Continuous Glucose Monitoring in Pediatric Diabetic Ketoacidosis

BACKGROUND

Use of real-time continuous glucose monitoring (rtCGM) in ambulatory settings improves overall glycemic control and reduces the incidence of diabetic ketoacidosis (DKA) in adults and children/adolescents with type 1 diabetes (T1D). However, the use of rtCGM in children with DKA has not been well studied.

METHOD

This prospective, single-arm, single-center study assessed the accuracy, reliability, and feasibility of a commercially available rtCGM device compared with point-of-care (POC) capillary and serum glucose values in pediatric patients admitted to the pediatric intensive care unit for DKA. The primary outcome was the accuracy of rtCGM glucose values compared with POC capillary and serum glucose values during standard treatment of DKA as assessed by Clarke Error Grid (CEG) analysis. Secondary outcomes were assessment of the relationship between rtCGM readings and degree of acidosis and mean length of hospital stay (LOS).

RESULTS

Data from 35 hospitalized children (mean ± SD age, 11.9 ± 4.1 years) with DKA were included in our analysis. Five hundred twenty-four time-matched glucose values between serum glucose and rtCGM and 91 time-matched glucose values between POC capillary glucose and rtCGM were obtained. The effect of acidosis on accuracy CEG analysis showed 95.4% of the 524 matched CGM/POC pairs and 95.6% of the 91 matched CGM/serum glucose pairs in the clinically acceptable A + B zones. The average LOS was 1.32 ± 0.73 days. Serum bicarbonate level did not appear to affect the accuracy of rtCGM in the setting of DKA.

CONCLUSIONS

Continuous glucose monitoring use in inpatient pediatric DKA treatment was found to be feasible and reliable.

Effects of Endoscopic Sinus Surgery and Nasal Surgery in Patients with Obstructive Sleep Apnea

OBJECTIVES

To evaluate the impact of combined nasal surgery and endoscopic sinus surgery on the objective measurements of obstructive sleep apnea (OSA) and sleep architecture by comparing polysomnographic data before and after combined surgery in patients with OSA.

STUDY DESIGN

Case series with chart review.

SETTING

A single clinical site.

SUBJECTS AND METHODS

Patients with OSA and chronic rhinosinusitis who underwent combined nasal surgery and endoscopic sinus surgery and preoperative and postoperative polysomnography were identified. Patient charts were reviewed and preoperative and postoperative body mass index, apnea-hypopnea index (AHI), mean and minimum oxygen saturation, sleep efficiency, and sleep staging were compared.

RESULTS

Fifty-six patients were included in our study. Patients were divided into 3 groups on the basis of the severity of OSA: those with mild OSA (n = 9), those with moderate OSA (n = 23), and those with severe OSA (n = 24). After combined nasal and sinus surgery, the mean AHI significantly decreased from 33.5 ± 22.0 to 29.4 ± 20.8 (P = .009) in our overall population. Specifically, AHI improved significantly in patients with moderate OSA (from 22.3 ± 4.8 to 20.7 ± 8.2, P = .023) and severe OSA (from 52.3 ± 21.4 to 43.6 ± 23.9, P = .034), while patients with mild OSA did not have significant changes in AHI. Successful surgical procedures were achieved in only 2 of 56 patients.

CONCLUSION

Although combined nasal and sinus surgery may slightly improve AHI in a certain group of patients, it does not cure OSA or have a significant clinical impact.

Effects of Proton Pump Inhibitor Therapy for Laryngopharyngeal Reflux on Posttreatment Symptoms and Hypopharyngeal pH

OBJECTIVE

To determine the effect of twice-daily proton pump inhibitor (PPI) treatment on the relationship between laryngopharyngeal pH environment and symptoms in patients with laryngopharyngeal reflux (LPR).

STUDY DESIGN AND SETTING

Retrospective analysis of records from consecutive patients seen at a single clinical site between 2009 and 2012.

