Veno-venous extracorporeal membrane oxygenation for COVID-19-associated pediatric acute respiratory distress syndrome.

BACKGROUND: The SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) coronavirus has emerged as a highly contagious respiratory pathogen causing severe acute lung injury. Extracorporeal membrane oxygenation is a standard tool for the management of life-threatening acute respiratory distress syndrome, but the use of this resource-intensive therapy has come into question due to strained medical systems and limited proven treatments for COVID-19. CASE SUMMARY: A 16-year-old female with obesity presented with fever, myalgias, cough, and tachypnea and was diagnosed with COVID-19. She progressed to severe pediatric acute respiratory distress syndrome requiring intubation on hospital day 4 and cannulation to veno-venous extracorporeal membrane oxygenation on hospital day 6. The patient received remdesivir, steroids, and anakinra. The patient was successfully decannulated on hospital day 12 and was discharged home on hospital day 21. CONCLUSION: We report the use of veno-venous extracorporeal membrane oxygenation as a bridge to lung recovery in a pediatric patient with severe pediatric acute respiratory distress syndrome due to COVID-19.

Using Pleth Variability as a Triage Tool for Children With Obstructive Airway Disease in a Pediatric Emergency Department.

OBJECTIVES: Patients with obstructive airway disease have varying degrees of pulsus paradoxus that correlate with illness severity. Pulsus paradoxus can be measured using plethysmography. We investigated whether plethysmograph (pleth) variability on admission to the pediatric emergency department (ED) could predict patient disposition. We hypothesized that patients with a larger pleth variability would have a higher likelihood of being admitted to a general pediatrics unit or the intensive care unit (ICU). METHODS: We conducted a prospective single-center study of children aged 1 to 18 years who presented to a pediatric ED with a diagnosis of asthma or reactive airway disease. The pleth variability index (PVI) was calculated from their initial plethysmography tracing. Disposition from the ED was recorded as discharge, admission to the floor, or admission to the ICU. RESULTS: A total of 117 patients were included in our study. Forty-eight patients were discharged home, 61 were admitted to the floor, and 8 were admitted to the ICU. The median PVI for each of these groups was 0.27 (interquartile range [IQR], 0.19-0.39) for discharges, 0.29 (IQR, 0.20-0.44) for patients admitted to the floor, and 0.56 (IQR, 0.35-0.70) for patients admitted to the ICU. A Kruskal-Wallis test demonstrated a significant difference in the PVI between each of the groups (P = 0.0087). CONCLUSIONS: Our results suggest that PVI may be a useful tool in the triage of children who present to the ED with obstructive airway disease. Further studies should aim to assess the validity of PVI in predicting the response to bronchodilator therapy during the course of a patient's hospitalization.

An Analysis of the Daily Work-Rounding Process in a Pediatric Intensive Care Unit.

OBJECTIVE: To complete an objective analysis of the activities that occur during the course of daily rounds in a high acuity academic tertiary care pediatric intensive care unit (PICU). DESIGN: Prospective observational work sampling design. SETTING: Tertiary care academic Children's Hospital Pediatric Intensive Care Unit. SUBJECTS: Multidisciplinary PICU teams. INTERVENTIONS: None. METHODS: Intensive care unit rounds were observed as part of an initiative to improve efficiency over a 2-month period. The number of observations required was determined by Neibel's work sampling method. Rounds were broken into various constituent events and then later classified as "value-added/essential," "value-added/nonessential," and "nonessential" based on whether the observed event was essential to the core mission of PICU rounds. RESULTS: The mean time spent per patient for all observed teams was 17.9 min (SD 1.3 min). Teams spent 64% of their time doing value-added/essential tasks (11.2 min, SD 2.2 min) and 13% of their time doing value-added/nonessential tasks (2.4 min, SD 0.9 min). Teams spent 23% of their time on non-value-added activities (4.1 min, SD 2.3 min). The top three non-value-added activities conducted during rounds were travel, waiting, and interruptions regarding care of other patients. Given the consistency of time spent on value-added activities among attendings, these non-value-added activities might explain the significant variability observed among attendings in total time spent rounding. CONCLUSIONS: This was an observational study to characterize the activities that occur during the course of a routine PICU work rounds. Although there was significant consistency in the time spent per patient in value-added activities, there was significant disparity in time spent on nonessential activities, such as travel and waiting. A dedicated attempt to reduce time spent on nonessential activities can substantially reduce rounding times and improve the efficiency and value of rounds.

