How to place a FreeStyle Libre in veterinary patients

Diabetes mellitus (DM) is a common endocrinopathy in canine and feline medicine, and its treatment requires commitment from both the client and veterinary team (Behrend, et al, 2018). In human medicine, the disease is characterised by primary pancreatic beta cell deficiency and insufficient insulin production (typically termed type I), or initial insulin resistance which can result in beta cell damage and eventually beta cell loss (type II). Canine patients often present with a ‘type I like’ diabetes and feline patients most commonly present with a ‘type II like’ disease (Fults, 2016; Cornell University, 2017). Clinical signs include polyuria, polydipsia and weight loss. If treatment is delayed or unsuccessful, patients may develop diabetic ketoacidosis (DKA). At this stage, the patient is likely to present dehydrated (severe dehydration will result in hypovolaemic shock), with a metabolic acidosis. DKA can be confirmed based on presenting clinical signs, such as those mentioned above, in addition to the presence of excessive urine or serum ketones and a metabolic acidosis (Scudder et al, 2016). Patients in DKA can often present in critical conditions requiring intensive nursing and medical care (Hamlin, 2010). This highlights the importance of recognising those clinical signs related to diabetes to allow prompt veterinary treatment for improved patient outcome.

The registered veterinary nurse's role in diabetic patients

The registered veterinary nurse (RVN) has a large role to play in helping manage and monitor diabetic patients. A sound understanding of the disease itself, common clinical signs and the treatment process is essential to support patients, clients and the veterinary team. The RVN is likely to be involved with hospitalised patient care, client support and continued patient monitoring after discharge (Box 1).

Box 1.Advice to owners

• Monitor patient's glucose regularly throughout each day at similar time points (every 4 hours but at least every 8 hours, before insulin and feeding)
• Ensure understanding of clinical signs related to poor glycaemic control including signs associated with hypo- and hyperglycaemic states (Table 1)
• Avoid patient swimming/bathing while wearing the FreeStyle Libre
• If sensor becomes detached contact veterinary surgery for replacement
• Ensure reader is charged regularly
• If reading ‘LO’ or ‘HI’ then check blood glucose with an ear prick blood sample using a glucometer. If this confirms a clinically relevant hypoglycaemia (blood glucose <3.5 mmol/litre), contact your veterinary surgeon and offer the pet an oral rapidly acting carbohydrate (i.e. Glucogel® or honey), and also offer food while monitoring for signs of hypoglycaemia (see Table 1 for clinical signs)
• Ensure the glucometer being used at home is set for the correct species prior to use
• Do not get too concerned if the reader reports ‘HI’ and your pet is clinically well. The overall pattern of results will be interpreted by your veterinary team.
• FreeStyle Libres will measure interstitial glucose readings for up to 2 weeks — at which point it should be changed or removed by your veterinary surgeon or veterinary nurse
• Sensor can be monitored using a mobile phone application however each sensor can only be synced to one mobile phone and one wireless monitoring device
• Record insulin dose, amount and type of food eaten and any changes to the daily routine while the sensor is in place

Hospitalised treatment

During hospitalisation patients will require close monitoring of vital parameters, blood glucose measurements, in-house urinalysis and food and water intake (Donovan, 2010). This monitoring will predominantly be performed by the RVN nursing the patient in the ward area, and reporting abnormalities and changes to the veterinary surgeon. It is important to identify any other underlying conditions that may have contributed to the development of the diabetes mellitus or make the management of the diabetes mellitus more complex; therefore, further diagnostic investigations including blood and urine tests and diagnostic imaging (e.g. abdominal ultrasound) may be required (Donovan, 2010).

Outpatient treatment

A newly diagnosed diabetic pet can sometimes first appear overwhelming to owners as there is a large amount of information to retain regarding their pet's new condition. Often both the clinician and RVN will be involved with the patient's discharge consultation to ensure the owner understands fully what is required from them going forward. Good client communication is vital at this stage and should be maintained throughout treatment and patient monitoring (Scudder et al, 2016). Predominantly the RVN will demonstrate to the owner how to give the subcutaneous injections (first with sterile water) to ensure they are happy with this process before leaving the hospital. Following this, a further discussion on which clinical signs to monitor at home will be key to help assess the response to treatment, and to determine if the level of insulin prescribed is appropriate. Owners can be advised to monitor clinical signs such as polyuria/polydipsia by measuring water intake and urine output where possible. Furthermore, weight loss in addition to polyphagia is a common presenting clinical sign of diabetes mellitus that should be monitored closely. Glucosuria and ketonuria can also be monitored at home using dipsticks (Multistix SG, Siemens Healthcare Limited); when demonstrated to owners this is a good marker of patient response to treatment, and ketonuria should prompt veterinary attention immediately (Scudder et al, 2016).

