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A hybrid, potentially green solvent system composed of tetraethylene glycol (TEG) and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) was investigated across all mole fractions with regard to the solvent properties of the mixture. For this purpose, a suite of absorbance- and fluorescence-based solvatochromic probes were utilized to explore solute-solvent and solvent-solvent interactions existing within the [bmim][PF(6)] + TEG system. These studies revealed an interesting and unusual synergistic solvent effect. In particular, a remarkable "hyperpolarity" was observed in which the E(T) value, comprising dipolarity/polarizability and hydrogen bond donor (HBD) acidity contributions, at intermediate mole fractions of the binary mixture well exceeded that of the most polar pure component (i.e., [bmim][PF(6)]). Independently determined dipolarity/polarizability (pi*) and HBD acidity (alpha) Kamlet-Taft values for the [bmim][PF(6)] + TEG mixtures were also observed to be anomalously high at intermediate mole fractions, whereas hydrogen bond acceptor (HBA) basicities (beta values) were much more in line with the ideal arithmetic values predicted on a mole fraction basis. Two well-established fluorescent polarity probes (pyrene and pyrene-1-carboxaldehyde) further illustrated notable hyperpolarity within [bmim][PF(6)] + TEG mixtures. Moreover, the steady-state fluorescence anisotropy of the molecular rotor rhodamine 6G and the excimer-to-monomer fluorescence ratio exhibited by the fluidity probe 1,3-bis-(1-pyrenyl)propane demonstrated that solute rotation and microfluidity within the [bmim][PF(6)] + TEG mixture were significantly reduced compared with expectations based on simple solvent mixing. A solvent ordering via formation of HBD/HBA complexes involving the C-2 proton of the [bmim(+)] cation and oxygen atoms of TEG, as well as interactions between [PF(6)(-)] and the terminal hydroxyl groups of TEG, is proposed to account for the observed behavior. Further spectroscopic evidence of strong intersolvent interactions occurring within the [bmim][PF(6)] + TEG mixture was provided, inter alia, by substantial frequency shifts in the [PF(6)(-)] asymmetric stretching mode observed in the infrared spectra as TEG was incrementally added to [bmim][PF(6)]. Overall, our observations contribute to a growing literature advocating the notion that ionic liquids and certain organic solvents form ordered, nanostructured, or microsegregated phases upon mixing.

Spectroscopic responses of absorbance probes, betaine dye 33, N,N-diethyl-4-nitroaniline, and 4-nitroaniline, and fluorescence dipolarity probes, pyrene (Py) and pyrene-1-carboxaldehyde (PyCHO) within ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and aqueous mixtures of [bmim][BF4] are used to assess the changes in important physicochemical properties with temperature in the range 10-90 degrees C. ETN obtained from betaine dye 33, indicating dipolarity/polarizability and/or hydrogen bond donating (HBD) acidity, decreases linearly with increasing temperature within the two ILs. Changes in Kamlet-Taft parameters dipolarity/polarizability (pi*), HBD acidity (alpha), and HB accepting (HBA) basicity (beta) with temperature show interesting trends. While pi* and alpha decrease linearly with increasing temperature within the two ILs, beta appears to be independent of the temperature. Similar to ETNand pi*, the first-to-third band intensity ratio of probe Py also decreases linearly with increasing temperature within the ILs. The lowest energy fluorescence maxima of PyCHO, though it decreases significantly within water as the temperature is increased from 10 to 90 degrees C, it does not change within the two ILs investigated. The temperature dependence of the dipolarity/polarizability as manifested via betaine dye 33 behavior is found to be more within the aqueous mixtures of [bmim][BF4] as compared to that within neat [bmim][BF4] or neat water. The sensitivity of pi* toward temperature increases as IL is added to water and that of alpha decreases. The temperature dependent Py behavior shows no clear-cut trend within aqueous mixtures of [bmim][BF4]; insensitivity of the PyCHO response toward temperature change is reasserted within aqueous IL mixtures. All-in-all, the temperature-dependent behavior of solvatochromic probes within [bmim][PF6], [bmim][BF4], and aqueous mixtures of [bmim][BF4] is found to depend on the identity of the probe.

Mixtures of ionic liquid (IL) with poly(ethylene glycol) (PEG) may afford media with favorable properties. Dynamic viscosities of mixtures of a common and popular IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) with PEGs of average molecular weight (MW) 200 (PEG200), average MW 400 (PEG400), number-average MW M(n) 570-630 (PEG600), and number-average MW M(n) 950-1050 (PEG1000) over a complete composition range at 10° intervals in the temperature range of 10-90 °C are measured. The temperature dependence of the dynamic viscosity shows ([bmim][PF(6)] + PEG) mixtures to behave as Newtonian fluids and is found to follow Arrhenius-type behavior. In the IL-rich region, excess logarithmic viscosities for the ([bmim][PF(6)] + PEG200) mixture are found to be negative and independent of the temperature. Mixtures of ([bmim][PF(6)] + PEG600) and ([bmim][PF(6)] + PEG1000) show rare and unusual viscosity "synergism" or "hyperviscosity" in the sense that the mixture viscosity is observed to be significantly higher than the viscosity of both the neat components forming the mixture, giving rise to large positive excess logarithmic viscosities. These positive excess logarithmic viscosities decrease with increasing temperature. Formation of extensive H-bonding between the IL and PEG more than compensates for the losses in Coulombic attractive and van der Waals interactions within [bmim][PF(6)] and PEG600/PEG1000, respectively, giving rise to viscosity synergism. This compensation is not enough for ([bmim][PF(6)] + PEG200) and ([bmim][PF(6)] + PEG400) mixtures. The evidence for H-bonding in the mixtures is provided by FTIR absorbance data. The product of the monomer-to-excimer emission intensity ratio and the lifetime of the intramolecular excimer fluorescence of a microfluidity probe, 1,3-bis(1-pyrenyl)propane (BPP), is used as a reflection of the microviscosity of the mixture at different temperatures. The microviscosity shows synergistic effects in all four ([bmim][PF(6)] + PEG) mixtures. The contribution of H-bonding to the microviscosity reported by BPP is observed to be more then that as compared to contributions of Coulombic and van der Waals interactions. Synergism in the dynamic viscosity and microviscosity of ([bmim][PF(6)] + PEG) mixtures is a complex interplay of inter- and intramolecular H-bonding as well as Coulombic and van der Waals type interactions.

