The Basal Rate Parallax


I've been an endo for decades and a PWD over half a century. I've learned my trade firsthand by meeting and helping tens of thousands of children and adults with diabetes, clinical research, plus lots of hard study and reading. What I'm about to discuss next might challenge many readers. But it's not meant to be dismissive or demeaning in any way, simply something for you to reflect on. It’s what’s called a parallax: how something appears to differ when viewed from different positions. I have a different point of view to present to you. Read on.

I have prescribed or myself used insulin pump therapy for 35 years. It started for me in 1982. Pumps were novel and exciting back then, but quite primitive by today’s standards. Once these devices entered the world of direct patient care, we quickly found the need to create “users’ manuals”. I don’t mean how to operate the machine. Rather how to properly apply it into daily life of the person with diabetes. In time, clinical guidelines and popular books came around to serve in that capacity. Dosing ratios were created. Unavoidably, diabetes science and diabetes lore became intertwined.

There is a well-established belief and practice that multiple pre-programmed basal insulin delivery settings using the pump are important for obtaining the best possible results. It's not uncommon that I encounter pump using PWD's and CWD's wearing insulin pumps with up to a dozen basal rates, sometimes more. At the same time, I note their overall control may still be struggling (based on high A1C results). It's the basis of my first rule of insulin pumping: that the pump is no better or worse than its user's abilities and interest.

When questioned further, many pumpers seem to have fallen into a cognitive trap. They (or their endo team) analyze their blood sugar data and its variance, then may insert a basal rate change (or many) into the device. One or two different rates might be helpful over a 24-hour day, but adding more than that (if any) might not truly be needed. A little tweak here, another there. It can quickly get out of hand, and does.

Why is this so widespread? Daily basal insulin needs are often overestimated. The commonly used dosing formulas and ratios which endos use will start by assigning half of ones estimated daily insulin needs towards the basal category. This is an example of static diabetes management. I was taught to believe this and preached it fervently for years. Decades of experience combined with Sugar Surfing (Dynamic thinking) has taught me something quite different. Recent clinical research has tended to affirm my positions.

This revelation shouldn't be that surprising. When pumps first came onto the scene, by definition no one had decades of clinical experience using or wearing them. We didn’t have continuous glucose monitoring either. This became an "on the job training" experience. Over time, books and workshops arose and codified earlier observations, and clinical research generally supported the superiority of insulin pump therapy over injections. But pump "lore" never went away.

My parallax view arose from being an endo who also lived with the condition itself and choosing to become an insulin pump early adopter/user. Later when I adopted real time CGM, my parallax view was fully realized.

To this day I still work with patients who believe their diabetes control relies on numerous basal insulin settings. When possible, I aim to reduce, not increase, the number of rates. If I start them on pump therapy, it’s almost always a single rate at the beginning.

You see, my parallax view is that basal insulin needs are not easy to predict in advance. The human body is too dynamic. A minimal number of rates combined with good Sugar Surfing technique, mimicking the human body, is superior to an unchanging daily procession of shifting programmed basal rates. This idea is challenging to many. It would have challenged me a few years ago and I would have clung dearly to my biases. But that has changed.

The two images in this post reveal two consecutive overnight BG trendlines. The first one appears to be quite challenging and chaotic whereas the other looks peaceful and serene.

Since we make choices based on our own interpretation of the data we collect, imagine how a series of intermingled days like these might prompt someone (or their endo), to alter a basal rate on a pump to influence future tracings. The doc might not appreciate the reasons for the erratic night (in this case, a long acting carb meal) and the patient might not appreciate the fact that foods can last longer than a single insulin injection or bolus (even a dual wave or combo bolus).

Take a step back and imagine making those kinds of decisions with only a few single blood sugar data points from a meter versus a continuous glucose monitor (CGM). You now get an appreciation why so many of us using or prescribing pump therapy were snared by the belief in numerous basal rate settings. Imagine the dog chasing its tail for a good visual metaphor.

My thinking has evolved and with it my control improved significantly. Mid 5% A1C levels for years now. The purpose of basal insulin is to maintain stability in blood sugar trending. This is carefully discussed in the book Sugar Surfing and emphasized at patient workshops of the same name. Occasionally the basal insulin delivery is used to lower the BG level “in advance”. By that, I mean a conscious action (or it should be) to gradually reduce or raise and out of range blood sugar reading/trend. The two examples are the "sleep bolus" and the “engine brake”, which are both discussed in the book.

Outcomes are what we want. I prefer to ask the pumper the following question: if your BG trendline maintains stability in the absence of any known influences which would deviate it significantly up or down (30 mg/dL or ~ 2 mmol/L) then I feel your basal settings (however many you use), probably work for you. But I'm not just talking about every now and then, I mean consistently keep you steady.

In these two images, the same basal insulin dose was in use. These overnight readings occurred on consecutive nights. It's evident that the busier night had less to do with basal needs but rather the additional challenge of a complex carb meal earlier in the evening, requiring application of Sugar Surfing methods to rein things in. The next night was not influenced that way since the evening meal was a bit lower in carbs and complexity, allowing a single meal time dose to manage the meal's blood sugar effect, compared to the evening before.

Insulin dosing often ignores the impact of food, beyond a gross estimate of carbohydrate count. And many don't even bother to count carbs, preferring fixed doses. It often does get the job done, but there can be some compromise in the quality of the glycemic response after the meal and higher A1C levels as a result. Remember, the first day required an aggressive Surfing response to contain. The second didn’t. Had that not happened, my BG would have been much higher, much longer.

Some people intentionally use basal insulin as a lever and not a level. My use focuses on leveling. For if my preprogrammed basal rate lowers my bedtime high BG consistently, what happens when my bedtime BG is in range or even a touch low? In that case I'm obligated to “feed my insulin” to prevent a low since my basal insulin is too "heavy handed". As an aside I don't eat a bedtime snack as part of my control unless I a) want to have a snack "just because" or b) I'm making a strategic choice for that night, such as trying to offset post-exercise hypoglycemia from a highly active day before.

Every morning I awaken I "look back" at my overnight trend line. It's reassuring to see the steadier line, but when I don't I can often determine that overnight BG shifts and drifts were due to delayed food or exercise effects.

In closing, this post may not loosen the grip many people have on their numerous basal rate settings. But think about this: all these images represent the use of a single nightly dose of INJECTED basal insulin (degludec, brand name Tresiba) and not an insulin pump.

I’m just a recovering multiple basal rate user/prescriber who just wants to share another point of view. Share this parallax view freely with others.

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