BACKGROUND: Anesthetic agents or some pathophysiological conditions can affect transcranial motor evoked potentials (TcMEP) monitoring. However, the influence of depth of anesthesia on TcMEP reproducibility in youth rema...BACKGROUND: Anesthetic agents or some pathophysiological conditions can affect transcranial motor evoked potentials (TcMEP) monitoring. However, the influence of depth of anesthesia on TcMEP reproducibility in youth remains unclear due to limited data. We tested the hypothesis that a deeper level of total intravenous anesthesia (TIVA) can affect surgeon-directed TcMEP reproducibility and the surgical team's interpretation of TcMEP. METHODS: We conducted a single-center, prospective before-and-after study in 150 youths undergoing TIVA for scoliosis surgery with surgeon-directed TcMEP. A combination of propofol and remifentanil was administered to all patients. TIVA was initially maintained at a set bispectral index (BIS) level: mean (range) 60 (55-65) (BIS60). We deepened the anesthesia to a set BIS level: mean (range) of 40 (55-65) (BIS40) before the skin incision. The surgical team recorded and interpreted TcMEP at both BIS levels. The primary outcome was the effect of anesthesia depth (BIS60 vs BIS40) on TcMEP reproducibility and the surgical team's interpretation. The secondary outcome was to compare changes in relativized TcMEP parameters (amplitude and latency) as a percentage at different levels of anesthesia (BIS60 vs BIS40). RESULTS: Surgeons successfully recorded and interpreted TcMEP in all patients on both levels of depth of anesthesia. The mean ± standard deviation TcMEP amplitudes and latencies at BIS40 were statistically significantly different from the initial TcMEP parameters at BIS60 78.7% ± 15.0 (P < .001) for amplitudes, and 102.7% ± 2.9 (P < .001) for latencies. However, these alterations did not affect the surgical team's interpretation of TcMEP and were therefore not clinically significant. CONCLUSIONS: Keeping TIVA within the recommended BIS mean (range) of 40 to 60 (35-65) did not affect TcMEP reproducibility or surgeons' interpretation of TcMEP. Surgeon-directed TcMEP, along with appropriate depth of anesthesia, may represent a promising alternative when neurophysiologists are unavailable.
BACKGROUND: During one-lung ventilation (OLV) with low tidal volumes, asymmetric intrathoracic pressures may blunt the cardiopulmonary interactions on which conventional dynamic indices rely, limiting their usefulness fo...BACKGROUND: During one-lung ventilation (OLV) with low tidal volumes, asymmetric intrathoracic pressures may blunt the cardiopulmonary interactions on which conventional dynamic indices rely, limiting their usefulness for guiding fluid therapy. The positive end-expiratory pressure (PEEP) test, a reduction in PEEP to augment venous return, has been proposed as a fluid-free assessment of preload responsiveness in mechanically ventilated patients. However, whether its diagnostic performance is retained during OLV is unknown. We therefore hypothesized that the stroke-volume change (ΔSVPEEP test) induced by the PEEP test would predict fluid responsiveness during OLV. METHODS: We conducted a single-center prospective interventional study (June to September 2024) in adults undergoing elective lung resection requiring OLV. The primary objective was to evaluate the diagnostic accuracy of the ΔSVPEEP test for predicting fluid responsiveness. Secondary objectives were to assess the diagnostic performance of the PEEP test-induced change in mean arterial pressure (ΔMAPPEEP test) and baseline stroke volume variation (SVV), and to compare their predictive abilities. After stabilization using OLV (PEEP 10 cm H2O) but before skin incision (closed-chest conditions), baseline hemodynamics were recorded; stroke volume (SV) was measured by arterial pulse-contour analysis. PEEP was then reduced from 10 to 0 cm H2O, and variables were re-measured. Subsequently, a 15° head-down tilt (Trendelenburg) served as an autotransfusion challenge; patients with ≥10% SV increase were classified as responders. Receiver operating characteristic (ROC) analysis was used to assess the predictive ability of each index. A gray-zone analysis was performed for the ΔSVPEEP test to delineate the range of diagnostic uncertainty. RESULTS: Of 43 patients screened, 38 were analyzed; 18 (47%) were responders. ΔSVPEEP test was larger in responders than in nonresponders (16.7% ± 8.9 vs 4.6% ± 4.3; P < .0001). ΔSVPEEP test predicted fluid responsiveness with an area under the ROC curve (AUC) of 0.95 (95% confidence interval [CI], 0.82-0.99; P < .0001), and the optimal cutoff of 8.6% yielded 94.4% sensitivity (95% CI, 72.7-99.9) and 80.0% specificity (95% CI, 56.3-94.3). ΔMAPPEEP test showed an AUC of 0.84 (95% CI, 0.68-0.94; P < .0001), whereas SVV was not predictive (AUC 0.64, 95% CI, 0.47-0.79; P = .12). The gray zone for the ΔSVPEEP test was 3.6% to 12.5%, comprising 14 of 38 (36.8%) of patients. CONCLUSIONS: During OLV, the relative increase in SV elicited by the PEEP test predicted fluid responsiveness as defined by the Trendelenburg maneuver. This simple, fluid-free maneuver may assist intraoperative fluid management during thoracic anesthesia.
