Effect of Extended Prone Positioning in Intubated COVID-19 Patients with Acute Respiratory Distress Syndrome, a Revision Letter.

The systematic review and meta-analysis performed by Kang et al about the effect of extended prone positioning in intubated COVID-19 patients with ARDS presents valuable findings on the effectiveness and safety of extended prone positioning, but also raises several concerns which require clarifications. The inclusion of observational studies without any control group, the use of crude rather than adjusted estimates in key variables from observational studies, an error in data extraction from randomized clinical trials, and the employment of odds ratios rather than risk ratios, may mislead interpretations of the aforementioned intervention.

Safety and Pharmacokinetics of a Combined Antioxidant Therapy against Myocardial Reperfusion Injury: A Phase 1 Randomized Clinical Trial in Healthy Humans.

Myocardial reperfusion injury (MRI) accounts for up to 50% of the final size in acute myocardial infarction and other conditions associated with ischemia-reperfusion. Currently, there is still no therapy to prevent MRI, but it is well known that oxidative stress has a key role in its mechanism. We previously reduced MRI in rats through a combined antioxidant therapy (CAT) of ascorbic acid, N-acetylcysteine, and deferoxamine. This study determines the safety and pharmacokinetics of CAT in a Phase I clinical trial. Healthy subjects (n = 18) were randomized 2:1 to CAT or placebo (NaCl 0.9% i.v.). Two different doses/infusion rates of CATs were tested in a single 90-minute intravenous infusion. Blood samples were collected at specific times for 180 minutes to measure plasma drug concentrations (ascorbic acid, N-acetylcysteine, and deferoxamine) and oxidative stress biomarkers. Adverse events were registered during infusion and followed for 30 days. Both CAT1 and CAT2 significantly increased the CAT drug concentrations compared to placebo (P < .05). Most of the pharmacokinetic parameters were similar between CAT1 and CAT2. In total, 6 adverse events were reported, all nonserious and observed in CAT1. The ferric-reducing ability of plasma (an antioxidant biomarker) increased in both CAT groups compared to placebo (P < .001). The CAT is safe in humans and a potential treatment for patients with acute myocardial infarction undergoing reperfusion therapy.

Coronary artery disease as a risk factor for metabolic dysfunction-associated steatotic liver disease and liver fibrosis.

INTRODUCTION AND OBJECTIVES: Patients with metabolic dysfunction-associated steatotic liver disease (MASLD) are at an increased cardiovascular risk. On the contrary, non-alcoholic fatty liver disease (NAFLD) is highly prevalent in patients with coronary heart disease (CHD). However, it is not known whether patients with significant CHD show a higher frequency of liver fibrosis. This study aimed to determine the frequency of MASLD and liver fibrosis in patients with CHD and to assess whether coronary stenosis is significantly associated with MASLD and fibrosis. PATIENTS AND METHODS: This observational and analytical study included adult patients without any known liver disease who underwent coronary angiography for suspected coronary artery disease (Jul 2021-Jul 2022). The presence of significant CHD (> 50% stenosis of at least one coronary artery) was determined. Liver elastography (FibroScan®) was performed up to 6 months after the coronary angiographic study to determine liver fibrosis, a measurement of liver stiffness (> 6.5 Kpa). Fisher's test, Mann-Whitney U test, and logistic regression models were used (p < 0.05). RESULTS: The study included 113 patients (76% men, average age: 63 years [standard deviation: 9.9]), of which 72% presented with significant CHD. The prevalence rate of MASLD was 52%. Liver fibrosis was present in 12% of the patients and all patients in the significant CHD group (p = 0.007). An increase in the number of vessels with significant CHD increased the probability of liver fibrosis (odds ratio, 1.79; 95% confidence interval, 1.06-3.04; p = 0.029). CONCLUSIONS: MASLD is highly prevalent in patients with significant CHD but without known liver damage. These data suggest that MASLD and liver fibrosis should be investigated in patients with CHD. The presence of confounding variables, especially the presence of type 2 diabetes mellitus, should be evaluated in further studies.

