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Biomedical subjects

G Park

Publications and source records attributed to G Park.

At least 19 recordsLinked to original sources
PubMed2007

A comparison of hypnotic and analgesic based sedation in a general intensive care unit.

BACKGROUND: Sedation of the critically ill patient has several components including hypnosis and analgesia. Hypnotic-based sedation (HBS), where midazolam and/or propofol are used, with morphine or another analgesic added as needed has been common. The advent of remifentanil has allowed greater use of analgesia-based sedation (ABS) where relief of discomfort from the tracheal tube or pain are the important objectives, and hypnosis is given as necessary. Method. We compared HBS and ABS (remifentanil-based sedation) within a general intensive care unit (ICU). During the first study period of 12 weeks, 111 patients received HBS. After the development of new guidelines for the use of remifentanil in the ICU, a second 12 week study period used an analgesia-based regimen, with hypnotics added only if needed. RESULTS: Ninety-six patients received ABS, and 79 received remifentanil. It was possible to manage 29 (37%) of the patients receiving remifentanil without the use of supplementary hypnotic agents. In the remaining 63% the use of remifentanil was associated with a reduction in the amount and duration of propofol used. Significantly more patients receiving ABS had satisfactory levels of sedation during synchronized intermittent mandatory ventilation (19 [2,55] vs 50 [14,83], P<0.001). CONCLUSIONS: The use of ABS allowed patients to be managed more comfortably, either without a hypnotic drug or with less hypnotic drug, than using conventional HBS.

Adolescent↗
PubMed2006

Interaction between two inhomogeneously charged parallel surfaces in the strong coupling regime.

The counterion density profile and pressure between two inhomogenously charged parallel plates are analyzed analytically and numerically in the strong-coupling regime. Point charges are used and the surface charges are immobile. It is found that when the surface charge distribution is inhomogeneous, the charge coupling effect becomes stronger, the counterion spatial distribution is more localized toward the plate surfaces, and, thus, the pressure between two plates becomes lower than in the case when the surface charge distribution is homogeneous.

Journal Article↗
PubMed2004

Properties of 137Cs in marine sediments off Yangnam, Korea.

Concentrations of 137Cs in sediment and seawater samples in the East Sea (Japan Sea) adjacent to Yangnam, Korea were measured and data on the physical and chemical properties of the sediments were collected. The concentrations of 137Cs in the sediment samples were in the range of less than the minimum detectable activity (MDA)-7.19 Bq/kg-dry, and the values were linearly correlated with particle size, total organic carbon (TOC), H, N or S content of the sediment. The 137Cs concentrations in the sediment samples were well fitted to a multiple regression equation with TOC contents and particle size distributions. The distribution coefficients, which indicate the degree of adsorption, of 137Cs to the sediments were strongly dependent on particle size and TOC content.

Adsorption↗
PubMed2003

Appropriate antimicrobial treatment in nosocomial infections-the clinical challenges.

Resistance to antimicrobial agents is emerging in a wide variety of pathogens, particularly those that cause nosocomial infections. As a consequence of this increasing resistance, morbidity and mortality in nosocomial infections is also increasing. It is therefore critical to treat nosocomial infections appropriately by starting antimicrobial treatment early in the course of infection, using the correct agent, at the most appropriate dose, and for an adequate duration. Indeed, early 'appropriate' antibiotic prescribing has been shown significantly to reduce mortality, length of intensive care unit and hospital stay and overall costs. Early use of the correct antibiotic at the appropriate dose and for an adequate duration are key to initial appropriate antibiotic prescribing. Choosing the right antibiotic depends mainly on the likely pathogen(s) and the expected local susceptibility patterns. Selection of appropriate antimicrobial therapy requires a thorough understanding of the likely microbial cause of the infection, including local susceptibility patterns, as well as the properties of the antimicrobials available for treating these infections, namely spectrum of activity and potency (including activity versus known resistance mechanisms), pharmacokinetic profile and tolerability and safety. This review, based on a series of presentations at the 5th International Conference of the Hospital Infection Society (Edinburgh, 2002) examines the importance of appropriate antimicrobial therapy in nosocomial infections, and provides guidance on how to achieve this.

