The Effects of Uniform and Nonuniform Magnetic Fields in Plant Growth: A Meta-Analysis Approach.

Magnetic field (MF) effects have been reported in plants' growth, seed germination, gene expression, and water consumption. Accordingly, magnetic treatments have been proposed as a sustainable alternative to improve yields. Nevertheless, a comprehensive quantitative assessment is needed to understand whether their effects are general, species-specific, or dependent on the experimental setting. We conducted a multilevel meta-analysis of 45 articles that studied 29 different plant species. A positive and neutral effect of a nonuniform MF was found on fresh weight and germination rate, respectively. A significant association was found between a uniform MF and germination. These results suggest that MFs improve plant growth. However, the effects are highly dependent on the experimental setting. This opens exciting questions about the biophysical mechanisms underlying the perception and transduction of this environmental cue and about the possible translation to agricultural practices. © 2023 Bioelectromagnetics Society.

Magnetoelectric Effect in Dipolar Clusters.

We combine the anisotropy of magnetic interactions and the point symmetry of finite solids in the study of dipolar clusters as new basic units for multiferroics metamaterials. The Hamiltonian of magnetic dipoles with an easy axis at the vertices of polygons and polyhedra, maps exactly into a Hamiltonian with symmetric and antisymmetric exchange couplings. The last one gives rise to a Dzyaloshinskii-Moriya contribution responsible for the magnetic modes of the systems and their symmetry groups, which coincide with those of a particle in a crystal field with spin-orbit interaction. We find that the clusters carry spin current and that they manifest the magnetoelectric effect. We expect our results to pave the way for the rational design of magnetoelectric devices at room temperature.

Designing Hysteresis with Dipolar Chains.

Materials that have hysteretic response to an external field are essential in modern information storage and processing technologies. A myriad of magnetization curves of several natural and artificial materials have previously been measured and each has found a particular mechanism that accounts for it. However, a phenomenological model that captures all the hysteresis loops and at the same time provides a simple way to design the magnetic response of a material while remaining minimal is missing. Here, we propose and experimentally demonstrate an elementary method to engineer hysteresis loops in metamaterials built out of dipolar chains. We show that by tuning the interactions of the system and its geometry we can shape the hysteresis loop which allows for the design of the softness of a magnetic material at will. Additionally, this mechanism allows for the control of the number of loops aimed to realize multiple-valued logic technologies. Our findings pave the way for the rational design of hysteretical responses in a variety of physical systems such as dipolar cold atoms, ferroelectrics, or artificial magnetic lattices, among others.

Costal mesenchymal chondrosarcoma with diffuse pleural and pericardial explantation in a pygmy goat.

A 3 year old intact male pygmy goat developed progressive weakness and eventual recumbancy over the course of 1 week, while maintaining its ability to eat and drink. The animal died and at necropsy, the parietal pleural surfaces and the pericardial surface were noted to be covered with firm, white, variably sized nodules that often formed linear arrays or coalesced into larger clumped aggregates. The visceral pleural surfaces of the ventral lung lobes were also covered with similar nodules. Histopathological and immunohistochemical evaluation of the submitted tissues revealed a diagnosis of mesenchymal chondrosarcoma with extensive seeding throughout the thoracic cavity.

Pro-adrenomedullin, pro-endothelin-1, procalcitonin, C-reactive protein and mortality risk in critically ill children: a prospective study.

