Insulin pumps and artificial pancreas

As expert patients go, there are few as expert as type 1 diabetics when it come to the latest technology. Patients with diabetes who turn up unwell in the ED with high blood sugars and an insulin pump can get diabetes nurse input before a transfer to ITU. However, ED docs and GPS can use the tech to help them out with some basic knowledge of how it works.

Insulin pumps

No access? Insulin pumps deliver insulin via a sub cut catheter which is changed every 48-72h. This catheter can be used to continue delivering insulin if:

– a blocked catheter is not the cause of the presenting compliant (DKA in it’s extreme)

  • Check for signs of infection around the catheter site
  • Ask when it was last changed – if high BMs have started after a catheter change this may be the cause although most DM patients know themselves to put insert a new one in if high BMs after a change.
  • Does the patient think it might be blocked?

no air bubbles are present in the tubing. Bubbles once identified can be purged and again the best person to ask is the patient themselves.

– the pump insulin is effective

  • Extreme heat and cold can affect the potency of the insulin itself but also the patient requirements themselves. Especially important to bear in mind with unexpected heat waves.
  • The cold chain needs to be maintained from buying to starting to use the insulin. Although once starting to use the insulin, it can be kept in a pump or bag if in an insulin pen, if there has been a break in the cold chain at the time of getting it from the pharmacy to the home fridge it may be a reason for it not being effective. It might be the case that if the patient has various boxes stocked at home they might not even remember this break in the chain.

If the diabetes team have reviewed the catheter and pump, you can ask about the possibilities of delivering ongoing insulin through the pump especially if the main presenting complaint is not specifically related to diabetes. All pumps work delivering a continuous infusion of fast acting insulin with boluses also of fast acting insulin. This is also the reason why insulin pump users are at a higher risk of DKA. They have no long acting insulin in their body should there be a problem with the pump delivery of  said short acting insulin.

DIY pancreas systems involve using the hardware of existing pumps and open source software with differing goals according to the software used. Generally the idea is to automate insulin delivery as much as possible, delivering more if the tendency is for blood glucose levels to increase and to stop basal delivery if levels are decreasing. Some commercial pumps also do this. The important point to remember are that if levels are falling quicker than expected, the pump may not stop in time so low blood sugar levels that need treating may still occur. Meal boluses that have been delivered can also not be taken back should the meal not be eaten or a greater quantity of insulin be delivered than needed according to the carbs eaten. Most of the pumps show active insulin i.e. recent boluses of fast acting insulin which are still active in the body.

CGM / Glucose level sensors

Many patients now have CGM or continuous glucose monitoring in one form or another. Results are sent to receptors which can be phones, smartwatches, insulin pumps and sensor specific receptors. These can avoid constant finger pricks and have the additional advantage of giving trends of blood glucose showing rapid falls or increases, and stability.

All results should be initially checked with finger pricks to ensure they are working properly and significant treatment decisions need finger pricks.

Unexpected results or feelings of hypo or hyper that do not correlate with the sensor reading need to be checked with a finger prick.

Furthermore, as there is a 5-10 minute time lag with the results of finger pricks due to being placed in the interstitial fluid, hypo or low blood sugar levels need finger prick checks.

They usually store 12-24h information within the receptor and weeks or months online which can be invaluable when it comes to finding out when alterations started.

trends

  • Freestyle libre is a 35mm disc which if interrogated by a receiver can tell you the current glucose levels. It will only give you that information if it is interrogated. It may also not update properly especially if consistently at higher levels, so results should always be checked initially and periodically with a finger prick. It cannot be calibrated with a finger prick blood sample.

Freestyle libre

  • Dexcom is a true CGM in the sense that even if you do not interrogate it, it will continue sending the blood glucose levels every 5-10 minutes to the receptor which can be a phone, pump or dexcom receptor. The newer dexcoms don’t need to be calibrated with finger prick but the older ones will need a finger prick 2-3 times a day. Calibrating at times of rapid change will lead to inaccuracies and over calibrating too will affect the sensor algorithm. Having said that they are usually accurate although sensors can fail and inaccuracies can be the first signs of this.

dexcom

  • Enlite sensors are linked to the Medtronic pumps and send the information directly to the pump every 5-10 minutes, or if using open source apps such as nightscout to a phone or smartwatch. Again these need to be calibrated a couple of times a day and the same points as to not over calibrating and checking against finger pricks is valid.

 

enlite sensornightscout

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