Pituitary Abscess Causing Panhypopituitarism in a Patient With Neurobrucellosis: Case Report.

Background/Objective: Pituitary abscess is an uncommon life-threatening disease that could lead to panhypopituitarism. It is important to suspect its prevalence in regions with endemic infectious diseases. Case Report: A 55-year-old man, a farmer, with a background of consumption of unpasteurized dairy products, presented with headache, impaired consciousness, and fever that started in February 2023. Initial test results were consistent with neuroinfection. Brain MRI showed ventriculitis; the pituitary gland was heterogeneous with the presence of an 8 × 8 mm abscess. The pituitary hormone axis was evaluated, and it showed results compatible with the results of panhypopituitarism with central hypothyroidism, central hypocortisolism, central hypogonadism, and growth hormone deficiency. Hormone replacement treatment with hydrocortisone and levothyroxine was started. The Rose Bengal test for Brucella spp. and 2-mercaptoethanol Brucella agglutination test showed positive results. After neurobrucellosis (NB) was diagnosed, antibiotic treatment was commenced. The patient was discharged 6 weeks later and treatment with prednisone, levothyroxine, recombinant somatropin, testosterone, as well as doxycycline, and rifampin was continued for another 4 months. Discussion: NB and pituitary abscess are rare manifestations of brucellosis and are challenging to diagnose due to their nonspecific clinical presentation and cerebrospinal fluid (CSF) findings. NB diagnosis relies on neurologic symptoms and serological evidence of Brucella infection. Magnetic resonance imaging is the preferred diagnostic tool for pituitary abscesses. Medical management may be sufficient, while transsphenoidal drainage is not always necessary. Hormonal deficits typically remain permanent. Conclusion: Pituitary abscess could be suspected in patients presenting with symptoms of neuroinfection, panhypopituitarism, and heterogenous image in the magnetic resonance imaging differential diagnosis. Opportune management can lead to reduced mortality and improved recovery of the pituitary hormone function.

Pendelluft in hypoxemic patients resuming spontaneous breathing: proportional modes versus pressure support ventilation.

BACKGROUND: Internal redistribution of gas, referred to as pendelluft, is a new potential mechanism of effort-dependent lung injury. Neurally-adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV +) follow the patient's respiratory effort and improve synchrony compared with pressure support ventilation (PSV). Whether these modes could prevent the development of pendelluft compared with PSV is unknown. We aimed to compare pendelluft magnitude during PAV + and NAVA versus PSV in patients with resolving acute respiratory distress syndrome (ARDS). METHODS: Patients received either NAVA, PAV + , or PSV in a crossover trial for 20-min using comparable assistance levels after controlled ventilation (> 72 h). We assessed pendelluft (the percentage of lost volume from the non-dependent lung region displaced to the dependent region during inspiration), drive (as the delta esophageal swing of the first 100 ms [ΔPes 100 ms]) and inspiratory effort (as the esophageal pressure-time product per minute [PTPmin]). We performed repeated measures analysis with post-hoc tests and mixed-effects models. RESULTS: Twenty patients mechanically ventilated for 9 [5-14] days were monitored. Despite matching for a similar tidal volume, respiratory drive and inspiratory effort were slightly higher with NAVA and PAV + compared with PSV (ΔPes 100 ms of -2.8 [-3.8--1.9] cm H2O, -3.6 [-3.9--2.4] cm H2O and -2.1 [-2.5--1.1] cm H2O, respectively, p < 0.001 for both comparisons; PTPmin of 155 [118-209] cm H2O s/min, 197 [145-269] cm H2O s/min, and 134 [93-169] cm H2O s/min, respectively, p < 0.001 for both comparisons). Pendelluft magnitude was higher in NAVA (12 ± 7%) and PAV + (13 ± 7%) compared with PSV (8 ± 6%), p < 0.001. Pendelluft magnitude was strongly associated with respiratory drive (ß = -2.771, p-value < 0.001) and inspiratory effort (ß = 0.026, p < 0.001), independent of the ventilatory mode. A higher magnitude of pendelluft in proportional modes compared with PSV existed after adjusting for PTPmin (ß = 2.606, p = 0.010 for NAVA, and ß = 3.360, p = 0.004 for PAV +), and only for PAV + when adjusted for respiratory drive (ß = 2.643, p = 0.009 for PAV +). CONCLUSIONS: Pendelluft magnitude is associated with respiratory drive and inspiratory effort. Proportional modes do not prevent its occurrence in resolving ARDS compared with PSV.

