Respiratory system compliance during anesthesia induction and postoperative mechanical ventilation needs: An observational study.

Background and Aims: Respiratory system compliance (Crs) is a simple indicator of lung flexibility. However, it remains unclear whether a low Crs during anesthesia induction (iCrs) is associated with an increased risk of postoperative mechanical ventilation. Methods: This retrospective observational study was conducted using a local database. All mechanically ventilated postoperative ICU patients were included in this study. The duration of postoperative mechanical ventilation, length of hospital stay, and in-hospital mortality were compared between the low iCrs group (<25% of distribution) and the normal iCrs group. Results: A total of 315 patients were classified into the low iCrs (<39 mL/cmH2O) group (n = 78) or the normal iCrs group (n = 237). Low iCrs was associated with a higher chance of mechanical ventilation in 28 days (log-rank test, p < 0.001). The duration of hospital stay was similar. Multivariate analysis showed that in-hospital mortality was higher in the low iCrs group than in the normal iCrs group (adjusted odds ratio, 6.04 [1.13, 32.26]; p = 0.04). Conclusion: Low iCrs was associated with an increased risk of requiring postoperative mechanical ventilation. An additional result of poor survival related to low iCrs may require further study.

Asymmetric Lipid Bilayers and Potassium Channels Embedded Therein in the Contact Bubble Bilayer.

Cell membranes are highly intricate systems comprising numerous lipid species and membrane proteins, where channel proteins, lipid molecules, and lipid bilayers, as continuous elastic fabric, collectively engage in multi-modal interplays. Owing to the complexity of the native cell membrane, studying the elementary processes of channel-membrane interactions necessitates a bottom-up approach starting from forming simplified synthetic membranes. This is the rationale for establishing an in vitro membrane reconstitution system consisting of a lipid bilayer with a defined lipid composition and a channel molecule. Recent technological advancements have facilitated the development of asymmetric membranes, and the contact bubble bilayer (CBB) method allows single-channel current recordings under arbitrary lipid compositions in asymmetric bilayers. Here, we present an experimental protocol for the formation of asymmetric membranes using the CBB method. The KcsA potassium channel is a prototypical model channel with huge structural and functional information and thus serves as a reporter of membrane actions on the embedded channels. We demonstrate specific interactions of anionic lipids in the inner leaflet. Considering that the local lipid composition varies steadily in cell membranes, we `present a novel lipid perfusion technique that allows rapidly changing the lipid composition while monitoring the single-channel behavior. Finally, we demonstrate a leaflet perfusion method for modifying the composition of individual leaflets. These techniques with custom synthetic membranes allow for variable experiments, providing crucial insights into channel-membrane interplay in cell membranes.

The Relationship between the Measured Blood Concentration of Rocuronium in Stable Muscle Relaxation with a Closed-Loop Control and the Estimated Blood Concentration from a Pharmacokinetic Simulation.

We developed a system to adjust the rate of a continuous rocuronium (Rb) infusion to achieve 3 ≤ %T1 ≤ 10 with a closed-loop control. Samples were collected from 15 patients, and Rb blood concentrations were measured at the following time points: (1) when %T1 recovered to 3% or more after the initial Rb infusion; (2) when %T1 stabilized within the target range; (3) at the cessation of the Rb infusion; (4) 5 min after the sugammadex administration. The predicted Rb blood concentration at each time point was calculated and recorded using the pharmacokinetic parameters of Wierda et al. At time points (1), (2), and (3), the predicted blood concentrations were in good agreement with the measured values, but after the administration of sugammadex, the blood concentrations were higher than the predicted values because the Rb distributed in the tissues migrated into the blood. From the above, it was confirmed that the predicted blood concentration of Rb can be a good indicator for the automatic Rb administration control.

Comparison of Left Ventricular End-Diastolic Volume Approximated from Mean Blood Pressure and Stroke Volume and End-Diastolic Volume Calculated from Left Ventricular-Aortic Coupling.