SUBJECTS AND METHODS

Forty-three records of patients diagnosed with LPR who underwent pre- and posttreatment pH studies were included. Prior to treatment, all had a Reflux Symptom Index (RSI) > 13 and an abnormal pH study. Patients were treated for ≥ 4 weeks with twice-daily PPIs. Following treatment, patients completed a second RSI and pH study.

RESULTS

Most patients (67.4%) had symptom normalization; however, most patients (60.5%) did not have pH normalization. For all patients whose symptoms did not normalize, pH scores also did not normalize; 32.6% of patients showed no subjective or objective treatment response. For individuals whose symptoms normalized but whose pH scores did not normalize, there was a significant decrease in upright pH score. For the entire group, pretreatment symptom and upright pH scores were strongly positively correlated. Improvements in symptom and upright pH scores following treatment were moderately positively correlated.

CONCLUSION

Laryngopharyngeal pH failed to normalize for most individuals after PPI treatment; only pH improvement was necessary for symptom normalization. Many patients had no treatment response. Laryngopharyngeal reflux patients may make up a heterogeneous group, and PPI responsivity may help explain conflicting results from previous studies. Posttreatment pH monitoring is recommended in studies investigating the efficacy of PPI therapy for LPR.

Diagnostic Value of the Friedman Tongue Position and Mallampati Classification for Obstructive Sleep Apnea

Objective

To assess the association between the Mallampati classification and Friedman tongue position for obstructive sleep apnea severity as determined by apnea-hypopnea index and to determine which method is most closely correlated with prediction of obstructive sleep apnea severity.

Data Sources

English-language searches of PubMed, MedLine, and the Cochrane database. Reference sections of identified studies were examined for additional articles.

Review Methods

Databases through December 2011 were searched, combined with review of relevant article bibliographies, and assessed by 4 reviewers. Systematic review and random-effects meta-analysis of studies evaluating tongue position and obstructive sleep apnea severity were performed. Outcomes were reported as correlations.

Results

Ten studies met inclusion criteria and had data for pooling (2513 patients). Friedman tongue position and Mallampati classification were significantly associated with obstructive sleep apnea severity, with a correlation of 0.351 (0.094-0.564, P = .008). Analysis of the correlation of tongue position with obstructive sleep apnea severity reveals correlations of 0.184 (0.052, 0.310, P = .006) and 0.388 (0.049, 0.646, P = .026) for the Mallampati classification and Friedman tongue position, respectively. Publication bias does not yield a significant Egger regression intercept; however, 4 imputed values to the right of the mean were found using Duval and Tweedie’s trim-and-fill method, yielding an overall correlation of 0.498 (confidence interval = 0.474-0.521).

Conclusion

The Mallampati classification and Friedman tongue position assessment techniques are significantly correlated with predicting obstructive sleep apnea severity. Publication bias does not significantly affect our results. The strength of this correlation is higher for Friedman tongue position, although 95% confidence intervals for the respective correlation coefficients overlap.

Advantages of statistical analysis of giant vesicle flickering for bending elasticity measurements

We show how to greatly improve precision when determining bending elasticity of giant unilamellar vesicles. Taking advantage of the well-known quasi-spherical model of liposome flickering, we analyze the full probability distributions of the configurational fluctuations instead of limiting the analysis to the second moment measurements only as usually done in previously published works. This leads to objective criteria to reject vesicles that do not behave according to the model. As a result, the confidence in the bending elasticity determination of individual vesicles that fit the model is improved and, consequently, the reproducibility of this measurement for a given membrane system. This approach uncovers new possibilities for bending elasticity studies like detection of minute influences by solutes in the buffer or into the membrane. In the same way, we are now able to detect the inhomogeneous behavior of giant vesicle systems such as the hazardous production of peroxide in bilayers containing fluorescent dyes.

Conception and realization of a non-cationic non-viral DNA vector

Cationic non-viral DNA vectors are very successful in in vitro transfections but less efficient in in vivo tests. This seems mainly due to the cationic nature of the molecules used to complex DNA. In this article, we describe the design and the route towards the realization of a non-viral non-cationic vector. The strategy follows three steps: first, the incorporation of DNA to a lamellar phase; second, the making of multilamellar vesicles containing a high loading of DNA by shearing the lamellar phase and, finally, the grafting of peptides onto the surface of the vesicles to target a specific receptor on the cells. Throughout this process, we had to overcome many obstacles; this review describes the present state of our work and summarizes the remaining steps.