BACKGROUND: Large language models (LLMs) show promise for perioperative decision support, but persistent issues, including hallucinations, miscalibration, and biases, indicate they require rigorous evaluation before clin...BACKGROUND: Large language models (LLMs) show promise for perioperative decision support, but persistent issues, including hallucinations, miscalibration, and biases, indicate they require rigorous evaluation before clinical use. As LLM adoption increases in perioperative settings, systematic evaluation is needed to determine how patient and surgical factors affect performance. METHODS: We evaluated five general-purpose LLMs (DeepSeek 3.2, Gemini 2.5 Flash, GPT-5, GPT-5 mini, GPT-5 nano) using 216 standardized hip fracture surgery vignettes crossing six surgery types, two sexes, and 18 patient variables. We generated 50 samples per combination for 54,000 total responses and collected both structured recommendations and free-text justifications. We used logistic regression to estimate effects on three primary outcomes: anesthesia type, peripheral nerve block placement, and arterial line placement. In a limited sensitivity analysis, we evaluated two clinical LLMs (OpenEvidence, Doximity GPT) with 36 responses each. RESULTS: All models favored neuraxial over general anesthesia (76.1%-88.6% of responses), and all but DeepSeek 3.2 appropriately adjusted recommendations for relevant medical contraindications. All models except GPT-5 nano recommended preoperative peripheral nerve blocks (92.6%-99.3%) and were appropriately conservative regarding arterial line placement. However, free-text justifications frequently cited neuraxial benefits unsupported by recent randomized trials, and most models issued strong neuraxial recommendations despite a lack of clinical justification. We identified limited sociodemographic biases, with only one significant and clinically meaningful effect across 150 comparisons. Clinical LLMs provided similar recommendations to general-purpose models. CONCLUSIONS: While LLMs provided generally reasonable recommendations, systematic preferences diverging from contemporary evidence suggest uncritical use could shift practice patterns without improving patient outcomes.
Vasoplegia is a form of distributive shock that commonly occurs after cardiac surgery involving cardiopulmonary bypass. Although a formal definition does not exist, it is generally characterized by low systemic vascular...Vasoplegia is a form of distributive shock that commonly occurs after cardiac surgery involving cardiopulmonary bypass. Although a formal definition does not exist, it is generally characterized by low systemic vascular resistance with a maintained or elevated cardiac index that tends to be resistant to treatment with fluid or vasopressor. Postoperative vasoplegia in cardiac surgery patients is associated with increased morbidity and mortality. This article reviews the current understanding of the pathophysiology of vasoplegia in cardiac surgery, including risk factors for its development, and evolving strategies for prediction, diagnosis, and treatment. Prominent preoperative risk factors include patient demographics (older age, male sex, elevated body mass index), comorbid conditions (heart failure with reduced ejection fraction, chronic kidney disease, anemia, infective endocarditis, hemodynamic instability, thyroid dysfunction, diabetes mellitus, tobacco use), medications (renin-angiotensin-aldosterone axis blockers, calcium channel blockers, beta-blockers, inotropes, antiplatelets and anticoagulants, amiodarone, diuretics, anesthetic agents), and the type of surgical procedure performed. Prominent intraoperative risk factors include the use of cardiopulmonary bypass, blood product transfusion, and poor temperature control. Multiple biomarkers and dynamic monitoring systems are being studied as predictors for the development of vasoplegia. An overview of available treatments is presented along with up-to-date evidence supporting their use in multimodal vasopressor regimens.
