Determinants of acute kidney injury during high-power mechanical ventilation: secondary analysis from experimental data.

BACKGROUND: The individual components of mechanical ventilation may have distinct effects on kidney perfusion and on the risk of developing acute kidney injury; we aimed to explore ventilatory predictors of acute kidney failure and the hemodynamic changes consequent to experimental high-power mechanical ventilation. METHODS: Secondary analysis of two animal studies focused on the outcomes of different mechanical power settings, including 78 pigs mechanically ventilated with high mechanical power for 48 h. The animals were categorized in four groups in accordance with the RIFLE criteria for acute kidney injury (AKI), using the end-experimental creatinine: (1) NO AKI: no increase in creatinine; (2) RIFLE 1-Risk: increase of creatinine of > 50%; (3) RIFLE 2-Injury: two-fold increase of creatinine; (4) RIFLE 3-Failure: three-fold increase of creatinine; RESULTS: The main ventilatory parameter associated with AKI was the positive end-expiratory pressure (PEEP) component of mechanical power. At 30 min from the initiation of high mechanical power ventilation, the heart rate and the pulmonary artery pressure progressively increased from group NO AKI to group RIFLE 3. At 48 h, the hemodynamic variables associated with AKI were the heart rate, cardiac output, mean perfusion pressure (the difference between mean arterial and central venous pressures) and central venous pressure. Linear regression and receiving operator characteristic analyses showed that PEEP-induced changes in mean perfusion pressure (mainly due to an increase in CVP) had the strongest association with AKI. CONCLUSIONS: In an experimental setting of ventilation with high mechanical power, higher PEEP had the strongest association with AKI. The most likely physiological determinant of AKI was an increase of pleural pressure and CVP with reduced mean perfusion pressure. These changes resulted from PEEP per se and from increase in fluid administration to compensate for hemodynamic impairment consequent to high PEEP.

Causes of Hypoxemia in COVID-19 Acute Respiratory Distress Syndrome: A Combined Multiple Inert Gas Elimination Technique and Dual-energy Computed Tomography Study.

BACKGROUND: Despite the fervent scientific effort, a state-of-the art assessment of the different causes of hypoxemia (shunt, ventilation-perfusion mismatch, and diffusion limitation) in COVID-19 acute respiratory distress syndrome (ARDS) is currently lacking. In this study, the authors hypothesized a multifactorial genesis of hypoxemia and aimed to measure the relative contribution of each of the different mechanism and their relationship with the distribution of tissue and blood within the lung. METHODS: In this cross-sectional study, the authors prospectively enrolled 10 patients with COVID-19 ARDS who had been intubated for less than 7 days. The multiple inert gas elimination technique (MIGET) and a dual-energy computed tomography (DECT) were performed and quantitatively analyzed for both tissue and blood volume. Variables related to the respiratory mechanics and invasive hemodynamics (PiCCO [Getinge, Sweden]) were also recorded. RESULTS: The sample (51 ± 15 yr; Pao2/Fio2, 172 ± 86 mmHg) had a mortality of 50%. The MIGET showed a shunt of 25 ± 16% and a dead space of 53 ± 11%. Ventilation and perfusion were mismatched (LogSD, Q, 0.86 ± 0.33). Unexpectedly, evidence of diffusion limitation or postpulmonary shunting was also found. In the well aerated regions, the blood volume was in excess compared to the tissue, while the opposite happened in the atelectasis. Shunt was proportional to the blood volume of the atelectasis (R2 = 0.70, P = 0.003). V˙A/Q˙T mismatch was correlated with the blood volume of the poorly aerated tissue (R2 = 0.54, P = 0.016). The overperfusion coefficient was related to Pao2/Fio2 (R2 = 0.66, P = 0.002), excess tissue mass (R2 = 0.84, P < 0.001), and Etco2/Paco2 (R2 = 0.63, P = 0.004). CONCLUSIONS: These data support the hypothesis of a highly multifactorial genesis of hypoxemia. Moreover, recent evidence from post-mortem studies (i.e., opening of intrapulmonary bronchopulmonary anastomosis) may explain the findings regarding the postpulmonary shunting. The hyperperfusion might be related to the disease severity.

Prolonged Opioid Use and Pain Outcome and Associated Factors after Surgery under General Anesthesia: A Prospective Cohort Association Multicenter Study.

