved compared to when things were simpler and fewer in number. They might even be worse.
Growing ever more frustrated, you try altering eating habits or meal macronutrient composition (e.g., go ‘lo-carb’). These efforts may reveal improvements and encourage even more changes in your daily macronutrient intake. But you may remain flummoxed by the unpredictability of the blood sugar responses you see, even when you dose the same insulin amount for identical blood sugar levels and/or carb counts. You are now ready to ditch the static style and embrace a dynamic approach.
It's about keeping your head in the game.
Dynamic diabetes management is based on the fundamental appreciation that glycemic control rests on an ever-shifting glycemic foundation. Flux (rapid) and drift (slow) changes in the CGM trendline reveal the true nature of blood sugar levels in the human body. Remember, the only person with a straight-line blood sugar is a dead person!
Once a static thinking approach is discarded and a dynamic approach is embraced, your methods to estimate insulin and carbohydrate effects become more subjective. Static methods of insulin dosing now become a starting point for further refinement. Know that dynamic thinking still rests on a static foundation. The subjective (dynamic) refines the objective (static).
The use of trendline arrows to modify insulin dosing is an attempt to account for glycemic trending when modifying an insulin or carb dose. It’s a good first step. Fixed percentage adjustments of an insulin or carb dose based on trend arrow direction are themselves static by nature. This concept can be taken further.
Other situational considerations for rapid acting insulin dose modification are worthy of review and are listed below. They are largely intuitive and worthy of consideration when modifying a statically calculated dose of rapid insulin or carb.
Activity level (recent, current, and/or immediately anticipated)
Blood sugar “altitude” (low, in range, high BG)
Glycemic raising ‘speed’ of the meal or food to be consumed (fast, medium, or slow)
Trending direction (dropping, steady or rising, plus speed of change, if any).
Type of insulin used (inhaled, ultra-rapid injected insulin or even old-school Regular insulin).
Time since last insulin dose. Where along the prior insulin action curves are you now? (peak time or at the end of the effect).
Estimated duration of the food or meal to be consumed (short, medium, or long)
After these considerations are made and a dose is chosen, the next two choices will be “when” and “how”.
Timing of the dose (if insulin is being given for a meal). Keep in mind there are some instances when eating before dosing insulin would be a best choice.
Will the dose be taken at once, or over time (more and one injection or by an extended or combination bolus (if using an insulin pump)?
You might have additional modifiers of how much insulin you might take and how it will be delivered.
Reflection on the above list of variables highlights why blood sugar results can vary so much from day to day. Blood glucose management in the CGM is as much an art as it is a science.
Rapid interpretation of CGM data by rapidly “seeing” a trendline pattern(s) allows a dynamically thinking person (or their parent) with diabetes to effectively manage situations as events are unfolding or about to unfold. Sugar Surfing™ is the process of capturing blood sugar trend patterns ‘in the moment’, then choosing whether to act (or not act) to alter the BG trending trajectory.
To dynamically manage glucose trending, one must be ‘situationally aware’, like our shortstop above. Practically speaking, this means periodically glancing at the trendline itself. Or, as one of my young surfing patients once told me: “be alert”.
Trendlines are visual renderings of individual blood sugar readings plotted along a time window of the viewer’s choice. Altering the window being viewed can either compress or dilate the visual impact of the trendline. Most Sugar Surfers will use a 3, 6 or at most 12-hour time window when searching for significant BG trendline patterns.
There are a few core patterns that Surfers need to become familiar with. Like letters of a basic alphabet, once these can be visualized, the next action becomes the relevance or significance of that pattern at that moment in time. This is when situational thinking kicks in.
Recent, current, and anticipated diabetes self-care actions flow into one’s stream of consciousness as contemplation about what actions could be taken are considered in response to a ‘significant’ trendline pattern.
Common considerations include the last insulin dose, how much and when. What activity has, is or might be done soon. If food is part of the decision, then what, when and how much are worthy of reflection. You cannot ignore impact of stress, illness, or medications too. Finally, what prior experience do you have based on prior events like the one you are confronting now?
Some of you might be thinking right now: “Wow, that’s a lot to remember and process”. Then imagine the shortstop.
If you need another metaphor, consider the numerous split-second decisions and choices you make as you steer a 2,000-pound automobile loaded with your loved ones at 75 MPH in a crowded highway. The mind can quickly and efficiently process these inputs. It takes patience and practice, as with any other mastered skill. You have already applied dynamic decision making successfully in very many other aspects of your life.
The era of partial closed loop insulin pumping is quickly growing in popularity. Insulin delivery has been taken to new mathematical heights in commercial and DIY systems using real-time CGM feedback. But as I write this post, no ambulatory diabetes management system has been able to fully remove the user from the process. Perhaps this will happen someday.
So, for now, our daily blood sugar profiles are the net result of our planned (proactive) actions and the quality and speed of our responses to life’s surprises (reactive). Aim to manage the situation and strike out diabetes!