The respiratory exchange ratio (RER), defined as the ratio of carbon dioxide (CO2) production to oxygen (O2) consumption, may be a non-invasive and continuously measurable alternative to lactate for identifying patients at risk of postoperative complications that has been examined in non-cardiac surgery. We investigated whether intraoperative RER predicts blood lactate levels and postoperative complications in cardiac surgery. This retrospective cohort study included adult patients undergoing cardiac surgery with cardiopulmonary bypass at Beth Israel Deaconess Medical Center in Boston, USA, between 2008 and 2020. Intraoperative minute-by-minute data of inspired and expired fractions of CO2 and O2 were analyzed. Univariable and a priori-defined multivariable logistic regression models were used to evaluate the association between the median RER during surgery, intraoperative lactate and 7-day major postoperative complications (European Perioperative Clinical Outcome Definitions). 324,646 RER calculations of 4,058 patients were included. 1,745 (43.0

BACKGROUND:Clinicians often administer 100% inspired oxygen (fraction of inspired oxygen [Fio2] = 1) for washout of volatile anaesthetics before tracheal extubation, potentially aggravating atelectasis formation and compromising oxygenation. We evaluated whether lower Fio2 during emergence from anaesthesia reduces atelectasis and improves oxygenation. METHODS:We conducted a single-centre, randomised controlled trial (NCT06538740) in 48 adult participants undergoing elective surgery under general anaesthesia. Participants were randomised to receive either pure oxygen (100%) or lower (70% or 40%) Fio2 for anaesthetic washout before extubation. The primary outcome was atelectasis, assessed as changes in centre of ventilation and end-expiratory lung volume using electrical impedance tomography. RESULTS:Twenty-four participants (mean age 57 [range: 19-82] yr; 42% female) were randomly allocated to receive pure oxygen and 24 received 40% or 70% Fio2. Participants receiving pure oxygen had a more ventral shift in the centre of ventilation (median [IQR], -0.3% [-2.2 to 1.3]), compared with lower Fio2 (1.3% [0.0-2.8]; P=0.041). Participants receiving pure oxygen also had a greater reduction in end-expiratory lung volume after extubation (-1067 [-1839 to -589] ml) compared with participants receiving lower Fio2 (-423 ml [-873 to -53]; P=0.006). There was no difference in end-expiratory lung volume between patients receiving 70% or 40% Fio2 (P=0.39). Spo2 (oxygen saturation measured by pulse oximetry) 10 min after extubation was higher in participants receiving 70% Fio2 (interaction P=0.028). CONCLUSIONS:Avoiding pure oxygen before extubation preserved end-expiratory lung volume with more dorsal distribution of ventilation. Postextubation oxygenation was optimal with 70% Fio2.

Background: Postoperative pneumonia carries substantial mortality. Recent studies showed increased risk under exposure to pollutants. Ambient ozone has been linked to pneumonia-related admissions, yet evidence among adult surgical populations remains limited. Methods: We conducted a retrospective cohort study of adult surgical patients in two countries (2008–2024). Analyses were stratified by admission status: same-day admission patients at Beth Israel Deaconess Medical Center (BIDMC, Boston, U.S.) and inpatients from BIDMC and Peking Union Medical College Hospital (Beijing, China). Residential ozone exposure during the 14 preoperative days was estimated from monitoring stations within ZIP code boundaries. Postoperative pneumonia within seven days was identified using diagnostic codes and chart review. Covariates were adjusted using logistic regression with distributed lag non-linear exposure functions. Findings: A total of 246,668 patients were included (145,398 same-day admissions and 101,270 inpatients). The median ozone concentrations were 61.8 (same-day admission), 52.9 (Boston inpatient), and 57.9 (Beijing inpatient) μg/m3 with pneumonia incidences of 0.7%, 4.2%, and 0.7%, respectively. A higher short-term preoperative ozone exposure was associated with a greater likelihood of developing postoperative pneumonia among same-day admission patients, peaking on the day of surgery (adjusted OR 1.02 per 10 μg/m3, 97.5% confidence interval 1.00–1.04, P = 0.005), attenuating as the lag window increased, and losing significance before preoperative day 5. No association between ozone exposure during the preoperative hospitalization period and postoperative pneumonia was detected among inpatients (pooled adjusted OR 0.98 per 10 μg/m3, 97.5% CI 0.94–1.02; P = 0.22 at lag 0). Interpretation: Higher ambient ozone concentrations within five days before surgery are associated with a higher risk of postoperative pneumonia among adult surgical patients admitted on the day of surgery, but not among patients already hospitalized preoperatively. These findings support recommendations for personal protective strategies before surgery to reduce susceptibility to postoperative pneumonia.

