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Department
of Podiatry - Vascular Assessment
Five
minute reactive hyperaemic test
The
5 minute reactive hyperaemia test is easy to perform and when performed
correctly can provide valuable information through which the clinician
can more accurately ascertain the patency of the lower limb vascular tree.
METHOD
1. Have the patient lay supine, knees slightly flexed with the feet at
the level of the heart. A pressure cuff is placed around the patients
ankle and the ankle blood pressure determined.
2. The limb under investigation is then raised to 30 degrees and the patient
asked to dorsiflex-plantarflex several times in order expel venous blood
from the foot. The pressure cuff is then elevated to 100mmHg above the
ankle blood pressure – the blood flow to the foot should cease.
3. The foot is lowered to heart level, after several minutes the foot
will appear blanched and pale.
4. After 5 minutes the pressure is released quickly and the time it takes
for maximum blood perfusion to the foot is noted.
The
underlying pathophysiology of this test is relatively easy to understand.
When blood flow into the foot is ceased, vasodilatory metabolites accumulate
and cause relaxation of smooth muscle in the arterioles, venules and the
pre-capilllary sphincters. Resistence in these vessels then decreases.
Because blood flow is proportional to pressue/resistence, blood flow to
the foot should increase proportionately. When there is significant organic
occlusion in the foot or proximal to it, even though the resistence in
the foot is decreased, the volume of blood that can flow past the obstruction
per unit time is limited. In lay terms, it takes longer for the blood
to reach the foot when compared with normal rates. With this in mind it
is possible for the clinician to make a qualitive evaluation of the foot
noting uniformity and level of erythema as well as time of colour return
(Hoffman, 1998).
NORMAL EVALUATION
In the normal healthy individual, color return to the foot is uniform
and instantaneous, maximum erythema occurs at approximately 1 minute,
and the foot is noticeably eryrthematous (Hoffman, 1998).
Those individuals who suffer from vasospastic phenomena with no organic
occlusion, color return is uniform but slightly delayed, a time of 5-8
seconds being reprasentative. The time for maximum erythema is approximately
2 minutes with the hallmark of vasospastic
disease being that the foot and toes become markedly erythematous
(Hoffman, 1998).
In patients with severe organic occlusion the colour return is not uniform
and may take longer than 10-12 seconds. Maximum erythema will take longer
than 2 minutes and the degree of erythema will be less – in severe
cases of occlusion erythema may never be noted (Hoffman, 1998).
When used in conjunction with other methods of non-invasive arterial evaluation,
the 5 minute reactive hyperemia test can be valuable in differentiating
between functional vasospastic phenomena and organic disease. It can be
useful in the evaluation of a patient who in anxious, cold, or in pain
as the test can override sympathetic tone. It must however be taken into
consideration the test is extremely reliant upon the skill and faculty
of the examiner in determining what he or she is seeing in the foot. Medial
wall calcification can also impair on the accuracy of the examination.
Aside from all of the above, the test can be extremely painful in even
the healthiest individual and as such the clinician must carefully question
whether the end justifies the means.
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