(Study Group 4) INTRODUC TION Some patients with lesions of the spinal cord may have substantial difficulty in thermoregulating under a heat s t r e s s considered mild by able-bodied persons. These patients easily develop heat exhaustion, c h a r a c t e r i z e d by cardiovascular i r r e g u l a r i t i e s , weakness and fatigue, headache, and sometimes syncope. Previous l i t e r a t u r e states that the skin of men or animals with spinal cord injury is g e n e r a lly anhidrotic in a r e a s below the level of the lesion (Leithead and Lind, 1964; Randall, W u r s t e r and Lewin, 1966;Rawson, 1963; Seckendorff and Randall, 1961). If anhidrosis is widespread, as is the case in the c e r v i c a l lesions, the patient may develop hyperthermia.Quantitative studies on spinal man r e v e a l a significant impairment of the t h e r m oregulatory sweat response over a wide area of the body. Guttmann, Silver and Wyndham (1958) observed the behavior of the c o r e t e m p e r a t u r e s of spinal man in the warm air of open wards. Patients with high c e r v i c a l lesions were largely anhidrotic over their body surface and had difficulty in maintaining normal body temperature. Nevertheless, Randall, Wurster and Lewin(1966) concluded that the isolated spinal cord is still capable of mediating a sweat reflex as did Cooper, F e r r e s and Guttmann (1951).We s u r m i s e d that quadriplegies might become hyperthermic when exposed to high ambient t e m p e r a t u r e s or to e x e r c i s e . Therefore, we studied quadriplegic subjects under a controlled heat s t r e s s and measured their thermoregulatory r esponses, thereby further c h a r a c t e r i z i n g quantitatively the quadriplegic disability.
MATERIALS AND METHODS
SUBJECTS:Six men, each having chronic spinal cord injury in the cervical region (CS to C3), participated in these experiments.Descriptions of their disability, age, and medications are given in Table 1. Nine control experiments were conducted on three able-bodied men under conditions identical to those in the quadriplegic experiments. Table 2 gives the characteristics of all the subjects. Each subject was tested every time at approximately the same time of the day.
CONDITIONS:The subjects were submitted to total body heat exposure in an environmental chamber.Base line readings were taken at room temperature, prior to entering the hot chamber.Room conditions were T a 25°C and 50% rh, while those in the hot chamber were T a 38°C and 9% rh. Following base line readings for one hour the subjects were transferred into the environmental chamber for a maximum of 2½ hr. The subject sat inactive throughout the experimental period.
A B S T R A C T The rate of eccrine sweating has been studied by collecting samples in unventilated capsules from human subjects following subdermal or intradermal injections of acetyl-j3-methylcholine and under moderate total body heat exposure. The rate of sweating in a given area of skin could increase by recruitment of fresh glands, enhanced output of the already active glands, or some combination of both.A theoretical analysis shows how recruitment and enhancement can be calculated separately, assuming the existence of a maximal rate of sodium reabsorption by eccrine sweat glands, a sodium concentration of 145 ,oEq/ml in the precursor fluid, the absence of significant water reabsorption, and the absence of back-diffusion of sodium. The results indicate that, depending on the experimental conditions, an increased rate of sweating can be attributed mainly to recruitment, to enhancement, or to a combination of both.
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