Anti-Infective Agents↗
PubMed2002

Novel cytotoxic chelators that bind iron(II) selectively over zinc(II) under aqueous aerobic conditions.

To achieve cellular iron deprivation by chelation, it is important to develop chelators with selective metal-binding properties. Selectivity for iron has long been the province of certain oxygen-donor chelators such as desferrioxamine, which target Fe(III) and exploit the strength of a relatively ionic Fe(III)-O interaction. We have been studying novel chelators that possess mechanisms to selectively chelate +2 biometals, particularly tachpyr [N,N',N"-tris(2-pyridylmethyl)-1,3,5-cis,cis-triaminocyclohexane] and derivatives from N,N',N"-trialkylation and pyridine ring alkylation. Metal-exchange and metal-binding competition reactions have been conducted at pH 7.4, 37 degrees C and time periods until no further change was observed (generally 24-48 h). Under anaerobic conditions, tachpyr is strongly selective for iron, binding 95+/-5% Fe(II) versus 5+/-5% Zn(II) in the forms [Fe(tachpyr)](2+) and [Zn(tachpyr)](2+) respectively. Under aerobic conditions, tachpyr complexes Fe(II) more effectively than Fe(III), forming iminopyridyl complexes [Fe(tachpyr-ox-n)](2+) (n=2, 4) by O(2)-induced and iron-mediated oxidative dehydrogenation. Complexes [Fe(tachpyr-ox-n)](2+) are also strongly bound forms of iron that are unaffected by an excess of Zn(II) (75 mol zinc:1 mol iron complex). The preference of tachpyr for iron over zinc under aerobic conditions appears to be hindered by oxidation of Fe(II) to Fe(III), such that the proportions bound are 44+/-10% Fe(II) versus 56+/-10% Zn(II), in the respective forms [Fe(tachpyr-ox-n)](2+) and [Zn(tachpyr)](2+). However, upon addition of the reducing agent Na(2)S(2)O(4) that converts Fe(III) to Fe(II), the binding proportions shift to 76+/-10% Fe(II) versus 24+/-10% Zn(II), demonstrating a clear preference of tachpyr for Fe(II) over Zn(II). Iron(II) is in the low-spin state in [Fe(tachpyr)](2+) and [Fe(tachpyr-ox-n)](2+) (n=2, 4), which is a likely cause of the observed selectivity. N-methylation of tachpyr [giving (N-methyl)(3)tachpyr] results in the loss of selectivity for Fe(II), which is attributed to the steric effect of the methyl groups and a resulting high-spin state of Fe(II) in [Fe(N-methyl)(3)tachpyr)](2+). The relationship of chelator selectivity to cytotoxicity in the tach family will be discussed.

Aerobiosis↗
PubMed2002

Body computed tomography in critically ill patients.

The aim of the study was to assess the effectiveness of computed tomography in the management of critically ill patients. We performed a prospective study over a 4-month period. The requesting clinician was asked to document their clinical diagnosis and confidence thereof on a visual analogue scale. They were also asked about their management plan if computed tomography had not been available. After imaging, any change in the management plan was assessed. During the study period, 16 computed tomograms were performed on 14 patients. There were 21 possible clinical diagnoses: of these eight were confirmed, and 13 were refuted. Seven new diagnoses were established. Computed tomography did not help in the management of two patients and it led to more confusion in the management of one patient. The management of seven patients was altered after computed tomography and in six the management depended solely on computed tomography findings.

Confidence Intervals↗
PubMed2002

Stress in UK intensive care unit doctors.

BACKGROUND: Doctors have long been considered at risk of occupational stress. METHODS: A postal survey of all members of the Intensive Care Society using validated instruments. RESULTS: Eight-five per cent of members returned questionnaires and 70% were eligible for the study. Twenty-nine per cent were suffering General Health Questionnaire-12 (GHQ-12) identified distress and 12% Symptom Checklist-Depression (SCL-D) defined depression. There were no significant age or sex differences between staff suffering distress or depression and those who did not. Dissatisfaction with career correlated highly with both distress and depression (P<0.01). Twenty doctors (3%) were bothered by suicidal thoughts. The most stressful aspects of work were bed allocation, being over-stretched, effect of hours of work and stress on personal/family life, and compromising standards when resources are short. Logistic regression revealed mental health problems were predicted by five stressors: 'lack of recognition of one's own contribution by others'; 'too much responsibility at times'; 'effect of stress on personal/family life'; 'keeping up to date with knowledge'; and 'making the right decision alone'. CONCLUSIONS: Nearly one in three ICU doctors appeared distressed (GHQ), and one in 10 depressed (SCL-D); this is no greater than that reported in other specialities. Perceived stressors reveal some key areas of concern for the employer and the specialty.