INTRODUCTION: We tested the hypothesis that higher mid-regional pro-adrenomedullin (MR-proADM), carboxy-terminal pro-endothelin-1 (CT-proET-1), procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations would be associated with increased prediction of mortality risk scores. METHODS: Prospective observational study set in two pediatric intensive care units (PICUs). Two-hundred-thirty-eight patients were included. MR-proADM, CT-proET-1, PCT and CRP levels were compared between children with PRISM III and PIM 2 > p75 (Group A; n = 33) and the rest (Group B; n = 205). RESULTS: Median (range) MR-proADM levels were 1.39 nmol/L (0.52-12.67) in group A versus 0.54 (0.15-3.85) in group B (P < 0.001). CT-proET-1 levels were 172 pmol/L (27-500) versus 58 (4-447) (P < 0.001). PCT levels were 7.77 ng/mL (0.34-552.00) versus 0.28 (0.02-107.00) (P < 0.001). CRP levels were 6.23 mg/dL (0.08-28.25) versus 1.30 mg/dL (0.00-42.09) (P = 0.210). The area under the ROC curve (AUC) for the differentiation of group A and B was 0.87 (95% CI:0.81-0.821) for MR-proADM, 0.86 (95% CI:0.79-0.92) for CT-proET-1 and 0.84 (95% CI:0.74-0.94) for PCT. A MR-proADM > 0.79 nmol/L had 93% sensitivity and 76% specificity to differentiate groups, whereas a CT-proET-1 > 123 pmol/L had 77% sensitivity and 84% specificity, and a PCT concentration > 2.05 ng/mL had 80% sensitivity and specificity. CONCLUSIONS: In critically ill children, high levels of MR-proADM, CT-proET-1 and PCT were associated with increased prediction of mortality risk scores. MR-proADM, CT-proET-1 and PCT concentrations higher than 0.80 nmol/L, 123 pmol/L and 2 ng/mL, respectively, could be used by clinicians to identify critically ill children at higher prediction of risk death scores.

Intrinsic chiral field as vector potential of the magnetic current in the zig-zag lattice of magnetic dipoles.

Chiral magnetic insulators manifest novel phases of matter where the sense of rotation of the magnetization is associated with exotic transport phenomena. Effective control of such phases and their dynamical evolution points to the search and study of chiral fields like the Dzyaloshinskii-Moriya interaction. Here we combine experiments, numerics, and theory to study a zig-zag dipolar lattice as a model of an interface between magnetic in-plane layers with a perpendicular magnetization. The zig-zag lattice comprises two parallel sublattices of dipoles with perpendicular easy plane of rotation. The dipolar energy of the system is exactly separable into a sum of symmetric and antisymmetric long-range exchange interactions between dipoles, where the antisymmetric coupling generates a nonlocal Dzyaloshinskii-Moriya field which stabilizes winding textures with the form of chiral solitons. The Dzyaloshinskii-Moriya interaction acts as a vector potential or gauge field of the magnetic current and gives rise to emergent magnetic and electric fields that allow the manifestation of the magnetoelectric effect in the system.

Macroscopic magnetic frustration.

Although geometrical frustration transcends scale, it has primarily been evoked in the micro- and mesoscopic realm to characterize such phases as spin ice, liquids, and glasses and to explain the behavior of such materials as multiferroics, high-temperature superconductors, colloids, and copolymers. Here we introduce a system of macroscopic ferromagnetic rotors arranged in a planar lattice capable of out-of-plane movement that exhibit the characteristic honeycomb spin ice rules studied and seen so far only in its mesoscopic manifestation. We find that a polarized initial state of this system settles into the honeycomb spin ice phase with relaxation on multiple time scales. We explain this relaxation process using a minimal classical mechanical model that includes Coulombic interactions between magnetic charges located at the ends of the magnets and viscous dissipation at the hinges. Our study shows how macroscopic frustration arises in a purely classical setting that is amenable to experiment, easy manipulation, theory, and computation, and shows phenomena that are not visible in their microscopic counterparts.

Predicting the Risk of Mortality in Children using a Fuzzy-Probabilistic Hybrid Model.

