DM and HCP

Early Detection of Heat and Cold Perception in Diabetic Neuropathy Issues and Reasons Dhananjay Kelkar Dhansai Laboratory, Mumbai

Anatomy of Heat, Cold and Pain Perception Small Fibers sub-serve warm cold and

pain sensation – The C fibers C Fibers – Unmyelinated, without

specialized Nerve endings, lying naked in tissues

Distinct from A delta – deep aches and pain

Symptoms 1

Diabetic foot ulcers has great impact on morbidity and mortality of life

First symptoms to appear – pain, hyperesthesia, hyperalgesia, allodynia - that is contact pain

Abnormalities of C fibers supposedly responsible for early occurrence of symptoms

Symptoms 2

Other somatic sensations of pressure, touch, vibration, proprioception are likely as not, not affected at this stage

Makes more sense to detect HC thresholds Early pain and heat hyperalgesia and later

hypoalgesia>Further damage to C fibers Also impairs the warm thermal perceptions (Aron Vinik – Exp Clin Endocrinol Diabetes- 109 (2001) (Suppl 2)

Time of Damage

Other authors have also considered these to be the first fibers to be affected in diabetic neuropathy

(Jamal et al, 1987, Dyck, 1988, Hanson et al, 1992, as quoted by Vinik vide above)

Various symptoms occur when there is on going damage to the nerves initially

Time and Sequence of Damage

Pain of A delta – thinly myelinated is deep seated and gnawing,

Pain of C fibers is described in most vivid terms like burning, bursting, walking on hot pebbles and sand etc

Symptoms occur when structural damage has occurred - not without it

Some More Concerns

Diabetes affects rhythmic vasomotion of small arterioles due to sympathetic damage early in disease,

Loss of warm thermal threshold also occurs early with C fiber damage and correlates significantly to reduced vasomotion

(Vinik – ibid) Exact cause effect or association between

vasomotion and C fiber damage as a time relationship is not established (ibid)

Pathological Evidence

Skin biopsies in persons with Diabetes show – uniform depletion of substance P, CGRP and the cytoplasmic proteins PGP 9.5 for small fiber specificity

(Levy et al, 1992,Wallargren et al, 1995, Lauria et al, 1998,and others)

Glabrous skin of the foot is far more affected by Diabetes than that of hand

Can we do something? Detect early? Of what use? Cost effective? Other benefits? Can we stop progression? Can we reverse abnormalities? Is detection easy?

Can we do something? - 2

Can we stop progression? Can we reverse abnormalities? Enough medical evidence to say

yes to these questions – if the detection is early enough

Malady is – failure of early detection

Can we do something?- 3 Detect early? Yes. Sensitive and simple instrument for

detection, detects heat, cold, heat pain and cold pain thresholds,

Used by many – Further simplified on feedback after field study

Reliable and reproducible thresholds Needs grasp of the working of the instrument

Can we do something? - 4 Cost effective? Needs time, about 15 to 20 minutes of

technician, Used carefully – no maintenance cost, after sales service, no consumables required etc;

Can we do something? - 5 Other benefits? Indicates simultaneous

possibility of Autonomic dysfunction

Acts as motivator for better glucose control

Tissue Damage Heat pain threshold range is 42

to 45 0C Erythema takes place after an

hour at 45 0C Needs 10 second to a minute at

50 0C And just One second at 55 0C

A Little Physiology - 1 C fibers carry sensations slower, have a

period of latency of about 500 milliseconds before the impulse gets initiated

Consequently there is a further delay in reaching the sensation to the cortical areas as the velocities are slow, therefore

There is a further delay for the registration of the sensation and response to it

A Little Physiology - 2 These factors dictate the working of he

instrument These factors determine the rise of

temperature in degrees as well as the time taken to change the level of temperature

Applies also to the rate of fall of temperature in time

A Little Physiology - 3

A rate of one degree per second is generally recommended

For heat and cold thresholds the rate of rise or fall of temperature seems best at 1 degree Celsius over 4 seconds

This makes testing a little longer but gives precise thresholds, reduces the need for many readings, averaging etc

Needed

Early detection Early detection of the early

fibers that are affected HCP is an answer

Sensitometer-HCP Made in India

HCP Probe

A Little Physiology - 4

Concept of heat pain and cold pain should be understood; these thresholds are higher and lower than heat and cold respectively

Cool pain is sensation of coolness with an additional component of un-comfort

Heat pain is warmth plus pricking sensation It is the slight un-comfort and not, not the

ability to bear

A Little Physiology - 5 The rate of rise or fall of temperature to

detect Heat pain & Cool Pain also seems best at 1 degree Celsius over 4 seconds

Two additional thresholds make testing a little longer but gives precise thresholds,

Only cool and heat pain thresholds are enough for clinical practice

Operation of the instrument 1

Operation of the instrument 2

Normal range 32 to 34 oC is neutral zone Just bellow 32 oC & up to 30 oC is the Cool

threshold range -age dependant 27 to 25 oC Cool pain 36 to 38 oC warm And 42 to 45 oC Heat pain zone Above ranges are true for clinical practice in

an ambiant temperature of 27 to 37 oC

Other featchers It can be operated through PC Report can be generated through PC Data can be stored and retrieved for

future use Data can be picked by hospital/clinic

management system as well

Thank you for a patient hearing