Comparison of the effect of the right lateral tilt position and Trendelenburg position on the right internal jugular vein in healthy volunteers: A prospective observational study.

BACKGROUND: Central venous cannulation is an invasive procedure commonly used by many physicians. The aim of this study was to evaluate the effects of the right lateral tilt position on the cross-sectional area and size of the right internal jugular vein, and the relationship between the right internal jugular vein and the carotid artery. METHOD: Forty healthy volunteers aged over 18 years were included in this prospective, observational study. The right internal jugular vein cross-sectional area and the anatomic relationship with the carotid artery were assessed using ultrasound imaging. This measurement was repeated for four positions (baseline position, 10° right tilt position, 10° Trendelenburg position, and 10° right tilt + 10° Trendelenburg position). The head was rotated 30° to the contralateral side in all patients. RESULTS: The mean (standard deviation) right internal jugular vein cross-sectional area, transverse diameter, and anteroposterior diameter were significantly increased with the Trendelenburg position and 10° right tilt + 10° Trendelenburg position (p < 0.05). There were no significant differences in right internal jugular vein cross-sectional area, transverse diameter, and anteroposterior diameter between the baseline position and 10° right tilt position (p > 0.05). CONCLUSION: We found that the right lateral tilt position had no effect on the internal jugular vein cross-sectional area and that the Trendelenburg position was still the most valid position for safely increasing the right internal jugular vein cross-sectional area.

Evaluation of the stability and stratification of propofol and ketamine mixtures for pediatric anesthesia.

BACKGROUND: The combination of propofol and ketamine is commonly used for total intravenous anesthesia. These drugs can be delivered in different syringes or in the same syringe. We hypothesized that the drugs might separate and different concentrations of each drug could be found in different parts of the syringe during the procedure period when they were mixed in 1 syringe. METHODS: Twelve 60-mL polypropylene syringes were prepared by mixing propofol and ketamine as 4 groups on the basis of propofol/ketamine mixture ratios (5:1 and 6.7:1) and propofol solution concentrations. Syringes were placed upright in the vertical position into a rack and kept at room temperature (21.5-22.5°C), in daylight conditions and were not moved for 360 minutes. Samples of the mixture were taken from both the top and the bottom of the syringe. The first 1 mL of the samples was discarded, the following second 1 mL of the samples was filtered using 0.2-µm polytetrafluoroethylene filters and measured twice (n = 6). Samples were taken at the following time intervals: T0, T10, T30, T60, T90, T120, T180, T240, T300, and T360 min. Syringes were checked visually for any color change and separation lines between the drugs. RESULTS: There were no significant differences between the propofol and ketamine concentrations of the top and bottom samples in all 4 groups. In addition, there were no statistically significant changes of propofol and ketamine concentrations of samples over 360 minutes in any of the 4 groups. No visual changes were observed during 6 hours' observation. CONCLUSION: The results of our measurements demonstrated that mixtures of propofol (1% and 2%) and ketamine at 5:1 and 6.7:1 ratios could be used in terms of mixture homogeneity and stability in a polypropylene syringe during a 6-hour period at room temperature.