Introduction: The mortality risk in children admitted to Pediatric Intensive Care Units (PICU) is usually estimated by means of validated scales, which only include objective data among their items. Human perceptions may also add relevant information to prognosticate the risk of death, and the tool to use this subjective data is fuzzy logic. The objective of our study was to develop a mathematical model to predict mortality risk based on the subjective perception of PICU staff and to evaluate its accuracy compared to validated scales. Methods: A prospective observational study in two PICUs (one in Spain and another in Latvia) was performed. Children were consecutively included regardless of the cause of admission along a two-year period. A fuzzy set program was developed for the PICU staff to record the subjective assessment of the patients' mortality risk expressed through a short range and a long range, both between 0% and 100%. Pediatric Index of Mortality 2 (PIM2) and Therapeutic Intervention Scoring System 28 (TISS28) were also prospectively calculated for each patient. Subjective and objective predictions were compared using the logistic regression analysis. To assess the prognostication ability of the models a stratified B-random K-fold cross-validation was performed. Results: Five hundred ninety-nine patients were included, 308 in Spain (293 survivors, 15 nonsurvivors) and 291 in Latvia (282 survivors, 9 nonsurvivors). The best logistic classification model for subjective information was the one based on MID (midpoint of the short range), whereas objective information was the one based on PIM2. Mortality estimation performance was 86.3% for PIM2, 92.6% for MID, and the combination of MID and PIM2 reached 96.4%. Conclusions: Subjective assessment was as useful as validated scales to estimate the risk of mortality. A hybrid model including fuzzy information and probabilistic scales (PIM2) seems to increase the accuracy of prognosticating mortality in PICU.

Non invasive ventilation after extubation in paediatric patients: a preliminary study.

BACKGROUND: Non-invasive ventilation (NIV) may be useful after extubation in children. Our objective was to determine postextubation NIV characteristics and to identify risk factors of postextubation NIV failure. METHODS: A prospective observational study was conducted in an 8-bed pediatric intensive care unit (PICU). Following PICU protocol, NIV was applied to patients who had been mechanically ventilated for over 12 hours considered at high-risk of extubation failure -elective NIV (eNIV), immediately after extubation- or those who developed respiratory failure within 48 hours after extubation -rescue NIV (rNIV)-. Patients were categorized in subgroups according to their main underlying conditions. NIV was deemed successful when reintubation was avoided. Logistic regression analysis was performed in order to identify predictors of NIV failure. RESULTS: There were 41 episodes (rNIV in 20 episodes). Success rate was 50% in rNIV and 81% in eNIV (p = 0.037). We found significant differences in univariate analysis between success and failure groups in respiratory rate (RR) decrease at 6 hours, FiO2 at 1 hour and PO2/FiO2 ratio at 6 hours. Neurologic condition was found to be associated with NIV failure. Multiple logistic regression analysis identified no variable as independent NIV outcome predictor. CONCLUSIONS: Our data suggest that postextubation NIV seems to be useful in avoiding reintubation in high-risk children when applied immediately after extubation. NIV was more likely to fail when ARF has already developed (rNIV), when RR at 6 hours did not decrease and if oxygen requirements increased. Neurologic patients seem to be at higher risk of reintubation despite NIV use.

[Validation of a Therapeutic Intervention Scoring System (TISS-28) in critically ill children]. / Validación de la escala simplificada de puntuación de intervenciones terapéuticas (TISS-28) en niños críticamente enfermos.

INTRODUCTION: There are numerous scales in intensive care units that are used to quantify the severity of patients. Most of them are very useful, although sometimes laborious to complete, thus limiting their use in usual practice. One of these scales, the Therapeutic Intervention Scoring System (TISS 76), has been validated in adult and paediatric units. Its simplified and updated version, the Simplified Therapeutic Intervention Scoring System (TISS 28), has not yet been validated in paediatric units. The aim of this study is to validate TISS 28, in order to have a simple and rapid scale. MATERIAL AND METHOD: A prospective non-interventional observational study was conducted in a Paediatric Intensive Care Unit (PICU) of a university hospital. Data were collected from 935 consecutive patients admitted to the PICU over a 3-year period. These included the values of TISS 76 and TISS 28 during the first 4days of admission and the subsequent outcome of the patients. RESULTS: The mean values of TISS 76 and TISS 28 for the first day of admission were 18.27 and 18.02, respectively. Values were higher in patients who had sequelae or died (17.58 versus 27.23 and 37.44, respectively for TISS 76 (P<.01); and 17.51 versus 23.80 and 33.44, respectively for TISS 28 (P<.01). A very good correlation was found between TISS 76 and TISS 28, with Pearson correlation and intraclass correlation coefficients> 0.9 (except for the 2nd day). The correlation equation for the overall 4 days was: TISS76=- 1.74+1.05×TISS28. TISS 28 was able to explain 82.4% of variability of TISS 76. The area under the curve with a confidence interval (CI) of 95% for the first day was 0.80 (0.73-0.87) for TISS 76, and 0.76 (0.67-0.84) for TISS 28. CONCLUSIONS: On observing the results obtained, TISS 28 can replace TISS 26 in our PICU, without worsening the information provided. Being a reliable scale and easier to apply, its practical application could be useful.

