ELECTRICAL-STIMULATION AS A SUBSTITUTE FOR THE TAIL CLAMP IN THE DETERMINATION OF MINIMUM ALVEOLAR CONCENTRATION

Circumstances may preclude the use of standard stimuli, namely tail cl amp or surgical incision, to determine minimum alveolar concentration. In rats anesthetized with isoflurane, an alternative stimulus, electr ical currents (10, 15, 20, or 40 V; biphasic pulses of 6.5 ms duration ; 50 Hz), gave results comparable to those obtained with the tail clam p and the results did not change with repeated measurements if care wa s taken to avoid desensitization by exhaustion of a particular set of electrodes. The 40 V stimulation gave slightly higher values (4%; P < 0.006) than tail clamp, but the difference was too small to be of expe rimental significance. More importantly, the higher voltages produced desensitization after fewer attempts at stimulation. In addition to th ese results with isoflurane, we found that 15 V stimulation and tail c lamp produced comparable minimum alveolar concentration values for hal othane and for desflurane.