Background For a large variety of surgeries and interventional procedures, monitored anaesthesia care (MAC) can be a viable alternative to general anaesthesia (GA). MAC can avoid risks associated with intubation and deep sedation while increasing the risk of aspiration and intra-procedural respiratory complications due to the lack of a definitive airway. It remains unclear how these competing risks impact postoperative complications and the level of healthcare utilisation after procedures where both approaches are viable options. Methods This retrospective cohort study included adult patients undergoing procedures feasible under MAC and GA at Beth Israel Deaconess Medical Center in Boston, Massachusetts, USA. Advanced postoperative healthcare utilisation (7-day unplanned intensive care unit (ICU) admission, 30-day hospital readmission, or non-home discharge) after MAC versus GA was analysed using multivariable logistic regression adjusted for a priori defined confounders and an inverse probability weighted regression adjustment analysis. Results Among 63,224 included patients, 29,611 (46.8%) patients underwent MAC, and 33,613 (53.2%) underwent GA. 1,714 (2.7%) underwent postoperative ICU admission, 2,678 (4.2%) patients were readmitted, and 3,771 (6.0%) were discharged to a non-home setting. Overall, 7,020 (11.1%) patients required advanced postoperative healthcare utilisation. MAC was associated with a lower risk of advanced postoperative healthcare utilisation (ORadj 0.69;95%CI 0.64 to 0.74;ATEadj -2.3%;95%CI -3.0% to -1.7%; P < 0.001), with 16.6% of this association mediated by lower rates of haemodynamic instability. Conclusions Among procedures where either technique is a viable option, MAC was associated with a lower risk of advanced postoperative healthcare utilisation.

BACKGROUND:A previous large clinical trial demonstrated an increased risk of perioperative stroke with beta blockers initiated just before surgery. This study evaluated the association between long-term beta blocker prescription and ischaemic stroke after noncardiac surgery. METHODS:We conducted a multicentre retrospective study of male and female adults undergoing noncardiac surgery between 2005 and 2021 at two academic healthcare networks in the USA. The primary exposure was long-term beta blocker prescription within 1 yr before surgery. We assessed postoperative ischaemic stroke risk at 30 and 365 days using modified Poisson regression with robust error variances, and conducted effect modification analyses. RESULTS:Long-term beta blocker prescription was associated with an increased risk of postoperative stroke at 30 days (adjusted relative risk [RRadj] 1.26, 95% confidence interval [CI] 1.17-1.36, P<0.001) and 365 days (RRadj 1.22, 95% CI 1.16-1.28, P<0.001). For stroke within 365 days of surgery, this association was amplified in patients with ASA physical status of 1-2 (RRadj 1.96, 95% CI 1.56-2.45, P<0.001) compared with that in patients with ASA physical status of 3-4 (RRadj 1.20, 95% CI 1.15-1.26, P<0.001; P for interaction <0.001). No significant association was observed in patients with severe heart failure. CONCLUSIONS:Long-term beta blocker prescription was associated with increased risk of ischaemic stroke within 30 days and up to 365 days after surgery. No association of beta blocker use and ischaemic stroke risk was observed in patients with severe heart failure, or a history of stroke.