Acute-phase reactants after paediatric cardiac arrest. Procalcitonin as marker of immediate outcome.

OBJECTIVE: Procalcitonin (PCT) and C reactive protein (CRP) have been used as infection parameters. PCT increase correlates with the infection's severity, course, and mortality. Post-cardiocirculatory arrest syndrome may be related to an early systemic inflammatory response, and may possibly be associated with an endotoxin tolerance. Our objective was to report the time profile of PCT and CRP levels after paediatric cardiac arrest and to assess if they could be use as markers of immediate survival. MATERIALS AND METHODS: A retrospective observational study set in an eight-bed PICU of a university hospital was performed during a period of two years. Eleven children younger than 14 years were admitted in the PICU after a cardiac arrest. PCT and CRP plasma concentrations were measured within the first 12 and 24 hours of admission. RESULTS: In survivors, PCT values increased 12 hours after cardiac arrest without further increase between 12 and 24 hours. In non survivors, PCT values increased 12 hours after cardiac arrest with further increase between 12 and 24 hours. Median PCT values (range) at 24 hours after cardiac arrest were 22.7 ng/mL (0.2 - 41.0) in survivors vs. 205.5 ng/mL (116.6 - 600.0) in non survivors (p < 0.05). CRP levels were elevated in all patients, survivors and non-survivors, at 12 and 24 hours without differences between both groups. CONCLUSION: Measurement of PCT during the first 24 hours after paediatric cardiac arrest could serve as marker of mortality.

Helmet Versus Nasal-Prong CPAP in Infants With Acute Bronchiolitis.

BACKGROUND: Nasal prongs are frequently used to deliver noninvasive CPAP in bronchiolitis, especially in the youngest children. A helmet interface is an alternative that might be comparable to nasal prongs. We sought to compare these interfaces. METHODS: We performed a prospective, randomized, crossover, single-center study in an 8-bed multidisciplinary pediatric ICU in a university hospital. Infants age <3 months who were consecutively admitted to the pediatric ICU during a bronchiolitis epidemic season and fulfilled inclusion criteria were recruited. Subjects were randomly allocated to receive CPAP via a helmet or nasal prongs for 60 min. The subjects were then placed on the other CPAP system for another 60-min period (helmet then nasal prongs [H-NP] or nasal prongs then helmet [NP-H]). Measurements were taken at 30, 60, 90, and 120 min. Failure was defined as the need for further respiratory support. RESULTS: Sixteen subjects were included, with 9 in the H-NP group and 7 in the NP-H group. CPAP significantly reduced respiratory distress, showing no differences between the H-NP and NP-H groups in terms of improving the Modified Wood's Clinical Asthma Score from 4.8 ± 1 to 3 ± 0.9 and 2.7 ± 1.7 points at 60 min and 120 min in the H-NP group, respectively, and from 4.2 ± 0.9 to 2.8 ± 0.9 and to 2.9 ± 0.9 at 60 min and 120 min, respectively, in the NP-H group. Sedatives were used in only 3 subjects (2 in the NP-H group, P = .77). The failure rate was similar in both groups (3 of 9 subjects vs 3 of 7 subjects, P = .70). No significant differences were seen for heart rate, breathing frequency, FIO2 , or transcutaneous oxygen saturation response. CONCLUSIONS: Our results suggest that CPAP delivered by nasal prongs and CPAP delivered by helmet are similar in terms of efficacy in young infants with acute bronchiolitis.