Dynamic relative regional lung strain estimated by computed tomography and electrical impedance tomography in ARDS patients.

BACKGROUND: In the acute distress respiratory syndrome (ARDS), specific lung regions can be exposed to excessive strain due to heterogeneous disease, gravity-dependent lung collapse and injurious mechanical ventilation. Computed tomography (CT) is the gold standard for regional strain assessment. An alternative tool could be the electrical impedance tomography (EIT). We aimed to determine whether EIT-based methods can predict the dynamic relative regional strain (DRRS) between two levels of end-expiratory pressure (PEEP) in gravity-non-dependent and dependent lung regions. METHODS: Fourteen ARDS patients underwent CT and EIT acquisitions (at end-inspiratory and end-expiratory) at two levels of PEEP: a low-PEEP based on ARDS-net strategy and a high-PEEP titrated according to EIT. Three EIT-based methods for DRRS were compared to relative CT-based strain: (1) the change of the ratio between EIT ventilation and end-expiratory lung impedance in arbitrary units ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]), (2) the change of ΔZ/EELI ratio calibrated to mL ([ΔZml low-PEEP/EELIml low-PEEP]/[ΔZml high-PEEP/EELIml high-PEEP]) using CT data, and (3) the relative change of ∆ZAU (∆ZAU low-PEEP/∆ZAU high-PEEP). We performed linear regressions analysis and calculated bias and limits of agreement to assess the performance of DRRS by EIT in comparison with CT. RESULTS: The DRRS assessed by (ΔZml low-PEEP/EELIml low-PEEP)/(ΔZml high-PEEP/EELIml high-PEEP) and ∆ZAU low-PEEP/∆ZAU high-PEEP showed good relationship and agreement with the CT method (R2 of 0.9050 and 0.8679, respectively, in non-dependent region; R2 of 0.8373 and 0.6588, respectively, in dependent region; biases ranging from - 0.11 to 0.51 and limits of agreement ranging from - 0.73 to 1.16 for both methods and lung regions). Conversely, DRRS based on EELIAU ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]) exhibited a weak negative relationship and poor agreement with the CT method for both non-dependent and dependent regions (R2 ~ 0.3; bias of 3.11 and 2.08, and limits of agreement of - 2.13 to 8.34 and from - 1.49 to 5.64, respectively). CONCLUSION: Changes in DRRS during a PEEP trial in ARDS patients could be monitored using EIT, based on changes in ΔZmL/EELIml and ∆ZAU. The relative change ∆ZAU offers the advantage of not requiring CT data for calibration.

Continuous prolonged prone positioning in COVID-19-related ARDS: a multicenter cohort study from Chile.

