Risk factors for overnight respiratory events following sedation for magnetic resonance imaging in children with sleep apnea.

PURPOSE: Children with sleep apnea may be at increased risk for overnight respiratory events (ORE) following anesthesia. We sought to identify ORE risk factors in sleep apnea patients sedated for magnetic resonance imaging (MRI). METHODS: One thousand four hundred seven hospitalizations for children with sleep apnea (by ICD-9 code) occurred at our institution from 5/1/2011 to 2/1/2015. One hundred twenty-seven (9 %) encounters were solely for post-MRI observation representing 96 unique patients. The first post-MRI admission for each patient underwent chart review. ORE was defined as sustained oxygen saturation <90 % with need for increased oxygen or adjustment of respiratory support after release from recovery. Characteristics of patients with and without ORE were compared by chi-squared analysis or independent samples t test. Logistic regression identified associations with ORE. RESULTS: Ten out of 96 (10.4 %) patients had ORE. The average time following sedation to ORE was 10.25 h. ORE patients were hospitalized longer (median 2 vs. 1 day, p < 0.001). Overall, patients were 55 % male, 60 % Hispanic, with median age of 5 years [IQR 2-10] and median body mass index (BMI) of 17.9 [IQR 15.2-24]. On logistic regression, apnea-hypopnea index (AHI; OR 1.007 [95 % CI 1.002-1.011]), anesthesia complication (OR 1.13 [95 % CI 1.01-1.28]), and home non-invasive positive pressure ventilation (NIV; OR 6.08 [95 % CI 1.57-26.17]) were associated with ORE. CONCLUSION: Ninety percent of children with sleep apnea admitted for overnight observation following sedated MRI did not have an ORE. AHI, anesthesia complications, and NIV use may help target higher-risk patients and avoid unnecessary hospitalizations.

A comparison of methods for total community DNA preservation and extraction from various thermal environments.

The widespread use of molecular techniques in studying microbial communities has greatly enhanced our understanding of microbial diversity and function in the natural environment and contributed to an explosion of novel commercially viable enzymes. One of the most promising environments for detecting novel processes, enzymes, and microbial diversity is hot springs. We examined potential biases introduced by DNA preservation and extraction methods by comparing the quality, quantity, and diversity of environmental DNA samples preserved and extracted by commonly used methods. We included samples from sites representing the spectrum of environmental conditions that are found in Yellowstone National Park thermal features. Samples preserved in a non-toxic sucrose lysis buffer (SLB), along with a variation of a standard DNA extraction method using CTAB resulted in higher quality and quantity DNA than the other preservation and extraction methods tested here. Richness determined using DGGE revealed that there was some variation within replicates of a sample, but no statistical difference among the methods. However, the sucrose lysis buffer preserved samples extracted by the CTAB method were 15-43% more diverse than the other treatments.

Molecular characterization of the diversity and distribution of a thermal spring microbial community by using rRNA and metabolic genes.

The diversity and distribution of a bacterial community from Coffee Pots Hot Spring, a thermal spring in Yellowstone National Park with a temperature range of 39.3 to 74.1 degrees C and pH range of 5.75 to 6.91, were investigated by sequencing cloned PCR products and quantitative PCR (qPCR) of 16S rRNA and metabolic genes. The spring was inhabited by three Aquificae genera--Thermocrinis, Hydrogenobaculum, and Sulfurihydrogenibium--and members of the Alpha-, Beta-, and Gammaproteobacteria, Firmicutes, Acidobacteria, Deinococcus-Thermus, and candidate division OP5. The in situ chemical affinities were calculated for 41 potential metabolic reactions using measured environmental parameters and a range of hydrogen and oxygen concentrations. Reactions that use oxygen, ferric iron, sulfur, and nitrate as electron acceptors were predicted to be the most energetically favorable, while reactions using sulfate were expected to be less favorable. Samples were screened for genes used in ammonia oxidation (amoA, bacterial gene only), the reductive tricarboxylic acid (rTCA) cycle (aclB), the Calvin cycle (cbbM), sulfate reduction (dsrAB), nitrogen fixation (nifH), nitrite reduction (nirK), and sulfide oxidation (soxEF1) by PCR. Genes for carbon fixation by the rTCA cycle and nitrogen fixation were detected. All aclB sequences were phylogenetically related and spatially correlated to Sulfurihydrogenibium 16S rRNA gene sequences using qPCR (R(2) = 0.99). This result supports the recent finding of citrate cleavage by enzymes other than ATP citrate lyase in the rTCA cycle of the Aquificaceae family. We briefly consider potential biochemical mechanisms that may allow Sulfurihydrogenibium and Thermocrinis to codominate some hydrothermal environments.

Volcanic calderas delineate biogeographic provinces among Yellowstone thermophiles.

It has been suggested that the distribution of microorganisms should be cosmopolitan because of their enormous capacity for dispersal. However, recent studies have revealed that geographically isolated microbial populations do exist. Geographic distance as a barrier to dispersal is most often invoked to explain these distributions. Here we show that unique and diverse sequences of the bacterial genus Sulfurihydrogenibium exist in Yellowstone thermal springs, indicating that these sites are geographically isolated. Although there was no correlation with geographic distance or the associated geochemistry of the springs, there was a strong historical signal. We found that the Yellowstone calderas, remnants of prehistoric volcanic eruptions, delineate biogeographical provinces for the Sulfurihydrogenibium within Yellowstone (chi(2): 9.7, P = 0.002). The pattern of distribution that we have detected suggests that major geological events in the past 2 million years explain more of the variation in sequence diversity in this system than do contemporary factors such as habitat or geographic distance. These findings highlight the importance of historical legacies in determining contemporary microbial distributions and suggest that the same factors that determine the biogeography of macroorganisms are also evident among bacteria.