Nurse clinics

The RVN is crucial in client education, patient re-examinations and diabetic monitoring, therefore demonstrating the large role they play in veterinary patients with diabetes mellitus.

Nurse clinics can be set up in the veterinary practice where the RVN will see the patients for routine testing to include: blood glucose, Free-Style Libre placements, urinalysis and weight checks (Donovan, 2010) (Box 2). A brief recent history should be taken and any concerns can subsequently be raised to the clinician responsible for the case (Schermerhorn, 2019). It is also an ideal opportunity to check in with the owners themselves and understand how they are coping with their pet's new condition. Diabetes mellitus patients require a large commitment from the owner often including a change of routine and lifestyle in order to care for their diabetic pet. This requirement will be life long and therefore as veterinary professionals and the advocates for veterinary patients, the client must feel supported and educated enough in order to manage their pet's new health condition appropriately.

Box 2.Top tips for placing the FreeStyle Libre

• Have all equipment ready, including the monitoring device that will be used
• Have the patient well restrained for placement to avoid having to repeat it
• Ensure area is well clipped and cleaned prior to placement
• Ideal location for placement is the back of the neck between the shoulder blades
• Check with client prior to placement if the patient wears a harness so that placement will not interfere with this and could be placed while wearing, for example
• Confirm the device is well adhered to skin so it does not dislodge after discharge
• Allow time for 60 minutes to set up and calibrate the device using peripheral blood glucose
• If placing subsequent sensors, the location should be varied to reduce the risk of erythema around the insertion site

What is a FreeStyle Libre?

A FreeStyle Libre (Abbott Diabetes Care, Abbott Laboratories Limited, Berkshire, UK) is a flash glucose monitoring system that records interstitial glucose (IG) readings every minute for up to 14 days. The lightweight (5 g) small circular sensor (35 mm) contains a filament that remains in situ in the subcutaneous space for repeated IG measurements. The sensor will record glucose readings within a range between 2.2 to 27.8 mmol/litre, and readings outside of these ranges will be reported as ‘LO’ or ‘HI’ when below or above this range, respectively. A wireless electronic reader or mobile phone via an app is then paired with this sensor and provides the values of the patient's IG at different time points (Gunter, 2018). Recorded data from the wireless electronic reader can be viewed directly on the reader and a comprehensive report can be created after downloading the data via a USB cable when inserted into any computer. The sensor should be read by the recording device at least every 8 hours to ensure all the data from the sensor are transferred to the reader. There is a gradient between the blood and IG that can vary between 20 to110% at its highest when big fluctuations in blood glucose take place. A delay is reported (in minutes) before both compartments are equal; as a result, the FreeStyle Libre may not always report rapid changes in a patient's blood glucose. This is of particular concern when the patient is close to a hypoglycaemic state, as this can have detrimental influences on the veterinary patient (Schermerhorn, 2019). The Bluetooth device cannot be confirmed 100% accurate as a result of the sensor providing a reading that has been recorded in the last 15 minutes. As a result of this, and the lag between IG and blood glucose readings, any suspected hypoglycaemic events should be checked. This should be done using a hand-held glucometer to measure the patient's blood glucose (Table 1). The Free Style Libre kit can be purchased online via the Free Style Libre Abbot website, and it is agreed that whenever there is a shortage (as demonstrated earlier this year (2020)) supply should be reserved for human medicine.

Current literature

In 2017, the United States Food and Drug Administration (FDA) approved the glucose monitoring device, Free Style Libre, for personal use in human diabetic patients, reducing the need for repeated phlebotomies, while still allowing patients to self-monitor their diabetes accurately (Blum, 2018). The device has not been adapted for veterinary patients currently, but it is hoped that with further evidence-based research this will change in the future (Hammond-Lenzer et al, 2019).