The Impact and Statistical Analysis of a Multifaceted Anticoagulation Strategy in Children Supported on ECMO: Performance and Pitfalls.

BACKGROUND: We sought to determine whether the introduction of a new anticoagulation protocol improved the frequency with which target anticoagulation parameters were met in children supported with extracorporeal membrane oxygenation (ECMO). Additionally, we sought to correlate the results of various tests of anticoagulation with the heparin infusion dose (HID) for patients on ECMO and to evaluate the utility of these anticoagulation monitoring tests for the titration of the HID. METHODS: A retrospective chart review of 18 patients who received ECMO at an academic tertiary care children's hospital. Nine patients who were managed using a new anticoagulation protocol were matched by age and diagnosis with 9 patients managed with the old protocol. We collected data relating to patient demographics, type of extracorporeal support, disease process, and incidence of bleeding or thrombosis. Anticoagulation parameters collected include the activated clotting time (ACT), activated partial thromboplastin time (aPTT), prothrombin time/international normalized ratio, anti-factor Xa level, and antithrombin 3 level along with the HID at each time point. Patient groups were compared using a Generalized Linear Mixed Model, a mixed model analysis of variance, and correlational studies. MAIN RESULTS: The percentage of in-range ACT values was not different between the 2 protocols, whereas the percentage of in-range aPTT values was higher in the new anticoagulation protocol (ACT: 37.7% vs 39.5%; aPTT: 25.1% vs 39.8%). After accounting for repeated and variable measures within patients, the probability of obtaining an in-range ACT and aPTT did not differ significantly between the 2 protocols (ACT: P = .3488; aPTT: P = .16). The mean HID did not differ between the 2 groups (35.0 unit/kg/h vs 37.6 unit/kg/h, P = .56). Correlation coefficients demonstrated a significant inverse correlation between the ACT and the HID in both the groups (old: r = -.22, P < .0001; new: r = -.26, P < .0001). We observed a significant positive correlation between the aPTT and the HID in the historical group (r = .25, P < .0001), but no correlation between the aPTT and the HID in the current group (r = -.02, P = .71). The anti-factor Xa level showed a significantly positive correlation with the HID in the current group (r = .62, P < .0001). CONCLUSIONS: A multipronged monitoring regimen slightly increased the amount of time that anticoagulation parameters were within range. Correlations between the HID and the aPTT differed based on anticoagulation protocol, with a positive correlation in the older protocol and no correlation in the new protocol. This may highlight a problem in study design and analysis that requires further examination. Further trials are needed to assess the most useful markers with which anticoagulation protocols for ECMO can be created, adjusted, and evaluated.

Impact of monitoring endotracheal tube cuff leak pressure on postextubation stridor in children.

