Effects of low-dose isoflurane on saccadic eye movement generation

The effects of 0.15% quasi-steady-state end-tidal isoflurane on two saccadi c eye-movement tests were examined in five volunteers using a newly devised computer-based recording system. The tests were saccadic latency and a cou ntermanding task, the latter being an indicator of the highest levels of co nscious performance. A moving light-emitting diode target was displayed on a screen and in the saccadic-latency task the latency of eye movement to th e target was measured. In all five subjects the latency increased with anae sthetic by an amount which varied from 8 to 45 Ins. This result was signifi cantly different (p<0.05) from subjects without anaesthetic. ill the counte rmanding task, the subject had to voluntarily inhibit movement to the targe t. Again anaesthetic increased the latency of response, which varied from 6 to 33 ms. This result was significantly different (p<0.05) from subjects w ithout anaesthetic. In these studies it appeared that two tasks, one a simp le latency test and the other, the countermanding task, requiring higher co rtical processing were equally impaired at subanaesthetic concentrations of isoflurane.