[This corrects the article DOI: 10.1016/j.eclinm.2026.103885.].

BACKGROUND:Inflammatory phenotypes of acute respiratory distress syndrome (ARDS) predict outcomes and can respond differently to treatment strategies. We aimed to establish whether these phenotypes differ in respiratory mechanics and in response to lung-protective ventilation strategies. METHODS:In this retrospective cohort study, data from two cohorts were harmonised. Patients with moderate-to-severe ARDS with oesophageal manometry data from the EPVent-2 trial (14 hospitals across the USA and Canada) and a retrospective cohort at Beth Israel Deaconess Medical Center (Boston, MA, USA) were merged and lung mechanics were compared. Patients had to be aged 18 years or older, have moderate to severe ARDS, and be monitored with oesophageal manometry. To analyse the primary outcome of 60-day mortality after ARDS onset, we used multivariable Cox models for each inflammatory phenotype to study the associations between measures of lung-protective ventilation (driving pressure, transpulmonary driving pressure, and end-expiratory transpulmonary pressure) and 60-day mortality in all patients who had complete data for all variables. FINDINGS:Between Jan 1, 2008, and Jan 31, 2024, 5778 patients were assessed for eligibility (200 in the EPVent-2 cohort and 5578 in the BIDMC cohort). Of these patients, 890 were included in this study cohort (200 from the EPVent-2 trial and 690 from the retrospective cohort), of whom 424 (48%) had the hyperinflammatory phenotype and 466 (52%) had the hypoinflammatory phenotype. 232 (55%) patients in the hyperinflammatory group and 136 (29%) patients in the hypoinflammatory group died within 60 days (p<0·0001). The effects on 60-day mortality were more pronounced among patients with the hypoinflammatory phenotype than the hyperinflammatory phenotype for high respiratory system driving pressure (≥15 cm H2O; adjusted hazard ratio 2·01 [95% CI 1·39-2·91] vs 1·46 [1·11-1·94]; pinteraction=0·033) and high transpulmonary driving pressure (≥12 cm H2O; 2·36 [1·64-3·39] vs 1·18 [0·84-1·60]; pinteraction=0·0010). In addition, having an end-expiratory transpulmonary pressure within plus or minus 2 cm H2O was protective among the hypoinflammatory (0·66 [0·46-0·93]) but not the hyperinflammatory phenotype (0·97 [0·73-1·27]). Excess mortality among the hyperinflammatory phenotype was mediated by extrapulmonary organ failure (proportion mediated 46% [+17 to +79]) but not respiratory failure (0% [-3 to +4]). INTERPRETATION:Our findings suggested that in ARDS, the association between lung-protective mechanical ventilation and 60-day mortality is greater in patients with the hypoinflammatory phenotype than the hyperinflammatory phenotype, therefore patients with hypoinflammatory ARDS could be an important target population for enrichment of future clinical trials. However, our findings do not support different ventilation strategies based on phenotype. Although both phenotypes present with similar lung mechanics, extrapulmonary organ failure is the key driver of excess mortality among patients with the hyperinflammatory phenotype. FUNDING:Société Française d'Anesthésie-Réanimation, the University Hospital of Montpellier, Philippe Foundation, the Department of Anesthesia at Beth Israel Deaconess Medical Center, and Jeffrey and Judy Buzen.