BACKGROUND: There is insufficient prospective evidence regarding the relationship between surgical experience and prolonged opioid use and pain. The authors investigated the association of patient characteristics, surgical procedure, and perioperative anesthetic course with postoperative opioid consumption and pain 3 months postsurgery. The authors hypothesized that patient characteristics and intraoperative factors predict opioid consumption and pain 3 months postsurgery. METHODS: Eleven U.S. and one European institution enrolled patients scheduled for spine, open thoracic, knee, hip, or abdominal surgery, or mastectomy, in this multicenter, prospective observational study. Preoperative and postoperative data were collected using patient surveys and electronic medical records. Intraoperative data were collected from the Multicenter Perioperative Outcomes Group database. The association between postoperative opioid consumption and surgical site pain at 3 months, elicited from a telephone survey conducted at 3 months postoperatively, and demographics, psychosocial scores, pain scores, pain management, and case characteristics, was analyzed. RESULTS: Between September and October 2017, 3,505 surgical procedures met inclusion criteria. A total of 1,093 cases were included; 413 patients were lost to follow-up, leaving 680 (64%) for outcome analysis. Preoperatively, 135 (20%) patients were taking opioids. Three months postsurgery, 96 (14%) patients were taking opioids, including 23 patients (4%) who had not taken opioids preoperatively. A total of 177 patients (27%) reported surgical site pain, including 45 (13%) patients who had not reported pain preoperatively. The adjusted odds ratio for 3-month opioid use was 18.6 (credible interval, 10.3 to 34.5) for patients who had taken opioids preoperatively. The adjusted odds ratio for 3-month surgical site pain was 2.58 (1.45 to 4.4), 4.1 (1.73 to 8.9), and 2.75 (1.39 to 5.0) for patients who had site pain preoperatively, knee replacement, or spine surgery, respectively. CONCLUSIONS: Preoperative opioid use was the strongest predictor of opioid use 3 months postsurgery. None of the other variables showed clinically significant association with opioid use at 3 months after surgery.

Evaluation of the non-invasive Temple Touch Pro temperature monitoring system compared with oesophageal temperature in paediatric anaesthesia (PETER PAN): A prospective observational study.

BACKGROUND: Monitoring peri-operative body temperature in children is currently mainly achieved through invasive devices. The Temple Touch Pro Temperature Monitoring System estimates core temperature noninvasively based on heat flux thermometry. OBJECTIVE: To investigate the agreement of this noninvasive sensor against standard oesophageal core temperature. DESIGN: A prospective observational study. SETTING: University hospital recruiting between April and July 2021. PATIENTS: One hundred children (32 girls) aged 6 years or younger scheduled for noncardiac surgery, resulting in 6766 data pairs. Exclusion criteria were contraindication for the insertion of an oesophageal temperature probe, and procedures in which one of the measurement methods would interfere with the surgical field. MAIN OUTCOME MEASURES: Primary outcome was the agreement analysis by a Bland-Altman comparison with multiple measurements. Posthoc, we performed another agreement analysis after exclusion of a statistically determined equilibration time. Secondary outcomes were the temperature differences over time and subgroup analysis of hypothermic, normothermic and hyperthermic temperature ranges, age, sex and sensor's side by type III analysis of variance. Further, we correlated the sonographically determined depth of the artery with trueness. RESULTS: The mean difference was -0.07°C (95% CI -0.15 to +0.05) with limits of agreement of -1.00 and +0.85°C. After adjusting for an equilibration time of 13 min, the mean difference improved to -0.04°C (95% CI -0.08 to +0.01) with limits of agreement of -0.68 and +0.60°C. Concordance correlation coefficient was 0.83 (95% CI 0.82 to 0.84). Differences between the skin sensor and oesophageal reference increased over time by -0.05°C per hour. Subgroup analysis showed no clinically relevant differences. Depth of artery negatively correlated with trueness by 0.03°C per millimetre. CONCLUSIONS: Although the Temple Touch Pro sensor showed acceptable accuracy after allowing for an equilibration time, it still needs further investigation for routine use in children. This particularly affects accuracy in hypothermic ranges, imprecise positioning and applicability in children with immature or vulnerable skin. TRIAL REGISTRATION: German Clinical Trials Register, identifier: DRKS00024703.

Mechanical Power Ratio and Respiratory Treatment Escalation in COVID-19 Pneumonia: A Secondary Analysis of a Prospectively Enrolled Cohort.

