SYNOPSISThe effect of local and whole-body heating and cooling on plasma fibrinolytic activity has been investigated in 59 subjects. An increase in whole-body temperature and both local cooling and heating increased the fibrinolytic activity. The results demonstrate that the application of local heat or cold will produce a local increase in fibrinolytic activity which is independent of general factors such as emotion and stress.Much is known about the physiological factors which influence blood fibrinolytic mechanisms, for example, exercise (Biggs, MacFarlane, and Pilling, 1947;Fearnley and Lackner, 1955) and emotion (MacFarlane, 1947;Ogston, McDonald, and Fullerton, 1962) increase fibrinolytic activity whereas increasing weight reduces fibrinolytic activity (Grace, 1967). In view of our interest in cutaneous vascular disorders and their possible precipitation by a cold environment, eg, Raynaud's phenomenon, we looked further into the effects of temperature on plasma fibrinolysis. In support of this investigation was the observation by Cunliffe and Menon (1969) that infusions of low molecular weight dextran have beneficial effects on the clinical state and blood fibrinolytic activity in patients with Raynaud's phenomenon.
Subjects and MethodsThe investigation consisted of exposing 59 volunteers, 34 females and 25 males aged 17-47 years, to local and whole body heat and cold and measuring the blood fibrinolytic activity before and after exposure. Fibrinolytic activity was measured by the euglobulin lysis time (ELT) which was estimated by the method of von Kaulla (1963) modified by Menon (1967). The investigations were carried out at a constant time, the patients resting and fasting before the test was performed.Central temperature was measured orally and the skin temperature was measured by a thermister (Brighton Laboratories) placed on the skin. Twenty other subjects placed one arm up to the elbow in a water bath at 4°C for four minutes, the appropriate arm remaining at room temperature and acting as a control. A mean decrease in skin temperature of 11-5 degrees was produced in the immersed arm. There was no decrease in general body temperature.In 32 subjects the effect of heat was investigated: 18 of these subjects had a hot bath (45°C) for 10 minutes the subjects lying immersed in the bath up to the neck. This produced a significant increase in central body temperature of 2 1°C. Fourteen patients placed one arm in a water bath at 45°C for four minutes; this produced an increase in local skin temperature of 6 8°C in the immersed arm but in nopatient was there anyrise in body temperature.Blood was taken immediately before and immediately after the experiment in all subjects; wherever possible blood was taken from both arms before and after the investigation.
ResultsThere was a significant (p < 0-01) increase in fibrinolytic activity after exposure to generalized heat ( fig. 1) but not (p < 0 1) after exposure to generalized cold ( fig. 2). Localized heat produced a significant increase (p < 0-01) in fibrinol...