Continuous Glucose Monitoring

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Continuous Glucose Monitoring - Diabetes CCRE - University of ...

Continuous Glucose Monitoring

David O’Neal

University of Melbourne Dept. of Medicine

&

Dept of Endocrinology

St. Vincent’s Hospital, Fitzroy.


Plasma Glucose Normally

Maintained in Narrow Range

Insulin Secretion

Plasma Glucose

mg/dL (mmol/L)

200

(11.1)

100

(5.55)

Plasma Glucose

6 AM 10 AM 2 PM 6 PM 10 PM 2 AM

Time of Day

Data from Polonsky KS, et al. N Engl J Med. 1988;318:1231-1239.


Requirements for the Replacement of

Pancreatic Islet Cell Function

• A target glucose range needs to be defined

• Circulating glucose levels need to be

measured

• Based upon glucose levels insulin

requirements need to be determined to

ensure normoglycaemia

• Insulin needs to be provided commensurate

with the body’s changing requirements


Factors Limiting the Replacement of

Pancreatic Islet Cell Function

• Measurement of circulating glucose

levels (Frequency/ Accuracy/

Convenience)

• Deriving insulin requirements from glucose

measurements

• Dynamic and accurate delivery of insulin in

accord with physiological requirements


Requirement for Glucose Monitoring

• Type 2 Diabetes

– On Diet/ Metformin/ DPP IV inh/ GLP-1 Analogues/

TZDs (+)

– On Sulphonylureas ++

– On Insulin +++/ ++++

• Type 1 Diabetes

++++


100

90

80

70

60

50

40

30

20

10

0

Insulin Requirement vs Insulin Dose

Mismatch

Hypoglycaemia

Complications

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5

HbA1c (%)

DCCT Research Group. N Engl J Med 1993;329:977–986

Risk of developing

Risk of developing

hypoglycaemia / complications (%)


Glucose Monitoring

• Home Glucose Monitoring

Glucose Readings in Rooms

• Fructosamine

• HbA1c

Continuous Glucose Monitors


Evolution of Technology

First Commercial

Insulin Pump

Human

Monocomponent Insulin Pens

Insulin

Dual Wave Bolus,

Multiple Daily Basal, Levemir

DCCT

Improved Alarms,

Safety Features

Bolus

Lispro Aspartate Calculator

Glargine

1980 1990

Amperometric

Glucometers

First

Retrospective

Continuous

Glucose

Monitoring

System

2000

Sensor Augmented

Real-Time Pump, Stand

Alone RT-CGM devices


Finger-prick Glucose Measurements:

Limitations

25Y T1D HbA1c 8.4%

Lispro TDS

Glargine Nocte

● Few time points (determined by the patient)

● No information regarding rate of change


Finger-prick Glucose Measurements:

Limitations

● Few time points (determined by the patient)

● No information regarding rate of change


All CGM Systems Measure Glucose

in Interstitial Fluid, Not Blood

Capillary Blood Interstitial Space Cell

[Glucose] [Glucose] [Glucose]

C1 C2 C3

Glucometer

reading

CGM reading

15 min time lag


Continuous Glucose Monitoring

Interstitial fluid (ISF)

surrounds cells

ISF glucose correlates with

blood glucose

Blood Glucose (mg/dl)

500

400

300

200

100

SMBG

Sensor

Meal

0

-40 -20 0 20 40 60 80 100 120 140

Time (minutes) (0 = start of meal)

Illustration adapted from Rebrin K, et al., Amer Phys Soc 1999; E562.

Halvorson MJ et al., Diabetes 2004; 53 (Suppl 2): 3-LB


Correlation of ISF Glucose and Venous Glucose

in ESRD on CAPD

mmol / L

mmol / L

J Marshall et al Kidney International, Vol. 64 (2003), pp. 1480–1486


Limitations of CGM: Technical

• Time lag Difference in glucose values from

blood.

• Require calibration from a (stable) glucose meter

reading, preferably 4 X D -1 .

• Better CGM accuracy with wider range of calibrating

glucose levels.

