Sónia Campos

Performance of Anesthetic Depth Indexes in Rabbits under Propofol Anesthesia Prediction Probabilities and Concentration-effect Relations

Background:The permutation entropy, the approximate entropy, and the index of consciousness are some of the most recently studied electroencephalogram-derived indexes. In this work, a thorough comparison of these indexes was performed using propofol anesthesia in a rabbit model. Methods:Six rabbits were anesthetized with three propofol infusion rates: 70, 100, and 130 mg · kg −1 · h−1, each maintained for 30 min, in a random order for each animal. Data recording was performed in the awake animals 20, 25, and 30 min after each infusion rate was begun in the recovered animals and consisted of electroencephalogram recordings, evaluation of depth of anesthesia according to a clinical scale, and arterial blood samples for plasma propofol determination. Median and spectral edge frequencies were analyzed for single-scale permutation entropy and composite multiscale permutation entropy, approximate entropy, index of consciousness, and the spectral parameters. The spectral parameters and single-scale and multiscale permutation entropies were corrected for the presence of burst suppression. Performance of the indexes was compared by prediction probability and pharmacodynamic analysis. Results:The single-scale and composite multiscale permutation entropies with a burst suppression correction showed better prediction probabilities than did the other electroencephalogram-derived parameters but not better than the electromyographic activity. Conclusion:Single-scale and multiscale permutation entropies may be promising measures of propofol anesthetic depth when corrected for burst suppression. Additional studies should investigate the information measured by electromyography algorithms from commercial monitors of anesthetic depth. The rabbit may be a promising animal model for electroencephalographic studies because it provides a good-quality signal.

Embryonic Stage-Dependent Teratogenicity of Ketamine in Zebrafish (Danio rerio)

Ketamine, a widely used anesthetic, has been shown to have NMDA receptor dependent and independent actions during zebrafish (Danio rerio) embryogenesis. Notwithstanding, the effects of developmental toxicity and the mechanisms of ketamine action on fish embryos are still not well understood, and its implications for early vertebrate development remains to be clarified. In this work, zebrafish embryos were exposed to ketamine (0.2, 0.4, and 0.8 mg mL(-1)) in order to study the stage-developmental toxicity of this pharmaceutical. During 256-cell (2.5 h post-fertilization, hpf), 50% epiboly (5.5 hpf) and 1-4 somites (10.5 hpf), embryos were exposed to the referred ketamine concentrations for a period of 20 min and were allowed to grow until 144 hpf. Both lethal and nonlethal parameters were evaluated. Skeletal development was assessed by alcian blue and calcein staining. Additionally, the expression of the developmental genes sonic hedgehog a (shh a) and noggin 3 (nog3) was evaluated. Similar to our previous work, bone and cartilage malformations were observed after 256-cell exposure. During 50% epiboly, ketamine exposure induced concentration-dependent mortality and malformations, such as lordosis and/or kyphosis and microcephaly, namely, at higher concentrations. Conversely, exposure during 1-4 somites showed the induction of nonspecific effects with no rise in mortality. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis showed differences in shh a and nog3 expressions comparatively to the control group. Overall, this study shows that the ketamine toxic profile is developmental phase-dependent with 256-cell being the most susceptible phase. The effects observed may result from ketamine interaction with cellular signaling pathways that merits further investigation.

Ketamine-induced oxidative stress at different developmental stages of zebrafish (Danio rerio) embryos

Ketamine, a widely used anesthetic in a variety of species, has been shown to exert a potential teratogenic effect during the early life stages of zebrafish. A number of mechanisms have been suggested for the etiology of teratogens. One of the most studied involves reactive oxygen species (ROS) formation and oxidative damage. In this study, zebrafish embryos were used to analyze oxidative stress as a potential mechanism of ketamine-induced toxicity. The changes in the accumulation and in vivo patterns of ROS, enzymatic activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE)), glutathione levels (oxidized (GSSG) and reduced (GSH)), oxidative damage (lipid peroxidation (LPO) and protein carbonyls (CO)) and gene expression (gclc, gstp1, sod1 and cat) were evaluated at 8 and 24 hours post fertilization (hpf) in zebrafish embryos exposed during 20 minutes to 0.2, 0.4 and 0.8 mg mL−1 ketamine in the course of blastula (2.5 hours post fertilization-hpf), gastrula (5.5 hpf) and segmentation (10.5 hpf). Although no changes in ROS patterns were visible after all ketamine exposures, an increase in GSH levels was observed after exposure during blastula, indicating possible alterations in cell oxidative capacity. After exposure in gastrula, an increase in SOD and CAT enzymatic activities along with an increase in GSSG levels were observed at 8 hpf. At 24 hpf, CAT activity remained higher in ketamine exposed groups. The expression of the cat gene was also augmented at this time point. The changes were related with the ability of the embryo to handle oxidative stress and to a turning point during development of the oxidative defense system. At segmentation, the exposure to ketamine induced changes in the accumulation of ROS and sod gene expression which were related to protective mechanisms against ketamine-induced oxidative stress. Changes in acetylcholinesterase were also observed which may be related to changes in ROS. The overall results show that ketamine induces phase-dependent oxidative stress misregulation that could be the key factor for ketamine toxicity and could help to elucidate and provide more information on the mechanism of embryotoxicity of ketamine.

