Effect of tourniquet-induced ischemia on cutaneous thermal thresholds.

The effect of tourniquet-induced ischemia on human thermal thresholds was studied. After the development of the A-fibre block (= a sharp elevation of cool threshold) the heat-pain threshold was still uninfluenced. This result supports previous evidence indicating that C-fibres mediate the liminal heat pain sensation. Thus, the quantitative determination of cutaneous heat pain thresholds provides a rather selective method for testing C-fibre mediated pain sensitivity, at least when a contact thermostimulator with a slow or moderate rise of stimulus temperature is used. The second aim of this study was to examine whether ischemia or mechanical pressure is the cause of the tourniquet-induced block of A-fibres. This was studied by varying the mechanical pressure and the amount of ischemia. With increased ischemia (with muscle work) the A-fibre block (increased cool threshold) came earlier, but this finding was not significant.