Procalcitonin and C-reactive protein as markers of systemic inflammatory response syndrome severity in critically ill children.

OBJECTIVES: To analyse the clinical value of procalcitonin (PCT), C-reactive protein (CRP) and leucocyte count in the diagnosis of paediatric sepsis and in the stratification of patients according to severity. DESIGN: Prospective, observational study. SETTING: Paediatric intensive care unit (PICU). PATIENTS: Ninety-four children. MEASUREMENT AND RESULTS: Leucocyte count, PCT and CRP were measured when considered necessary during the PICU stay. Patients were classified, when PCT and CRP were measured, into one of six categories (negative, SIRS, localized infection, sepsis, severe sepsis, and septic shock) according to the definitions of the American College of Chest Physicians /Society of Critical Care Medicine. A total of 359 patient day episodes were obtained. Leucocyte count did not differ across the six diagnostic classes considered. Median plasma PCT concentrations were 0.17, 0.43, 0.79, 1.80, 15.40 and 19.13 ng/ml in negative, systemic inflammatory response syndrome (SIRS), localized infection, sepsis, severe sepsis, and septic shock groups, respectively, whereas median plasma CRP concentrations were 1.35, 3.80, 6.45, 5.70, 7.60 and 16.2 mg/dl, respectively. The area under the ROC curve for the diagnosis of septic patients was 0.532 for leucocyte count (95% CI, 0.462-0.602), 0.750 for CRP (95% CI, 0.699-0.802) and 0.912 for PCT (95% CI, 0.882-0.943). We obtained four groups using CRP values and five groups using PCT values that classified a significant percentage of patients according to the severity of the different SIRS groups. CONCLUSIONS: PCT is a better diagnostic marker of sepsis in critically ill children than CRP. The CRP, and especially PCT, may become a helpful clinical tool to stratify patients with SIRS according to disease severity.

Cystatin C and beta2-microglobulin: markers of glomerular filtration in critically ill children.

INTRODUCTION: Parameters allowing regular evaluation of renal function in a paediatric intensive care unit (PICU) are not optimal. The aim of the present study was to analyse the utility of serum cystatin C and beta2-microglobulin (B2M) in detecting decreased glomerular filtration rate in critically ill children. METHODS: This was a prospective, observational study set in an eight-bed PICU. Twenty-five children were included. The inverses of serum creatinine, cystatin C, and B2M were correlated with creatinine clearance (CrC) using a 24-hour urine sample and CrC estimation by Schwartz formula (Schwartz). The diagnostic value of serum creatinine, cystatin C, and B2M to identify a glomerular filtration rate under 80 ml/minute per 1.73 m(2) was evaluated using receiver operating characteristic (ROC) curve analysis. RESULTS: Mean age was 2.9 years (range, 0.1 to 13.9 years). CrC was less than 80 ml/minute per 1.73 m(2) in 14 children, and Schwartz was less than 80 ml/minute per 1.73 m(2) in 9 children. Correlations between inverse of B2M and CrC (r = 0.477) and between inverse of B2M and Schwartz (r = 0.697) were better than correlations between inverse of cystatin C and CrC (r = 0.390) or Schwartz (r = 0.586) and better than correlations between inverse of creatinine and CrC (r = 0.104) or Schwartz (r = 0.442). The ability of serum cystatin C and B2M to identify a CrC rate and a Schwartz CrC rate under 80 ml/minute per 1.73 m(2) was better than that of creatinine (areas under the ROC curve: 0.851 and 0.792 for cystatin C, 0.802 and 0.799 for B2M, and 0.633 and 0.625 for creatinine). CONCLUSION: Serum cystatin C and B2M were confirmed as easy and useful markers, better than serum creatinine, to detect acute kidney injury in critically ill children.