BACKGROUND: Under the hypothesis that mechanical power ratio could identify the spontaneously breathing patients with a higher risk of respiratory failure, this study assessed lung mechanics in nonintubated patients with COVID-19 pneumonia, aiming to (1) describe their characteristics; (2) compare lung mechanics between patients who received respiratory treatment escalation and those who did not; and (3) identify variables associated with the need for respiratory treatment escalation. METHODS: Secondary analysis of prospectively enrolled cohort involving 111 consecutive spontaneously breathing adults receiving continuous positive airway pressure, enrolled from September 2020 to December 2021. Lung mechanics and other previously reported predictive indices were calculated, as well as a novel variable: the mechanical power ratio (the ratio between the actual and the expected baseline mechanical power). Patients were grouped according to the outcome: (1) no-treatment escalation (patient supported in continuous positive airway pressure until improvement) and (2) treatment escalation (escalation of the respiratory support to noninvasive or invasive mechanical ventilation), and the association between lung mechanics/predictive scores and outcome was assessed. RESULTS: At day 1, patients undergoing treatment escalation had spontaneous tidal volume similar to those of patients who did not (7.1 ± 1.9 vs. 7.1 ± 1.4 ml/kgIBW; P = 0.990). In contrast, they showed higher respiratory rate (20 ± 5 vs. 18 ± 5 breaths/min; P = 0.028), minute ventilation (9.2 ± 3.0 vs. 7.9 ± 2.4 l/min; P = 0.011), tidal pleural pressure (8.1 ± 3.7 vs. 6.0 ± 3.1 cm H2O; P = 0.003), mechanical power ratio (2.4 ± 1.4 vs. 1.7 ± 1.5; P = 0.042), and lower partial pressure of alveolar oxygen/fractional inspired oxygen tension (174 ± 64 vs. 220 ± 95; P = 0.007). The mechanical power (area under the curve, 0.738; 95% CI, 0.636 to 0.839] P < 0.001), the mechanical power ratio (area under the curve, 0.734; 95% CI, 0.625 to 0.844; P < 0.001), and the pressure-rate index (area under the curve, 0.733; 95% CI, 0.631 to 0.835; P < 0.001) showed the highest areas under the curve. CONCLUSIONS: In this COVID-19 cohort, tidal volume was similar in patients undergoing treatment escalation and in patients who did not; mechanical power, its ratio, and pressure-rate index were the variables presenting the highest association with the clinical outcome.

Association of Anesthesiologist Staffing Ratio With Surgical Patient Morbidity and Mortality.

Importance: Recent studies have investigated the effect of overlapping surgeon responsibilities or nurse to patient staffing ratios on patient outcomes, but the association of overlapping anesthesiologist responsibilities with patient outcomes remains unexplored to our knowledge. Objective: To examine the association between different levels of anesthesiologist staffing ratios and surgical patient morbidity and mortality. Design, Setting, and Participants: A retrospective, matched cohort study consisting of major noncardiac inpatient surgical procedures performed from January 1, 2010, to October 31, 2017, was conducted in 23 US academic and private hospitals. A total of 866 453 adult patients (aged ≥18 years) undergoing major inpatient surgery within the Multicenter Perioperative Outcomes Group electronic health record registry were included. Anesthesiologist sign-in and sign-out times were used to calculate a continuous time-weighted average staffing ratio variable for each operation. Propensity score-matching methods were applied to create balanced sample groups with respect to patient-, operative-, and hospital-level confounders and resulted in 4 groups based on anesthesiologist staffing ratio. Groups consisted of patients receiving care from an anesthesiologist covering 1 operation (group 1), more than 1 to no more than 2 overlapping operations (group 1-2), more than 2 to no more than 3 overlapping operations (group 2-3), and more than 3 to no more than 4 overlapping operations (group 3-4). Data analysis was performed from October 2019 to October 2021. Exposure: Undergoing a major inpatient surgical operation that involved an anesthesiologist providing care for up to 4 overlapping operations. Main Outcomes and Measures: The primary composite outcome was 30-day mortality and 6 major surgical morbidities (cardiac, respiratory, gastrointestinal, urinary, bleeding, and infectious complications) derived from International Classification of Diseases, Ninth Revision and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision discharge diagnosis codes. Results: In all, 578 815 adult patients (mean [SD] age, 55.7 [16.2] years; 55.1% female) were analyzed. After matching operations according to anesthesiologist staffing ratio, 48 555 patients were in group 1; 247 057, group 1-2; 216 193, group 2-3; and 67 010, group 3-4. Increasing anesthesiologist coverage responsibilities was associated with an increase in risk-adjusted surgical patient morbidity and mortality. Compared with patients in group 1-2, those in group 2-3 had a 4% relative increase in risk-adjusted mortality and morbidity (5.06% vs 5.25%; adjusted odds ratio [AOR], 1.04; 95% CI, 1.01-1.08; P = .02) and those in group 3-4 had a 14% increase in risk-adjusted mortality and morbidity (5.06% vs 5.75%; AOR, 1.15; 95% CI, 1.09-1.21; P < .001). Conclusions and Relevance: This study's findings suggest that increasing overlapping coverage by anesthesiologists is associated with increased surgical patient morbidity and mortality. Therefore, the potential effects of staffing ratios in perioperative team models should be considered in clinical coverage efforts.

Outlying End-Tidal Carbon Dioxide During General Anesthesia Is Associated With Postoperative Pulmonary Complications: A Multicenter Retrospective Observational Study From US Hospitals Between 2010 and 2017.

