A Nurse's Guide to COVID-19.

ABSTRACT: To assist nurses caring for hospitalized adults with coronavirus disease 2019 (COVID-19), the authors synthesize evidence-based information on the disease, providing background on the epidemiology and history of severe acute respiratory syndrome coronavirus 2, the causative virus. They also discuss the risks for severe effects of the illness, the multiple signs and symptoms hospitalized adults with COVID-19 may manifest, and the precautions hospitals should take to keep health care providers and patients safe during the course of this pandemic.

Relating Structure and Ice Nucleation of Mixed Surfactant Systems Relevant to Sea Spray Aerosol.

Ice nucleating particles (INPs) influence weather and climate by their effect on cloud phase state. Fatty alcohols present within aerosol particles confer a potentially important source of ice nucleation activity to sea spray aerosol produced in oceanic regions. However, their interactions with other aerosol components and the influence on freezing were previously largely unknown. Here, we report quantitative measurements of fatty alcohols in model sea spray aerosol and examine the relationships between the composition and structure of the surfactants and subphase in the context of these measurements. Deposited mixtures of surfactants retain the ability to nucleate ice, even in fatty acid-dominant compositions. Strong refreezing effects are also observed, where previously frozen water-surfactant samples nucleate more efficiently. Structural sources of refreezing behavior are identified as either kinetically trapped film states or three-dimensional (3D) solid surfactant particles. Salt effects are especially important for surfactant INPs, where high salt concentrations suppress freezing. A simple water uptake model suggests that surfactant-containing aerosol requires either very low salt content or kinetic trapping as solid particles to act as INPs in the atmosphere. These types of INPs could be identified through comparison of different INP instrument responses.

Ice nucleation by particles containing long-chain fatty acids of relevance to freezing by sea spray aerosols.

Heterogeneous ice nucleation in the atmosphere regulates cloud properties, such as phase (ice versus liquid) and lifetime. Aerosol particles of marine origin are relevant ice nucleating particle sources when marine aerosol layers are lifted over mountainous terrain and in higher latitude ocean boundary layers, distant from terrestrial aerosol sources. Among many particle compositions associated with ice nucleation by sea spray aerosols are highly saturated fatty acids. Previous studies have not demonstrated their ability to freeze dilute water droplets. This study investigates ice nucleation by monolayers at the surface of supercooled droplets and as crystalline particles at temperatures exceeding the threshold for homogeneous freezing. Results show the poor efficiency of long chain fatty acid (C16, C18) monolayers in templating freezing of pure water droplets and seawater subphase to temperatures of at least -30 °C, consistent with theory. This contrasts with freezing of fatty alcohols (C22 used here) at nearly 20 °C warmer. Evaporation of µL-sized droplets to promote structural compression of a C19 acid monolayer did not favor warmer ice formation of drops. Heterogeneous ice nucleation occurred for nL-sized droplets condensed on 5 to 100 µm crystalline particles of fatty acid (C12 to C20) at a range of temperatures below -28 °C. These experiments suggest that fatty acids nucleate ice at warmer than -36 °C only when the crystalline phase is present. Rough estimates of ice active site densities are consistent with those of marine aerosols, but require knowledge of the proportion of surface area comprised of fatty acids for application.

Environmental Processing of Lipids Driven by Aqueous Photochemistry of α-Keto Acids.

Sunlight can initiate photochemical reactions of organic molecules though direct photolysis, photosensitization, and indirect processes, often leading to complex radical chemistry that can increase molecular complexity in the environment. α-Keto acids act as photoinitiators for organic species that are not themselves photoactive. Here, we demonstrate this capability through the reaction of two α-keto acids, pyruvic acid and 2-oxooctanoic acid, with a series of fatty acids and fatty alcohols. We show for five different cases that a cross-product between the photoinitiated α-keto acid and non-photoactive species is formed during photolysis in aqueous solution. Fatty acids and alcohols are relatively unreactive species, which suggests that α-keto acids are able to act as radical initiators for many atmospherically relevant molecules found in the sea surface microlayer and on atmospheric aerosol particles.

pH Dependence of the Aqueous Photochemistry of α-Keto Acids.

α-Keto acids are important, atmospherically relevant species, and their photochemistry has been considered in the formation and processing of aerosols. Despite their atmospheric relevance, the photochemistry of these species has primarily been studied under extremely low pH conditions. Using a variety of analytical techniques, we characterize the extent of hydration and deprotonation for solutions of two α-keto acids, pyruvic acid and 2-oxooctanoic acid, as a function of pH. We find that changes in the initial solution composition govern the accessibility of different photochemical pathways, resulting in slowed photolysis under high pH conditions and a shift in photoproducts that can be predicted mechanistically.