Validación de la escala simplificada de puntuación de intervenciones terapéuticas (TISS-28) en niños críticamente enfermos / Validation of a Therapeutic Intervention Scoring System (TISS-28) in critically ill children

INTRODUCCIÓN: En el ámbito de los cuidados intensivos, existen numerosas escalas para cuantificar la gravedad de los pacientes. La mayoría de ellas son muy útiles, aunque en ocasiones laboriosas de completar, por lo que su implantación en la práctica habitual es escasa. Una de ellas es la escala de puntuación de intervenciones terapéuticas (TISS 76), que ha sido validada en unidades de adultos y pediátricas. Su versión simplificada y actualizada, la escala simplificada de puntuación de intervenciones terapéuticas (TISS 28), no ha sido validada en unidades pediátricas, siendo este el objetivo del estudio, con idea de disponer de una escala sencilla y rápida. MATERIAL Y MÉTODO: Estudio observacional prospectivo sin intervención, en la Unidad de Cuidados Intensivos Pediátricos (UCIP) de un hospital universitario. Se recogieron datos de 935 pacientes ingresados consecutivamente en la UCIP durante un periodo de 3 años, incluyendo los valores de TISS 76 y TISS 28 de todos durante los 4 primeros días de ingreso y la posterior evolución de los pacientes. RESULTADOS: Los valores medios de TISS 76 y TISS 28 para el primer día de ingreso fueron de 18,27 y de 18,02, respectivamente, siendo más elevados en los pacientes con secuelas o que fallecían. Se encontró muy buena correlación entre la TISS 76 y la 28, con coeficiente de correlación de Pearson y de correlación intraclase > 0,9 (excepto para el segundo día). La ecuación de correlación para los 4días fue: TISS76 = -1,74+1,05×TISS28. La TISS 28 fue capaz de explicar el 82,4% de la variabilidad de la TISS 76. El área bajo la curva con un intervalo de confianza del 95% para el primer día fue de 0,80 para la TISS 76 y de 0,76 para la TISS 28. CONCLUSIONES: Con los resultados obtenidos, la TISS 28 puede reemplazar a la TISS 26 en nuestra UCIP, sin empeorar la información proporcionada. Siendo una escala fiable y más sencilla de aplicar, podría ser útil su aplicación práctica

INTRODUCTION: There are numerous scales in intensive care units that are used to quantify the severity of patients. Most of them are very useful, although sometimes laborious to complete, thus limiting their use in usual practice. One of these scales, the Therapeutic Intervention Scoring System (TISS 76), has been validated in adult and paediatric units. Its simplified and updated version, the Simplified Therapeutic Intervention Scoring System (TISS 28), has not yet been validated in paediatric units. The aim of this study is to validate TISS 28, in order to have a simple and rapid scale. MATERIAL AND METHOD: A prospective non-interventional observational study was conducted in a Paediatric Intensive Care Unit (PICU) of a university hospital. Data were collected from 935 consecutive patients admitted to the PICU over a 3-year period. These included the values of TISS 76 and TISS 28 during the first 4days of admission and the subsequent outcome of the patients. RESULTS: The mean values of TISS 76 and TISS 28 for the first day of admission were 18.27 and 18.02, respectively. Values were higher in patients who had sequelae or died (17.58 versus 27.23 and 37.44, respectively for TISS 76 (P < .01); and 17.51 versus 23.80 and 33.44, respectively for TISS 28 (P < .01). A very good correlation was found between TISS 76 and TISS 28, with Pearson correlation and intraclass correlation coefficients > 0.9 (except for the 2 nd day). The correlation equation for the overall 4 days was: TISS76=- 1.74 + 1.05 × TISS28. TISS 28 was able to explain 82.4% of variability of TISS 76. The area under the curve with a confidence interval (CI) of 95% for the first day was 0.80 (0.73-0.87) for TISS 76, and 0.76 (0.67-0.84) for TISS 28. CONCLUSIONS: On observing the results obtained, TISS 28 can replace TISS 26 in our PICU, without worsening the information provided. Being a reliable scale and easier to apply, its practical application could be useful

Oscillation of the velvet worm slime jet by passive hydrodynamic instability.