BackgroundWe aim to report the incidence of post-intubation hypotension in the critically ill, to report in-hospital mortality and length of stay in those who developed post-intubation hypotension, and to explore possible risk factors associated with post-intubation hypotension.Material/MethodsAdult (≥18 years) ICU patients who received emergent endotracheal intubation were included. We excluded patients if they were hemodynamically unstable 60 minutes pre-intubation. Post-intubation hypotension was defined as the administration of any vasopressor within 60 minutes following intubation.ResultsTwenty-nine patients developed post-intubation hypotension (29/147, 20%). Post-intubation hypotension was associated with increased in-hospital mortality (11/29, 38% vs. 19/118, 16%) and length of stay (21 [10–37] vs. 12 [7–21] days) on multivariate analysis. Three risk factors for post-intubation hypotension were identified on multivariate analysis: 1) decreasing mean arterial pressure pre-intubation (per 5 mmHg decrease) (p-value=0.04; 95% CI 1.01–1.55); 2) administration of neuromuscular blockers (p-value=0.03; 95% CI 1.12–6.53); and 3) intubation complication (p-value=0.03; 95% CI 1.16–15.57).ConclusionsPost-intubation hypotension was common in the ICU and was associated with increased in-hospital mortality and length of stay. These patients were more likely to have had lower mean arterial pressure prior to intubation, received neuromuscular blockers, or suffered a complication during intubation.

Poly(ethylene glycols) (PEGs) and room-temperature ionic liquids (ILs) are both projected as possible alternatives to volatile organic compounds (VOCs). Their potential usage in chemical applications, however, is often hampered by their limited and, in some cases, undesired individual physicochemical properties. Properties of mixtures of PEG with a common IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) are assessed via responses of three fluorescence probes: pyrene (Py) and pyrene-1-carboxaldehyde (PyCHO) are the dipolarity sensing probes and 1,3-bis-(1-pyrenyl) propane (BPP) is the probe for microfluidity. All three probes demonstrate anomalous fluorescence behavior within the mixture of [bmim][PF6] with four different PEGs of average molecular weight (MW) 200, 400, 600, and 1500 g.mol(-1), respectively, across complete composition range. Cybotactic region dipolarity of the probe Py within the mixtures is observed to be higher than that expected from ideal additive behavior. PyCHO lowest energy fluorescence maxima implying the static dielectric constant around the cybotactic region shows values within the mixtures to be even higher than that in neat PEG, the component having higher static dielectric constant of the two, clearly indicating the milieu to have anomalously high dipolarity. "Hyperpolarity" inherent to the PEG+[bmim][PF6] mixture is confirmed. Intramolecular excimer-to-monomer fluorescence intensity ratio of BPP indicates the microfluidity within the mixture to be even lower than that within neat [bmim][PF6], the component with lowest microfluidity. Presence of strong solvent-solvent interactions within the mixture is proposed to be the major reason for the anomalous fluorescence probe responses. Specifically, extensive hydrogen-bonded network involving termini hydroxyls of PEGs and PF6- as well as ethoxy/hydroxyl oxygens of PEGs and the C2-H of bmim+ is proposed to be responsible for the unusual outcomes. Fluorescence probe responses are shown to be adequately predicted by a four-parameter simplified combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) model. Unusually altered physicochemical properties are demonstrated to be the key feature of the "hybrid green" PEG+IL systems.

Hybrid "green" solvent systems composed of room-temperature ionic liquids (ILs) and poly(ethylene glycols) (PEGs) may have enormous future potential. Solvatochromic absorbance probe behavior is used to assess the physicochemical properties of the mixture composed of IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) and PEG (average molecular weights of 200, 400, 600, and 1500) at ambient conditions. Lowest energy intramolecular charge-transfer absorbance maxima of a betaine dye, i.e., E(T)(N), indicates the dipolarity/polarizability and/or hydrogen-bond donating (HBD) acidity of the [bmim][PF 6] + PEG mixtures to be even higher than that of neat [bmim][PF(6)], the solution component with higher dipolarity/polarizability and/or HBD acidity. Dipolarity/polarizability (pi*) obtained separately from the electronic absorbance response of probe N, N-diethyl-4-nitroaniline shows a trend similar to E(T)(N ) thus confirming the unusually high dipolarity/polarizability of the [bmim][PF(6)] + PEG mixtures. Similar to E(T)(N ) and pi*, the HBD acidity (alpha) of [bmim][PF(6)] + PEG mixtures is also observed to be anomalously high. Contrary to what is observed for E(T)(N ), pi*, and alpha, the hydrogen-bond accepting (HBA) basicity (beta) of the [bmim][PF(6)] + PEG mixtures is observed to be lower than that predicted from ideal additive behavior indicating diminished HBA basicity of the mixture as compared to its neat components. A four-parameter simplified combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation is shown to satisfactorily predict the solvatochromic parameters within [bmim][PF(6)] + PEG mixtures. It is demonstrated that [bmim][PF(6)] + PEG mixtures possess physicochemical properties that are superior to those of either the neat IL or the neat PEG.

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