Phenylalanine Increases Membrane Permeability.

Biological membranes are a crucial aspect of living systems, controlling the organization and distribution of different chemical components. Control of membrane permeability is especially important for processes such as electron transport in metabolism and signal propagation in nerve cells. In this work, we show that the amino acid phenylalanine produces increased membrane permeability, which is likely responsible for some of the deleterious symptoms associated with high biological phenylalanine concentrations that occur with the genetic disorder phenylketonuria.

Mechanistic Description of Photochemical Oligomer Formation from Aqueous Pyruvic Acid.

The aqueous phase photochemistry of pyruvic acid, an important oxidation product of isoprene, is known to generate larger oligomeric species that may contribute to the formation of secondary organic aerosol in the atmosphere. Using high resolution negative mode electrospray ionization mass spectrometry, the aqueous photochemistry of dilute solutions of pyruvic acid (10, 1, and 0.5 mM) under anaerobic conditions was investigated. Even at the lowest concentration, covalently bonded dimers and trimers of pyruvic acid were observed as photochemical products. We calculate that it is energetically possible to photochemically generate parapyruvic acid, a dimer of pyruvic acid that is known to form via dark oligomerization processes. Subsequent photochemical reactions of parapyruvic acid with pyruvic acid form larger oligomeric products, such as 2,4-dihydroxy-2-methyl-5-oxohexanoic acid. A robust and relatively simple photochemical mechanism is discussed that explains both the conditional dependence and wide array of products that are observed.

Photochemical Synthesis of Oligomeric Amphiphiles from Alkyl Oxoacids in Aqueous Environments.

The aqueous phase photochemistry of a series of amphiphilic α-keto acids with differing linear alkyl chain lengths was investigated, demonstrating the ability of sunlight-initiated reactions to build molecular complexity under environmentally relevant conditions. We show that the photochemical reaction mechanisms for α-keto acids in aqueous solution are robust and generalizable across alkyl chain lengths. The organic radicals generated during photolysis are indiscriminate, leading to a large mixture of photoproducts that are observed using high-resolution electrospray ionization mass spectrometry, but these products are identifiable following literature photochemical mechanisms. The alkyl oxoacids under study here can undergo a Norrish Type II reaction to generate pyruvic acid, increasing the diversity of observed photoproducts. The major products of this photochemistry are covalently bonded dimers and trimers of the starting oxoacids, many of which are multi-tailed lipids. The properties of these oligomers are discussed, including their spontaneous self-assembly into aggregates.

A retrospective review of anesthesia and perioperative care in children with medium-chain acyl-CoA dehydrogenase deficiency.

BACKGROUND: Medium-chain acyl-CoA dehydrogenase deficiency is the most common genetically determined disorder of mitochondrial fatty acid oxidation. Decompensation can result in hypoglycemia, seizures, coma, and death but may be prevented by ensuring glycogen stores do not become depleted. Perioperative care is of interest as surgery, fasting, and infection may all trigger decompensation and the safety of anesthetic agents has been questioned. Current guidelines from the British Inherited Metabolic Disease Group advise on administering fluid containing 10% glucose during the perioperative period. AIM: To review the management of anesthesia and perioperative care for children with medium-chain acyl-CoA dehydrogenase deficiency and determine the frequency and nature of any complications. METHOD: A retrospective review of case notes of children with medium-chain acyl-CoA dehydrogenase deficiency undergoing anesthesia between 1997 and 2014. RESULTS: Fourteen patients underwent 21 episodes of anesthesia. In 20 episodes, the patient received a glucose-containing fluid during their perioperative fast, of which eight received fluid containing 10% dextrose throughout the entire perioperative period. No episodes of hypoglycemia or decompensation occurred, but perioperative hyperglycemia occurred in five episodes. A propofol bolus was administered at induction in 16 episodes and volatile agents were administered for maintenance of anesthesia in all episodes without any observed complications. In one episode, delayed offset of atracurium was reported. CONCLUSIONS: Perioperative metabolic decompensation and hypoglycemia appear to be uncommon in children who are well and receive glucose supplementation. Hyperglycemia may occur as a consequence of surgery and glucose supplementation. Propofol boluses and volatile anesthetic agents were used without any apparent complications. Prolonged action of atracurium was reported in one case, suggesting that nondepolarizing muscle relaxants may have delayed offset in this patient group. We do not recommend any particular approach to anesthesia but would advise administering glucose supplementation according to current guidelines, frequent monitoring of blood glucose perioperatively, and monitoring of neuromuscular blockade.

Chemical Equilibria and Kinetics in Aqueous Solutions of Zymonic Acid.