BACKGROUND: Cannabidiol (CBD) inhibits voltage-gated sodium channels (Nav). CBD is highly lipophilic and exhibits slow binding kinetics on Navs, a property that may enable CBD to enhance and prolong regional anesthesia....BACKGROUND: Cannabidiol (CBD) inhibits voltage-gated sodium channels (Nav). CBD is highly lipophilic and exhibits slow binding kinetics on Navs, a property that may enable CBD to enhance and prolong regional anesthesia. Here we explored the effects of CBD on lidocaine-induced Nav-inhibition and neurotoxicity. METHODS: Patch clamp recordings were performed on tetrodotoxin (TTX)-sensitive Navs and the TTX-resistant Nav1.8 in ND7/23 cells or murine dorsal root ganglion neurons (DRG). Cytotoxicity was analyzed using flow cytometry. RESULTS: CBD induced a potent tonic inhibition of sodium currents with slow onset and offset kinetics. Nav1.8 exhibited a higher sensitivity to tonic block (IC50 1.4 µM) as compared to TTX-sensitive sodium channels (IC50 2.9 µM). Similar to local anesthetics, CBD also induced a shift of the steady-state inactivation and a modest use-dependent block at 10 Hz. In contrast to local anesthetics, inhibition of Navs by CBD is pH-independent. The co-application of CBD and lidocaine resulted in an additive tonic block of sodium currents in ND7/23 cells, but not in DRG neurons. While only high concentrations of CBD induced cytotoxicity, it potentiated lidocaine-induced cytotoxicity. CONCLUSIONS: CBD demonstrates promising characteristics as a long-lasting local anesthetic, or as an adjunct to local anesthetics used for regional or topical anesthesia.
BACKGROUND: In patients with anticipated difficult airways, suboptimal airway management may increase perioperative morbidity and mortality. Combining video laryngoscopy (VL) with a flexible intubation scope (FIS) has be...BACKGROUND: In patients with anticipated difficult airways, suboptimal airway management may increase perioperative morbidity and mortality. Combining video laryngoscopy (VL) with a flexible intubation scope (FIS) has been shown to enhance visualization and facilitate endotracheal tube passage in patients with known or anticipated difficult airways. To date, randomized evidence supporting this approach remains limited. METHODS: In this prospective, randomized trial, 135 adults with anticipated difficult airways undergoing elective surgery were randomized 1:1 to intubation with FIS alone or a combined technique using FIS with VL (FIS/VL). The primary end point was the composite rate of difficult endotracheal tube (ETT) placement, defined by one or more of the following: (1) first-attempt intubation time >60 seconds; (2) failure to intubate on the first attempt; or (3) provider assessment of the intubation process as difficult. Provider-rated ease of intubation was recorded immediately following the procedure by the anesthesiologist performing the intubation using a 5-point Likert scale. Scores of 1 (extremely easy), 2 (somewhat easy), and 3 (resistance to tube advancement) were classified as Not Difficult, whereas scores of 4 (difficult) and 5 (unsuccessful) were classified as Difficult/Unsuccessful. For analysis and reporting, the Likert-scale ratings were dichotomized into a binary outcome (Not Difficult vs Difficult/Unsuccessful). The secondary outcome was total intubation time. RESULTS: A total of 144 patients were screened and enrolled, and 135 patients were randomized. Of these, 66 patients were assigned to the FIS/VL arm and 69 patients to the FIS arm. Among the 135 randomized patients, 128 provided analyzable data for the composite primary end point. Overall, the first-pass success rate was 54/58 (93.1%) in the FIS/VL group versus 50/64 (78.1%) in the FIS group; P = .020. Intubation time greater than 60 seconds was similar between groups (33/66 [52.4%] in the FIS arm vs 24/61 [39.3%] in the FIS/VL arm; P = .145). Provider-rated ease of intubation considered difficult or unsuccessful occurred in 4/64 (6.1%) of FIS/VL compared to 13/67 (19.4%) of FIS cases (P = .025). Among the 128 evaluable patients (61 FIS/VL, 67 FIS), the composite primary end point- difficult ETT placement defined as (1) first-attempt intubation time >60 seconds, (2) failure on first attempt at intubation, or (3) provider-rated difficult intubation occurred in 28/61 (45.9%) of FIS/VL versus 40/67 (59.7%) of FIS cases [Risk difference (95% CI) = -0.14 (-0.31 to 0.03); P = .118]. CONCLUSIONS: In adults with anticipated difficult airways, adding VL to FIS did not significantly reduce the composite rate of difficult ETT placement, although it was associated with fewer repeat attempts and fewer provider-rated difficult/unsuccessful intubations. These findings support the clinical value of dual-visualization strategies to improve first-pass performance metrics, whereas larger trials are needed to determine their effect on composite difficulty end points.
