ABSTRACT
Numerous studies support the idea that neuromuscular blockade facilitates facemask ventilation after induction of anaesthesia. Although improved airway patency or pulmonary compliance and a resolution of laryngospasm have been suggested as possible causes, the exact mechanism remains unclear. We aimed to assess whether neuromuscular blockade improves facemask ventilation and to clarify whether this phenomenon is associated with the vocal cord angle. This prospective observational study included patients aged between 20 and 65 years scheduled for elective surgery under general anaesthesia. After induction of anaesthesia, patients' lungs were ventilated with pressure-controlled ventilation using a facemask. During facemask ventilation, a flexible bronchoscope was inserted through a self-sealing diaphragm at the elbow connector attached to the facemask and breathing circuit and positioned to allow a continuous view of the vocal cords. The mean tidal volume and vocal cord angle were measured before and after administration of neuromuscular blocking drugs. Of 108 patients, 100 completed the study. Mean (SD) tidal volume ((11.0 (3.9) ml.kg-1 vs. 13.6 (2.6) ml.kg-1 ; p < 0.001) and mean (SD) vocal cord angle (17° (10°) vs. 26° (5°); p < 0.001) increased significantly after neuromuscular blockade. The proportional increase in mean tidal volume after neuromuscular blockade was positively correlated with vocal cord angle (Spearman's ρ = 0.803; p < 0.001). In conclusion, neuromuscular blockade facilitated facemask ventilation, and the improvement was correlated with further opening of the vocal cords.
Subject(s)
Neuromuscular Blockade , Adult , Aged , Anesthesia, General , Humans , Lung , Masks , Middle Aged , Vocal Cords , Young AdultABSTRACT
Compared to nerve stimulation or classic paraesthesia techniques, ultrasound (US)-guided popliteal sciatic nerve block requires a smaller volume of local anaesthetic. The up-and-down method was used to determine the minimum effective anaesthetic volume of 0.5% ropivacaine necessary for US-guided popliteal sciatic nerve block to achieve successful surgical anaesthesia for foot and ankle surgery. The study included 32 patients receiving an US-guided popliteal sciatic nerve bock. The starting dose of 0.5% ropivacaine was set at 30 ml, which was decreased by 3 ml if the block succeeded and increased by 3 ml if the block failed. After the injection of local anaesthetic, the degree of sensory and motor blockade of the tibial and common peroneal nerves was assessed every 5 minutes for 30 minutes. The ED50 and ED95 volumes of local anaesthetic were 6 ml and 16 ml, respectively. The success rates of sensory blockade of the tibial nerve and common peroneal nerve were 69% and 88%, respectively. The success rates of motor blockade of these nerves were 75% and 90%, respectively. The ED50 and ED95 of 0.5% ropivacaine for US-guided popliteal sciatic nerve block were 6 ml and 16 ml, respectively.