• Limits of detection - 2.1 & 22.0mmol/L

• Interfering substances

- paracetamol, ascorbate, urate


CGM: Devices

CGM

Retrospective

Real- Time

Stand Alone

Device + Pump


Real Time CGM: Stand Alone Devices

Dexcom STS

Abbott-Freestyle Navigator

Medtronic-Guardian-RT


Insulin Pumps and Real Time-Glucose Sensors

Animas

Dana

Roche Spirit

Medtronic

Paradigm / Veo

Medtronic Guardian

Dexcom STS

Abbott Freestyle Navigator

An insulin pump is a mechanical device

that delivers short acting insulin

subcutaneously continuously in finely

Controlled manner

A continuous glucose monitor

provides information regarding the

patients glucose levels and rate of

change on an near continuous basis


15 Days Battery 6 Days Sensor

Transmitter

> 10cm


Real Time CGM Provides

Recent Glucose levels and Trends

6.5


3 Hour Glucose Screen

Stable Glucose


24 Hour Glucose Screen

6.8

NIGHT


Trend Arrows

– Rising 1 to 2 mmol/L per 20 minutes

– Rising >2mmol/L per 20 minutes

– Falling 1 to 2 mmol/L per 20 minutes

– Falling >2mmol/L per 20 minutes


CGM Data Can Viewed Retrospectively


RT-CGM: Glycaemic Outcomes (ASAPS)

HbA1c (%)

8.0

7.9

7.8

7.7

7.6

7.5

7.4

7.3

7.2

7.1

7.0

6.9

6.8

– A significant difference in HbA 1C emerged between study groups at

the end of the 3 month study period:

intervention group 7.1% (+/- 0.8%)

control group 7.7% (+/- 0.8%)

Baseline

12 Weeks

Adjusted for baseline HbA 1C, the difference between

groups at 3 months was 0.5%; p


RT-CGM: Sensor Use – Relation to HbA 1C (ASAPS)

Study

9

protocol – sensor

*

usage at least 70% of total study

period

8

=70% sensor usage

*

7

6

5

* P=0.04

HbA 1c

pre

HbA 1c

post

Despite no difference at baseline, HbA 1C was 0.5% lower in the ‘compliant’

subgroup at the end of the study period

O’Connell et al Diabetologia 2009


RT-CGM: Glycaemic Outcomes

JDRF Study: Subjects & Protocol

• 165 RT-CGM and 157 Control

• > 75% Rx CSII

• Visits at 1, 4, 8, 13, 19, and 26 weeks (±1 week) + one

telephone contact between each visit, to review glucose

data and adjust diabetes management

• Blinded glucose monitor at baseline, 13 and 26 weeks

• HbA1c at baseline, 13 and 26 weeks

N Engl J Med 359:1464-1476


JDRF: Primary Outcome

165 RT-CGM and 157 Control

HbA1c RT-CGM vs SMBG:

>25Y: −0.53% ( 95% CI −0.71 to −0.35); P


N Engl J Med 359:1464-1476


RTCGM: Sensor Compliance

9.5%

9.6%

Compliance: % Sensor

Usage

(6 days/week = 100%)

Baseline A1C

8.6%

8.4%

24W A1C

% A1C

7.7%

7.7%

8.2%

7.5%

vs


RT-CGM: Impact of Withdrawal

Jenkins AJ et al Diabetes Care 2010


Type I Diabetes: Glucose Monitoring

& Insulin Administration

Exogenous Insulin

Plasma Glucose


RT-CGM: An Algorithm Guiding Patient Responses

Paper-based algorithm (www.diabetesccre.unimelb.edu.au)

informing CSII-using patient responses to RT-CGM data

Reactive Algorithm

Suggested responses to (high, target [4-

10mmol/L] or low) glucose range, trend

arrows and time of day (e.g. pre-meal, bed)

Wallet card

Proactive Algorithm

Upload to Medtronic Care Link

(www.carelink.medtronicdiabetes.com) Wall

chart to facilitate pattern recognition and

suggest changes in CSII programming

≈ 90 minutes teaching


RT-CGM: Impact of Education upon Outcome

p=0.0045

80

p=0.015

p=0.0009

Percent of Subjects at HbA1c < 7%

70

60

50

40

30

20

10

0

p=0.0005

Algorithm No Algorithm Algorithm No Algorithm Algorithm No Algorithm

All Subjects Adult Subjects Adolescent Subjects

n= 57 n= 35 n= 22

Baseline

16 Weeks

Jenkins AJ et al Diabetes Care 2010


Adapted by I Hirsch 2009


O’Neal et al Infusystems Asia 2010


RT-CGM: HbA1c Benefit in T2D

on OHGA and /or Insulin

N=28 N=29

Yoo et al Diabetes Research and Clinical Practice 2009


RT-CGM: The Burden

• Cost (Sensor $78 for 6 days + $1200-2000 for initial outlay)