INTRODUCTION:Dexmedetomidine can attenuate delirium in patients who are critically ill, but evidence with regards to its preventive effect on postoperative delirium remains equivocal. We hypothesised that the risk of delirium after intra-operative dexmedetomidine administration varies depending on the dose administered and aimed to identify the optimum dose to mitigate delirium. METHODS:We included 114,786 adults undergoing general anaesthesia for non-cardiac, non-transplant surgery. Primary exposure was intra-operative dexmedetomidine dose in cumulative μg.kg-1 body weight, dichotomised into high vs. low dose based on the cohort median (0.49 μg.kg-1). Primary outcome was delirium within 7 days, identified from discharge notes, Confusion Assessment Method assessments and diagnostic codes. RESULTS:A total of 4804 (4.2%) patients received dexmedetomidine, with a median (IQR [range]) cumulative dose of 0.49 (0.28-0.84 [0.01-2.50]) μg.kg-1. Postoperative delirium occurred in 3227 (2.8%) patients. Compared with no dexmedetomidine, the risk of delirium was lower in patients receiving low doses (≤ 0.49 μg.kg-1) of dexmedetomidine (adjusted odds ratio 0.61, 95%CI 0.44-0.85, p = 0.004), but not among those receiving high doses (> 0.49 μg.kg-1) (adjusted odds ratio 1.06, 95%CI 0.84-1.34, p = 0.62). Fractional polynomial regression analyses suggested that doses between 0.25 μg.kg-1 and 0.35 μg.kg-1 were associated with the lowest delirium risk. Threshold regression and restricted cubic splines confirmed these findings. DISCUSSION:Low, but not high, dose dexmedetomidine administration was associated with lower risks of delirium, with optimal doses ranging between 0.25 μg.kg-1 and 0.35 μg.kg-1.

Low tidal volume (Vt) ventilation is the standard of care among critically ill patients. Guidelines recommend scaling Vt to the predicted body weight (PBW) to avoid ventilator-induced lung injury (VILI). Concerns exist that the PBW overestimates lung volumes of critically ill females. We investigated whether this applies to clinically relevant measures of lung volume, whether PBW-guided mechanical ventilation yields comparable risk of lung stress among male and female patients, and whether this affects mortality. Mechanically ventilated, critically ill patients from ten randomized trials and two real-world retrospective clinical datasets were analyzed. Risk of high driving pressures (≥ 15 cmH2O) at comparable Vt/kg PBW as well as measures of anatomical and functional lung sizes, including computed tomography-measured lung volumes at the same PBW were compared between female and male patients. Among 30,516 patients (39.4

Background:Postoperative delirium is a frequent, serious complication triggered by various factors including systemic inflammation. Dexamethasone, an inexpensive anti-inflammatory steroid frequently administered for prophylaxis of postoperative nausea and vomiting, attenuates inflammation. We hypothesised that intraoperative dexamethasone administration is associated with a lower risk of postoperative delirium and assessed whether this is modified by the occurrence of its key side effect, hyperglycaemia. Methods:This retrospective cohort study analysed electronic health data from adult hospitalised patients undergoing non-cardiac, non-neurosurgical, and non-transplant procedures at Beth Israel Deaconess Medical Center (Boston, MA, USA) between January 1, 2008, and January 15, 2024. Patients with missing data, preoperative delirium or glucocorticoid use, mechanical ventilation for 72 h or more, and those not expected to survive without the procedure, were excluded. The primary exposure was intraoperative administration of intravenous dexamethasone. The primary outcome was 7-day postoperative delirium, identified by keyword-triggered manual discharge note reviews, diagnostic codes, and the Confusion Assessment Method. Hyperglycaemia was defined as peak 24-h postoperative blood glucose of more than 180 mg/dL. All analyses were adjusted for 43 patient-related and procedure-related variables. Findings:92,832 patients were included (55.8% female, median age 60 years [IQR 48-70]), of which 41,983 (45.2%) received dexamethasone at a median dose of 8 mg (IQR 4-8). 2575 (2.8%) patients developed postoperative delirium. Emergency procedures accounted for 11,970 (12.9%) of cases. Intraoperative administration of dexamethasone was associated with a lower risk of delirium (adjusted odds ratio [aOR] 0.63, 95% CI 0.56-0.70; p < 0.001; adjusted absolute risk difference -1.1%, 95% CI -1.3 to -0.8). The exploratory four-way mediation analysis suggested a 10.4% greater dexamethasone-associated reduction of postoperative delirium risk when hyperglycaemia did not occur (no hyperglycaemia aOR 0.59, 95% CI 0.51-0.67; p < 0.001; hyperglycaemia aOR 0.85, 95% CI 0.68-1.07; p = 0.17). Interpretation:Intraoperative dexamethasone administration is associated with a lower risk of postoperative delirium, although this association was not evident in patients experiencing hyperglycaemia. Prospective studies should investigate the role of dexamethasone and optimised blood glucose control in delirium prevention. Funding:Unrestricted philanthropic grant by Dr. J. and J. Buzen.

