| Education Material for Health Care Professionals: Book Version
THE FEET AND DIABETES
Here again, a detailed history often suffices. If a person has intermittent claudication or rest pain (especially the latter), there is sufficiently severe peripheral vascular disease to predispose to vascular ulceration.
If a person has no claudication or rest pain, then one relies on physical examination and, if necessary, investigations to determine the risk.
Looking at the feet to see if there is any mottling and feeling them to see if they are cold give important clue that the circulation may be impaired.
If pulses in the foot can be clearly felt, the risk of foot ulceration due to vascular disease is small. At the same time, one must remember that in patients with severe autonomic neuropathy, as we have discussed above, the peripheral arteries may be well filled, but the tissues may be ischemic as the blood bypasses the capillaries. Well filled and prominent veins on the dorsum of the feet especially when the patient is lying down flat is a clue to this possibility.
In most cases, looking at the feet and palpating the foot pulses are all that is required to assess the risk of vascular ulceration. When the foot pulses are very weak or not palpable, then it is necessary to carry out "non-invasive vascular tests" to assess the risk.
This is most easily done by measuring what is called the Ankle Brachial Index. It is as easy as having blood pressure checked.
The following steps are involved :
Taking blood pressure in the arm. This is called the brachial pressure because the artery being measured is the brachial artery.
Taking blood pressure in the ankle. This is called the ankle pressure because either of the two arteries in the ankle can be measured.
A couple of examples for the calculation of the ankle brachial index.
Lets say someone has a brachial pressure of 120mmHg and an ankle pressure of 132mmHg.
- Ankle brachial index = 132 / 120 = 1.1
Lets say someone has a brachial pressure of 120mmHg and an ankle pressure of 96mmHg
Ankle brachial index = 96 / 120 = 0.8
The following can be used as a guide to interpreting results of ankle brachial index :
||0.9 - 1.2
||Risk of vascular foot ulcer is small
|Definite vascular disease
||0.6 - 0.9
||Risk of vascular ulcer moderate and depends on other risk factors
|Severe vascular disease
||Less than 0.6
||Risk of vascular foot ulcer very high
Sometimes the arteries in the ankles are calcified due to diabetes.
This makes measurement of blood pressure at the ankle unreliable. In this situation, more information is obtained by measuring pressure at the toe. As a guide, a toe brachial index less than 0.5 indicates the presence of peripheral vascular disease
If necessary, the following tests should be considered :
Doppler studies for blood flow.
All these investigations may not be necessary in every patient and the range of investigations should be individualised.