Measuring capillary blood ketones

Adult clinical services at LTHT

Summary document

• 
• Appendix A: Ketone Flow Chart

1. Background
2. Indications for measuring capillary blood ketones
3. How to measure capillary blood ketones
4. What to do if capillary blood ketone not immediately available?
5. What to do if patient has a normal glucose (below 11 mmol/L) AND high ketone?
6. What to do if patient has a high glucose (above 11 mmol/L) AND high ketone?
7. Acting on the result of capillary blood ketone measurement in patients with diabetes AND hyperglycaemia
8. Location in the trust of blood ketone meters

• Appendix A: Ketone Flow Chart

1. Background

Ketones (acetoacetate and b-hydroxybutyrate) are metabolic products resulting from increased use of body fat as an energy source.

Blood ketone levels become elevated in the following circumstances:

1. Diabetic ketoacidosis, in which blood glucose is usually elevated  **
2. Fasting can cause mild ketosis
3. Prolonged starvation can cause ketotic hypoglycaemia
4. Patients presenting after alcoholic excess, in the context of normal or low blood glucose
5. Patients on a very low carbohydrate ketogenic diet

** Note diabetic ketoacidosis with normal or only slightly elevated blood glucose has been reported in some patients taking SGLT2 inhibitors (the ‘gliflozins), on insulin pumps (CSII) and can also occur in pregnancy .

The two main ketones are hydroxybutyrate and acetoacetate.
Capillary blood ketone testing measures blood hydroxybutyrate. This usually comes in an exact measureable numerical value in mmol/Litre.
Urine ketone testing measures acetoacetate and only gives a semi-quantitative result measured based on the urine ketone strips ranging from ‘+’ to ‘++++’

Hydroxybutyrate is the predominant ketone present in diabetic ketoacidosis and therefore this will be detected on capillary blood ketone testing. As diabetic ketoacidosis ( DKA) is treated, hydroxybutyrate is converted to acetoacetate. Hence, capillary blood ketones will fall but urine ketones will increase as acetoacetate increases. For this reason, blood ketone testing is a more reliable measure of the resolution of DKA.

EXCEPTIONS:

• See separate guidance for ketone measurement and guidance in pregnancy http://nww.lhp.leedsth.nhs.uk/common/guidelines/detail.aspx?id=1920#13

• See separate guidance for ketone measurement and guidance in surgery (http://nww.lhp.leedsth.nhs.uk/common/guidelines/other_versions/434glycaemia.pdf)

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2. Indications for measuring capillary blood ketones

Measure blood ketones in the following circumstances as stated by the LTH Capillary Blood Glucose Chart (Adults):

1. Type 1 diabetes where patient has one capillary blood glucose above 14mmol/L, OR is clinically unwell.
   
2. If patient does not have type 1 diabetes, but is treated with insulin AND is unwell with two consecutive capillary blood glucose readings above 14mmol/L .
   
3. Patients on SGLT2 inhibitor (‘gliflozin’) who are hospitalised for major surgical procedures or have acute serious medical illnesses
   
4. All patients with new hyperglycaemia > 11mmol/L ( not known to have diabetes)
   
5. All patients with diabetes (of any type) and urine ketones 3+ or 4+ (to further quantify of the risk of DKA).
   
6. Any patient with diabetes (of any type) with blood pH < 7.3 and/or serum bicarbonate < 15 mmol/L.
   
7. Any patient without diabetes and blood pH < 7.3 and/or serum bicarbonate < 15 mmol/L where non-diabetic ketosis is suspected (discuss with Endocrinology).

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3. How to measure capillary blood ketones

The meter in use is Nova Biomedical StatStrip glucose/ketone (GLU/KET) monitoring system.  This is a glucose meter which has the additional function of ketone measurement enabled. These meters are networked and managed by Point of Care.
 
Only use these ketone-measurement-enabled capillary blood glucose meters to analyse blood ketones if you have been trained to do so. The meters will not allow ketone analysis to be performed by a user who has not had this specific training.  Training is provided by the company or by Point of Care to the ward and disseminated through key trainers.

