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Biomedical subjects

A Chaumont

Publications and source records attributed to A Chaumont.

17 recordsLinked to original sources
PubMed2005

Aqueous interfaces with hydrophobic room-temperature ionic liquids: a molecular dynamics study.

We report a molecular dynamics study of the interface between water and (macroscopically) water-immiscible room-temperature ionic liquids "ILs", composed of PF6(-) anions and butyl- versus octyl-substituted methylimidazolium+ cations (noted BMI+ and OMI+). Because the parameters used to simulate the pure ILs were found to exaggerate the water/IL mixing, they have been modified by scaling down the atomic charges, leading to better agreement with the experiment. The comparison of [OMI][PF6] versus [BMI][PF6] ILs demonstrates the importance of the N-alkyl substituent on the extent of solvent mixing and on the nature of the interface. With the most hydrophobic [OMI][PF6] liquid, the "bulk" IL phase is dryer than with the [BMI][PF6] liquid. At the interface, the OMI+ cations retain direct contacts with the bulk IL, whereas the more hydrophilic PF6(-) anions gradually dilute in the local water micro-environment and are thus isolated from the "bulk" IL. The interfacial OMI+ cations are ordered with their imidazolium moiety pointing toward the aqueous side and their octyl chains toward the IL side of the interface. With the [BMI][PF6] liquid, the system gradually evolves from an IL-rich to a water-rich medium, leading to an ill-defined interfacial domain with high intersolvent mixing. As a result, the BMI+ cations are isotropically oriented "at the interface". Because the imidazolium cations are more hydrophobic than the PF6(-) anions, the charge distribution at the interface is heterogeneous, leading to a positive electrostatic potential at the interface with the two studied ILs. Mixing-demixing simulations on [BMI][PF6]/water mixtures are also reported, comparing Ewald versus reaction field treatments of electrostatics. Phase separation is very slow (at least 30 ns), in marked contrast with mixtures involving classical organic liquids, which separate in less than 0.5 ns at the microscopic level. The results allow us to better understand the specificity of the aqueous interfaces with hydrophobic ionic liquids, compared with classical organic solvents, which has important implications as far as the mechanism of liquid-liquid ion extraction is concerned.

Journal Article↗
PubMed1997

Comparative hemodynamic depression of sevoflurane versus halothane in infants: an echocardiographic study.

BACKGROUND: The cardiovascular side effects of volatile anesthetics are one of the chief causes of postoperative complications in children, and infants seem to be at the greatest risk for this. This study compared cardiovascular changes at equipotent concentrations of sevoflurane and halothane in infants. METHODS: Thirty infants classified as American Society of Anesthesiologists physical status I or II who required elective surgery were randomized to receive either halothane or sevoflurane for inhalation induction. Cardiovascular and echocardiographic data were recorded in both groups at baseline and at end-tidal concentrations of 1 and 1.5 minimum alveolar concentration (MAC). RESULTS: Sevoflurane did not alter heart rate or cardiac index at all concentrations compared with awake values. Sevoflurane significantly decreased blood pressure and systemic vascular resistance compared with awake values at all concentrations. Shortening fraction and rate-corrected velocity of circumferential fiber shortening decreased at 1.5 but not at 1 MAC. Myocardial contractility assessed by stress-velocity index and stress-shortening index decreased significantly at all concentrations, but did not fall into the abnormal range at any concentration. Halothane caused a greater decrease in heart rate, shortening fraction, stress-shortening index, velocity of circumferential fiber shortening, stress-velocity index, and cardiac index at all concentrations than did sevoflurane. CONCLUSION: Sevoflurane causes a lesser decrease in cardiac output than does halothane in infants.

Anesthetics, Inhalation↗
PubMed1996

[Analgesia controlled by the patient in pediatrics].

The development of patient controlled analgesia (PCA) in children is the result of a search for an analgesia being both maximally efficient and secure, in the management of severe pain. The technique is based on self infusions of an analgesic, mainly morphine, by the child, through a special pump. The quality of the pump is essential in order to exclude any risk of overdosage. In order to prevent potential secondary effects and complications, a careful supervision is mandatory (clinical, by pulse oximetry, regular checking of pump parameters). PCA is applicable to children older than 5 years. The main indications are post-operative and oncological pains.

Adolescent↗
PubMed1994

[Pain conduction tracts. From physiology to practice].

Some new theories concerning pain physiology have recently been suggested. Experimental facts show that despite its complexity, neuroplasticity is an established fact. The concept of preemptive analgesia is about to receive clinical applications. Nevertheless, the role of many opioid ligands which are involved in the pain physiology can explain the efficacy of some analgesia techniques. The authors review the physiological process of pain from its periphery to its centre and the ensuing practical applications. They point out the difficulty to apprehend peripheral analgesia, and the necessity of further researches concerning especially NMDA spinal receptors and other specific receptors.

Animals↗
PubMed1992

[Complementing loco-regional anesthesia in children].

An accomplishment to loco-regional anesthesia. Yes! but dependent on the age of the child; rather mild general anesthesia than progressive sedation. This should not lead to the neglect of certain basic principles: a faultless technique including the highest security standards without neglecting the psychological aspect. Use of these technique as means of outpatient treatment will be the future outlook.

Anesthesia, Conduction↗
PubMed1990

Toxicological findings after fatal amitriptyline self-poisoning.

A case of fatal self-poisoning with amitriptyline is reported. Both the drug and its metabolite nortriptyline were quantified in several post-mortem tissues and fluids, including vitreous humor. Results are discussed in the light of the existing literature.

Adult↗
PubMed1989

Toxicological findings after fatal dextromoramide injection.

A death involving dextromoramide injection is presented. The drug was analyzed in whole blood, bile, stomach contents, kidney, brain and liver. The whole blood concentration was 1526 ng/ml. The results are compared with the existing literature.

Adult↗
PubMed1989

Subnanogram GC/NPD method for the determination of sparteine in biological fluids.

A gas chromatographic method is presented for identification and quantification of sparteine in biological fluids using cyclizine as an internal standard. No derivation is necessary and after a single alkaline extraction, GC analysis of sparteine is achieved in less than 8 min. A subnanogram limit of detection is allowed by the use of a nitrogen phosphorous detector (NPD). This method is simple, reproducible, selective, and applicable in both clinical and pharmacokinetic studies.

Chromatography, Gas↗