The tourniquet is not only used for facilitation of microaurgery by the bloodless surgical field on the extremities but prepared for the intravenous regional anesthesia and isolation arm test estimated the degree of the neuromuscular transmission in the anesthetic field. On the contrary, there are various complications, such as nerve paralysis and tissue damage from compression, and metabolic and hemodynamic changes from ischemia after application of the tourniquet. Since a sudden increase in PaCO2 immediately following tourniquet deflation is one of the important factors in the hemodynamic changes, we have observed the ehanges of PaCO2 and PCO2, after release of the tourniquet on the upper and the lower extremity under the general anesthesia with enflurane, N2O and respiratory control maintaining PaCO2 level (35 mmHg). The results obtained were as follows; PETCO2, PaCO2 and HCO2- were significantly elevated to peak level within 1 minutue after tourniquet release on the upper and the lawer extremity, except HCO2 on the upper extremity, and there were more severe changes on the lower extremity. pH and base excess were reduced to significantly lowest level 1 minutue and 5 minutes after tourniquet release respectively, and their changes were more reduction on the lower extremity. There were no statistically significant variations in PaO2 on the extremities. In the relationship between tourniquet time and P, it was statistically significant linear on the lower extremity (p<0.05) only. Conlusively, since the sudden changes of PaCO2, pH and base excess after release of tourniquet are closely related with PaCO2, on time and degree, noninvasive monitoring of PaCO2 has rapid interpre- tation to change in PaCO2 after release of tourniquet.