BACKGROUND: Prone positioning is currently applied in time-limited daily sessions up to 24 h which determines that most patients require several sessions. Although longer prone sessions have been reported, there is scarce evidence about the feasibility and safety of such approach. We analyzed feasibility and safety of a continuous prolonged prone positioning strategy implemented nationwide, in a large cohort of COVID-19 patients in Chile. METHODS: Retrospective cohort study of mechanically ventilated COVID-19 patients with moderate-to-severe acute respiratory distress syndrome (ARDS), conducted in 15 Intensive Care Units, which adhered to a national protocol of continuous prone sessions ≥ 48 h and until PaO2:FiO2 increased above 200 mm Hg. The number and extension of prone sessions were registered, along with relevant physiologic data and adverse events related to prone positioning. The cohort was stratified according to the first prone session duration: Group A, 2-3 days; Group B, 4-5 days; and Group C, > 5 days. Multivariable regression analyses were performed to assess whether the duration of prone sessions could impact safety. RESULTS: We included 417 patients who required a first prone session of 4 (3-5) days, of whom 318 (76.3%) received only one session. During the first prone session the main adverse event was grade 1-2 pressure sores in 97 (23.9%) patients; severe adverse events were infrequent with 17 non-scheduled extubations (4.2%). 90-day mortality was 36.2%. Ninety-eight patients (24%) were classified as group C; they exhibited a more severe ARDS at baseline, as reflected by lower PaO2:FiO2 ratio and higher ventilatory ratio, and had a higher rate of pressure sores (44%) and higher 90-day mortality (48%). However, after adjustment for severity and several relevant confounders, prone session duration was not associated with mortality or pressure sores. CONCLUSIONS: Nationwide implementation of a continuous prolonged prone positioning strategy for COVID-19 ARDS patients was feasible. Minor pressure sores were frequent but within the ranges previously described, while severe adverse events were infrequent. The duration of prone session did not have an adverse effect on safety.

Inflammatory biomarkers and pendelluft magnitude in ards patients transitioning from controlled to partial support ventilation.

The transition from controlled to partial support ventilation is a challenge in acute respiratory distress syndrome (ARDS) patients due to the risks of patient-self-inflicted lung injury. The magnitude of tidal volume (VT) and intrapulmonary dyssynchrony (pendelluft) are suggested mechanisms of lung injury. We conducted a prospective, observational, physiological study in a tertiary academic intensive care unit. ARDS patients transitioning from controlled to partial support ventilation were included. On these, we evaluated the association between changes in inflammatory biomarkers and esophageal pressure swing (ΔPes), transpulmonary driving pressure (ΔPL), VT, and pendelluft. Pendelluft was defined as the percentage of the tidal volume that moves from the non-dependent to the dependent lung region during inspiration, and its frequency at different thresholds (- 15, - 20 and - 25%) was also registered. Blood concentrations of inflammatory biomarkers (IL-6, IL-8, TNF-α, ANGPT2, RAGE, IL-18, Caspase-1) were measured before (T0) and after 4-h (T4) of partial support ventilation. Pendelluft, ΔPes, ΔPL and VT were recorded. Nine out of twenty-four patients (37.5%) showed a pendelluft mean ≥ 10%. The mean values of ΔPes, ΔPL, and VT were - 8.4 [- 6.7; - 10.2] cmH2O, 15.2 [12.3-16.5] cmH2O and 8.1 [7.3-8.9] m/kg PBW, respectively. Significant associations were observed between the frequency of high-magnitude pendelluft and IL-8, IL-18, and Caspase-1 changes (T0/T4 ratio). These results suggest that the frequency of high magnitude pendelluft may be a potential determinant of inflammatory response related to inspiratory efforts in ARDS patients transitioning to partial support ventilation. Future studies are needed to confirm these results.

Pharmacological Basis for Abrogating Myocardial Reperfusion Injury Through a Multi-Target Combined Antioxidant Therapy.

The main goal of the treatment for acute myocardial infarction is to achieve reperfusion of the affected myocardial tissue, with percutaneous coronary angioplasty being the gold standard procedure. However, this strategy has been associated with additional heart damage termed "lethal reperfusion injury," which is responsible for up to half of the final infarct size. Among the possible underlying mechanisms that are likely to explain this damage, studies suggest that oxidative stress plays a key role. Although this has not been translated into clinical benefits in most studies, recent preclinical studies reported promising results and a possible synergy with the combined use of vitamin C (VC), N-acetylcysteine (NAC), and deferoxamine (DFO). However, to implement a combined therapy with these drugs for patients requires further studies to understand their pharmacokinetic properties. Available data of the clinical trials have not been validated by looking into the pharmacokinetics in their design. Therefore, this article presents an update and comparison of the evidence for the efficacy of these administration schemes for each drug in cardioprotection, their pharmacokinetic properties and mechanisms of action for their use against "lethal reperfusion injury." To achieve a cardioprotective effect using a new pharmacological strategy before the onset of reperfusion, it is helpful to consider the pharmacokinetics of each drug. In this regard, to design a fast and short pharmacologic therapeutic strategy, theoretically VC and DFO concentrations could be modeled by a one-compartment model whereas NAC could be modeled by a three-compartment model with an initial short half-life.