• Second Line (additional device)

• Outcome depends on patient wearing the sensor > 60% of

time

• Patient requires education to respond to information

• Healthcare workers require upskilling + additional demands

on resources

• Emotional Burden


Real Time Continuous Glucose Monitoring:

Requirements for Success






Realistic expectations

Motivated to wear the sensor >60% of the time

Intellectual and emotional capacity to deal with the

technology and the information

Financial resources enabling them to purchase and

wear the device on an ongoing basis

Experienced and supportive diabetes care team


Summary:

Real Time Continuous Glucose Monitoring

● Reduces HbA1c without increasing hypoglycaemia

(adults)JDRF, NEJM, 2008 / O’Connell et al Diabetologia, 2009

● Reduces incidence of hypoglycaemiaJDRF, Diabetes Care, In Press

● Greatest benefit in those who wore the sensors >60%

of the time Hirsch et al, DT&T, 2008 / JDRF , NEJM 2008

● Greater benefit if patients were educated on how to

deal with the information Jenkins et al, Diabetes Care 2010

● Quality of life


Retrospective / Masked CGM

– Device initiated by hospital staff.

– Device worn 3-6 days.

– Patient does not have access to information

at time.

– At end of study device downloaded and

information provided to Patient / Diabetes

Team.


TM

CGMS - System Components

Monitor

Com-Station

Software

Sensor

Recorder

iPro TM CGM Components


20/9/05-23/9/05


Retrospective / Masked CGM

Advantages:

– More accurate than real time monitors.

– More robust technology.

– More easily interpretable information.

Disadvantages:

– Information not immediately available.

– Wearing the device can alter behaviour.

– Cost.


Retrospective CGM Utility:

Insights Regarding Pathophysiology

Monnier and Owens. Diabetes Care. 2007;30:263-269. N = 130. Type 2 diabetes patients.


Retrospective CGM Utility: Research

Glycaemia in diabetic patients on CAPD

lactate/bicarbonate-buffered 1.36% X 3

lactate/bicarbonate-buffered 3.86% X 1

CGMS Glucose (mmol /L)

lactate-buffered 1.36% X 3

lactate-buffered 3.86% X 1

lactate/bicarbonate-buffered 1.36 X 2

1.1% amino acids X1

icodextrin X1

Time (hours)

J Marshall et al Kidney International, Vol. 64 (2003), pp. 1480–1486


Retrospective CGM Utility:

Observational Guiding Clinical Care

100%

% Time in Range

80%

60%

40%

20%

*

>10 mmol / L

3.8-10 mmol / L


Retrospective CGM Utility:

Impact on Clinical Decisions

Type 1

(n=8*)

Type 2

(n=11)

GDM

(n=36)

Studies (n) 18 14 36

Median Gestation

19

20

32

(W)

(10-25)

(18-29)

Median HbA1c

6.3

5.7

_

(%)

Information not

(5.9-7.2) (5.4- 5.8)

89% 57% 56%

present on FP

K. McLachlan. ANZ J Obstet & Gynecol. 2007;47:186–190.


Record book high/

CGMS satisfactory

Hypoglycaemia noted

post CGMS data

Diet modified post

CGMS data

Insulin increased

post CGMS data

%

Insulin commenced

post CGMS data

Record Book and

CGMS agree

0 5 10 15 20 25 30 35 40 45

K. McLachlan. ANZ J Obstet & Gynecol. 2007;47:186–190 .


CGM Trace in Pregnancy with GDM-Patient 1

Patient Record & CGMS Trace Agree - Insulin


CGM Trace in Pregnancy with GDM-Patient 2

Patient Record & CGMS Trace Disagree – Insulin Commenced


2 Hour PP Fingerpricks Miss Glucose Peak

GDM-

Patient 2


HBGM Fingerpricks Miss Glucose Peak

GDM-Patient 2


Post CGM Maternal Perception of Glycaemia

Clearly

Better

Better

6%

Same

Worse

Clearly

Worse

0%

0%

23%

67%

K. McLachlan. ANZ J Obstet & Gynecol. 2007;47:186–190.


Retrospective CGM Utility:

Benefit in Clinical Care

n= 38

n= 33

H.R. Murphy et al Abstract 13, S12, Diabetolgia,Supp1,2008


CGM Devices: Relative Merits

*Clinical: Reactive Changes in Mx

Retrospective

CGM

X

RT-CGM

*Clinical: Hypo Alarm

X

*Clinical: Prospective Changes in Mx

*Clinical: Glycaemic Variability

Research/ Observational

*Ambulatory Setting


Continuous Glucose Monitoring: Summary

• Complements other glucose monitoring modalities

• Methodology validated

• Real Time CGM- Patients

• Real Time-CGM improves glycaemia

• Patient education important

• Target population important

• There is a burden associated with the technology

• The technology is evolving rapidly but the loop has not yet been

closed

• Retrospective CGM-Health Professional

• Not all patients have equal access to the technology


CGM IS NOT AN INTERVENTION

IT IS HOW THE INFORMATION IS

USED THAT IS OF IMPORTANCE


Insulin Pumps: Special Circumstances

David O’Neal

University of Melbourne Dept. of Medicine

& Dept of Endocrinology

St. Vincent’s Hospital, Fitzroy.


Special Circumstances

• Emergency Dept

• Inpatient

• Peri-operative

• Pregnancy

• Hyperglycaemia

• Hypoglycaemia


Inpatient Stay: General Dos and Don’ts

• In the setting of severe metabolic derangement the pump

does not substitute for an insulin infusion

• Do record pump settings in the admission notes

• Do notify diabetes team: Management and Review

education

• Do not bath (attend Hydrotherapy) with pump on

• Do disconnect for MRI, CT Scans and X-Rays

• If swapping from IV insulin infusion to pump do ensure

overlap preferably in the AM

• If swapping from long acting basal to pump do give half dose

the night before and commence pump in AM


Inpatient Stay: Absolute Contraindications

to Pump Use

• Impaired conscious state

• Critical illness requiring ICU

• Major Psychiatric disturbance

• Diabetic ketoacidosis

• Lack of supplies

• Physical Limitations

• MRI, CT or any radiological procedures must have their

pump temporarily removed

• Any other circumstances deemed unsuitable by the

supervising medical officer

Queensland Health Statewide Diabetes Clinical Network


Inpatient Stay: Patient Requirements

• If patient’s conscious state altered or physically limited:

suspend and disconnect (administer insulin by alternate

means and ensure pump is securely stored)

• If patient awake, metabolically stable and eating, pump is

more appropriate than an insulin infusion

• Patient or Guardian is primarily responsible for implementing

changes to pump settings

• Ensure that patient has sufficient disposables

• Ensure line change performed by patient every 3 days at

least

Queensland Health Statewide Diabetes Clinical Network


Inpatient Stay: Assessing Competency

• Can manage the menu of the device

• Are able to adjust the basal rate

• Are able to adjust the bolus dose

• Can demonstrate how to set a temporary basal rate

• Can describe how they would resite their pump line

• Can demonstrate competency on how they would

manage line obstructions / leaks

• Adequate supplies (infusion sets, batteries,

reservoirs)