The rapid squirt of a proteinaceous slime jet endows velvet worms (Onychophora) with a unique mechanism for defence from predators and for capturing prey by entangling them in a disordered web that immobilizes their target. However, to date, neither qualitative nor quantitative descriptions have been provided for this unique adaptation. Here we investigate the fast oscillatory motion of the oral papillae and the exiting liquid jet that oscillates with frequencies f~30-60 Hz. Using anatomical images, high-speed videography, theoretical analysis and a physical simulacrum, we show that this fast oscillatory motion is the result of an elastohydrodynamic instability driven by the interplay between the elasticity of oral papillae and the fast unsteady flow during squirting. Our results demonstrate how passive strategies can be cleverly harnessed by organisms, while suggesting future oscillating microfluidic devices, as well as novel ways for micro and nanofibre production using bioinspired strategies.

Fatal lactic acidosis during antiretroviral therapy.

OBJECTIVE: To describe the first pediatric case of fatal lactic acidosis in an antiretroviral-treated child with human immunodeficiency virus (HIV) infection. DESIGN: Case report. SETTING: Pediatric intensive care unit. PATIENTS: A patient with fatal antiretroviral therapy-associated type B lactic acidosis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We report the case of a 5-yr-old girl with HIV infection, receiving ritonavir, stavudine, and didanosine, who presented with a 10-day history of nausea and vomiting. Severe lactic acidosis was found. Her clinical condition worsened, with progressive increase in serum lactate, despite aggressive supportive therapy, including intravenous alkali and continuous arteriovenous hemodiafiltration. CONCLUSIONS: Fatal lactic acidosis is a complication of antiretroviral therapy in pediatric HIV patients, which has not been previously reported in children. Early recognition of mitochondrial dysfunction in these patients could prevent the development of fatal lactic acidosis.

Correlation of oxygen saturation as measured by pulse oximetry/fraction of inspired oxygen ratio with Pao2/fraction of inspired oxygen ratio in a heterogeneous sample of critically ill children.

PURPOSE: Oxygen saturation as measured by pulse oximetry (Spo2)/fraction of inspired oxygen (Fio2) (SF) ratio has demonstrated to be an adequate marker for lung disease severity in children under mechanical ventilation. We sought to validate the utility of SF ratio in a population of critically ill children under mechanical ventilation, noninvasive ventilation support, and breathing spontaneously. MATERIALS AND METHODS: A retrospective database study was conducted in a pediatric intensive care unit of a university hospital. Children with Spo2 less than or equal to 97% and an indwelling arterial catheter were included. Simultaneous blood gas and pulse oximetry were collected in a database. Derivation and validation data sets were generated, and a linear mixed modeling was used to derive predictive equations. Model performance and fit were evaluated using the validation data set. RESULTS: Three thousand two hundred forty-eight blood gas and Spo2 values from 298 patients were included. 1/SF ratio had a strong linear association with 1/Pao2/Fio2 (PF) ratio in both derivation and validation data sets, given by the equation 1/SF = 0.00164 + 0.521/PF (derivation). Oxygen saturation as measured by pulse oximetry/Fio2 values for PF criteria of 100, 200, and 300 were 146 (95% confidence interval [CI], 142-150), 236 (95% CI, 228-244), and 296 (95% CI, 285-308). Areas under receiver operating characteristic curves for diagnosis of PF ratio less than 100, 200, and 300 with the SF ratio were 0.978, 0.952, and 0.951, respectively, in the validation data set. CONCLUSIONS: Oxygen saturation as measured by pulse oximetry/Fio2 ratio is an adequate noninvasive surrogate marker for PF ratio. Oxygen saturation as measured by pulse oximetry/Fio2 ratio may be an ideal noninvasive marker for patients with acute hypoxemic respiratory failure.