A Clinical And Pharmacological Study Of The Combined Effects Of Tow Non Depolarizing Muscle Relaxants: Atracurium And Vecuronium

The ann of this study is to compare the onset and duration of neuromuscular blockade produced by atracurium and vecuronllllll each drug alone with that produced by both drugs in combination in different doses.Also the objective of this study is to compare the sensitivities of the orbicularis oculi, orbicularis oris and gastrocnemius muscles in rabbits to both atracurium and vecuronium alone and in combination.The clinical m rt:* This study was carried out on 60 patients ASA I or II physical status undergoing elective surgical interference that required endotracheal intubation and muscle relaxation. All patients were subjected to preoperative histOly taking, clinical examination and routine laboratory investigations.Patients were divided into 5 equal groups, including 12 patients each.The first group: patients received atracurium, full close.The second group: patients received vecuronium, full close.The third group: patients received quarter close combination ofatracurium and vecuronium.The fOUl1h group: patients received half dose combination of the both drugs.The fifth group patients received full dose combination of the both drugs.Anaesthesia was induced by fenta lyl 1.0 - 2.0 ).lg/kg and thiopentone 4.0 - 5.0 mg. kg LV. The muscle relaxant drug or the combination was given and the trachea was intubated by the proper sized cuffed endotracheal tube after oxygenation. Anaesthesia was mai ttained with 60% N20 in oxygen, 0.5% halothane and LV. supplemental doses of fentanyl.At the end of the surgelY any residual amount of neuroll1uscular blockade was reversed with neostigmine and atropine 1. V.The neuromuscular transmission in all patients was continuously monitored by myograph 2000 to detennine the onset time and duration of neuromuscular blockade by TOF stimulation.The experimental part:* The experimental p311 included 30 rabbits that were divided into 5 equal groups as in the clinical part and three nerve-muscle preparations were used to record the onset and duration of neuromuscular blockade produced by both atracuriull1 andvecuronium and their combinations. These preparations are:Facial nerve-upper lip muscle preparation. Facial nerve-upper eye lid muscle preparation. Sciatic nerve-gastrocnemius muscle preparation.The study dellOl1strated that the shortest onset time of neuromuscular blockade was produced by full-dose combination of atracurium and vecuronium but this combination produces the longest duration of blockade.It demonstrated a decrease in the onset time and an increase in duration of neuromuscular blockade when half dose combination of the both drugs are used.When a quarter dose combination IS used the onset time IS significantly longer and the duration of blockade is significantly sholier.The experimental part of this study demonstrated that there is a close cOITelation between orbicularis oculi and orbicularis oris as they are similar in their response to the muscle relaxants used and their combinations, also both muscles have a rapid onset of neuromuscular blockade and rapid recovery than the gastrocnemius muscle.