To date there are two published studies investigating the accuracy of FreeStyle Libres in veterinary patients. Corradini et al (2016) investigated the accuracy of the device in ten diabetic dogs documenting a good correlation between IG and peripheral blood glucose concentrations. This study also reported that application of the monitor was painless, easy to perform, and well tolerated by all dogs. At low, normal and high blood glucose concentrations the Free-Style Libre was found to be 93, 99 and 99% accurate, respectively. The authors also concluded that it was a beneficial monitoring device, documenting a relatively high level of accuracy in canine diabetic patients. Malerba et al (2020) investigated the accuracy in dogs with DKA. This study found a good agreement between IG and peripheral blood glucose measurements before and after the resolution of DKA. It also concluded that changes in metabolic variables, body condition score and duration that the device had been worn for did not affect accuracy. With only two studies published investigating the accuracy of the FreeStyle Libre in dogs, more research is required for a larger evidence-base. Furthermore, clinical research is required in feline diabetic patients.

Step-by-step guide on how to place the FreeStyle Libre

Contents of the FreeStyle Libre pack:

• Sensor
• Applicator
• Alcohol wipe (X2)
• Electronic reader
• USB cable

You will need:

• Clippers
• Skin glue
• Artery forceps

Step 1

An assistant should restrain the patient in a comfortable manner for both patient and handler.

Step 2

A small area on the dorsal neck region/between the shoulder blades should be clipped

Step 3

The kit contains two alcohol wipes that should be used over the clipped region to prepare the skin (Figure 2). If there is excessive dirt noticed when clipped, the area should be gently scrubbed with a 2% chlorhexidine solution and then wiped with a spirit swab. This should then be left for 60 seconds to air dry.

Step 4

Remove the film from the sensor pack and undo the cap on the sensor applicator.

Step 5

Line up the dark marks on the sensor pack and the sensor applicator (this should fit well) and push together firmly on a hard surface (Figures 3 and 4). Pull the sensor applicator away from sensor pack as this is now loaded and ready for use in the patient.

Step 6

Place the sensor applicator over the site prepared and push firmly (you will hear the sensor fired into place) (Figure 5).

Step 7

Gently remove the sensor applicator from the skin (Figure 6). Forceps can be used to hold the sensor in place temporarily to prevent inadvertent removal from the patient.

Step 8

A small amount of skin glue is placed underneath the paper on the circumference of the sensor to ensure it stays in place (Figure 7).

Step 9

The reader can now be placed over the sensor and there will be a prompt for a new patient set up. The information can be entered manually as instructed. The sensor will take 60 minutes to calibrate so should be read again 60 minutes after placement (Figure 8 and 9). This reading should then also be checked with a peripheral blood glucose to ensure similar readings are observed for accuracy and confirmation of placement.

When should a FreeStyle Libre be placed

The FreeStyle Libre can be placed in diabetic dogs and cats to monitor IG within the hospital and home environment. The sensor can remain in situ for up to 2 weeks before being removed and the data are then downloaded from the reader device. Predominantly the sensors are used at the start of a diabetic diagnosis in order to monitor glucose curves at home to determine if the insulin dose is appropriate for the patient. Patients that present critically ill as a result of their condition should be stabilised first before placement with closer monitoring of their peripheral blood glucose initially. Table 2 lists the advantages and disadvantages of the monitoring device.

Conclusion

Diabetes mellitus is a common presenting endocrinopathy in canine and feline patients to the veterinary practice (including first opinion and referral hospitals). These patients require a large amount of nursing care while hospitalised and following discharge to include client communication, patient monitoring and follow-up assessment. It is paramount the RVN understands this condition in veterinary patients and is aware of presenting clinical signs, patient monitoring and is able to educate the client how best to care for their diabetic pet in the home environment. This article has discussed a relatively new method of measuring IG in veterinary patients in the hospital or home and has provided a step-by-step guide for the RVN as a reference. The FreeStyle Libre is a valuable device to monitor diabetic patients guiding treatment and allowing close monitoring, reducing the requirement of repeated blood draws and hospital visits.

KEY POINTS

• Clinical signs of diabetes mellitus in veterinary patients include: polyuria, polydipsia, polyphagia and weight loss.
• Signs of hypoglycaemia include: collapse, weakness and seizure activity and in confirmed hypoglycaemic states oral carbohydrates such as glucogel or honey should be used subsequently seeking veterinary attention immediately.
• The registered veterinary nurse (RVN) plays a large role when nursing the diabetic patient in the veterinary hospital and following discharge with outpatient care.
• A FreeStyle Libre is a flash glucose monitoring system recording interstitial glucose measurements every minute for 14 consecutive days.
• The FreeStyle Libre is commonly used for the newly diagnosed diabetic patient often initially in the hospital to be continued in the home environment until appropriate insulin levels are determined for the patient.