• Regular glucose monitoring

Queensland Health Statewide Diabetes Clinical Network


Inpatient Stay: Documentation

• Document in Medical record and on the blood glucose

monitoring that patient is on an insulin pump

• The brand name and model of the pump must be

documented in the record

• Type of insulin must be recorded in the blood glucose

monitoring form

• Basal rates, insulin to carbohydrate ratios, correction

factor, duration of action of insulin and target blood

glucose levels must be documented in the medical

record

• All supplemental changes to insulin dosing

• Date/time of line and cartridge changes

• Assessment of line insertion sites

Queensland Health Statewide Diabetes Clinical Network


Inpatient Stay: Peri-operative

• Perform line change day before

• If fasting consider reduced basal eg 70%

• No bolus necessary unless for correction

• Monitor glucose with increased frequency

• Monitor ketones

• IV dextrose

• Option A / Option B


Option A: Pump Intra-operatively

• Procedure of Short duration

• Inform anaesthetist prior to Sx

• Medical and Anaesthetic staff familiar with pumps

• Patient awake intra-operatively

• Patient not severely unwell or metabolically unstable

• Patient alert and eating shortly after procedure

• Ensure insertion site is away from surgical field and anaesthetist has

access

• Consent patient to intra-operative use of pump

• Identification tag stating that patient is on a pump

• Diathermy

• Monitor glucose hourly


Option B: Intravenous Insulin Infusion Intra-operatively

• Prolonged and complicated procedure

• Medical and Anaesthetic staff unfamiliar with pumps

• Patient unconscious and paralysed

• Patient critically unwell and metabolically unstable

• Prolonged post operative recovery

• Suspend pump and disconnect in anaesthetic room

• Commence formal insulin infusion

• Place pump in secure labelled clear bag

• Monitor glucose hourly

• When patient awake and alert recommence pump


Pregnancy

• < 100 Years ago T1D did not live long enough to become

pregnant


Insulin Requirements in T1D During Pregnancy

Morning Sickness

Increased Insulin Sensitivity


Glycaemic Goals In Pregnancy

Whole Blood

Fasting (mmol/L) 3.3-5.0

Plasma

3.9-5.8

(4.0-5.5)

Premeal (mmol/L) 3.3-5.8 3.9-6.7

Post Meal

(mmol/L)

2.00AM-6.00AM

(mmol/L)

5.6-6.7

6.4-7.8

(


HbA1c Target in Pregnancy


Postprandial vs Preprandial

Blood Glucose Monitoring

De Veciana et al NEJM 1995


Pregnancy: Advantages / Risks of Insulin

Pumps.

Benefits

• More Flexible and accurate insulin delivery

• (?) Better glycaemia

• Reduced Hypoglycaemia Gabbe SG et al. An J Obstet 2000

Risks

• Rapid onset of hyperglycaemia or ketosis following

interruption of insulin delivery


Pregnancy: Pre-Planning

• Pre-planning: Commence pump therapy before

conception if possible (T1D >T2D)

• Dietician Review: Ensure carbohydrate counting is

accurate

• CDNE Review: General Education, Line changes,

Glucose Monitoring, Ketone Monitoring

• Complications review / Medication Review


Pregnancy: Ante-Natal / Labour

• During last 6 months of pregnancy basal and bolus doses may need to

be increased 7-10 Days

• Bolus may increase more than basal (particularly overnight)

• Watch out for (nocturnal) hypoglycaemia

• Consider CGM

• Infusion sites: Dry skin and Increased Irritation. Change line more

frequently. Site change from abdomen to buttocks or more laterally

• Labour:

(i) Frequent blood glucose and ketone monitoring.

(ii) Insulin requirements very low during labour (20% basal)

(iii) Caesarian section may increase basal requirements

(iv) Consider insulin infusion


Pregnancy: Post-Natal

• Pre-pregnancy settings as a guide

• Temporary Basal for breast feeding


Hyperglycaemia: Causes-1

• Excessive exercise without sufficient insulin

• Increased stress

• Concurrent Illness

• Underestimated carbohydrates & bolus

• Omission of bolus

• Incorrect bolus type for fatty food

• Inadequate basal rate

• Pump cartridge empty

• Incorrect technique when priming the pump and

changing the infusion set

Victorian CSII Working Party Guidelines July 2009


Hyperglycaemia: Causes-2

• Too long between infusion set changes

• Infusion set or site failure

• Infected infusion site

• Temporary basal rate decreased too much or run for

too long a period

• Suspended pump

• Failure to acknowledge auto-off alarm

• Failure to reconnect pump

• Pump failure

• Drugs e.g. corticosteroids

Victorian CSII Working Party Guidelines July 2009


Hyperglycaemia: Management

Vic CSII Guidelines 2009

Victorian CSII Working Party Guidelines July 2009


Hyperglycaemia: Management

Victorian CSII Working Party Guidelines July 2009


Pump Failure

Warning Signs

• No insulin delivery and no alarms

• Rising glucose levels and ketosis

• Warning on Screen

Management

• Suspend and disconnect pump

• Administer insulin via SC route using pen or via IV

infusion

• Contact helpline and arrange for replacement pump


Hypoglycaemia: Causes

Victorian CSII Working Party Guidelines July 2009


Hypoglycaemia (Mild-Mod): Management

Victorian CSII Working Party Guidelines July 2009


Hypoglycaemia (Severe): Management.

Victorian CSII Working Party Guidelines July 2009


Hypoglycaemia (LOC): Management

Victorian CSII Working Party Guidelines July 2009

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