Objectives: The purpose of this study was to compare left ventricular end-diastolic volume (EDV), derived from left ventricular arterial coupling (Ees/Ea), and mean arterial blood pressure. Both of these methods of measuring EDV require some invasive procedure. However, the method of measuring EDV approximate is less invasive than the EDV coupling measuring method. This is because EDV approximate only requires arterial pressure waveform as an invasive procedure. Methods: This study included 14 patients with normal cardiac function who underwent general anesthesia. The point when blood pressure stabilized after the induction of anesthesia was taken as a baseline according to the study protocol. At the point when systolic arterial blood pressure fell 10% or more from the baseline blood pressure, 300 mL of colloid solution was administered over 15 min. EDV approximate and EDV coupling were calculated for each of the 14 patients at three points during the course of anesthetic. Each value was obtained by calculating a 5 min average. The timing of these three points was 5 min before, 5 min during, and 5 min after infusion loading. Results: The total number of comparable points was 42; 3 points were taken from each of the 14 participants. Both EDV approximate and EDV coupling increased through the infusion load testing. Scatter plots were prepared, and regression lines were calculated from the obtained values. A high correlation was shown between EDV approximate and EDV coupling (R2 = 0.96, p < 0.05). Conclusions: In patients with good cardiac function, EDV approximate can be substituted for EDV coupling, suggesting the possibility that EDV can be continuously and less invasively calculated under the situation of general anesthesia.

Probing membrane deformation energy by KcsA potassium channel gating under varied membrane thickness and tension.

This study investigated how membrane thickness and tension modify the gating of KcsA potassium channels when simultaneously varied. The KcsA channel undergoes global conformational changes upon gating: expansion of the cross-sectional area and longitudinal shortening upon opening. Thus, membranes impose differential effects on the open and closed conformations, such as hydrophobic mismatches. Here, the single-channel open probability was recorded in the contact bubble bilayer, by which variable thickness membranes under a defined tension were applied. A fully open channel in thin membranes turned to sporadic openings in thick membranes, where the channel responded moderately to tension increase. Quantitative gating analysis prompted the hypothesis that tension augmented the membrane deformation energy when hydrophobic mismatch was enhanced in thick membranes.

Effect of age and gender on ventricular-arterial coupling estimated using a non-invasive technique.

BACKGROUND: Left ventricular-arterial coupling is assessed as the ratio of left ventricular end-systolic elastance (Ees) to arterial elastance (Ea). Previous studies have introduced non-invasive estimations of Ees/Ea. It requires only four variables, namely pre-ejection period, ejection time, end-systolic pressure and diastolic pressure. The aims of the present study were to clarify the reference values of Ees/Ea estimated using the noninvasive technique, and to investigate the effects of age and gender on Ees/Ea in healthy subjects. METHODS: This retrospective study utilized data from healthy, 30-79-year-old subjects. We recorded electrocardiogram, phonocardiogram, and brachial arterial pulse waves simultaneously using the vascular screening system, and used the observed variables to calculate Ees/Ea. We separated subjects into five groups according to their age and compared Ees/Ea among the different age groups. RESULTS: The study included 2114 males and 2292 females. Ees/Ea ranged from 1.87 to 2.04 in males, and 1.98 to 2.32 in females. We observed no age-related differences in Ees/Ea in males (p = 0.10), and significant differences in females (p < 0.001). Ees/Ea in males was not different compared to those in females in 60-69-year-old group (p = 0.92). Whereas Ees/Ea was higher in females compared to those in males in the other age groups. The differences between medians of Ees/Ea in males and those in females were 0.45 (p < 0.001), 0.24 (p < 0.001), 0.13 (p = 0.01), and 0.13 (p = 0.03) in 30-39, 40-49, 50-59, and 70-79-year-old age groups, respectively. CONCLUSIONS: We clarified the reference values of Ees/Ea in healthy subjects. The effect of age on Ees/Ea is different in males and females, although Ees/Ea is maintained within a relatively narrow range in all subjects.