Cerebral Oximetry for Detecting High-mortality Risk Patients with Cryptococcal Meningitis.

BACKGROUND: Cryptococcus is the commonest cause of adult meningitis in Africa, with 50%-70% experiencing increased intracranial pressure. Cerebral oximetry is a noninvasive near-infrared spectroscopy technology to monitor percent regional cerebral tissue oxygenation (rSO2). We assessed if cerebral oximetry predicts meningitis mortality. METHODS: We performed cerebral oximetry within 14 days of cryptococcal meningitis diagnosis on 121 Ugandans from April 2016 to September 2017. We evaluated baseline rSO2 association with mortality by multivariable logistic regression and correlation with other clinical factors. We compared groups formed by initial rSO2 <30% vs ≥30% for longitudinal change with mixed effects models. We measured change in %rSO2 before and after lumbar puncture (LP). RESULTS: The median initial rSO2 (interquartile range) was 36% (29%-42%), and it was <30% in 29% (35/121). For 30-day mortality, the unadjusted odds ratio (per 5% increase in rSO2) was 0.73 (95% confidence interval [CI], 0.58 to 0.91; P = .005). Those with initial rSO2 <30% had 3.4 (95% CI, 1.5 to 8.0) higher odds of 30-day mortality than those with initial rSO2 ≥30%. Hemoglobin correlated with initial rSO2 (rho = .54; P < .001), but rSO2 did not correlate with pulse oximetry, intracranial pressure, cerebral perfusion pressure, or quantitative cerebrospinal fluid culture, and rSO2 was unchanged pre/post-lumbar punctures. The longitudinal rSO2 measurements change was 15% (95% CI, 12% to 18%) lower in the group with initial rSO2 <30%. CONCLUSIONS: Individuals with cryptococcal meningitis and low cerebral oximetry (rSO2 < 30%) have high mortality. Cerebral oximetry may be useful as a prognostic marker of mortality. Targeted interventions to improve rSO2 should be tested in trials to try to decrease mortality in meningitis.

Determination of total biodiesel fatty acid methyl, ethyl esters, and hydrocarbon types in diesel fuels by supercritical fluid chromatography-flame ionization detection.

A method for determining total biodiesel methyl and ethyl ester content in diesel fuels by supercritical fluid chromatography-flame ionization detection (SFC-FID) is developed. A silica column typically used for determining aromatics in conventional diesel fuels by ASTM D5186 is back-flushed after separation of the hydrocarbons to allow elution of the various esters as a single "total biodiesel" distinct peak. The modification concurrently allows the determination of total aromatic hydrocarbons and their distribution as mono- and polynuclear compounds, as described in the current version of D5186. The instrument response is linear from 1.0% to 50% biodiesel esters with a signal-to-noise ratio of 25 at the 0.1% level. The short-term relative standard is 0.8%. Normalized percent quantitation using a hydrocarbon response factor of 1.00 and an ester response factor of 1.19 provide an average percentage error of 1.8% when measuring actual biodiesel/hydrocarbon fuel blends. The ester response factor is the average of the response factors of 10 pure ester compounds. These responses are calculated from respective solutions of each ester and the four compounds, hexadecane, toluene, tetralin, and naphthalene, as used for the D5186 response factor mixture.

Determination of aromatic hydrocarbons in gasolines by flow modulated comprehensive two-dimensional gas chromatography.

Valve based/flow modulated comprehensive two-dimensional gas chromatography-flame ionization detection (GC x GC-FID) was used for quantification of C6 through C12 aromatic hydrocarbons by carbon number in gasolines. A 0.53 mm i.d. non-polar first dimension column was coupled to a 0.53 mm i.d. polar second dimension column through a double loop eight port valve modulator. Depending on the sample type, normalized percent and internal standard (I.S.) quantification was performed. For normalized percent quantification, a one-point calibration performed with one aromatic compound per carbon number/class provided an average % accuracy of 2.1% and a short-term n--1 relative standard deviation of 1.0%. For total aromatic compounds good agreement with the more complex conventional multidimensional GC technique was obtained. However, GC x GC has certain advantages over most other methods, mainly increased selectivity for total and carbon number aromatic content. The identification of the aromatic hydrocarbons was confirmed by GC x GC-MS.

The coupling of supercritical fluid chromatography and field ionization time-of-flight high-resolution mass spectrometry for rapid and quantitative analysis of petroleum middle distillates.

We report the first coupling of supercritical fluid chromatography (SFC) with field ionization time-of-flight high-resolution mass spectrometry (FI-ToF HRMS), in parallel with ultraviolet (UV) detection and flame ionization detection (FID), for rapid and quantitative analysis of petroleum middle distillates. SFC separates petroleum middle distillates into saturates and 1- to 3-ring aromatics. FI generates molecular ions for hydrocarbon species eluted from the SFC. The high resolution and exact mass measurements by ToF mass spectrometry provide elemental compositions of the molecules in the petroleum product. The amounts of saturates and aromatic ring types were quantified using the parallel SFC-FID assisted by SFC-UV. With a proper carbon-number calibration, the detailed composition of the petroleum middle distillate was rapidly determined.