CHAPTER 25
DISTURBANCES OF VASOMOTOR CONTROL
POSTURAL HYPOTENSION
It has been known for a long time that change of posture from the supine to the erect
position or from sitting to standing in non-paralysed subjects is accompanied by changes
in systolic and diastolic blood pressure, which in certain individuals may be considerable,
and this phenomenon has been a subject of clinical and experimental studies (Bradbury
& Eggleston, 1927; Stead & Ebert, 1941; Jeffers
et
<2/., 1941; Bridgen, Howarth &
Sharpey-Schafer, 1950; Verel, 1951; Johnson
et at.,
1966, 1971; Spalding, 1969; and
others).
Hill (1895) studied the circulatory changes occurring as a result of passive tilting in
spinal dogs and demonstrated the importance of the splanchnic system in maintaining
homeostasis in the vertical position. Since 1945, I have carried out systematic studies
on this problem with my colleagues, to analyse the effects of postural changes on the
cardio-vascular system with a view to re-establishing vasomotor control in the spinal
man, and results have been published elsewhere (Guttmann, 1946, 1953; Jonasson,
1947; Guttmann, Munro, Robinson & Walsh, 1963).
The studies were carried out on patients with complete and incomplete lesions at
different levels of the spinal cord. The subject to be studied remained on a tilting table
in the supine position for about 30 min before being tilted into the vertical position.
During this time an E.C.G. record was taken and blood pressure and pulse rate measured.
Moreover, a blood sample was taken to determine plasma catecholamine levels before,
during and after the tilting experiment. My co-workers Munro & Robinson (1960)
have shown that spinal subjects with high cord lesions have a significantly lower level of
adrenaline and noradrenaline in the peripheral plasma than have normal controls.
Therefore it was of interest to examine also the effect of postural changes on plasma
catecholamine levels in relationship to the vascular changes during and after tilting.
Continuous E.C.G. recordings were made, starting from the time when the subject was
tilted vertically and continuing until he was tilted back to the horizontal and had recovered
from the effect of the vertical posture. The time elapsing before the plasma sample,
indicating the response to the vertical tilting, was taken depended upon how long this
position could be maintained without fainting occurring. If fainting did not occur, the
subject was held vertically for about 15 min before blood sampling and then returned
to the horizontal. The final blood sample was taken about 15 min after he had
resumed the horizontal position. The subject was encouraged to describe his sensation
during the procedure, in particular the premonitory signs of failing consciousness.
It was found that, while paraplegics with lesions of the distal cord and cauda equina
did not differ from other non-spinal convalescent patients, those with lesions above T5
showed a profound vascular maladaptation to the postural change from the horizontal
to the vertical tilting, as a result of the interruption of their splanchnic control. This
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