F- CLINICAL ASPECTS OF SPINAL CORD INJURIES
279
In co-operation with Gilliatt and Whitteridge (Gilliatt
et
a/., 1948) we studied further
reflex activities of the isolated cord which may play a part in the vasomotor readjustment
mechanism. It has been established from the results of earlier workers that a single deep
inspiration causes vasoconstriction and a decrease in electrical response of the skin
(Stump
et
a/., 1935). Table 12 and Figs. I22a-c demonstrate our findings on inspiratory
vasoconstriction from which it is clear that, in high complete cord lesions above the
sympathetic outflow to the hands, deep inspiration still elicits vasoconstriction in the
fingers, which can prevent or at least delay fainting due to postural hypotension in these
patients. From these observations, it can be assumed that inspiratory vasoconstriction
is purely a spinal reflex taking place in the thoracic region of the isolated cord. The
afferent fibres concerned in this reflex enter the spinal cord mainly in the upper thoracic
region, but the possibility that the limits of entry are somewhat wider than this cannot
be excluded. In this connection, it may be mentioned that a deep breath may cause
dilatation of the pupils (Somogy 1913). Recently, Silver (1971) has shown that this
inspiratory vasoconstrictor reflex can be elicited in complete cervical lesion even during
the stage of spinal shock at a vital capacity of the lung of 400-900 ml.
As a result of these and other observations, it has been possible to restore the redis
tribution of blood flow from the viscera by this vasoconstrictor reflex and other factors.
The application of an abdominal binder or cuffs around the calves and the prescription
of 20-25 mg of ephedrine before raising the patient from the horizontal to the vertical
position and, in particular, resistance exercises producing the squeezing effect ofmuscular
contraction on the vascular system have proved invaluable in overcoming circulatory
maladaptation to posture in these high cord lesions. They prevent the dangerous pooling
of blood in the paralysed parts of the body and promote the circulatory adjustments
necessary to meet the metabolic requirements not only for restoring the upright position
of the tetraplegic when sitting in a wheelchair and also standing in parallel bars (with the
help of a physiotherapist) but even for athletic performances. These patients are, for
instance, able to participate in archery and table tennis, with the bow or bat fixed to the
hand. The pull of the bow is accomplished by a hook fixed on the other hand, as the
fingers are paralysed (see Chapter on Sport).
Effects of the renin-angiotensin system on blood pressure
It is well known that the enzyme renin releases angiotension I and II which in turn
releases aldesterone from the adrenal cortex and acts as vasoconstrictor on blood vessels
(see also chapter on Renal Deficiency). Recently, Johnson, Park & Frankel (1971) have
been engaged in research on the effect of the renin-angiotensin system on postural
hypotension in cervical lesions. These authors investigated the action of angiotensin
following intravenous infusion in patients with cervical cord transection and found that
the fall of blood pressure was abolished when raising the patient from the horizontal
to 45° head up position. This is an important contribution to the problem of postural
hypotension in cord transection above Tf, where the splanchnic control is crippled, and
further investigations will establish how far the use of angiotensin injection can be
utilized in the prevention and treatment of postural hypotension in these patients.