Effects of 2019's social protests on emergency health services utilization and case severity in Santiago, Chile: a time-series analysis.

Background: On October 18th, 2019, protestors gathered across Chile to call for social equity, resulting in widespread civil unrest and violent confrontation with the police. In this study, we quantify the effects of the 2019 Chilean protests on emergency health services utilization and inpatient admission in Santiago. Methods: We used weekly emergency department (ED) admissions (2015-2019) from three large public hospitals near the focal point of protests in Santiago. The exposure period was from October 18th to December 31st, 2019. The outcomes were the number of weekly consultations and hospitalizations by trauma and respiratory causes and the proportion of hospitalizations among consultants per 1,000. We implemented Bayesian structural time series models to calculate the absolute and relative effects and 95% credible intervals (CrI). Findings: During the first ten weeks of protests ED consultations declined on average by 14% for trauma (95%CrI: -40·2%, 11·5%) and 30% for respiratory causes (95%CrI: -89·4%, 30·2%), 7% for respiratory hospitalizations (95%CrI: -43·6%, 30·8%); however, none of these three results were statistically distinguishable from the null. Trauma hospitalizations, on the other hand, increased by 15% (95%CrI: 4·0%, 26·4%), and the proportion of hospitalizations per consultations increased by 40% for trauma (95%CrI: 13·1%, 68·0%) and 59% for respiratory causes (95%CrI: 29·4%, 87·9%). Interpretation: The 2019 Chilean protests affected the use of emergency health services by increasing the trauma hospitalizations and the case hospitalization ratio per 1,000 consultations for trauma and respiratory causes. Crowd-control protocols must be reviewed to prevent the negative effects of civil unrest.

Clinical characteristics and in-hospital mortality of patients with COVID-19 in Chile: A prospective cohort study.

AIMS OF THIS STUDY: To describe the Latin American population affected by COVID-19, and to determine relevant risk factors for in-hospital mortality. METHODS: We prospectively registered relevant clinical, laboratory, and radiological data of adult patients with COVID-19, admitted within the first 100 days of the pandemic from a single teaching hospital in Santiago, Chile. The primary outcome was in-hospital mortality. Secondary outcomes included the need for respiratory support and pharmacological treatment, among others. We combined the chronic disease burden and the severity of illness at admission with predefined clinically relevant risk factors. Cox regression models were used to identify risk factors for in-hospital mortality. RESULTS: We enrolled 395 adult patients, their median age was 61 years; 62.8% of patients were male and 40.1% had a Modified Charlson Comorbidity Index (MCCI) ≥5. Their median Sequential Organ Failure Assessment (SOFA) score was 3; 34.9% used a high-flow nasal cannula and 17.5% required invasive mechanical ventilation. The in-hospital mortality rate was 14.7%. In the multivariate analysis, were significant risk factors for in-hospital mortality: MCCI ≥5 (HR 4.39, P < .001), PaO2 /FiO2 ratio ≤200 (HR 1.92, P = .037), and advanced chronic respiratory disease (HR 3.24, P = .001); pre-specified combinations of these risk factors in four categories was associated with the outcome in a graded manner. CONCLUSIONS AND CLINICAL IMPLICATIONS: The relationship between multiple prognostic factors has been scarcely reported in Latin American patients with COVID-19. By combining different clinically relevant risk factors, we can identify COVID-19 patients with high-, medium- and low-risk of in-hospital mortality.

Extracorporeal Membrane Oxygenation for COVID-19-associated Severe Acute Respiratory Distress Syndrome in Chile: A Nationwide Incidence and Cohort Study.

