On minimal extensions of rings

Given two rings $R \subseteq S$, $S$ is said to be a minimal ring extension of $R$ if $R$ is a maximal subring of $S$. In this article, we study minimal extensions of an arbitrary ring $R$, with particular focus on those possessing nonzero ideals that intersect $R$ trivially. We will also classify the minimal ring extensions of prime rings, generalizing results of Dobbs, Dobbs & Shapiro, and Ferrand & Olivier on commutative minimal extensions.Comment: 25 page

Effects and mechanisms of action of sildenafil citrate in human chorionic arteries

Objectives Sildenafil citrate, a specific phosphodiesterase-5 inhibitor, is increasingly used for pulmonary hypertension in pregnancy. Sildenafil is also emerging as a potential candidate for the treatment of intra-uterine growth retardation and for premature labor. Its effects in the feto-placental circulation are not known. Our objectives were to determine whether phosphodiesterase-5 is present in the human feto-placental circulation, and to characterize the effects and mechanisms of action of sildenafil citrate in this circulation. Study Design Ex vivo human chorionic plate arterial rings were used in all experiments. The presence of phosphodiesterase-5 in the feto-placental circulation was determined by western blotting and immunohistochemical staining. In a subsequent series of pharmacologic studies, the effects of sildenafil citrate in pre-constricted chorionic plate arterial rings were determined. Additional studies examined the role of cGMP and nitric oxide in mediating the effects of sildenafil. Results Phosphodiesterase-5 mRNA and protein was demonstrated in human chorionic plate arteries. Immunohistochemistry demonstrated phosphodiesterase-5 within the arterial muscle layer. Sildenafil citrate produced dose dependent vasodilatation at concentrations at and greater than 10 nM. Both the direct cGMP inhibitor methylene blue and the cGMP-dependent protein kinase inhibitor Rp-8-Br-PET-cGMPS significantly attenuated the vasodilation produced by sildenafil citrate. Inhibition of NO production with L-NAME did not attenuate the vasodilator effects of sildenafil. In contrast, sildenafil citrate significantly enhanced the vasodilation produced by the NO donor sodium nitroprusside. Conclusion Phosphodiesterase-5 is present in the feto-placental circulation. Sildenafil citrate vasodilates the feto-placental circulation via a cGMP dependent mechanism involving increased responsiveness to NO

Dangers of hyperoxia

Oxygen (O-2) toxicity remains a concern, particularly to the lung. This is mainly related to excessive production of reactive oxygen species (ROS). Supplemental O-2, i.e. inspiratory O-2 concentrations (FIO2) > 0.21 may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg) and, subsequently, hyperoxia (increased tissue O-2 concentration), thereby enhancing ROS formation. Here, we review the pathophysiology of O-2 toxicity and the potential harms of supplemental O-2 in various ICU conditions. The current evidence base suggests that PaO2 > 300 mmHg (40 kPa) should be avoided, but it remains uncertain whether there is an "optimal level" which may vary for given clinical conditions. Since even moderately supra-physiological PaO2 may be associated with deleterious side effects, it seems advisable at present to titrate O-2 to maintain PaO2 within the normal range, avoiding both hypoxaemia and excess hyperoxaemia.Peer reviewe

Patterns of use of adjunctive therapies in patients with early moderate- severe Acute Respiratory Distress syndrome: Insights from the LUNG SAFE Study

Background: Adjunctive strategies are an important part of the management of ARDS. However, their application in clinical practice remains inconsistent. Research Question: We wished to determine the frequency and patterns of use of adjunctive strategies in patients with moderate to severe ARDS (PaO2/FIO2 [P/F ratio] < 150) enrolled into the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Study Design and Methods: The LUNG SAFE study was an international, multicenter, prospective cohort study of patients with severe respiratory failure, conducted in 2014 in 459 ICUs from 50 countries. The primary objective of this substudy was to determine the frequency of use of widely available (neuromuscular blockade, prone position) adjuncts vs adjuncts requiring specialized equipment (extracorporeal membrane oxygenation, inhaled vasodilators, high-frequency ventilation) in patients in the first 48 h of moderate to severe ARDS (P/F ratio < 150). Results: Of 1,146 patients on invasive ventilation with moderate to severe ARDS, 811 patients (71%) received no adjunct within 48 h of ARDS onset. Of 335 (29%) that received adjunctive strategies, 252 (75%) received a single strategy, and 83 (25%) receiving more than one adjunct. Of ARDS nonsurvivors, 67% did not receive any adjunctive strategy in the first 48 h. Most patients (67%) receiving specialized adjuncts did not receive prone positioning or neuromuscular blockade. Patients that received adjuncts were more likely to have their ARDS recognized, be younger and sicker, have pneumonia, be more difficult to ventilate, and be in a European high-income country than those that did not receive adjuncts. Interpretation: Three in 10 patients with moderate to severe ARDS, and only one-third of nonsurvivors, received adjunctive strategies over the first 48 h of ARDS. A more consistent and evidence-driven approach to adjunct use may reduce costs and improve outcomes in patients with moderate to severe ARDS. Trial Registry: ClinicalTrials.gov; No.: NCT02010073; URL: www.clinicaltrials.go

Linear spanning sets for matrix spaces

Necessary and sufficient conditions are given on matrices $A$, $B$ and $S$, having entries in some field $F$ and suitable dimensions, such that the linear span of the terms $A^iSB^j$ over $F$ is equal to the whole matrix space. This result is then used to determine the cardinality of subsets of $F[A]SF[B]$ when $F$ is a finite field

Determination of the efficacy and side-effect profile of lower doses of intrathecal morphine in patients undergoing total knee arthroplasty

<p>Abstract</p> <p>Background</p> <p>Intrathecal (IT) morphine provides excellent post-operative analgesia, but causes multiple side effects including nausea and vomiting (PONV), pruritus and respiratory depression, particularly at higher doses. The lowest effective dose of spinal morphine in patients undergoing total knee arthroplasty is not known.</p> <p>Methods</p> <p>We evaluated the analgesic efficacy and side effect profile of 100 – 300 μg IT morphine in patients undergoing elective total knee replacement in this prospective, randomized, controlled, double-blind study. Sixty patients over the age of 60 undergoing elective knee arthroplasty were enrolled. Patients were randomized to receive spinal anaesthesia with 15 mg Bupivacaine and IT morphine in three groups: (i) 100 μg; (ii) 200 μg; and (iii) 300 μg.</p> <p>Results</p> <p>Both 200 μg and 300 μg IT morphine provided comparable levels of postoperative analgesia. However, patients that received 100 μg had greater pain postoperatively, with higher pain scores and a greater requirement for supplemental morphine. There were no differences between groups with regard to PONV, pruritus, sedation, respiratory depression or urinary retention.</p> <p>Conclusion</p> <p>Both 200 μg and 300 μg provided comparable postoperative analgesia, which was superior to that provided by 100 μg IT morphine in patients undergoing total knee arthroplasty. Based on these findings, we recommend that 200 μg IT morphine be used in these patients.</p> <p>Trial registration</p> <p>ClinicalTrials.gov Identifier NCT00695045</p