Effect of fazadinium on respiratory functions and its correlation with neuromuscular transmission in children.

Effects of fazadinium in doses of 0.75, 1.0 and 1.25 mg/kg and pancuronium 0.1 mg/kg on respiratory functions (tidal volume, minute volume and inspiratory force) and correlation between respiratory functions and neuromuscular transmission were evaluated in 64 children aged 6 months to 12 years undergoing various types of elective surgery. Neuromuscular transmission was evaluated by a digitial EMG system using train-of-four stimuli calculating T1 and T4 ratios. Time to apnea, duration of apnea, time and mode of recovery of respiratory functions and neuromuscular transmission when spontaneous respiration started and recovered completely were recorded. The speed, depth and duration of effect of fazadinium on respiration were dose related, 0.75 mg/kg being inadequate to produce apnea in the majority of cases. Duration of apnea increased significantly with increasing dosage (13 +/- 2, 17 +/- 2, 23 +/- 2 minutes respectively). At the end of surgery respiratory measurements reached control values either spontaneously or after reversal. Spontaneous recovery took significantly longer times (34 +/- 3, 51 +/- 5, 95 +/- 10 minutes respectively) depending on dosage. In the remaining patients recovery was complete within five minutes after reversal. Pancuronium could be placed between 1.0 and 1.25 mg/kg fazadinium regarding aspects other than speed of onset of effect. Neuromuscular transmission was still markedly depressed when spontaneous respiration started (T4/T1 of 7-24%) and recovered (T4/T1 of 35-57%) indicating that when recovery from neuromuscular blockade is to be evaluated clinically, adequancy of ventilation by itself should not be taken as a sign of recovery from the effect of relaxant.