F- CLINICAL ASPECTS OF SPINAL CORD INJURIES
281
This chapter is concerned with the disturbances of blood flow and temperature
regulation in paraplegics and tetraplegics due to environmental influences.
The maintenance of body temperature (homeothermia) depends on the nervous
integration and co-ordinated reflex function of three systems:
(a) Surface receptor system consisting of cold and warm receptors in skin and certain
mucous membranes. There are two main groups of temperature receptors associated
with the sensation of cold and heat respectively, those which react with a maximum
discharge at temperatures around 30°C and those with a maximum discharge around
4O°C. 'Cold spots' have been found associated with Krause's end bulbs which are
distributed in the skin (Weddell, 1941), while the corpuscles of Ruffini are associated
with spots sensitive to warmth. Hensel & Zotterman (1951) found that there are not only
separate types of receptors for warmth and cold but that the afferent fibres of the warmth
receptors are of larger caliper than those of cold receptors. Both have a steady discharge
rate at temperatures between 20° and 40°C. However, there is still some discrepancy of
opinion as to whether there are, in fact, separate receptors for warmth and cold or
whether the free endings which are concerned with pain sensation are also concerned
with temperature (Weddell
et
a/., 1955; Oppenheimer
el
a/., 1958).
(b) Afferent transmitter system which conveys impulses from the surface receptors
to the thermoreceptive and integrative structures in the anterior and posterior part of the
hypothalamus via peripheral nerves, sympathetic and spinal cord. It was found by Ranson
and his co-workers (1937, 1939) in long-term experiments on cats and monkeys that
small lesions in the anterior hypothalamus diminish or abolish the response to body
warming (heat loss mechanism), while lesions of the posterior hypothalamus also abolish
the response to body warming (heat production mechanism). These experimental find
ings in animals have been confirmed by clinical observations in man that anterior hypo-
thalamic lesions result in hypothermia. Widespread hypothalamic destruction tends to
result in poikilothermia (Erickson, 1938; Ranson 1940; Burgi, 1953; Haymaker &
Anderson, 1955).
(c) Efferent transmitter system which mediates impulses from the cerebral stations to
all peripheral organs subserving regulation of body temperature through descending
pathways which traverse the postero-lateral hypothalamus, tegmentum of the mid-brain
and pons, reticular formation of the oblongata, lateral columns of the spinal cord to the
anterior roots and sympathetic nerves.
It has been established from studies of earlier workers that animal and man with
transection of the cord at higher level at air temperature of 26-6°C are essentially poikilo-
therm (Pfliiger, 1878; Pembrey, 1897; Gardiner & Pembrey, 1912; Freund & Strassmann,
1912; Holmes, 1915; Sherrington, 1924; Foerster, 1936) but if they are kept at 20-2°C
they may regain some degree of temperature control against cold (Thauer, 1931; Clark,
1940).
The inability of tetraplegic patients to control their body temperature is particularly
apparent in the immediate stages following cervical cord transection, where these patients
behave as poikilotherms, and the mechanisms of heat production and heat loss are out of
control. In hot climates, environmental hyperthermia may have serious metabolic
effects, and, therefore, the nursing of these patients in an air-conditioned ward has been
