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You might have heard the words “basal” and “bolus” being used within the cortisol pumping community and are not quite sure what they mean. Below we will explain these terms. You can also check out our glossary for more definitions of cortisol pump terms.
Basal Rates: Your daily cortisol delivery rates
Basal is the cortisol that is being delivered by the pump 24/7. Your basal is always going as long as your pump is connected and the delivery hasn’t been suspended or blocked. Basal is delivered according to the pump’s basal program. The basal program consists of delivery rates grouped into time blocks. It’s a continuous schedule of cortisol.
Sick Dose Basal Rates
The cortisol pump supports multiple basal programs. It is typically a good idea to have a normal basal program, plus multiple “sick” or stress dosing basal programs. Pumpers may encounter other situations that also require their own unique basal program.
“Temp Basal” Rates
There is an option to run a “temp basal”. This is a temporary increase or decrease you make to a specific basal program. Typically the user selects a percentage in which to increase or decrease the program, and selects the amount of time the temp basal should run. Though a temp basal can also be defined as units per hour.
Most pumps will support temporary basal changes anywhere from 30 minutes to 24 hours. Omnipod supports a maximum of 12 hours on a temporary basal change. When a temp basal ends, the pump will revert back to the regularly programmed rates. If the pumper needs rates changed for longer that 24 hours, they will need to reset the temp basal, or consider programming a new basal program with those rate changes so that it will not expire.
Bolus: Cortisol that is delivered in ADDITION to your basal dose
In contrast to basal delivery, a bolus is only activated when the pumper selects the bolus option. It is a one time dose of hydrocortisone. The pumper selects the amount and it is delivered immediately all at once. In most cases. It takes about 30 minutes for the bolus to take effect (Cardini et al 2018).
Pumpers can also choose to extend the bolus. On Omnipod and Tandem this is called an “extended bolus.” On Medtronic pumps, they call this a “square wave bolus” and must be first activated in settings. Medtronic also offers the option for a “dual wave bolus” which is a combination of a normal (immediate) bolus and a “square wave bolus.”
An extended bolus allows the bolus to be spread out over a period of time vs. giving all of the bolus immediately. With an extended bolus, the pumper will select the amount to deliver immediately then the amount to be slowly delivered over a time period the user chooses. This can be anywhere from 30 minutes to several hours. Please see your pump’s instruction manual for more details.
One time brief stressors can usually be handled by a bolus. A stressor expected to last several hours may require an extended bolus. A stressor expected to last many hours or even days, may be best handled by a temp increase. Please note that a basal increase takes hours to build blood cortisol levels and a bolus is usually needed before starting a basal increase. (Hindmarsh, Geertsma 2017 p. 357)
Be mindful of total bolus amount.
Boluses more than 5-10u may not absorb properly and could cause the infusion site to leak or otherwise fail (Hindmarsh, Geertsma 2017 p. 357). For this reason, it might a good idea for the pumper to have access to subcutaneous needles (like those used with diabetes) in order to deliver larger boluses when necessary without causing damage to the infusion site. The more volume infused through an infusion site, the more likelihood of a site failure.
This tip is also handy in cases when the site has already failed unbeknownst to the pumper. Sometimes the only clue that a site has failed is extreme fatigue and confusion. In these situations an immediate bolus with a subcutaneous syringe may make the pumper alert enough to change out their infusion set and fix the problem. Alternatively, if the pumper can tolerate oral hydrocortisone, it may also be used as a sort of a backup “bolus” for this same situation.
Find out more:
Cardini, F., Torlone, E., Bini, V., & Falorni, A. (2018). Continuous subcutaneous hydrocortisone infusion in a woman with secondary adrenal insufficiency. Endocrine, 63(2), 398–400. doi: 10.1007/s12020-018-1780-4
Hindmarsh, P. C., & Geertsma, K. (2017). Congenital adrenal hyperplasia: a comprehensive guide. London: Elsevier/Academic Press.