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Background Obstructive sleep apnoea (OSA) is an independent risk factor of hypertension and cardiovascular diseases. Recurrent episodes of upper airways collapse during sleep causing blood oxygen desaturation, hypercapnia, and micro-arousals, are known to activate the sympathetic nervous system (SNS). However, whether changes in the renin-angiotensin-aldosterone system and endothelial activation also occur remains contentious. Methods Based on routine use of drug-induced sleep endoscopy (DISE) for the work-up of OSA patients in our centre, we designed a prospective study to investigate the haemodynamic and humoral changes occurring during the apnoeic episodes reproduced in vivo in the course of DISE. Specifically, plasma aldosterone concentration and renin activity, C-terminal fragment of proendothelin-1, as a marker of endothelial damage, and free plasma catecholamines, will be measured at fixed times during DISE. The activity of catechol-O-methyltransferase (COMT), a key catecholamine-inactivating enzyme that has been scantly investigated thus far owing to the lack of commercially available kits, will be also determined by a newly developed high performance liquid chromatography method, which is herein described. Results and conclusions The aim of this study is to provide novel information on the haemodynamic, hormonal, and SNS changes, and also on COMT activity modification concomitantly occurring during apnoea, thus contributing substantively to the understanding of the pathophysiology of OSA.

Background: The determination of urinary cortisol/cortisone ratio is of clinical utility in cases of Cushing's syndrome, apparent mineralocorticoid excess, and also provides information on 11β-hydroxysteroid dehydrogenase (11β-HSD) type 2 activity. It is therefore of utmost importance to ensure accurate cortisol and cortisone measurement and establish appropriate reference ranges., Methods: After the isotopic dilution of urine, sample cleanups were obtained with on-line solid-phase extraction and cortisol and cortisone, separated using a Zorbax Eclipse XDB-C18 HPLC analytical column, were analyzed by tandem mass spectrometry with an electrospray ionization source in positive ion mode operation., Results: The method was linear, with concentrations of up to 625 and 1125 nmol/L and lower limit of quantitation (LLOQ) of 5 and 6 nmol/L, for cortisol and cortisone, respectively. Within-run and between-run coefficients of variation were <5% and 6% for cortisol and 6% and 8% for cortisone, respectively. No ion suppression was observed. The non-parametric reference range for the cortisol/cortisone ratio was 0.14-1.09., Conclusions: A simple and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the measurement of cortisol and cortisone in urine. Our findings indicate that the proposed analytical method is suitable for routine purposes and useful in many pathological conditions.

Background: Immunosuppressant therapeutic drug monitoring (TDM) is an important requirement in post-transplant patient care. In recent years, high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) has become a valid alternative to antibody-based immunoassays in TDM due to its high specificity and sensitivity. Furthermore, this technology allows for the simultaneous measurement of several immunosuppressive drugs. The aim of the present study was to establish a straightforward, robust, and high-throughput LC-MS/MS method for the simultaneous determination of sirolimus and everolimus in whole blood in order to replace immunoassays in our routine practice., Methods: Five-level blood calibrators were employed for assay development, while three materials at different concentrations were used for internal quality control. The proposed method uses protein precipitation for sample preparation. Analyses were performed using a triple quadrupole LC-MS/MS, with a C18 held at 60°C. Using an appropriate gradient elution profile and SPE on-line, elution times for all compounds analysed were 2.6 min with a total run-time of 3.5 min., Results: Calibration curves were linear throughout the selected ranges. The intra- and inter-assay CVs (<7%), the limit of quantification (0.2 μg/L) and accuracy were highly satisfactory. On testing the results using the international proficiency testing scheme (UK-NEQAS), the performance of the proposed method was found to be highly reliable., Conclusions: The findings made by us indicate that the proposed method is of value, since it is speedy, straightforward, accurate, and applicable to different LC-MS/MS instruments for the routine TDM of organ transplant recipients.

Background: The relationship between asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) plasma concentrations and acute heart failure is unknown. We evaluated ADMA and SDMA in patients with acute dyspnea., Methods: We studied 57 dyspneic subjects (50-95 years), with estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m², presenting to the emergency department. Troponin I, N terminal-proBNP (NT-proBNP), ADMA, and SDMA were measured. Electrocardiogram, chest X-ray and lung ultrasound were performed. Patients were classified into cardiogenic dyspnea and non-cardiogenic dyspnea, and were also classified on the basis of renal function according to their eGFR., Results: Two-way analysis of variance demonstrated that ADMA and SDMA did not differ for type of dyspnea, but increased in renal dysfunction. NT-proBNP significantly increased both in cardiogenic dyspnea and renal dysfunction. Multiple regression analysis demonstrated that after adjustment for troponin and dyspnea, the only variables which significantly correlated with SDMA plasma concentrations were renal function (β = -0.47, p < 0.001) and NT-proBNP (β = 0.28, p = 0.02)., Conclusions: Neither type of dimethylarginine showed cardiogenic dyspnea to be a determinant for plasma concentrations. Renal dysfunction was a confounder for both ADMA and SDMA.