Adult↗
PubMed2001

Design and synthesis of glycolic and mandelic acid derivatives as factor Xa inhibitors.

A series of glycolic and mandelic acid derivatives was synthesized and investigated for their factor Xa inhibitory activity. These analogues are highly potent and selective inhibitors against fXa. In a rabbit deep vein thrombosis model, compound 26 showed significant antithrombotic effects (81% inhibition of thrombus formation) at 1.1 microM plasma concentration following intravenous administration.

Acetanilides↗
PubMed2001

Copper(II) complexes of novel N-alkylated derivatives of cis,cis-1,3,5-triaminocyclohexane. 1. Preparation and structure.

Novel N,N',N' '-trialkylated derivatives of cis,cis-1,3,5-triaminocyclohexane (tach), designated tach-R(3), were prepared through alkylation of N-protected tach with subsequent acid deprotection, to afford N-methyl, N-ethyl, and N-n-propyl derivatives as their trihydrobromide salts. The tach-neopentyl(3) and tach-furan(3) derivatives were prepared by formation of the imine from tach and pivaldehyde or furan-2-carboxaldehyde, respectively, followed by reduction of the imine. Complexes [Cu(tach-R(3))Cl(2)] (R = Me, Et, n-Pr, CH(2)-2-thienyl, and CH(2)-2-furanyl) were prepared from CuCl(2) in MeOH or MeOH-Et(2)O solvent. Crystallographic characterization of [Cu(tach-Et(3))Br(0.8)Cl(1.2)] (Pnma, a = 8.2265(1) A, b = 12.5313(1) A, c = 15.3587(3) A, Z = 4) reveals a square-based pyramidal CuN(3)X(2) coordination sphere in which one nitrogen donor occupies the apical position at a slightly longer distance (Cu-N = 2.218(5) A) than those of the basal nitrogens (Cu-N = 2.053(2) A). The solution-phase (pH 7.4 buffered and methanol) and solid-phase structures of [Cu(tach-R(3))Cl(2)] have been studied extensively by EPR and visible-near-IR spectroscopies. The square-based pyramidal structure is retained in solution, according to correspondence of solution and solid-state data. In aqueous solution, halide is replaced by water, as indicated by the high-energy UV-vis spectral shifts and bonding parameters of [Cu(tach-Et(3))](2+)(aq) derived from EPR data. The proposed aqueous-phase species, in the pH range 7.4 to 10.1, is [Cu(tach-Et(3))(H(2)O)(2)](2+). The complex [Cu(tach-Me(3))](2+)(aq) does not appear to dimerize or form metal-hydroxo species at pH 7.4, in contrast to other Cu(II)-triamine complexes, e.g., [Cu(1,4,7-triazacyclononane)](2+) (aq) and [Cu(tach-H(3))](2+)(aq) (the complex of unalkylated tach). This difference is attributed to the steric effect of the N-alkyl groups in the tach-R(3) series.

Alkylation↗
PubMed2001

Copper(II) complexes of novel N-alkylated derivatives of cis,cis-1,3,5-triaminocyclohexane. 2. Metal-promoted phosphate diester hydrolysis.

