| Popis: |
Twenty-eight ASA I or ASA II adults undergoing microsurgery were anaesthetized according to a standard protocol using droperidol, phenoperidine and thiopentone followed by enflurane. The patients were randomly assigned to two homogeneous groups: the first group (n = 14) received 0.2 mg · kg−1 alcuronium, whereas the second group (n = 14) received 0.08 mg · kg−1 vecuronium. There was no reinjection of either drug and curarization tapered off spontaneously. Neuromuscular monitoring was begun once anaesthesia was stable and after intentional isovolaemic haemodilution. The type of stimulus used was the train-of-four, delivered by a Relaxograph monitor to the ulnar nerve. Muscle response was measured at the hypothenar eminence. The kinetic study considered the time interval required between the injection of the muscle relaxant and the appearance of the minimal value of the twitch (first response of the train-of-four = T1min). The times to recovery of the twitch height to 25, 75 and 100 % of the reference value (T1/T0) and of the fourth response of the train-of-four to 25 and 75 % of the ratio (T4/T1) were also recorded. Finally, the recovery indexes represented by the times required for T1/T0 and T4/T1 to rise from 25 % to 75 % respectively were studied. The maximal twitch height inhibition was significantly greater (p < 0.001) in the vecuronium group (T1min = 0.36 ± 1.33 %) than in the alcuronium group (T1min = 4.36 ± 5.08 %); it occurred significantly more quickly (p < 0.001) with vecuronium (139 ± 48 s) than with alcuronium (316 ± 133 s). The surgical stage of muscle relaxation (T1/T0 = 25 %) was significantly longer (p < 0.0001) for alcuronium : 63 ± 29 min versus 42 ± 6 min for vecuronium. Spontaneous recovery of twitch and train-of-four was significantly slower (p < 10−4 to 10−6) with alcuronium : T1/T0 at 75 % in 116 ± 43 min, T1/T0 at 100 % in 173 ± 46 min, T4/T1 at 25 % in 104 ± 29 min, T4/T1 at 75 % in 192 ± 48 min, whereas these same parameters were respectively 59 ± 8 min, 86 ± 11 min, 63 ± 12 min and 96 ± 17 min with vecuronium. Recovery was three times quicker (p < 10−6) for vecuronium (17 ± 3.5 min for T1/T0 and 32 ± 8 min for T4/T1) than for alcuronium (53 ± 20 min for T1/T0 and 88 ± 30 min for T4/T1). The results showed that the kinetic actions of both these muscle relaxants were dissimilar. With a more rapid action, a more predictable duration of surgical curarization and a lesser and shorter residual curarization, vecuronium gave better quality muscle relaxation when compared with alcuronium, and its use should be preferred. In cases where alcuronium is to be used, monitoring should be used because of the variability in the length of its effects. |