BACKGROUND: Prematurity and anemia are common and clinically significant risk factors among neonates undergoing surgery. However, the burden of postoperative mortality associated with their combined effects remains unqua...BACKGROUND: Prematurity and anemia are common and clinically significant risk factors among neonates undergoing surgery. However, the burden of postoperative mortality associated with their combined effects remains unquantified. We aimed to determine the proportion of neonatal postoperative mortality attributable to their synergistic interaction. METHODS: We conducted a retrospective cohort study using the ACS NSQIP-P database to identify neonates (≤28 days) who underwent noncardiac inpatient surgery between 2012 and 2023. Prematurity was defined as gestational age <37 weeks, and anemia as preoperative hematocrit <40%. Neonates were grouped by prematurity and anemia status. Propensity score weighting was used to adjust for confounding. Robust Poisson regression estimated adjusted relative risks (aRR) for 30-day mortality. Additive interaction was evaluated using the relative excess risk due to interaction (RERI), attributable proportion (AP), and synergy index (SI). RESULTS: Among 29,281 neonates, 9.7% (n=2853) were both preterm and anemic. Overall, 30-day postoperative mortality was 3.2% (932/29,281), highest among preterm anemic neonates (12.1%; 344/2853). Compared to full-term, nonanemic neonates, the aRR for mortality was 1.66 (95% CI, 1.31-2.10; P <.001) for full-term anemic, 2.94 (95% CI, 2.42-3.58; P <.001) for preterm nonanemic, and 4.63 (95% CI, 3.80-5.64; P <.001) for preterm anemic neonates. RERI was 1.03 (95% CI, 0.29-1.77; P = 0.01), AP was 0.22 (95% CI, 0.08-0.37; P <.01), and SI was 1.40 (95% CI, 1.09-1.79; P = 0.01), indicating significant synergy. CONCLUSIONS: Prematurity and preoperative anemia synergistically increase the risk of postoperative mortality in neonates. These findings support targeted preoperative optimization and improved perioperative risk stratification in this high-risk population.
BACKGROUND: Oxytocin is the most widely used uterotonic for postpartum hemorrhage prevention, yet high-quality data comparing bolus versus infusion administration are limited. Given the very high uterine blood flow at te...BACKGROUND: Oxytocin is the most widely used uterotonic for postpartum hemorrhage prevention, yet high-quality data comparing bolus versus infusion administration are limited. Given the very high uterine blood flow at term, rapid achievement of uterine tone is critical to minimize blood loss. We hypothesized that bolus administration leads to a greater likelihood of attaining adequate uterine tone at 2 minutes. METHODS: In this randomized, double-blinded clinical trial, 121 patients undergoing elective cesarean delivery under spinal anesthesia were randomized 1:1 to receive oxytocin by bolus or infusion after cord clamping. Masked study drugs were prepared by the investigational pharmacy to maintain blinding of the anesthesiologist, obstetrician, and study personnel. The primary end point was adequate uterine tone at 2 minutes. Secondary end points included patient satisfaction, time to adequate uterine tone, quantitative blood loss, postpartum hemorrhage (blood loss greater than 1000 mL), and safety measures (heart rate, blood pressure, phenylephrine dose, chest pain, nausea/vomiting, additional uterotonic use, and intensive care unit admission). RESULTS: Of 121 patients enrolled, 115 were analyzable (6 screen failures received no study drug); 114/115 received oxytocin per protocol. Baseline characteristics were similar between groups. Adequate uterine tone at 2 minutes (primary end point) was similar in bolus (50/60, 83.3%) vs infusion (43/55, 78.2%), P = .483. Patient satisfaction scores were also not significantly different (P = .495) between the two arms, with both the bolus and infusion arms having medians and interquartile range (IQRs) of (10 [IQR 10-10]). Median blood loss was slightly lower with bolus (558 mL [IQR 429-733]) vs infusion (687 mL [IQR 480-826], P = .0438; Hodges-Lehmann estimate of 82 mL [95% confidence interval {CI}, 2-168 mL]). Phenylephrine dosage and rates of postpartum hemorrhage, nausea, and additional uterotonic use were similar between groups (all P > .28). Rates of postpartum hemorrhage, hypotension, phenylephrine use, nausea, and additional uterotonic use were similar. CONCLUSIONS: There was no statistically significant difference in the frequency of achieving adequate uterine tone at 2 minutes between oxytocin given by infusion or bolus. Although the bolus group demonstrated statistically lower blood loss, the magnitude of this difference was small (upper confidence limit of 168 mL) and is unlikely to be clinically significant. Both methods showed comparable safety profiles.
