方山 真朱

BACKGROUND: The airway closure phenomenon occurs when the airway collapses, isolating the proximal airway from the distal alveoli. Airway opening pressure (AOP) is required to reopen closed airways. Two methods are available to measure AOP: the low-constant flow (AOPflow) and constant low-slope pressure ramp methods (AOPpres). The discrepancies between these two methods remain unclear. We investigated whether there is a difference between AOPflow and AOPpres when used for mechanically ventilated patients. METHODS: In this single-center retrospective observational study, we included 42 patients who were mechanically ventilated owing to respiratory failure in the intensive care unit of a university hospital between January 2023 and October 2024. AOP was measured using two methods: AOPflow (5 L/min) and AOPpres (2 cmH2O/s). Agreement and correlation between the two methods were evaluated using Bland-Altman plots, Passing-Bablok regression, and Spearman's rank correlation. RESULTS: AOP measured using AOPflow (median: 4.7 cmH2O) was higher than that measured using AOPpres (median: 1.9 cmH2O, P < 0.001). Nevertheless, the two were strongly correlated (ρ = 0.86, P < 0.001) in all patients. The regression equation was y = 1.39x + 0.90 (95% confidence interval [CI] for slope b: 1.20-1.65, 95% CI for intercept a: 0.48-1.64). In patients with AOPflow ≥5cmH2O, AOPflow was moderately correlated with AOPpres (ρ = 0.77, P < 0.001). The regression equation was y = 0.82x + 4.51 (95% CI for slope b: 0.50-1.17, 95% CI for intercept a: 2.57-6.72). The rate of pressure increase from the pressure at the beginning (0 cmH2O) of inflation up to AOPflow was 26.4 cmH2O/s (10.5-30.0) in all patients and was moderately correlated with the difference between AOPflow and AOPpres (ρ = 0.61, P < 0.001). CONCLUSIONS: Systematic biases were observed between AOPflow and AOPpres, with AOPflow tending to yield higher values. However, the physiological significance of the AOP values obtained from each method remains unclear, and caution is needed for clinical application.

BACKGROUND: Postoperative delirium is a common complication associated with prolonged hospitalization, cognitive decline, and increased mortality. Intraoperative hypotension (IOH) is a potential modifiable risk factor for postoperative delirium, but previous studies have shown inconsistent results due to methodological limitations. High-risk surgical patients, particularly those with comorbidities or advanced age, may be especially vulnerable. We evaluated the association between IOH and postoperative ICU delirium within 48 h. METHODS: We conducted a single-center retrospective study of high-risk adult patients who underwent surgery under general anesthesia without cardiopulmonary bypass and were admitted to the ICU between 2017 and 2024. IOH exposure was quantified using the cumulative area where mean arterial pressure (MAP) was below 65 mmHg (hypotension area) and total time under this threshold (hypotension time). Multivariable logistic regression was used to assess the association between IOH and postoperative ICU delirium, adjusting for preoperative comorbidities, intraoperative medications, and anesthetic depth. Subgroup and interaction analyses explored effect modifiers. RESULTS: Among 4798 patients, both hypotension area (OR 1.16, 95% CI 1.05-1.29, P = 0.003) and hypotension time (OR 3.42, 95% CI 1.21-9.65, P = 0.02) were significantly associated with postoperative ICU delirium within 48 h. Subgroup analyses suggested stronger associations in patients with advanced age, higher ASA-PS, inhalational anesthesia, neurosurgery, and intubation at ICU admission. CONCLUSIONS: IOH was significantly associated with postoperative ICU delirium. These findings underscore the importance of vigilant blood pressure management during surgery, particularly in high-risk patients. Interventional studies are needed to confirm these results and guide preventive strategies.

BACKGROUND: The optimal strategy for discontinuing arginine vasopressin and norepinephrine in patients recovering from shock remains uncertain. Although prior studies have suggested a higher risk of hypotension when arginine vasopressin is discontinued first, these findings may have been influenced by baseline imbalances and tapering practices. We conducted a retrospective study to evaluate whether the order of discontinuation between arginine vasopressin and norepinephrine was associated with the incidence of hypotension during the recovery phase of shock, with vasopressor end doses converted to norepinephrine equivalents for analysis. METHODS: This was a single-center retrospective cohort study of intensive care unit patients with shock who received both arginine vasopressin and norepinephrine from August 2017 to March 2024. Patients were categorized based on whether arginine vasopressin or norepinephrine was discontinued first. The primary outcome was the incidence of hypotension within 24 h of vasopressor cessation, defined as mean arterial pressure < 60 mmHg requiring a ≥ 25% increase in the remaining vasopressor, reinstitution of the stopped agent, or a bolus of ≥ 500 mL crystalloid or 25 g albumin. Overlap weighting using propensity scores was applied to adjust for baseline imbalances both in the overall cohort and in the septic shock subgroup. Propensity scores were estimated using logistic model, including baseline characteristics, hemodynamic parameters, and vasopressor end doses in norepinephrine equivalents. RESULTS: A total of 524 patients were analyzed, with 293 discontinuing AVP first and 231 discontinuing NE first. In the unadjusted cohorts, hypotension occurred in 19% of the AVP-first group and 26% of the NE-first group. After overlap weighting, all baseline covariates were balanced between the groups, and the incidence of hypotension was not significantly different (19% vs 21%, P = 0.59). In the septic shock subgroup (n = 267), the weighted analysis showed no significant difference in the incidence of hypotension between groups. CONCLUSIONS: In patients recovering from shock who received both arginine vasopressin and norepinephrine, discontinuing arginine vasopressin first was not associated with a higher risk of hypotension.