Rationale: The role of and needs for extracorporeal membrane oxygenation (ECMO) at a population level during the coronavirus disease (COVID-19) pandemic have not been completely established. Objectives: To identify the cumulative incidence of ECMO use in the first pandemic wave and to describe the Nationwide Chilean cohort of ECMO-supported patients with COVID-19. Methods: We conducted a population-based study from March 3 to August 31, 2020, using linked data from national agencies. The cumulative incidence of ECMO use and mortality risk of ECMO-supported patients were calculated and age standardized. In addition, a retrospective cohort analysis was performed. Outcomes were 90-day mortality after ECMO initiation, ECMO-associated complications, and hospital length of stay. Cox regression models were used to explore risk factors for mortality in a time-to-event analysis. Measurements and Main Results: Ninety-four patients with COVID-19 were supported with ECMO (0.42 per population of 100,000, 14.89 per 100,000 positive cases, and 1.2% of intubated patients with COVID-19); 85 were included in the cohort analysis, and the median age was 48 (interquartile range [IQR], 41-55) years, 83.5% were men, and 42.4% had obesity. The median number of pre-ECMO intubation days was 4 (IQR, 2-7), the median PaO2/FiO2 ratio was 86.8 (IQR, 64-99) mm Hg, 91.8% of patients were prone positioned, and 14 patients had refractory respiratory acidosis. Main complications were infections (70.6%), bleeding (38.8%), and thromboembolism (22.4%); 52 patients were discharged home, and 33 died. The hospital length of stay was a median of 50 (IQR, 24-69) days. Lower respiratory system compliance and higher driving pressure before ECMO initiation were associated with increased mortality. A duration of pre-ECMO intubation ≥10 days was not associated with mortality. Conclusions: Documenting nationwide ECMO needs may help in planning ECMO provision for future COVID-19 pandemic waves. The 90-day mortality of the Chilean cohort of ECMO-supported patients with COVID-19 (38.8%) is comparable to that of previous reports.

Estimation of changes in cyclic lung strain by electrical impedance tomography: Proof-of-concept study.

RATIONALE: Cyclic strain may be a determinant of ventilator-induced lung injury. The standard for strain assessment is the computed tomography (CT), which does not allow continuous monitoring and exposes to radiation. Electrical impedance tomography (EIT) is able to monitor changes in regional lung ventilation. In addition, there is a correlation between mechanical deformation of materials and detectable changes in its electrical impedance, making EIT a potential surrogate for cyclic lung strain measured by CT (StrainCT ). OBJECTIVES: To compare the global StrainCT with the change in electrical impedance (ΔZ). METHODS: Acute respiratory distress syndrome patients under mechanical ventilation (VT 6 mL/kg ideal body weight with positive end-expiratory pressure 5 [PEEP 5] and best PEEP according to EIT) underwent whole-lung CT at end-inspiration and end-expiration. Biomechanical analysis was used to construct 3D maps and determine StrainCT at different levels of PEEP. CT and EIT acquisitions were performed simultaneously. Multilevel analysis was employed to determine the causal association between StrainCT and ΔZ. Linear regression models were used to predict the change in lung StrainCT between different PEEP levels based on the change in ΔZ. MAIN RESULTS: StrainCT was positively and independently associated with ΔZ at global level (P < .01). Furthermore, the change in StrainCT (between PEEP 5 and Best PEEP) was accurately predicted by the change in ΔZ (R2 0.855, P < .001 at global level) with a high agreement between predicted and measured StrainCT . CONCLUSIONS: The change in electrical impedance may provide a noninvasive assessment of global cyclic strain, without radiation at bedside.

Early Oxidative Stress Response in Patients with Severe Aortic Stenosis Undergoing Transcatheter and Surgical Aortic Valve Replacement: A Transatlantic Study.