The lipid charge density at the bilayer surface modulates the effects of melittin on membranes

The influence of melittin on two DMPA membrane systems at pH 4.2 and 8.2 has been investigated by solid-state 31P and 2H NMR, as a function of temperature and peptide concentration. Melittin promotes greater morphological changes for both systems in the fluid phase, the effect being larger at pH 4.2. Close inspection of fatty acyl chain dynamics suggests that some parallels can be drawn between the DMPA/melittin at pH 8.2 and PC/melittin systems. In addition, at pH 8.2 a direct neutralization at the interface of one of the lipid negative charges by a positive charge of the peptide occurs, as can be monitored by 31P NMR at the molecular level. For the system at pH 4.2 and at high temperature, a lipid-to-peptide molar ratio of 30 is sufficient to transform the whole system into an isotropic phase, proposed to be inverted micelles. When the system is cooled down towards the gel phase one observes an intermediate hexagonal phase in a narrow range of temperature.

Tryptophan-anchored transmembrane peptides promote formation of nonlamellar phases in phosphatidylethanolamine model membranes in a mismatch-dependent manner

To better understand the mutual interactions between lipids and membrane-spanning peptides, we investigated the effects of tryptophan-anchored hydrophobic peptides of various lengths on the phase behavior of 1,2-dielaidoylphosphatidylethanolamine (DEPE) dispersions, using (31)P nuclear magnetic resonance and small-angle X-ray diffraction. Designed alpha-helical transmembrane peptides (WALPn peptides, with n being the total number of amino acids) with a hydrophobic sequence of leucine and alanine of varying length, bordered at both ends by two tryptophan membrane anchors, were used as model peptides and were effective at low concentrations in DEPE. Incorporation of 2 mol % of relatively short peptides (WALP14-17) lowered the inverted hexagonal phase transition temperature (T(H)) of DEPE, with an efficiency that seemed to be independent of the extent of hydrophobic mismatch. However, the tube diameter of the H(II) phase induced by the peptides was clearly dependent on mismatch and decreased with shorter peptide length. Longer peptides (WALP19-27) induced a cubic phase, both below and above T(H). Incorporation of WALP27, which is significantly longer than the DEPE bilayer thickness, did not stabilize the bilayer. The longest peptide used, WALP31, hardly affected the lipid's phase behavior, and appeared not to incorporate into the bilayer. The consequences of hydrophobic mismatch between peptides and lipids are therefore more dramatic with shorter peptides. The data allow us to suggest a detailed molecular model of the mechanism by which these transmembrane peptides can affect lipid phase behavior.

A comparative study of the action of melittin on sphingomyelin and phosphatidylcholine bilayers

To investigate whether lipid solubilization is of relevance in describing the interaction between melittin and biological membranes, we studied melittin-induced polymorphism using model membranes composed of the biological lipid sphingomyelin (bovine brain). The behavior of the system was monitored by solid state 31P-NMR and turbidity measurements and compared to the peptides well-characterized action on the synthetic lipid dipalmitoylphosphatidylcholine. It was found that melittin-induced macroscopic changes of sphingomyelin membranes are qualitatively the same as in the case of dipalmitoyl-phosphatidylcholine bilayers. The sphingomyelin/melittin system is thus proposed to show a reversible vesicle-to-disc transition (fluid-to-gel phase) through an intermediate fusion or aggregation event centered at the main transition temperature, Tm, as reported in the case of saturated phosphatidylcholine. In the case of spontaneous disc formation at 37 degrees C, the lipid-to-peptide molar ratio in the discoidal objects was determined to be approximately 20 for dipalmitoylphosphatidylcholine and about 12 in the case of natural sphingomyelin. Melittin partition coefficients between membranes and the aqueous medium at 37 degrees C were found to be 6.1 +/- 0.8 mM-1 and 3.7 +/- 0.4 mM-1 for sphingomyelin and dipalmitoylphosphatidylcholine, respectively. For very high peptide quantities (lipid-to-peptide molar ratio, Ri < or = 5) mixed micelles are formed over the entire temperature range (20 degrees to 60 degrees C) for both kinds of lipids.

