EFFECTS OF PROPOFOL AND THIOPENTONE ON NE UROMUSCULAR BLOCKADE AFTER ADMINISTRATION OF ATRACURIUM AND ALCURONIUM

Does propofol or thiopentone enhance the effect of nondepolarizing mus cle relaxants? We evaluated the effects of propofol and thiopentone on the pharmacodynamics of atracurium and alcuronium in 43 surgical pati ents (ASA I and II) under general anaesthesia. Methods. The patients w ere randomized into five groups, A-E. Anaesthesia was induced in all p atients with fentanyl 4 mu g/kg i.v. Patients in groups A and C patien ts 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). E lectromyography (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 r ecorded. 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 e ffect on the TOF was measured. Patients in groups B and D patients rec eived total intravenous anaesthesia (TIVA) with propofol 1% 6-12 mg/kg per hour continuously after induction with 3 mg/kg. The action profil e 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 h our) under the use of atracurium 0.5 mg/kg, Ventilation was performed with 30%/70% oxygen and N2O. The results were analyzed for significanc e using the Mann-Whitney U-test (P=0.019). Results. A slight differenc e in AZ was noted for alcuronium under the use of TIVA between propofo l and thiopentone: 13 min and 5 min, respectively. Otherwise, the phar macodynamics (T% and recovery of neuromuscular function) of the two re laxants exhibited no major differences related to thiopentone, propofo l or their combination. The TOF was not influenced under additional pr opofol application. Noteworthy were the wide distribution of the time course of action (up to 3 h) and the magnitude of T% depression under alcuronium. Conclusion. 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 m uscle relaxants do not seem to be influenced by these two hypnotics.