BACKGROUND: Postoperative pulmonary complications (PPCs) occur in up to 33% of patients who undergo noncardiothoracic surgery. Emerging evidence suggests that permissive hypercapnia may reduce the risk of lung injury. We hypothesized that higher intraoperative end-tidal carbon dioxide (Etco2) concentrations would be associated with a decreased risk of PPCs. METHODS: This retrospective, observational, multicenter study included patients undergoing general anesthesia for noncardiothoracic procedures (January 2010-December 2017). The primary outcome was PPC within 30 postoperative days. Secondary outcomes were PPC within 1 week, postoperative length of stay, and inhospital 30-day mortality. The association between these outcomes, median Etco2, and 4 time-weighted average area-under-the-curve (TWA-AUC) thresholds (<28, <35, <45, and >45 mm Hg) was explored using a multivariable mixed-effect model and by plotting associated risks. RESULTS: Among 143,769 cases across 11 hospitals, 10,276 (7.1%) experienced a PPC. When compared to a baseline median Etco2 of 35 to 40 mm Hg, a median Etco2 >40 mm Hg was associated with an increase in PPCs within 30 days (median Etco2, 40-45 mm Hg; adjusted OR, 1.16 [99% confidence interval {CI}, 1.00-1.33]; P value = .008 and median Etco2, >45 mm Hg; OR, 1.64 [99% CI, 1.33-2.02]; P value < .001). The occurrence of any Etco2 value <28 mm Hg (ie, a positive TWA-AUC < 28 mm Hg) was associated with PPCs (OR, 1.40 [95% CI, 1.33-1.49]; P value < .001), mortality, and length of stay. Any Etco2 value >45 mm Hg (ie, a positive TWA-AUC >45 mm Hg) was also associated with PPCs (OR, 1.24 [95% CI, 1.17-1.31]; P < .001). The Etco2 range with the lowest incidence of PPCs was 35 to 38 mm Hg. CONCLUSIONS: Both a very low (<28 mm Hg) and a high Etco2 (>45 mm Hg) were associated with PPCs within 30 days. The lowest PPC incidence was found in patients with an Etco2 of 35 to 38 mm Hg. Prospective studies are needed to clarify the relationship between postoperative PPCs and intraoperative Etco2.

Target insertion depth of nasopharyngeal temperature probes in children: A prospective observational study analyzing magnetic resonance images.

BACKGROUND: Core temperature monitoring is indispensable to prevent children from perioperative thermal perturbations. Although nasopharyngeal measurements are commonly used in anesthesia and considered to reflect core temperature accurately, standardized target depths for probe insertion are unknown in children. AIMS: Our primary goal was to determine a target depth of nasopharyngeal temperature probe insertion in children by measuring distances on magnetic resonance imaging (MRI). Secondary aims were to correlate these measurements with biometric variables and facial landmark-distances to derive formulas estimating target depth. METHODS: We conducted a prospective observational study in children ≤12 years undergoing cranial MRI with anesthesia. We documented patient characteristics and measured the landmark-distances nostril-mandible, nostril-tragus, and philtrum-tragus on patient's faces. On MRI, the target point for the probe tip was considered to be the site of the nasopharyngeal mucosa with the closest proximity to the internal carotid artery. After its determination in the transverse axis and triangulation to the sagittal axis, we measured the distance to the nostril. This distance, defined as target insertion depth, was correlated with the patient characteristics and used for univariate and multiple linear regression analysis. RESULTS: One hundred twenty children with a mean age of 4.5 years were included. The target insertion depth ranged from 61.8 mm in infants to 89.8 mm in 12-year-old children. Height correlated best (ρ = 0.685, 95%-CI: [0.57-0.77]). The best-fit estimation in millimeters, "40.8 + height [cm] × 0.32,″ would lead to a placement in the target position in 67% of cases. A simplified approach by categories of 50-80, 80-110, 110-130, and >130 cm height with target insertion depths of 60, 70, 80, and 85 mm, respectively, achieved similar probabilities. CONCLUSIONS: Height-based formulas could be a valuable proxy for the insertion depth of nasopharyngeal temperature probes. Further clinical trials are necessary to investigate their measurement accuracy.

The role of the TMS parameters for activation of the corticospinal pathway to the diaphragm.