Measure capillary blood ketones using a capillary blood sample as for measuring capillary blood glucose.

In the clinical notes and on the Capillary Blood Glucose Chart for Adults or Adult DKA treatment chart, record capillary blood ketone levels (units mmol/L).

Do NOT send sample to laboratory for ketone measurement.  Blood ketone measurement- enabled meters are available on the wards listed below. (See Item 8)

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4. What to do if capillary blood ketone not immediately available?

Urinary ketone measurements can be used to aid both clinicians and patients in making a decision, mainly to consider a diagnosis diabetes ketoacidosis. Where capillary blood ketones are not immediately available, measure urinary ketones to aid further clinical decision. Patients with urinary ketones 2+ or more with the clinical indications in Section 2 needs to be referred to the ward senior doctor initially for further review whilst waiting capillary ketone testing.
For the purpose of insulin correction guidance in hospital, we recommend against using urinary ketones to guide glucose correction.

Ketone Meter Equipment Funding Application
Each ward in LTHT is able to obtain and apply for a capillary ketone meter using the template business case which can be obtained from point of care team contact as below. The funding and application for capillary ketone meter would have to be agreed within the department / CSU. The completed business case must be supported and signed by a Lead Clinician and a Ward/Departmental Manager prior to consideration by the POCT Committee.
Further details (including business template can be obtained via email:

leedsth-tr.PointofCare@nhs.net

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5. What to do if patient has a normal glucose (below 11 mmol/L) AND high ketone?

Please seek senior and expert medical help.
Do NOT use subcutaneous insulin correction to correct high ketone due to risk of hypoglycaemia.

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6. What to do if patient has a high glucose (above 11 mmol/L) AND high ketone?

See further guidance and ketone flow chart (Appendix)

Important Note:

1. The cut off use in this guidance for ketone measurement indication for patients known with diabetes is capillary blood glucose above 14 mmol/L. We acknowledge the difference where higher cut off glucose value (above 16mmol/L) for ketone measurement indication is used in the current nursing insulin plan and blood glucose monitoring form. This will be updated in the next planned review.

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7. Acting on the result of capillary blood ketone measurement in patients with diabetes AND hyperglycaemia

Guidance for action according to blood ketone (β-hydroxybutyrate) measurement:

*Please contact diabetes team for patients with elevated ketones on continuous subcutaneous insulin infusion (CSII) / ‘insulin pump’

Managing High Blood Glucose When Blood Ketone between 0.6 to 1.5mmol/L

Correction Insulin dose for moderate ketone levels

Note:

1. Additional insulin dose can be added as a ‘stat’ dose to patient’s usual insulin dose if this is already due.
2. Do NOT give a correction dose of rapid acting insulin when
   (i) the patient is due rapid acting or premixed insulin in the next 3 hours
   or
   (ii) when the patient has had rapid acting or premixed insulin in the previous 3 hours.
3. This can be repeated again in 2 hours if ketone still above range AND glucose above 11mmol/L AND usual insulin is not due
4. If ketone rises above 1.5mmol/L, seek medical help and see next guidance on ‘Managing blood glucose when ketone above 1.5mmol/L

Managing High Blood Glucose When Blood Ketone above 1.5mmol/L

Correction Insulin dose for high ketone level

Adapted from Trend UK and DAFNE sick day rule guidance

*Suggested rapid acting insulin:
Novorapid, Humalog, Apidra, Fiasp, Trurapi, Lispro Sanofi (list not exhaustive)

We recommend not using Actrapid as the half-life is longer compared to the newer analogue insulin above. For the purpose of ketone correction in hospital setting, we recommend using Novorapid insulin. However, if patient have their own insulin listed above, this can also be used if available immediately in the ward.

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8.   Location in the trust of blood ketone meters

In addition of the location of blood ketones in the trust (this will expand in the future), Point of Care Team contact detail are provided below for support and information on up-to-date location list in the trust. Details are as below:

Ext Number: 22338
Email: leedsth-tr.pointofcare@nhs.net

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Appendix A: Ketone Flow Chart