BACKGROUND: Anesthetic adjuvants used in multimodal analgesia-including intravenous lidocaine, dexmedetomidine, or intrathecal morphine (ITM)-may differentially affect immune responses and metastasis-related pathways in...BACKGROUND: Anesthetic adjuvants used in multimodal analgesia-including intravenous lidocaine, dexmedetomidine, or intrathecal morphine (ITM)-may differentially affect immune responses and metastasis-related pathways in colorectal cancer surgery. Their comparative effects on these pathways remain poorly understood. METHODS: In this prospective, randomized, patient- and assessor-blinded trial, adults undergoing elective laparoscopic or robotic colorectal cancer resection were allocated to receive intravenous lidocaine, dexmedetomidine, or ITM. The primary outcome was plasma matrix metalloproteinase-9 (MMP-9) concentration at 1 hour postoperatively. Secondary outcomes included other metastasis-promoting biomarkers (MMP-2, VEGF, IL-6), immune cell subsets (T and NK cells), and CD39/CD73 expression on T lymphocytes at 1 hour postoperatively and postoperative day 1. Clinical outcomes-including pain scores, opioid consumption, and complications-were also assessed. RESULTS: Of the 114 enrolled patients, 109 completed the study and were analyzed (ITM group = 37, DEX group = 34, LIDO group = 38). Overall group × time interaction was significant for MMP-9 (P = .028). At 1 hour, MMP-9 was higher in LIDO group than in the DEX group (difference on the log scale, 0.333; 95% confidence interval [CI], 0.0642-0.601; P = .009) and in the ITM group (0.424; 95% CI, 0.0248-0.823; P = .033). The DEX group was associated with increased CD73+CD8+ T cells compared with the LIDO group (difference on the logit scale: 0.669; 95% CI, 0.000987-1.34; P = .050), and with decreased CD39-CD73-CD8+ T cells compared with the ITM group (-0.695; 95% CI, -1.3 to -0.0908, P = .018) and the LIDO group (-0.645; 95% CI, -1.24 to -0.05, P = .029). The ITM group was associated with lower dynamic pain scores than the other groups. Rescue antiemetic use was less frequent with the DEX group, whereas other adverse events were mild and comparable across groups. CONCLUSIONS: Anesthetic adjuvants exerted differential effects on perioperative biomarkers and immune profiles relevant to tumor progression. Compared with the other groups, lidocaine was associated with higher MMP-9 levels, dexmedetomidine with relative shifts toward an immunosuppressive T-cell phenotype, and intrathecal morphine with superior analgesia with minimal immune impact. Further studies are warranted to determine whether multimodal analgesia strategies influence long-term oncologic outcomes.
BACKGROUND: The Non-Operating Room Anesthesia (NORA) Safety Project is an exploratory prospective cohort study examining the incidence of near-miss events in NORA settings. While adverse events are typically well capture...BACKGROUND: The Non-Operating Room Anesthesia (NORA) Safety Project is an exploratory prospective cohort study examining the incidence of near-miss events in NORA settings. While adverse events are typically well captured because of quality improvement programs that exist in most major health settings, near-miss events are often not documented, and safety standards are not well established. We present the results of a dedicated forum for near-miss reporting, including the incidence and type of near-miss events, as a first step toward understanding NORA near misses. By providing granular data from a highly engaged audience, we aimed to highlight evidence-backed opportunities for improving safety culture in the procedural landscape. METHODS: We surveyed all in-hospital NORA cases excluding pediatrics, those performed in the intensive care unit, or the peri-partum areas. The day of data collection was rotated weekly. Providers surveyed included anesthesiologists, nurse anesthetists, and anesthesiology residents. REDCap survey was sent via secure e-mail. If a near-miss event occurred, respondents were asked to classify their events in the following categories: patient, provider, and/or environment. RESULTS: Over a 42-week period, 1383 completed surveys were received in which 90 near-miss events were reported. Filtering for near misses reported on study data collection days and removing voluntary near misses from our total survey responses, our incidence rate was 3.22% (43/1336). The top near-miss locations were the magnetic resonance imaging suite (21/90 [23.3%]) and both neuro and body interventional radiology suites (15/90 [16.7%] and 11/90 [12.2%], respectively). The top near-miss category was environmental concerns (75/90 [83.3%]), and top subcategory was poor group dynamics (31/90 [34.4%]). Significant characteristics in the near-miss patients included older age (mean [±standard deviation {SD}] 60.8 [±16.9] vs 56.8 [±17.3] years [ P = .03]), male (52/90, 57.8% vs 586/1293, 45.3% [ P = .03]), higher American Society of Anesthesiologists (ASA) physical status (III and IV 65/90, 72.2% [ P < .001]), longer procedure (119.8 ± 108.9 minutes vs 63.1 ± 72.2 minutes [ P < .001]), emergent procedures (28/90, 31.1% vs 159/1293, 12.3% [ P < .001]), and involvement of resident providers (36/90, 40.0% vs 234/1293, 18.1% [ P < .001]). A Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression model confirmed a statistically significant relationship between the presence of a resident provider and near-miss events (odds ratio: 2.38 [ P = .02]). CONCLUSIONS: The NORA landscape is often remote in location, not as well-staffed or well-resourced, and with variable setups. With a systematic survey, we were able to capture near-miss events which would otherwise have been lost. These near-miss events cannot be evaluated in isolation. Future direction should focus on a systems-wide approach in safety surveillance that facilitates multidisciplinary collaboration and reporting. Our findings demonstrate near misses as an opportunity-to improve in-hospital access to care, promote quality assurance, and ultimately, make NORA a safer place.
BACKGROUND: Robotic-assisted laparoscopic surgery (RALS) in a steep Trendelenburg position creates conditions conducive to cyclical alveolar collapse when using standard lung protective ventilation settings (LPV). The ma...BACKGROUND: Robotic-assisted laparoscopic surgery (RALS) in a steep Trendelenburg position creates conditions conducive to cyclical alveolar collapse when using standard lung protective ventilation settings (LPV). The magnitude of force induced by alveolar collapse and expansion is predicted to cause a localized injury, but biological evidence of perioperative atelectrauma is lacking. We hypothesized that the negative transpulmonary pressures and increased dissipated power of ventilation encountered during RALS lead to injury of the dependent (apical) lung despite the use of LPV settings. METHODS: We conducted a single-center, observational study of lung mechanics and injury in 15 subjects (8 M/7F; mean ± standard deviation: 59.5 ± 7.4 years) without lung disease undergoing RALS with LPV at an academic hospital in the United States. Subjects had a median body mass index of 32.5 kg/m2 with a range of 24.3 to 50.9 kg/m2. We continuously measured lung mechanics, including transpulmonary pressures. Bronchoalveolar lavages (BAL) were obtained from apical and anteromedial subsegments after intubation and from contralateral subsegments before extubation. During RALS, the apical lung is dependent and the anteromedial lung in nondependent. BAL analyses included total protein concentrations, proteomics, lipidomics, and leukocyte counts. RESULTS: Lung mechanics were impaired, with elevated respiratory elastance and driving pressures, and negative end-expiratory transpulmonary pressures, despite standard LPV settings (tidal volume 7.0 ± 0.8 mL/kg ideal body weight; positive end-expiratory pressure 8.7 ± 3.4 cm H2O). Increases in total protein (median [interquartile range], 131 [27-193] µg/mL), extracellular matrix components (fibulin-1: 2.1 [1.6-4.0] fold; microfibril-associated glycoprotein-4: 2.2 [1.3-4.0] fold), and procoagulants (prothrombin: 1.7 [1.3-4.8] fold; plasminogen: 3.2 [1.9-4.5] fold) were observed in apical BAL after surgery (adj. P < .001 for all), but not in anteromedial BAL (adj. P > .05). No differences in percent leukocyte composition were observed among lavages (P > .287 for all cell types). Phosphatidylglycerol abundance was increased in apical BAL after surgery in unadjusted analyses (5.8 [1.9-7.9] %, P = .021), but no changes in phospholipid abundance were noted in adjusted analysis. Increases in apical BAL total protein were positively correlated with the dissipated mechanical power of ventilation (r2 = 0.434, P = .014). CONCLUSIONS: In this focused biomechanical study, we found molecular evidence for alveolar-capillary damage in the dependent apical lobes, consistent with localized atelectrauma. Regional atelectrauma from impaired lung mechanics can occur in the positionally dependent lung while using LPV settings during RALS, most likely from insufficient end-expiratory pressure.