OBJECTIVE: The influence of the TMS-parameters on the efficacy and reliability to induce diaphragmatic motor-evoked potentials (diMEPs) has not been studied so far. Therefore, the objective of the present research is to probe the role of TMS- waveform (monophasic- [Mo] vs. biphasic-pulses [Bi]) and current direction (posterior-anterior [Pa] vs. anterior-posterior [Ap]) in the activation of the diaphragm. METHODS: Four different pulse-configurations (Mo-Ap, Mo-Pa, Bi-Ap, Bi-Pa) were applied by means of neuronavigated-TMS and surface MEP-recordings at relaxed end-expiration in 19 healthy subjects. The parameters resting motor threshold (RMT), diMEP-amplitude and -latency, as well as best stimulation site (motor hotspot) and central motor conduction time were studied. Diaphragm movements were simultaneously recorded via ultrasound. To control for possible signal contamination the MEPs of muscles neighboring the diaphragm were also obtained. RESULTS: The motor hotspots of the diaphragm showed similar spatial distribution for the Mo-Ap, Mo-Pa, Bi-Ap and Bi-Pa. The biphasic-pulses yielded significantly lower RMTs and higher diMEP-amplitudes as the monophasic-pulses. Anterior to posterior oriented Bi- and Mo-pulses evoked significantly shorter diMEP-latencies than the posterior-anterior oriented ones. CONCLUSIONS: The present research demonstrates that biphasic- as compared to monophasic-pulses require significantly less charge and time for inducing diMEPs. SIGNIFICANCE: The biphasic-TMS is best suited for the demanding stimulation of the diaphragm.

Incidence of sedation-related adverse events during ERCP with anesthesia assistance: a multicenter observational study.

BACKGROUND AND AIMS: Anesthesia assistance is commonly used for ERCP. General anesthesia (GA) may provide greater airway protection but may lead to hypotension. We aimed to compare GA versus sedation without planned intubation (SWPI) on the incidence of hypoxemia and hypotension. We also explored risk factors for conversion from SWPI to GA. METHODS: This observational study used data from the Multicenter Perioperative Outcomes Group. Adults with American Society of Anesthesiologists physical status class I to IV undergoing ERCP between 2006 and 2019 were included. We compared GA and SWPI on incidence of hypoxemia (oxygen saturation <90% for ≥3 minutes) and hypotension (mean arterial pressure <65 mm Hg for ≥5 minutes) using joint hypothesis testing. The association between anesthetic approach and outcomes was assessed using logistic regression. The noninferiority delta for hypoxemia and hypotension was an odds ratio of 1.20. One approach was deemed better if it was noninferior on both outcomes and superior on at least 1 outcome. To explore risk factors associated with conversion from SWPI to GA, we constructed a logistic regression model. RESULTS: Among 61,735 cases from 42 institutions, 38,830 (63%) received GA and 22,905 (37%) received SWPI. The GA group had 1.27 times (97.5% confidence interval, 1.19-1.35) higher odds of hypotension but .71 times (97.5% confidence interval, .63-.80) lower odds of hypoxemia. Neither group was noninferior to the other on both outcomes. Conversion from SWPI to GA occurred in 6.5% of cases and was associated with baseline comorbidities and higher institutional procedure volume. CONCLUSIONS: GA for ERCP was associated with less hypoxemia, whereas SWPI was associated with less hypotension. Neither approach was better on the combined incidence of hypotension and hypoxemia.

Mechanical power thresholds during mechanical ventilation: An experimental study.

The extent of ventilator-induced lung injury may be related to the intensity of mechanical ventilation--expressed as mechanical power. In the present study, we investigated whether there is a safe threshold, below which lung damage is absent. Three groups of six healthy pigs (29.5 ± 2.5 kg) were ventilated prone for 48 h at mechanical power of 3, 7, or 12 J/min. Strain never exceeded 1.0. PEEP was set at 4 cmH2 O. Lung volumes were measured every 12 h; respiratory, hemodynamics, and gas exchange variables every 6. End-experiment histological findings were compared with a control group of eight pigs which did not undergo mechanical ventilation. Functional residual capacity decreased by 10.4% ± 10.6% and 8.1% ± 12.1% in the 7 J and 12 J groups (p = 0.017, p < 0.001) but not in the 3 J group (+1.7% ± 17.7%, p = 0.941). In 3 J group, lung elastance, PaO2 and PaCO2 were worse compared to 7 J and 12 J groups (all p < 0.001), due to lower ventilation-perfusion ratio (0.54 ± 0.13, 1.00 ± 0.25, 1.78 ± 0.36 respectively, p < 0.001). The lung weight was lower (p < 0.001) in the controls (6.56 ± 0.90 g/kg) compared to 3, 7, and 12 J groups (12.9 ± 3.0, 16.5 ± 2.9, and 15.0 ± 4.1 g/kg, respectively). The wet-to-dry ratio was 5.38 ± 0.26 in controls, 5.73 ± 0.52 in 3 J, 5.99 ± 0.38 in 7 J, and 6.13 ± 0.59 in 12 J group (p = 0.03). Vascular congestion was more extensive in the 7 J and 12 J compared to 3 J and control groups. Mechanical ventilation (with anesthesia/paralysis) increase lung weight, and worsen lung histology, regardless of the mechanical power. Ventilating at 3 J/min led to better anatomical variables than at 7 and 12 J/min but worsened the physiological values.

