SummaryThe pressure within latex balloons remains constant despite the balloons being in¯ated to more than 40 times their initial volume. We used this property to enable improved tracheal cuff pressure control. A latex balloon with an initial volume of 5 ml was connected via a vinyl duct attached with a roller clamp and three-way stopcock to a standard tracheal tube cuff. The 5 ml latex balloon was then in¯ated with 250 ml of air. The pressure within the tracheal tube cuff was monitored throughout anaesthesia with the in¯ated latex balloon acting as a pressure controller. Throat symptoms were recorded on the ®rst four postoperative days. The controller kept the tracheal tube cuff pressures constant, and reduced the incidence of postoperative throat symptoms. Variations in cuff pressures with and without the controller were investigated in an altitude chamber to simulatē ight. In the altitude chamber, cuff pressure reached over 200 cmH 2 O at 10 000 feet without the controller, whereas such variations were practically eliminated when the controller was used.
The purpose of this study was to identify the relationship between sensitivity of arterial baroreflex and plasma concentrations of lidocaine. Using twelve mongrel dogs anesthetized with alpha-chloralose, the left kidney was exposed retroperitoneally, and renal sympathetic nerve activity was recorded continuously. Lidocaine was infused in four different doses: 2 mg.kg BW-1 bolus + 100 micrograms.BW-1 x min; 3 mg.kg BW-1 bolus + 200 micrograms.kg BW-1 x min; 6 mg.kg BW-1 bolus + 400 micrograms.kg BW-1 x min; and 12 mg.kg BW-1 + 800 micrograms.kg BW-1 x min. Baroreflex depressor and pressor tests using sodium nitroprusside (5-10 micrograms.kg-1) and phenylephrine (2-4 micrograms.kg-1) were performed before and at 10 min after beginning lidocaine infusion. Plasma lidocaine concentrations determined by high performance liquid chromatography revealed that the steady-state levels were maintained during the baroreflex tests. Baroreflex sensitivity was preserved at plasma concentrations of lidocaine below 5 micrograms.ml-1. However, cardiac and sympathetic baroreflex sensitivity were significantly attenuated (P < 0.01) when plasma lidocaine concentrations were well above human convulsion levels (10 micrograms.ml-1). The results indicate that hemodynamic derangement observed in the lidocaine-induced central nervous system toxicity is, at least in part, due to the attenuated arterial baroreflex.
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