Aqueous copper(II) N,N',N' '-trimethyl-cis,cis-1,3,5-triaminocyclohexane (Cu(tach-Me(3))(2+)(aq)) promotes the hydrolysis of activated phosphate diesters in aqueous medium at pH 7.2. This complex is selective for cleavage of the phosphate diester sodium bis(p-nitrophenyl) phosphate (BNPP), the rate of hydrolysis of the monoester disodium p-nitrophenyl phosphate being 1000 times slower. The observed rate acceleration of BNPP hydrolysis is slightly greater than that observed for other Cu(II) complexes, such as [Cu([9]aneN(3))Cl(2)] ([9]aneN(3) identical with 1,4,7-triazacyclononane). The rate of hydrolysis is first-order in phosphate ester at low ester concentration and second-order in [Cu(tach-Me(3))](2+)(aq), suggesting the involvement of two metal complexes in the mechanism of substrate hydrolysis. The reaction exhibits saturation kinetics with respect to BNPP concentration according to a modified Michaelis-Menten mechanism: 2CuL + S <==> LCu-S-CuL --> 2CuL + products (K(M) = 12.3 +/- 1.8 mM(2), k(cat) = (4.0 +/- 0.4) x 10(-)(4) s(-1), 50 degrees C) where CuL (triple bond) [Cu(tach-Me(3))](2+), S (triple bond) BNPP, and LCu-S-CuL is a substrate-bridged dinuclear complex. EPR data indicate that the dicopper complex is formed only in the presence of BNPP; the active LCu-S-CuL intermediate species then slowly decays to products, regenerating monomeric CuL.

Copper↗
PubMed2001

Diffusion by extrinsic noise in a two-dimensional anisotropic web mapping.

Diffusion by an extrinsic noise is studied in a two-dimensional anisotropic web mapping where the intrinsic web diffusion is negligible, diffusion in one direction is dominant over the other, and the extrinsic noise enters in the dominant dimension only. It is found that the diffusion scaling is governed by the competition between the extrinsic noise and the intrinsic rotation. If the extrinsic noise is weaker than the intrinsic rotation, diffusion scales as lK(1/2) in the dominant direction and as lK(3/2) in the nondominant direction, where l is the extrinsic noise strength and K is the intrinsic perturbation parameter. If the extrinsic noise is stronger, diffusion behaves as l(2)/2 in the dominant direction and as K(2)/4 in the nondominant direction. Diffusion in the nondominant direction can be important if the equilibrium system is translationally invariant in the dominant direction.

Journal Article↗
PubMed2001

Diffusion by extrinsic noise in the kicked Harper map.

A significantly improved analytic understanding of the extrinsically driven diffusion process is presented in a nonlinear dynamical system in which the phase space is divided into periodic two-dimensional tiles of regular motion, separated by a connected separatrix network (web) [previously studied by A. J. Lichtenberg and Blake P. Wood, Phys. Rev. Lett. 62, 2213 (1989)]. The system is represented by the usual "kicked Harper map" with added extrinsic noise terms. Three different diffusion regimes are found depending upon the strength of the extrinsic perturbation l relative to the web and regular motions. When the extrinsic noise is dominant over the intrinsic stochasticity and the regular rotation motions in the tile, diffusion obeys the random phase scaling l(2). When the extrinsic noise is dominant over the intrinsic stochasticity, but weaker than the regular rotation motion, the diffusion scales as lK(1/2), where K is the strength of the intrinsic kick. These findings agree well with numerical simulation results. When the extrinsic noise process is weaker than the stochastic web process, we analytically reproduce the well-known numerical result: The web diffusion is reduced by the ratio of phase-space areas of intrinsic to extrinsic stochasticity.

Journal Article↗
PubMed2001

Commentary. Balancing sedation and analgesia in the critically ill.

The authors have presented a template for a systematic approach to comforting critically ill patients that can be modified to suit institutional preferences. In this algorithm, the cause of patient discomfort is sought with the priority given to pain and then to anxiety. Special attention is directed to the identification of correctable causes of pain and anxiety with application of nonpharmacologic techniques or medications to control patient discomfort. This step is followed by subsequent reassessment of the need for sedation or anxiolysis and titration or discontinuation of therapy as able. The benefits of protocol-driven care are becoming increasingly evident, and the authors believe the algorithm outlined here provides a rational and practical approach to patient management. It also prompts the caregiver to reevaluate patients' needs and to keep to patients at target sedation levels. Doing so can promote cost effectiveness, reduce side effects caused by drugs, and decrease morbidity and ICU stay. Any treatment protocol or algorithm is simply a guide to therapy and cannot address every clinical situation. The importance of individualized care and physician or care team judgment must be emphasized.

Algorithms↗