Epidural Needle Guidance Using Viscoelastic Tissue Response.

Objective: We designed, prototyped, and tested a system that measures the viscoelastic response of tissue using nondestructive mechanical probing, with the goal of aiding clinical providers during epidural needle placement. This system is meant to alert clinicians when an epidural needle is about to strike bone during insertion. Methods: During needle insertion, the system periodically mechanically stimulates and collects viscoelastic response information data from the tissue at the needle's tip using an intra-needle probe. A machine-learning algorithm detects when the needle is close to bone using the series of observed stimulations. Results: Tests run on ex vivo pig spine show that the system can reliably determine if the needle is pointed at and within 3 mm of bone. Conclusion: Our technique can successfully differentiate materials at and in front of the needle's tip. However, it does not provide the 5 mm of forewarning that we believe would be necessary for use in clinical epidural needle placement. The technique may be of use in other applications requiring tissue differentiation during needle placement or in the intended application with further technical advances. Clinical and Translational Impact Statement: This Early/Pre-Clinical Research evaluates the feasibility of a method for helping clinical providers receive feedback during epidural needle insertion-thereby reducing complication rates-without significant alterations from current workflow.

Lung Ultrasound and Electrical Impedance Tomography During Ventilator-Induced Lung Injury.

OBJECTIVES: Lung damage during mechanical ventilation involves lung volume and alveolar water content, and lung ultrasound (LUS) and electrical impedance tomography changes are related to these variables. We investigated whether these techniques may detect any signal modification during the development of ventilator-induced lung injury (VILI). DESIGN: Experimental animal study. SETTING: Experimental Department of a University Hospital. SUBJECTS: Forty-two female pigs (24.2 ± 2.0 kg). INTERVENTIONS: The animals were randomized into three groups (n = 14): high tidal volume (TV) (mean TV, 803.0 ± 121.7 mL), high respiratory rate (RR) (mean RR, 40.3 ± 1.1 beats/min), and high positive-end-expiratory pressure (PEEP) (mean PEEP, 24.0 ± 1.1 cm H2O). The study lasted 48 hours. At baseline and at 30 minutes, and subsequently every 6 hours, we recorded extravascular lung water, end-expiratory lung volume, lung strain, respiratory mechanics, hemodynamics, and gas exchange. At the same time-point, end-expiratory impedance was recorded relatively to the baseline. LUS was assessed every 12 hours in 12 fields, each scoring from 0 (presence of A-lines) to 3 (consolidation). MEASUREMENTS AND MAIN RESULTS: In a multiple regression model, the ratio between extravascular lung water and end-expiratory lung volume was significantly associated with the LUS total score (p < 0.002; adjusted R2, 0.21). The variables independently associated with the end-expiratory difference in lung impedance were lung strain (p < 0.001; adjusted R2, 0.18) and extravascular lung water (p < 0.001; adjusted R2, 0.11). CONCLUSIONS: Data suggest as follows. First, what determines the LUS score is the ratio between water and gas and not water alone. Therefore, caution is needed when an improvement of LUS score follows a variation of the lung gas content, as after a PEEP increase. Second, what determines the end-expiratory difference in lung impedance is the strain level that may disrupt the intercellular junction, therefore altering lung impedance. In addition, the increase in extravascular lung water during VILI development contributed to the observed decrease in impedance.

Mechanisms of oxygenation responses to proning and recruitment in COVID-19 pneumonia.

PURPOSE: This study aimed at investigating the mechanisms underlying the oxygenation response to proning and recruitment maneuvers in coronavirus disease 2019 (COVID-19) pneumonia. METHODS: Twenty-five patients with COVID-19 pneumonia, at variable times since admission (from 1 to 3 weeks), underwent computed tomography (CT) lung scans, gas-exchange and lung-mechanics measurement in supine and prone positions at 5 cmH2O and during recruiting maneuver (supine, 35 cmH2O). Within the non-aerated tissue, we differentiated the atelectatic and consolidated tissue (recruitable and non-recruitable at 35 cmH2O of airway pressure). Positive/negative response to proning/recruitment was defined as increase/decrease of PaO2/FiO2. Apparent perfusion ratio was computed as venous admixture/non aerated tissue fraction. RESULTS: The average values of venous admixture and PaO2/FiO2 ratio were similar in supine-5 and prone-5. However, the PaO2/FiO2 changes (increasing in 65% of the patients and decreasing in 35%, from supine to prone) correlated with the balance between resolution of dorsal atelectasis and formation of ventral atelectasis (p = 0.002). Dorsal consolidated tissue determined this balance, being inversely related with dorsal recruitment (p = 0.012). From supine-5 to supine-35, the apparent perfusion ratio increased from 1.38 ± 0.71 to 2.15 ± 1.15 (p = 0.004) while PaO2/FiO2 ratio increased in 52% and decreased in 48% of patients. Non-responders had consolidated tissue fraction of 0.27 ± 0.1 vs. 0.18 ± 0.1 in the responding cohort (p = 0.04). Consolidated tissue, PaCO2 and respiratory system elastance were higher in patients assessed late (all p < 0.05), suggesting, all together, "fibrotic-like" changes of the lung over time. CONCLUSION: The amount of consolidated tissue was higher in patients assessed during the third week and determined the oxygenation responses following pronation and recruitment maneuvers.