PURPOSE: To determine if implementing a protocol maintaining an air leak when using cuffed endotracheal tubes (ETT) throughout the course of mechanical ventilation (MV) in children would decrease the rate of postextubation stridor (PES). METHODS: All children requiring MV through a cuffed ETT were included, except those with (1) upper airway anomaly, (2) died while on MV, (3) received tracheostomy before extubation, and (4) transferred before extubation. We implemented a protocol limiting the volume of air instilled into the cuff, allowing an air leak by 25 cm H2O pressure or by peak inspiratory pressure, whichever was higher. Monitoring occurred every 6 hours, adjusting cuff volumes if necessary. Patients receiving nebulized racemic epinephrine within 24 hours of extubation for upper airway obstruction were defined as having PES. RESULTS: At baseline, 110 patients received cuffed ETTs. The proportion of patients who had an air leak at the time of extubation was 47.3%, and that who developed PES was 21.8%. During the intervention, 101 patients received cuffed ETTs. Most (72.3%) had an air leak at the time of extubation (P< .01), and 9.9% developed PES, a 54.6% relative decrease (relative risk, 0.45; 95% confidence interval, 0.22-0.90; P= .018). CONCLUSIONS: Maintaining an appropriate air leak throughout the course of MV using cuffed ETT decreases the rate of PES in children.

Characterization of caspofungin susceptibilities by broth and agar in Candida albicans clinical isolates with characterized mechanisms of azole resistance.

Caspofungin (CSP) susceptibilities of Candida albicans, as determined by broth microdilution methods, have not been found to be related to azole susceptibilities or resistance. In contrast, it has been observed that azole-resistant clinical isolates that overexpress the efflux pump gene CDR2 are less susceptible to CSP when tested using an agar dilution method commonly employed with Saccharomyces cerevisiae. The goal of this study was to further understand the effects of azole resistance mechanisms on CSP susceptibility testing. A collection of 69 isolates exhibiting known mechanisms of azole resistance and resistance-associated phenotypes were analyzed by broth microdilution methods to determine standard minimum inhibitory concentrations (MICs) for CSP. The same isolates were then analyzed as to their MIC to CSP by Etest strips, an agar-based method that has been shown generally to be comparable to broth methods. The MICs found with both methods were not significantly different. However, a collection of strains overexpressing the efflux pump CDR2 did exhibit a spectrum of CSP susceptibilities when examined by agar dilution susceptibility tests, ranging from standard to reduced susceptibilities. This work demonstrated that a change in CSP susceptibility with CDR2 overexpressing cells in agar dilution studies is a variable phenotype and it is not the result of growth conditions (i.e., broth versus agar).

Polyene susceptibility is dependent on nitrogen source in the opportunistic pathogen Candida albicans.

OBJECTIVES: Polyene antifungal drugs, including amphotericin B or nystatin, target ergosterol in the fungal plasma membrane and are used to treat systemic, vaginal and oral fungal infections. In the oral cavity, the available nitrogen sources are primarily in the form of proteins, which are poor nitrogen sources. This study evaluates the effect of protein as a nitrogen source on drug susceptibilities. METHODS: Candida albicans was grown in protein [bovine serum albumin (BSA) or casein (CSN)] as a sole nitrogen source, in ammonium sulphate (AS) as a nitrogen source, or in both protein and AS. RESULTS: Cells grown in BSA or CSN were 4- to 16-fold less susceptible to amphotericin B and nystatin than those grown in AS. Similar results were observed for cycloheximide, but not for fluconazole or caspofungin, and were observed for many C. albicans clinical isolates. The results were observed in two different media, and in broth and on agar. Cells grown under these nitrogen-poor conditions have a reduction in ergosterol sterol levels and a reduction in overall sterol synthesis. Quantitative real-time reverse transcription-polymerase chain reaction analysis shows that some genes involved in sterol biosynthesis are induced under nitrogen-limiting conditions, consistent with the lower sterol levels. CONCLUSIONS: The results demonstrate that nitrogen source has a significant effect on polyene susceptibilities. As these nitrogen-limiting conditions mimic oral nitrogen availability, they suggest that in vitro polyene susceptibilities may overestimate the in vivo susceptibilities to polyene drugs in the mouth.

Tetracycline alters drug susceptibility in Candida albicans and other pathogenic fungi.

