Neuromuskul�re Blockade nach Atracurium und Alcuronium unter dem Einflu� von Propofol und Thiopental

Abstract

Does propofol or thiopentone enhance the effect of nondepolarizing muscle relaxants? We evaluated the effects of propofol and thiopentone on the pharmacodynamics of atracurium and alcuronium in 43 surgical patients (ASA I and II) under general anaesthesia. The patients were randomized into five groups, A-E. Anaesthesia was induced in all patients with fentanyl 4 micrograms/kg i.v. Patients in groups A and C patients received thiopentone 7 mg/kg i.v., and relaxation was achieved with alcuronium 0.25 mg/kg (group A) and atracurium 0.5 mg/kg (group C). Electromyography (train of four, TOF) was used to determine the time of onset of relaxation (AZ) and the maximum degree of blockade (T%). The recovery times to 25%, 50% and 75% of baseline muscle strength were recorded. Additionally, the TOF ratio T4:T1 was calculated, indicating the probable end of relaxation at a ratio of 0.7. At the beginning of the recovery phase (T1 = 15%) propofol 1% 3 mg/kg was given, and the effect on the TOF was measured. Patients in groups B and D patients received total intravenous anaesthesia (TIVA) with propofol 1% 6-12 mg/kg per hour continuously after induction with 3 mg/kg. The action profile of alcuronium 0.25 mg/kg (group B) and atracurium 0.5 mg/kg (group D) were recorded. Group E patients received thiopentone (10 mg/kg per hour) under the use of atracurium 0.5 mg/kg. Ventilation was performed with 30%/70% oxygen and N2O. The results were analyzed for significance using the Mann-Whitney U-test (P = 0.019). A slight difference in AZ was noted for alcuronium under the use of TIVA between propofol and thiopentone: 13 min and 5 min, respectively. Otherwise, the pharmacodynamics (T% and recovery of neuromuscular function) of the two relaxants exhibited no major differences related to thiopentone, propofol or their combination. The TOF was not influenced under additional propofol application. Noteworthy were the wide distribution of the time course of action (up to 3 h) and the magnitude of T% depression under alcuronium. Propofol and thiopentone have no potentiating influence on the time course of action and the magnitude of relaxation with alcuronium and atracurium. Pharmacodynamics of nondepolarizing muscle relaxants do not seem to be influenced by these two hypnotics.