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Norcuron injection has been applied for the prolongation of the duration of muscle relaxing action of Arduan in 104 patients. The patients underwent major surgery and 1/5 of them were of advanced age. Neuromuscular blockade could be prolonged for the required duration of operation with lower doses of Norcuron (2 mg, 1 mg) than the currently used ones. For avoiding eventual cumulation or synergism the repetition of lower doses to meet the requirements seems to be the most advantageous method.

In two groups of patients the neuromuscular and circulatory effects of pipecuronium bromide (Arduan R), a new steroid type muscle relaxant were compared with those of pancuronium during balanced anaesthesia. Pipecuronium (n = 18) was found to be about 20% more potent than pancuronium (n = 20). The 95% blocking doses were: 0.059 mg kg-1 for pipecuronium and 0.075 mg kg-1 for pancuronium; these doses provided equal intubating conditions and relaxation. The onset, clinical relaxation time (clinical duration), recovery and the reversibility of the neuromuscular effects of the two agents in equipotent doses were similar. No cardiovascular or other side effects were observed with the use of pipecuronium.

The forced oscillatory impedance of the total respiratory system (Zrs) was measured in seven anaesthetized, paralysed rats weighing 351 +/- 55 g. Tracheotomy was performed, and the animals were placed in the supine position in a body box. Pseudo-random pressure variations between 0.5 and 10 Hz were applied around the chest. Central airflow was measured with a heated screen pneumotachograph. Total respiratory resistance (Rrs) and elastance (Ers), corrected for the impedance of the tracheal cannula, were markedly frequency-dependent: Rrs fell from 37.3 +/- 19.1 kPa.l-1.s at 0.5 Hz to 17.6 +/- 4.4 at 2 Hz and 10.3 +/- 3.3 at 10 Hz; the corresponding Ers values were 453 +/- 14, 594 +/- 90 and 713 +/- 104 kPa.l-1, respectively. This indicates that in the frequency range encompassing spontaneous breathing rates the classical resistance-intertance-compliance model provides an inadequate description of the respiratory mechanics in the rat.