ASSESSING THE LEVEL OF REGIONAL BLOCKADE UNDER GENERAL-ANESTHESIA USING THE SKIN VASOMOTOR REFLEX TEST

We investigated whether skin vasomotor reflex (SVmR) testing can be us ed to assess the sensory blockade level under Light general anesthesia . In 15 patients scheduled for abdominal gynecological surgery, the SV mR was tested under inhaled isoflurane or sevoflurane (0.5%-0.6%) with nitrous oxide (50%). Seven minutes after the epidural injection (5-10 mL of 2% lidocaine), a tetanic electrical stimulus (20 mA, 2 s) was a pplied to the skin and repeated sequentially from the L3 dermatome in the cephalad direction. Changes in the laser Doppler skin blood flow o n the index finger tip were assessed for the SVmR. If there was a posi tive response, SVmR testing was discontinued. The relationship between the uppermost dermatome of the negative SVmR response and the intraop erative effectiveness of the epidural block was determined. In 11 pati ents, we confirmed a clear boundary of skin dermatome by the SVmR test . The uppermost dermatome of the negative SVmR response at higher than the T7 level was necessary to maintain the combined epidural and ligh t general anesthesia for the transabdominal gynecological surgery (P = 0.002). We conclude that SVmR testing is useful in estimating the blo ckade level of regional anesthesia under light general anesthesia. Imp lications: Considering ''preemptive analgesia,'' a complete sensory bl ockade should be established before a skin incision. In 11 of 15 patie nts under epidural/general anesthesia, we confirmed a clear dermatome boundary using the skin vasomotor reflex test. This test could be an i ndicator for estimating the sensory blockade level of patients under g eneral anesthesia.