Resumo

STEINBERG, David. Relajantes musculares: Periodo de comienzo bifásico. Vecuronio: Bolo y Cebado. Rev. colomb. anestesiol. [online]. 2005, vol.33, n.2, pp.107-113. ISSN 0120-3347.

Objective: The aim of this trial is to analyze the development of neuromuscular block of vecuronium from a different perspective of the onset time. Speed of action is comparatively studied after bolus or primed administration, using properly designed parameters. Materials & Methods: Two groups of adults anesthetized with intravenous agents and nitrous oxide, received 40 µg.Kg-1 vecuronium, either by bolus (n= 38) or priming: 10 + 30 40 µg.Kg-1 (n= 34) 3 minutes apart. By electromyography, maximal effect and time to 80% and maximum block were assessed. Speed was estimated as the ratio between fractional block and time, as % / sec, during initial, final and global phases of onset time. Rapidity was considered as SEG / % ratio during the same periods. Results: Time to 80% and final blockade were statistically shortened by priming. Initial speed and rapidity were significantly increased by priming (0,31 and 0,49 %/sec and 3,4 and 2,5 SEC/% for bolus and priming respectively). Conclusions: Time to reach partial and final block were significantly shortened by priming technique. Newly defined and properly terms and parameters shows that initial phase of onset time is 4 to 7 times faster than final (biphasic) during development of neuromuscular block. Final period is so slow that couldn't be accelerate by priming. The possibility is discussed to proceed with tracheal intubation instead of waiting for a final and very slow maximal effect. Speculations are made on possible explanation of these findings.

Palavras-chave : Muscle relaxants; onset time; priming; speed of action; vecuronium.

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