The tetracycline (TET) promoter has been used in several systems as an inducible regulator of gene expression. In control analyses, the standard Candida albicans laboratory strain SC5314 was found to have altered susceptibility to a variety of antifungal drugs in the presence of relatively high concentrations (50-200 microg ml(-1)) of TET. Altered susceptibility was most notable with exposure to amphotericin B (AMB), with a 32-fold increase in susceptibility, and terbinafine (TRB), with a 32-fold decrease in susceptibility. The TET/AMB synergy was observed in several clinical isolates of C. albicans and in the distantly related species Aspergillus fumigatus and Cryptococcus neoformans. The TET/AMB synergy is not related to efflux pump activity, as determined by FACS analyses and by analysis of a strain containing efflux pump deletions. Gene expression analyses by luciferase and by quantitative real-time reverse transcriptase PCR failed to identify significant alterations in expression of any genes associated with resistance. C. albicans grown with TET for 48 h does show a reduction in total cellular ergosterol. Analysis of growth curves suggests that the TET effect is associated with lack of a diauxic shift, which is related to a loss of mitochondrial function. MitoTracker fluorescent dye was used to demonstrate that TET has a direct effect on mitochondrial function. These results demonstrate the need for careful analysis of TET effects when using a TET-inducible promoter, especially in studies that involve antifungal drugs. This study defines some limits to the use of the TET-inducible promoter, and identifies effects on cells that are the result of TET exposure alone, not the result of expression of a targeted gene.

Concomitant assessment of depth of sedation by changes in bispectral index and changes in autonomic variables (heart rate and/or BP) in pediatric critically ill patients receiving neuromuscular blockade.

OBJECTIVE: We evaluated whether or not changes in bispectral index (BIS) are associated with concomitant changes in autonomic variables that are in agreement with the different level of sedation that the changes in BIS indicate. DESIGN: A retrospective chart review. SETTING: A pediatric ICU of a children's hospital. METHODS AND MAIN RESULTS: Charts of patients who were receiving mechanical ventilation and IV sedation, neuromuscular blockade, and continuous BIS monitoring were enrolled in the study. Changes in BIS values > or = 30% from previous readings were evaluated to determine whether or not concomitant changes of > or = 10% in autonomic variables, in the same direction, coexisted. Forty-seven patients (35 male and 12 female) were enrolled in our study; ages ranged from 10 days to 18 years (mean, 4.2 +/- 6.2 years [+/- SD]). Twenty-five patients were < 1 year of age (53%). All patients were sedated and pharmacologically paralyzed. Overall, 387 BIS readings (15%) showed a > or = 30% change from the previously documented BIS number. These BIS changes were in agreement with heart rate (HR) changes, mean arterial pressure (MAP) changes, and both HR and MAP changes in 10.6%, 23.8%, and 5.7% of the time, respectively. The same analysis of agreement was done for patients < or = 1 year old, and results were no different from those of older patients. Among 21 patients who were not receiving any vasoactive drugs (alpha- and/or beta-adrenergic agonists) during the study period, 157 BIS recordings (15%) showed a > or = 30% change from the previously documented BIS number. The percents of agreement with HR, MAP, and HR and MAP for these patients were 14.6%, 17.2%, and 7.6%, respectively. In 26 patients who were receiving vasoactive medications during the study, 230 BIS recordings (15%) showed a > or = 30% change from the previously documented BIS number. For these patients, the percentages of agreement were 7.8%, 28.3%, and 4.3%, respectively. Agreement with MAP was significantly better than with HR for this group of patients (p < 0.05; Fisher Exact Test). SUMMARY: While significant changes in BIS are thought to reflect significant changes in depth of sedation, they have a very low rate of agreement with changes in vital signs. In the absence of BIS, the level of sedation of chemically paralyzed pediatric patients can be better guided by changes in MAP than in HR, particularly in patients receiving vasoactive drug treatment.

Drug-induced regulation of the MDR1 promoter in Candida albicans.

