Significance: Ion selectivity is a fundamental property of ion channels. Potassium channels exhibit an unusual selectivity, allowing passage of larger K ⁺ ions (ionic radius of 1.3 Å) over smaller Na ⁺ ions (1.0 Å); the mechanism underlying the small ion rejecting selectivity remains unknown. Here, we applied Na ⁺ as a probe for examining the pore of a prototypical potassium channel and found slight Na ⁺ conduction across the pore. Na ⁺ traced a tortuous trajectory in the narrow pore, with multiple Na ⁺ ions trapped here and there, leading to slow elution. Contrarily, K ⁺ passed straight, with three ions moving together rapidly. Na ⁺ and K ⁺ take different paths and interactions in the pore, which creates dramatic contrast in the conduction rates of Na ⁺ and K ⁺ .

Critically ill patients in the intensive care unit (ICU) develop muscle atrophy and decreased physical function. Though neuromuscular electrical stimulation (NMES) therapy has been shown to be effective in preventing this, but its effect on older patients is unknown. To examine the course of critically ill older patients treated with NMES in the ICU and to define the impact of its use. A retrospective cohort study was conducted using older ICU patients (≥65 years) categorized into a control group (n = 20) and an NMES group (n = 22). For subgroup analysis, each group was further classified into pre-old age (65–74 years) and old age (≥75 years). The control group showed significant decrease in muscle thickness during ICU and hospital stay. The NMES group showed lower reduction in muscle thickness and showed decrease in muscle echo intensity during hospital stay, compared to the control group. NMES inhibited decrease in muscle thickness in the pre-old age group versus the old age group. The decreasing effect of NMES on echo intensity during hospital stay manifested only in the pre-old age group. We did not find much difference in physical functioning between the NMES and control groups. Lower limb muscle atrophy reduces in critically ill older patients (≥65 years) with NMES and is pronounced in patients aged < 75 years. The impact of NMES on the physical functioning of older patients in ICU needs to be further investigated.

Background: We previously developed an automated total intravenous anesthesia control system that uses new closed-loop system algorithms to administer propofol, remifentanil, and rocuronium based on the bispectral index and train-of-four data. We recently improved this automated control system by adding a safety mechanism and using a modified monitoring device. Methods: Patients scheduled for elective surgery were randomly assigned to closed-loop feedback control (automatic group) or the manual administration of propofol, remifentanil, and rocuronium (manual group). The proportion of time during which the proper management of three-agent anesthesia was maintained during surgery was determined as the primary endpoint. Results: The proportion of time during which the three components of sedation, analgesia, and muscle relaxation were adequately controlled was 87.21 ± 12.79% in the automatic group, which was non-inferior to the proportion of 65.19 ± 20.16% in the manual group (p < 0.001). Adverse events during the operative or postoperative observation periods were significantly less frequent in the automatic group (54 patients, 90.0%) than in the manual group (60 patients, 100.0%; p = 0.027). Conclusion: Our three-agent automated control system, which features an improved muscle relaxation monitor and safety mechanism added to the basic control algorithms, maintained sedation, analgesia, and muscle relaxation appropriately in a manner non-inferior to anesthesiologists without compromising safety.

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.

Maintaining respiratory system compliance (Crs) is a clue for lung recruitment strategies during surgery; however, patients’ baseline Crs values have not been adequately addressed. We studied the association of low Crs at the induction of anesthesia (iCrs) with limited intraoperative respiratory management. We conducted a secondary analysis of retrospective study of consecutive surgical patients on ventilators between 2019 and 2020. The intra- and postoperative respiratory-related parameters were compared between the low iCrs group (<25% of the distribution) and others. Primary outcome was postoperative respiratory support related with iCrs and intraoperative Crs decline. Multivariate analysis and other root-cause analysis were performed to evaluate the relationships between low iCrs and outcomes. A total of 5568 patients were included and classified into either the low iCrs group (<43 mL/cmH₂O, n = 1392) or the other group (n = 4176). The age was older and both the duration of surgery and the duration of anesthesia were shorter in the low iCrs group than in the other groups. Unexpectedly, the low iCrs group was associated with a smaller decrease in hourly changes in Crs (−1.4% [−11.3% to 11.2%] vs −13.0% [−21.3% to −5.3%], P < .001). Despite the smaller decrease in Crs, the low iCrs group showed a higher incidence of > 3 days of postoperative oxygen therapy (adjusted OR 1.60 (1.29–1.97), P < .001) and > 3 days of mechanical ventilation following surgery (adjusted OR, 1.55 (1.02–2.36), P = .039) than the other group. The significances in postoperative therapies were exaggerated in emergency surgery. The low iCrs patients showed a smaller decline in hourly changes in Crs and longer postoperative respiratory supports. Not only the decrease in Crs during surgery but also the initial Crs value warrant the intra- and postoperative respiratory management.