Influence of extradural blockade and ephedrine on transcutaneous oxygen tension

The influence of lumbar extradural blockade with 0.5% pain bupivacaine on transcutaneous oxygen tension (PtcO2) and skin temperature was studied in 20 patients, 10 scheduled for vascular surgery and 10 for urological surgery. At the time of maximum extent of blockade, mean arterial pressure (MAP) had decreased significantly (P less than 0.001) from 96.6 +/- 18.8 mm Hg to 69.5 +/- 10.1 (mean +/- SD) in the vascular group and from 88.0 +/- 14.7 mm Hg to 71.1 +/- 12 mm Hg in the urological group. In the vascular group PtcO2 decreased significantly in the ischaemic (P less than 0.01) and non-ischaemic (P less than 0.001) limbs. In the urological group, there was a significant (P less than 0.001) decrease in PtcO2 in both limbs. There was no change in cutaneous temperature in the ischaemic limbs (vascular group), but the temperature in the non-ischaemic limbs increased significantly (P less than 0.01). In the urological group, the cutaneous temperature increased significantly (P less than 0.001) in both limbs. When ephedrine 10 mg was administered i.v., MAP increased significantly (P less than 0.001) in both groups to pre-blockade values. This was accompanied in both groups by significant increases in PtcO2' but not by a change in skin temperature. There was a significant correlation between change in MAP and change in PtcO2 in both groups after ephedrine.