Resistance of Candida albicans to azole antifungal drugs is mediated by two types of efflux pumps, encoded by the MDR1 gene and the CDR gene family. MDR1 mRNA levels in a susceptible clinical isolate are induced by benomyl (BEN) but not by other drugs previously shown to induce MDR1. To monitor MDR1 expression under several conditions, the MDR1 promoter was fused to the Renilla reniformis luciferase reporter gene (RLUC). The promoter was monitored for its responses to four oxidizing agents, five toxic hydrophobic compounds, and an alkylating agent, all shown to induce major facilitator pumps in other organisms. Deletion constructs of the MDR1 promoter were used to analyze the basal transcription of the promoter and its responses to the toxic compound BEN and the oxidizing agent tert-butyl hydrogen peroxide (T-BHP). The cis-acting elements in the MDR1 promoter responsible for induction by BEN were localized between -399 and -299 upstream of the start codon. The cis-acting elements responsible for MDR1 induction by T-BHP were localized between -601 and -500 upstream of the start codon. The T-BHP induction region contains a sequence that resembles the YAP1-responsive element (YRE) in Saccharomyces cerevisiae. This Candida YRE was placed upstream of a noninducible promoter in the luciferase construct, resulting in an inducible promoter. Inversion or mutation of the 7-bp YRE eliminated induction. Many of the drugs used in this analysis induce the MDR1 promoter at concentrations that inhibit cell growth. These analyses define cis-acting elements responsible for drug induction of the MDR1 promoter.

Role of Candida albicans transcription factor Upc2p in drug resistance and sterol metabolism.

In Candida albicans, drug resistance to clinically important antifungal drugs may be regulated through the action of transcription factors in a manner that may or may not be similar to regulation in Saccharomyces cerevisiae. A search of the C. albicans genome identified a single homolog of the S. cerevisiae transcription factor genes UPC2 (ScUPC2) and ECM22 (ScECM22) that have been associated with regulation of ergosterol biosynthesis. Sequence analysis of this C. albicans UPC2 (CaUPC2) gene identifies two domains, an anchoring transmembrane domain and a transcription factor region containing multiple nuclear localization signals and a fungal Zn(2)-Cys(6) binuclear cluster domain. Heterozygous deletion, homozygous deletion, and reconstructed strains of CaUPC2 as well as the parental strain were tested against several antifungal drugs, including ergosterol biosynthesis inhibitors. The CaUPC2 homozygous deletion strain showed marked hypersusceptibility to most drugs, compared to the parental and reconstructed strains. The deletion strains accumulate significantly less radiolabeled cholesterol, suggesting reduced ergosterol scavenging in those strains. When grown under azole drug pressure, the parental, heterozygous deletion and reconstructed strains of CaUPC2 upregulate the ERG2 and ERG11 ergosterol biosynthesis genes, while the homozygous deletion strain shows no such upregulation. Consistent with these results, CaUPC2 deletion strains show reduced ergosterol levels, which may explain the increased susceptibilities of the CaUPC2 deletion strains. Thus, it appears that CaUPC2 acts as a transcription factor involved in the regulation of ergosterol biosynthetic genes and as a regulator of sterol uptake across the plasma membrane.

Prone positioning of pediatric patients with ARDS results in improvement in oxygenation if maintained > 12 h daily.