Practice Patterns and Variability in Intraoperative Opioid Utilization: A Report From the Multicenter Perioperative Outcomes Group.

BACKGROUND: Opioids remain the primary mode of analgesia intraoperatively. There are limited data on how patient, procedural, and institutional characteristics influence intraoperative opioid administration. The aim of this retrospective, longitudinal study from 2012 to 2016 was to assess how intraoperative opioid dosing varies by patient and clinical care factors and across multiple institutions over time. METHODS: Demographic, surgical procedural, anesthetic technique, and intraoperative analgesia data as putative variables of intraoperative opioid utilization were collected from 10 institutions. Log parenteral morphine equivalents (PME) was modeled in a multivariable linear regression model as a function of 15 covariates: 3 continuous covariates (age, anesthesia duration, year) and 12 factor covariates (peripheral block, neuraxial block, general anesthesia, emergency status, race, sex, remifentanil infusion, major surgery, American Society of Anesthesiologists [ASA] physical status, non-opioid analgesic count, Multicenter Perioperative Outcomes Group [MPOG] institution, surgery category). One interaction (year by MPOG institution) was included in the model. The regression model adjusted simultaneously for all included variables. Comparison of levels within a factor were reported as a ratio of medians with 95% credible intervals (CrI). RESULTS: A total of 1,104,324 cases between January 2012 and December 2016 were analyzed. The median (interquartile range) PME and standardized by weight PME per case for the study period were 15 (10-28) mg and 200 (111-347) µg/kg, respectively. As estimated in the multivariable model, there was a sustained decrease in opioid use (mean, 95% CrI) dropping from 152 (151-153) µg/kg in 2012 to 129 (129-130) µg/kg in 2016. The percent of variability in PME due to institution was 25.6% (24.8%-26.5%). Less opioids were prescribed in men (130 [129-130] µg/kg) than women (144 [143-145] µg/kg). The men to women PME ratio was 0.90 (0.89-0.90). There was substantial variability in PME administration among institutions, with the lowest being 80 (79-81) µg/kg and the highest being 186 (184-187) µg/kg; this is a PME ratio of 0.43 (0.42-0.43). CONCLUSIONS: We observed a reduction in intraoperative opioid administration over time, with variability in dose ranging between sexes and by procedure type. Furthermore, there was substantial variability in opioid use between institutions even when adjusting for multiple variables.

High class filtering facepiece (FFP) are fundamental and effective in protection of emergency health care workers: an observational cohort study in a German community.

BACKGROUND: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly contagious airborne virus inducing pandemic coronavirus disease 2019 (COVID-19). This is most relevant for medical staff working under harmful conditions in emergencies often dealing with patients and an undefined SARS-CoV-2 status. We aimed to measure the effect of high-class filtering facepieces (FFP) in emergency medical service (EMS) staff by analyzing seroprevalence and history of positive polymerase chain reaction (PCR) for SARS-CoV-2. METHOD: This observational cohort study included workers in EMS, who were compared with hospital staff (HS) and staff, which was not directly involved in patient care (NPC). All direct patient contacts of EMS workers were protected by FFP2/N95 (filtering face piece protection class 2/non-oil-based particulates filter efficiency 95%) masks, whereas HS was protected by FFP2/N95 exclusively when a patient had a proven or suspected SARS-CoV-2 infection. NPC was not protected by higher FFP. The seroprevalence of SARS-CoV-2 antibodies was analyzed by immunoassay by end of 12/2020 together with the history of a positive PCR. In addition, a self-assessment was performed regarding the quantity of SARS-CoV-2 positive contacts, about flu symptoms and personal belief of previous COVID-19 infections. RESULTS: The period in which contact to SARS-CoV-2 positive patients has been possible was 10 months (March to December 2020)-with 54,681 patient contacts documented for EMS-either emergencies (n = 33,241) or transportation services (n = 21,440). Seven hundred-thirty (n = 730) participants were included into the study (n = EMS: 325, HS: 322 and NPC: 83). The analysis of the survey showed that the exposure to patients with an unknown and consecutive positive SARS-CoV-2 result was significantly higher for EMS when compared to HS (EMS 55% vs. HS 30%, p = 0.01). The incidence of a SARS-CoV-2 infection in our cohort was 1.2% (EMS), 2.2% (HS) and 2.4% (NPC) within the three groups (ns) and lowest in EMS. Furthermore, the belief of previous COVID-19 was significant higher in EMS (19% vs. 10%), CONCLUSION: The consistent use of FFP2/N95 in EMS is able to prevent work-related SARS-CoV-2 infections in emergency situations. The significance of physical airway protection in exposed medical staff is still relevant especially under the aspect of new viral variants and unclear effectiveness of new vaccines.