Myocardial ischemia/reperfusion-related oxidative stress as a result of cardiopulmonary bypass is thought to contribute to the adverse clinical outcomes following surgical aortic valve replacement (SAVR). Although the acute response following this procedure has been well characterized, much less is known about the nature and extent of oxidative stress induced by the transcatheter aortic valve replacement (TAVR) procedure. We therefore sought to examine and directly compare the oxidative stress response in patients undergoing TAVR and SAVR. A total of 60 patients were prospectively enrolled in this exploratory study, 38 patients undergoing TAVR and 22 patients SAVR. Reduced and oxidized glutathione (GSH, GSSG) in red blood cells as well as the ferric-reducing ability of plasma (FRAP) and plasma concentrations of 8-isoprostanes were measured at baseline (S1), during early reperfusion (S2), and 6-8 hours (S3) following aortic valve replacement (AVR). TAVR and SAVR were successful in all patients. Patients undergoing TAVR were older (79.3 ± 9.5 vs. 74.2 ± 4.1 years; P < 0.01) and had a higher mean STS risk score (6.6 ± 4.8 vs. 3.2 ± 3.0; P < 0.001) than patients undergoing SAVR. At baseline, FRAP and 8-isoprostane plasma concentrations were similar between the two groups, but erythrocytic GSH concentrations were significantly lower in the TAVR group. After AVR, FRAP was markedly higher in the TAVR group, whereas 8-isoprostane concentrations were significantly elevated in the SAVR group. In conclusion, TAVR appears not to cause acute oxidative stress and may even improve the antioxidant capacity in the extracellular compartment.

Autonomic nervous system assessment by pupillary response as a potential biomarker for cardiovascular risk: A pilot study.

BACKGROUND: Cardiovascular risk (CVR) biomarkers are of increasing interest because of their potential utility in management of cardiovascular diseases. The activity of the autonomic nervous system (ANS) is known to be highly correlated with CVR and therefore, is a putative biomarker. Common ANS measurement tools have several technological limitations and high-variance signals. The pupillary responses (PR) is controlled by both components of the ANS, and recent advances in pupillometry are making this measurement, easy and reliable. Thus, PR assessment could become a useful clinical tool to measure the ANS modulation and its relation to CVR. Here, we aimed to evaluate differences in PR between low CVR and moderate/high CVR individuals. METHODS: We performed a cross-sectional study. We recruited voluntaries with low CVR (group 1, n = 12) and patients with moderate/high CVR (group 2, n = 7). An eye tracker was used to measure PR to different visual stimulus that included colors (white, black, gray) and images with known emotional valence (pleasant, unpleasant and neutrals), which were intercalated by pink "noise" images. Differences in PR between both CVR groups were assessed by Mann Whitney U test of different epochs of the PR. RESULTS: PR was significantly different between both CVR groups (p-value < 0,05) when the observed images were unpleasant, neutral, and pink noise, for different epochs of the PR. CONCLUSIONS: This is the first study that demonstrates that PR is different according to CVR. Thus, PR could be considered as a novel biomarker of CVR to be tested in prospective studies.

Autonomic imbalance in cardiac surgery: A potential determinant of the failure in remote ischemic preconditioning.

Remote ischemic preconditioning (RIPC) is a cardioprotective strategy against myocardial damage by ischemia-reperfusion. Many in-vivo and ex-vivo animal researches have demonstrated that RIPC decreases significantly the ischemia-reperfusion myocardial damage, by up to 58% in isolated rat heart. Cardiac artery bypass graft surgery (CABG) is a clinical model of myocardial ischemia-reperfusion and a clinical potential application to RIPC. However, although RIPC has shown successful results in experimental studies, clinical trials on CABG have failed to demonstrate a benefit of RIPC in humans. Strikingly, the main proposed factors associated with this translational failure also impair the balance of the autonomic nervous system (ANS), which has shown to play a key role in RIPC cardioprotection in animal models. Comorbidities, chronic pharmacological treatment and anesthesic drugs - common conditions in CABG patients - cause an ANS imbalance through parasympathetic activity decrement. On the other hand, ANS and specially the parasympathetic branch are essentials to get cardioprotection by RIPC in animal models. Consequently, we propose that ANS imbalance in CABG patients would explain the failure of RIPC clinical trials. Whether our hypothesis is true, many patients could be benefited by RIPC: a cheap, simple and virtually broad-available cardioprotective maneuver. In this paper we discuss the evidence that support this hypothesis and its clinical implications.