The chemistry of pyruvic acid is of great interest due to its essential role in metabolism for all life and its role in atmospheric chemistry. Pyruvic acid under a wide range of conditions, including normal storage conditions, will spontaneously dimerize to form zymonic acid. We isolated zymonic acid and, using a variety of 1D and 2D NMR techniques, identified it as a single structure as a solid or dissolved in DMSO. When in aqueous solution, however, we identified a mixture of five different tautomers and hydrates in equilibrium with each other with no single dominant form. The kinetics of this conversion were studied in situ via NMR. The reactivity of the tautomers and hydrates in aqueous solution is investigated and discussed in terms of aqueous reaction mechanisms. There is strong evidence for a direct, reversible conversion from an enol to a geminal diol without passing through a ketone intermediate, which implies the reversible addition of water across a double bond under ambient conditions. Additionally, there is evidence for a base catalyzed lactone ring formation, which is in essence a base catalyzed esterification reaction. The equilibrium between pyruvic acid and its oligomers in aqueous solution is of consequence in the natural environment.

The Partitioning of Small Aromatic Molecules to Air-Water and Phospholipid Interfaces Mediated by Non-Hydrophobic Interactions.

Phenylalanine has an important role both in normal biological function and in disease states such as phenylketonuria (PKU) and amyloid fibril diseases. Two crucial aspects of phenylalanine behavior in biological systems are its preferential partitioning into membranes and its propensity to cluster. In order to examine the intermolecular interactions that give rise to this behavior, the surface partitioning behavior was investigated for a series of molecules structurally related to phenylalanine (phenylglycine, phenylacetic acid, and tyrosine) both experimentally and by molecular dynamics simulations. Surface tension measurements were performed over time for aromatic solutions both in the presence and in the absence of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) monolayer films, which functioned as simple model membranes. The observed trends in surface activity defy simple predictions based on solubility and hydrophobicity. The possibility of clustering is investigated through a combination of Langmuir trough, nuclear magnetic resonance (NMR), fluorescence self-quenching, and mass spectroscopy measurements. It is concluded that clustering does not occur in solution to a significant extent for these molecules, but interfacial clustering is likely. An explanation for observed trends in surface activity is presented on the basis of cluster stability and molecular conformational flexibility.

Interaction of L-Phenylalanine with a Phospholipid Monolayer at the Water-Air Interface.

The interaction of L-phenylalanine with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air-water interface was explored using a combination of experimental techniques and molecular dynamics (MD) simulations. By means of Langmuir trough methods and Brewster angle microscopy, L-phenylalanine was shown to significantly alter the interfacial tension and the surface domain morphology of the DPPC film. In addition, confocal microscopy was used to explore the aggregation state of L-phenylalanine in the bulk aqueous phase. Finally, MD simulations were performed to gain molecular-level information on the interactions of L-phenylalanine and DPPC at the interface. Taken together, these results show that L-phenylalanine intercalates into a DPPC film at the air-water interface, thereby affecting the surface tension, phase morphology, and ordering of the DPPC film. The results are discussed in the context of biological systems and the mechanism of diseases such as phenylketonuria.

Tracheal intubating conditions and pharmacodynamics following cisatracurium in infants and children undergoing halothane and thiopental-fentanyl anesthesia.

BACKGROUND: The aims of the present study were to determine the tracheal intubating conditions, onset time, duration of action, and hemodynamic responses following the administration of cisatracurium 0.15 mg x kg(-1) to infants and children. METHODS: One hundred and eighty-one infants and children aged 1 month to 12 years were randomized to two groups to receive anesthesia with nitrous oxide-oxygen-halothane (group H) or nitrous oxide-oxygen-thiopental-fentanyl (group TF). Intubation conditions were assessed 120 s after cisatracurium administration using a 4-part scale. Neuromuscular transmission was monitored by recording the evoked compound electromyogram of the adductor pollicis. RESULTS: The proportion of patients with excellent or good intubating conditions was similar in both groups (88 of 90, 98% in group H; 85 of 90, 94% in group TF). However, there was a significantly greater proportion of excellent intubating conditions in group H (79 of 90, 88%) compared with group TF (65 of 90, 72%) (P = 0.01) and recovery time was significantly longer in group H compared with group TF (P < 0.001). There was also a higher proportion of excellent intubating conditions in infants compared with older subjects (P = 0.02) and a shorter onset time (P < 0.001) and longer recovery time (P < 0.001) in younger compared with older patients. Changes in heart rate and arterial pressure were negligible 1 min following the cisatracurium administration. CONCLUSIONS: Cisatracurium 0.15 mg x kg(-1) produces acceptable intubating conditions at 120 s in the great majority of infants and children. Anesthesia background and age have significant effects on intubating conditions and duration of action of cisatracurium.