Using Artificial Intelligence for Automatic Segmentation of CT Lung Images in Acute Respiratory Distress Syndrome.

Knowledge of gas volume, tissue mass and recruitability measured by the quantitative CT scan analysis (CT-qa) is important when setting the mechanical ventilation in acute respiratory distress syndrome (ARDS). Yet, the manual segmentation of the lung requires a considerable workload. Our goal was to provide an automatic, clinically applicable and reliable lung segmentation procedure. Therefore, a convolutional neural network (CNN) was used to train an artificial intelligence (AI) algorithm on 15 healthy subjects (1,302 slices), 100 ARDS patients (12,279 slices), and 20 COVID-19 (1,817 slices). Eighty percent of this populations was used for training, 20% for testing. The AI and manual segmentation at slice level were compared by intersection over union (IoU). The CT-qa variables were compared by regression and Bland Altman analysis. The AI-segmentation of a single patient required 5-10 s vs. 1-2 h of the manual. At slice level, the algorithm showed on the test set an IOU across all CT slices of 91.3 ± 10.0, 85.2 ± 13.9, and 84.7 ± 14.0%, and across all lung volumes of 96.3 ± 0.6, 88.9 ± 3.1, and 86.3 ± 6.5% for normal lungs, ARDS and COVID-19, respectively, with a U-shape in the performance: better in the lung middle region, worse at the apex and base. At patient level, on the test set, the total lung volume measured by AI and manual segmentation had a R 2 of 0.99 and a bias -9.8 ml [CI: +56.0/-75.7 ml]. The recruitability measured with manual and AI-segmentation, as change in non-aerated tissue fraction had a bias of +0.3% [CI: +6.2/-5.5%] and -0.5% [CI: +2.3/-3.3%] expressed as change in well-aerated tissue fraction. The AI-powered lung segmentation provided fast and clinically reliable results. It is able to segment the lungs of seriously ill ARDS patients fully automatically.

Role of Fluid and Sodium Retention in Experimental Ventilator-Induced Lung Injury.

Background: Ventilator-induced lung injury (VILI) via respiratory mechanics is deeply interwoven with hemodynamic, kidney and fluid/electrolyte changes. We aimed to assess the role of positive fluid balance in the framework of ventilation-induced lung injury. Methods: Post-hoc analysis of seventy-eight pigs invasively ventilated for 48 h with mechanical power ranging from 18 to 137 J/min and divided into two groups: high vs. low pleural pressure (10.0 ± 2.8 vs. 4.4 ± 1.5 cmH2O; p < 0.01). Respiratory mechanics, hemodynamics, fluid, sodium and osmotic balances, were assessed at 0, 6, 12, 24, 48 h. Sodium distribution between intracellular, extracellular and non-osmotic sodium storage compartments was estimated assuming osmotic equilibrium. Lung weight, wet-to-dry ratios of lung, kidney, liver, bowel and muscle were measured at the end of the experiment. Results: High pleural pressure group had significant higher cardiac output (2.96 ± 0.92 vs. 3.41 ± 1.68 L/min; p < 0.01), use of norepinephrine/epinephrine (1.76 ± 3.31 vs. 5.79 ± 9.69 mcg/kg; p < 0.01) and total fluid infusions (3.06 ± 2.32 vs. 4.04 ± 3.04 L; p < 0.01). This hemodynamic status was associated with significantly increased sodium and fluid retention (at 48 h, respectively, 601.3 ± 334.7 vs. 1073.2 ± 525.9 mmol, p < 0.01; and 2.99 ± 2.54 vs. 6.66 ± 3.87 L, p < 0.01). Ten percent of the infused sodium was stored in an osmotically inactive compartment. Increasing fluid and sodium retention was positively associated with lung-weight (R 2 = 0.43, p < 0.01; R 2 = 0.48, p < 0.01) and with wet-to-dry ratio of the lungs (R 2 = 0.14, p < 0.01; R 2 = 0.18, p < 0.01) and kidneys (R 2 = 0.11, p = 0.02; R 2 = 0.12, p = 0.01). Conclusion: Increased mechanical power and pleural pressures dictated an increase in hemodynamic support resulting in proportionally increased sodium and fluid retention and pulmonary edema.