EVALUATION OF SACCADIC EYE-MOVEMENTS AS AN OBJECTIVE TEST OF RECOVERYFROM ANESTHESIA

Saccadic eye movements have been previously used to assess residual ef fect of anaesthetics, but this test is seldom compared to other psycho motor tests. The aim of the present study was to validate saccades as a recovery index in relation to frequently referred subjective and psy chometric tests. Eight healthy subjects were tested before and after i ntra-muscular injection of either placebo or 0.15 mg . kg(-1) of midaz olam. Each session consisted of a saccadic rest (recorded by electro-o culography), a choice-reaction-time test (CRT), a subjective state-of- alertness test (11 visual analogic scales) and blood sampling (to moni tor midazolam plasma concentration), before and 30 (t30), 60 (t60), 12 0 (t120), 180 (t180), 240 (t240) minutes after drug administration In the placebo group, there was no change in subjective assessment, sacca de characteristics (latency, peak velocity and duration) or CRT result s. In the midazolam group, 6 subjective items changed with different t ime-courses, when compared to baseline: from t30 to t120 (drowsy, in s hape, tired, clumsy strong) and at t120 (woolly). Saccade latency and duration were significantly different from 130 to t120 and until t180 for peak velocity. CRT performance was significantly altered From t30 to t120. Midazolam plasma concentration decreased From 177+/-33 ng . m l(-1) at t30 to 47+/-12 ng . ml(-1) at t240. At this latter time, sens orimotor functions returned to the baseline. All subjects fulfilled th e clinical conditions for home discharge 4 hours after administration. These results suggest that a saccadic eye movement test is a sensitiv e and reliable tool for the assessment of residual effect of anaesthet ics. This test was found to be more sensitive than CRT test since peak saccadic velocity was the last psychometric parameter to be returned to baseline after midazolam injection. This study also confirms the po or reliability of subjective assessment, as subjects tended to underes timate the alteration of their performance immediately following drug injection.