In the course of balanced anaesthesia, the degree of neuromuscular block must be sufficient to provide adequate surgical conditions but not as excessive as to make it difficult to antagonize at the end of surgery. An appropriate technique for longlasting operations is continuous relaxant infusion but manual control of the pump speed can be time-consuming. We have presented a device (both hardware and software) for fuzzy control of neuromuscular block during general anaesthesia. The system (Relax 2005) was clinically used in 80 patients undergoing an intracranial neurosurgical intervention to maintain a stable depth of neuromuscular blockade during total intravenous anaesthesia. The degree of block (TOF-ratio, T1) was determined using Datex-Ohmeda S/5TM monitor wirelessly interfaced to a PC for the data collection; the computer was programmed to ensure a stable level (target T1 = 10 % of baseline) of block by controlling the rocuronium infusion pump. Based on mean T1 deviation from the target (-0.19 %), the precision of regulation was far beyond clinical requirements.

        Key words: neuromuscular block, rocuronium, fuzzy logic, automatic control