Study objective:Evaluate the national burden, predictors, and causes of 90-day readmission following coronary artery bypass grafting (CABG), and to examine temporal trends and demographic disparities in readmission risk. Design:Retrospective cohort study. Setting:United States hospitals participating in the Nationwide Readmissions Database. Participants:Adult patients (≥18 years) undergoing isolated CABG between 2016 and 2022 were identified using ICD-10 codes. Patients who died during the index hospitalization, underwent concomitant valve surgery were excluded. Main outcome measures:The primary outcome was all-cause 90-day readmission. Secondary outcomes included 30-day readmission, in-hospital complications, and causes of 90-day readmission. Results:Among 681,833 patients undergoing isolated CABG, 111,024 (16.3%) were readmitted within 90 days; notably, 36% occurred between 31 and 90 days after discharge. Heart failure was the leading cause of readmission (13.6%), followed by infection (6.7%), coronary artery disease-related diagnoses (6.7%), and atrial fibrillation (4.1%). Readmitted patients had higher rates of perioperative complications, including acute renal failure (28% vs 17%), respiratory failure (26% vs 17%), pneumonia (7% vs 3%), and transfusion (18% vs 12%). Independent predictors included female sex (adjusted odds ratio [aOR] 1.38), age ≥ 85 years (aOR 1.27), congestive heart failure (aOR 1.46), diabetes with complications (aOR 1.38), peripheral vascular disease (aOR 1.39), chronic kidney disease (aOR 1.30), and chronic obstructive pulmonary disease (aOR 1.34). Risk-adjusted readmission rates remained consistently higher among women across all age groups, with age-related patterns differing by sex. Conclusion:Our findings suggest that reliance on 30-day metrics may underestimate postoperative morbidity and highlight opportunities for extended post-discharge surveillance and complication prevention.

BACKGROUND:Intraoperative dexamethasone is routinely administered to prevent postoperative nausea and vomiting. Limited research has investigated dexamethasone safety during pancreatectomy. We investigated whether intraoperative dexamethasone administration affects clinically relevant postoperative pancreatic fistula (CR-POPF) development. METHODS:We performed a retrospective cohort study of patients undergoing pancreatoduodenectomy or distal pancreatectomy at a single academic institution (2014-2021). Impact of dexamethasone administration on CR-POPF (ISGPF Grade B/C) was assessed using multivariable logistic regression and inverse probability weighted regression analysis. RESULTS:503 patients were included (pancreatoduodenectomy n=307; distal pancreatectomy n=196). Of these, 59 (11.7%) received low-dose dexamethasone (4-6 mg) and 100 (19.9%) received high-dose dexamethasone (8-10 mg). High dose dexamethasone (aOR:2.47, 95% CI:1.40-4.36), but not low dose dexamethasone (aOR:1.32, 95% CI:0.61-2.86), was associated with increased odds of CR-POPF. After inverse probability weighted regression adjustment, the average treatment effect of high dose dexamethasone on CR-POPF was +11.1% (95% CI:1.7-20.3%) above the baseline risk of 12.5% (95% CI:9.0-16.1%) in patients receiving no dexamethasone. DISCUSSION:Intraoperative administration of high dose (8-10mg) dexamethasone was associated with a meaningfully increased risk of CR-POPF after pancreatectomy. High-dose dexamethasone is a modifiable risk factor for CR-POPF and should be avoided unless there is clear clinical indication.