The concordance of the current research is that muscle relaxants can improve the conditions of laryngeal mask incubation and reduce the related complications (such as laryngeal spasm and postoperative throat pain ) of laryngeal mask incubation. It is necessary to use muscle relaxants in laryngeal mask incubation under non-special circumstances. However, the dosages of muscle relaxants used in various researches vary greatly of normal endotracheal intubation. Previous studies have shown that the amount of muscle relaxant required for laryngeal mask intubation is smaller than that required for endotracheal intubation. Although the dosage of muscle relaxant required for tracheal intubation can ensure the smooth insertion of laryngeal mask airway, laryngeal mask airway is mostly used for short surgery, which is prone to postoperative muscle relaxation residue and prolongs the recovery. We planning use the most classical method for determining the ED50 or half effective concentration of cis-atracurium using sequential method, which is also called  up and down method and  ladder method.
The muscle relaxants can improve the conditions of laryngeal mask incubation and reduce the related complications (such as laryngeal spasm and postoperative throat pain)~The dosages of muscle relaxants used in various researches vary greatly.~We are planning use the most classical method for determining the ED50 or half effective concentration of cis-atracurium using sequential method, which is also called  up and down method and  ladder method.