Bending elasticities of model membranes: influences of temperature and sterol content

Giant liposomes obtained by electroformation and observed by phase-contrast video microscopy show spontaneous deformations originating from Brownian motion that are characterized, in the case of quasispherical vesicles, by two parameters only, the membrane tension sigma and the bending elasticity k(c). For liposomes containing dimyristoyl phosphatidylcholine (DMPC) or a 10 mol% cholesterol/DMPC mixture, the mechanical property of the membrane, k(c), is shown to be temperature dependent on approaching the main (thermotropic) phase transition temperature T(m). In the case of DMPC/cholesterol bilayers, we also obtained evidence for a relation between the bending elasticity and the corresponding temperature/cholesterol molecular ratio phase diagram. Comparison of DMPC/cholesterol with DMPC/cholesterol sulfate bilayers at 30 degrees C containing 30% sterol ratio shows that k(c) is independent of the surface charge density of the bilayer. Finally, bending elasticities of red blood cell (RBC) total lipid extracts lead to a very low k(c) at 37 degrees C if we refer to DMPC/cholesterol bilayers. At 25 degrees C, the very low bending elasticity of a cholesterol-free RBC lipid extract seems to be related to a phase coexistence, as it can be observed by solid-state (31)P-NMR. At the same temperature, the cholesterol-containing RBC lipid extract membrane shows an increase in the bending constant comparable to the one observed for a high cholesterol ratio in DMPC membranes.

Effects of pH and cholesterol on DMPA membranes: a solid state 2H- and 31P-NMR study

The effect of pH and cholesterol on the dimyristoylphosphatidic acid (DMPA) model membrane system has been investigated by solid state 2H- and 31P-NMR. It has been shown that each of the three protonation states of the DMPA molecule corresponds to a 31P-NMR powder pattern with characteristic delta sigma values; this implies additionally that the proton exchange on the membrane surface is slow on the NMR time scale (millisecond range). Under these conditions, the 2H-labeled lipid chains sense only one magnetic environment, indicating that the three spectra detected by 31P-NMR are related to charge-dependent local dynamics or orientations of the phosphate headgroup or both. Chain ordering in the fluid phase is also found to depend weakly on the charge at the interface. In addition, it has also been found that the first pK of the DMPA membrane is modified by changes in the lipid lateral packing (gel or fluid phases or in the presence of cholesterol) in contrast to the second pK. The incorporation of 30 mol% cholesterol affects the phosphatidic acid bilayer in a way similar to what has been reported for phosphatidylcholine/cholesterol membranes, but to an extent comparable to 10-20 mol % sterol in phosphatidylcholines. However, the orientation and molecular order parameter of cholesterol in DMPA are similar to those found in dimyristoylphosphatidylcholine.

Action of melittin on the DPPC-cholesterol liquid-ordered phase: a solid state 2H-and 31P-NMR study

Solid-state deuterium and phosphorus-31 nuclear magnetic resonance studies of deuterium-labeled beta--[2,2',3,4,4',6-2H6]-cholesterol and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine have been undertaken to monitor the action of melittin on model membranes containing 30 mol% cholesterol, both at the molecular and macroscopic level. Cholesterol totally inhibits the toxin-triggered formation of large unilamellar vesicles and strongly restricts the appearance of small discs. The latter remain stable over a wide temperature range (20-60 degrees C) because of an increase in their cholesterol content as the temperature increases. This process is related to a constant disc hydrophobic thickness of approximately 29 A. The system, when not in the form of discs, appears to be composed of very large vesicles on which melittin promotes magnetically induced ellipsoidal deformation. This deformation is the greatest when the maximum of discs is observed. A model to describe both the disc formation and stability is proposed.