OBJECTIVES: To evaluate changes in oxygenation index (OI) in pediatric patients with ARDS during the first 24 h of prone positioning (PP), and to determine whether or not longer periods of PP (> 12 h) result in a more pronounced improvement in oxygenation. DESIGN: A retrospective chart review of patients with ARDS who had been placed in PP for their management. SETTING: Pediatric ICU of a children's hospital. MEASUREMENTS AND MAIN RESULTS: We retrieved the charts of patients with ARDS who had been admitted to our pediatric ICU over a 3-year period and placed in PP for their management. The patients received mechanical ventilation, were sedated and pharmacologically paralyzed, and underwent arterial blood gas analysis, with concomitant documentation of ventilator settings, at a frequency of once every 4 h or more often. We divided the first 24 h of PP into two periods, brief and prolonged. The brief period was defined as duration of PP between 6 h and 10 h, and the prolonged period was between 18 h and 24 h. We compared pre-PP OI values to values after brief periods and prolonged periods of PP. Values of the PaO(2)/fraction of inspired oxygen (P/F) ratio and the mean airway pressure (MAP) were similarly evaluated. We also evaluated the degree of OI fluctuations during 24 h of PP by identifying the time points at which the best OI and the worst OI were observed. Data from a total of 40 pediatric patients with ARDS were evaluated. Twenty-one of the patients were male, and 19 were female; their ages ranged from 1 month to 18 years (mean +/- SD, 6.22 +/- 6.27 years). Thirty-two patients received conventional mechanical ventilation, and 8 patients received high-frequency oscillatory ventilation. Thirty-three patients survived, and 7 patients (21%) died. The mean duration of PP was 67 +/- 64 h (2.8 +/- 2.7 days), the mean number of ventilator days was 32 +/- 32, and the mean interval between endotracheal intubation and placing the patients in PP was 107 +/- 108 h (4.5 +/- 4.5 days). Thirty-seven patients completed 20 h of PP or more. The mean post-PP time points at which OI values were actually evaluated for these patients were 8 +/- 2 h (brief) and 21 +/- 4 h (prolonged), respectively. Overall, the OI decreased from a pre-PP value of 24.8 +/- 13.0 to 16.7 +/- 13.7 after a brief period of PP (p < 0.05 when compared to baseline) and 11.4 +/- 6.3 after prolonged period (p < 0.05 when compared to baseline and brief period values). This improvement in OI followed the improvement seen in the P/F ratio, whereas the MAP remained unchanged. The best mean OI value, with patients in PP, was 11 +/- 9 (p < 0.05 when compared to baseline) that occurred at 16 +/- 6 h, and the worst was 22 +/- 15 (p = not significant when compared to baseline) that occurred at 9 +/- 7 h. CONCLUSIONS: PP of pediatric patients with ARDS for prolonged periods (18 to 24 h) results in a more pronounced and more stable reduction in their OI values than those observed after brief periods (6 to 10 h). This improvement in OI was not associated with changes in MAP during the first 24 h of mechanical ventilation. OI values tend to fluctuate more during the first 12 h of PP then they do during the subsequent 12 h.

Cephalad movement of endotracheal tubes caused by prone positioning pediatric patients with acute respiratory distress syndrome.

OBJECTIVE: To test the hypothesis that prone positioning of patients with acute respiratory distress syndrome results in significant cephalad movement of their endotracheal tubes (ETT). DESIGN: A retrospective review of chest radiographs and patient information. SETTING: Pediatric intensive care unit of a children's hospital. MEASUREMENTS AND MAIN RESULTS: Patients with acute respiratory distress syndrome had digital chest radiographs performed before and immediately after prone positioning as per our routine practice. Based on measurements of the length of the thoracic trachea and the length of the thoracic segment of the ETT, the movement of the ETT subsequent to prone positioning was calculated. Fifteen pairs of radiographs of 14 consecutive patients were evaluated. There were seven girls and seven boys, with ages ranging from 2 months to 18 yrs. All patients had a cephalad movement of their ETT ranging from 10% to 57% of their thoracic tracheal length (p < .001) associated with prone positioning. The mean amplitude of this movement was 34% +/- 16%, indicating that if the tip of the ETT is not deeper than one third of the thoracic tracheal length before prone positioning, it might slide into the cervical trachea as a result of this procedure. CONCLUSIONS: Prone positioning results in cephalad movement of ETT within the trachea. The tip of the ETT should be deeper than one third of the total length of the thoracic trachea before prone positioning to prevent it from moving into the cervical trachea. When prone positioning is done with an ETT originally not deeper than one third of the thoracic trachea, obtaining a chest radiograph immediately after prone positioning is important to determine whether the ETT remained safely situated in the trachea.