Evidence of Different Propofol Pharmacokinetics under Short and Prolonged Infusion Times in Rabbits

Propofol is an anaesthetic widely used in both human beings and animals. However, the characterization of propofol pharmacokinetics (PK) is not well understood when long‐term infusions are used. The main objective of this study was to explore the PK behaviour of propofol in a rabbit model during short and prolonged propofol infusions and to develop an internally validated PK model, for propofol dose individualization in the rabbit for future use. Population 1 (P1) was constituted by seven New Zealand rabbits and was used to characterize the PK profile of propofol at short infusions. Animals were anaesthetized with a bolus of 20 mg/kg, followed by an infusion rate of 50 mg/kg/hr of propofol at 1%, which was then maintained for 30 min. A second rabbit population (P2, n = 7) was sedated according to reflexes responses and Index of Consciousness values, for 20 consecutive hours using propofol 2% aiming at characterizing propofol behaviour at long‐term infusions. Clinical data and blood samples were collected at specific time‐points in both populations. Propofol plasma concentrations were determined by gas chromatography/ion trap mass spectrometry. The NONMEM VII software was used to evaluate the relationships between dose and plasma concentrations. A linear two‐compartment model with different central compartment volume and plasma clearance (separately modelled in the two populations) was the one that best described propofol concentrations. The time course of propofol plasma concentrations was well characterized by the PK model developed, which simultaneously accounts for propofol short‐ and long‐term infusions and can be used to optimize future PK studies in rabbits.

Expression of CYP1A1 and CYP1A2 in the liver and kidney of rabbits after prolonged infusion of propofol.

BACKGROUND Propofol biotransformation occurs in the liver via hydroxylation by CYP450 enzymatic complex and by glucuronidation, however extra-hepatic metabolism has also been described. OBJECTIVES To better understand the metabolic pathways involved in propofol biotransformation, the expression of CYP1A1, CYP1A2, the enzymatic and non-enzymatic antioxidant activity and the amount of propofol and its non-conjugated metabolites were investigated. METHODS Twenty-one NewZealand rabbits were allocated into three groups continuously treated for 20h. Each group received: NaCl 0.9%, vehicle (SMOFlipid) and propofol 2% (Lipuro). At the end, liver and kidney samples were collected for histopathology and immunohistochemistry and plasma for quantification of propofol and its metabolites. RESULTS CYP1A1 and CYP1A2 were observed in zone 1 and zone 3 regions of the liver acinus. The propofol and saline groups showed a higher expression of CYP1A1 when compared to vehicle group. Propofol significantly increased CYP1A2 expression, compared to saline. CYP1A1 and CYP1A2 immunoexpression were observed in the kidney but no differences were registered between groups. CONCLUSIONS This suggests that propofol may act as selective inhibitor of CYP1A1 and an inducer of CYP1A2 expression in different regions of the liver. Propofol seems to have an antioxidative protective effect on liver parenchyma, comparatively to the emulsion alone. In the rabbit, extra-hepatic propofol biotransformation may also occur in the kidney.

Time to death in a prospective cohort of 252 patients treated for fracture of the proximal femur in a major hospital in Portugal

Los objetivos del estudio fueron analizar la supervivencia tras un ano y los factores asociados para enfermos con fractura de la cadera (bajo impacto). Fue constituida una cohorte con todos los enfermos hospitalizados en el servicio de ortopedia del segundo mayor hospital de Portugal (mayo/2008 – abril/2009). La supervivencia fue evaluada a los 3, 6, 9 y 12 meses tras la fractura y relacionada con factores demograficos, estilo de vida, historia clinica y factores medicos (tipo de fractura, fecha de la cirugia, tratamiento y riesgo preoperatorio). De los 340 enfermos hospitalizados, 252 (78,9% mujeres) fueron incluidos. La mortalidad a los 3, 6, 8 y 12 meses de seguimiento fue de un 21,2%, 20%, 28,8%, 34,6% en hombres y un 7,8%, 13,5%, 19,2%, 21,4% en mujeres. Los factores asociados con la mortalidad fueron: sexo masculino (HR = 2,54; IC95%: 1,40-4,58), ASA puntuacion mas elevada, III/IV vs. I/II (HR = 1,95; IC95%: 1,10-3,47), edad (HR = 1,06; IC95%: 1,03-1,10) y dias de retraso en la cirugia (HR = 1,07; IC95%: 1,03-1,12). Los factores estan en su mayoria relacionados con las caracteristicas del enfermo en la admision.

Propofol affinity to mitochondrial membranes does not alter mitochondrial function

Abstract The molecular mechanisms of hepatotoxicity after propofol anaesthesia have not been fully elucidated, although there is a relation with mitochondrial dysfunction. The action of propofol on mitochondrial hepatic functions in a rat model was evaluated by infusion for 4 h with 25 and 62.5 mg/kg/h propofol or 3.125 ml/kg/h (vehicle). Liver mitochondrial respiratory rates were evaluated as well as mitochondrial transmembrane potential (&Dgr;&PSgr;), calcium fluxes, mitochondrial enzymatic activities (Complex I–V) and oxidative stress biomarkers (superoxide dismutase, catalase, glutathione reductase, glutathione S‐transferase, lipid peroxidation and the oxidised/reduced glutathione ratio). Biophysical interactions with membrane models were also performed. The mitochondrial transmembrane potential was decreased and the opening time of the mitochondrial permeability transition pore was slightly reduced for the highest dose. The activity of complex II was stimulated by propofol, which also causes fluctuations on some respiratory parameters, whereas the antioxidant system was affected in a nonspecific manner. Fluorescence quenching studies suggested that propofol is preferably located in deeper regions of the bilayer and has a high affinity to mitochondrial membranes. It is suggested that propofol interacts with liver mitochondrial membranes with mild modification in mitochondrial function.

Recreational Use of Ketamine and Its Interaction with NMDA Receptors

Abstract Ketamine was first synthesized in the early 1960s for use as an anesthetic and analgesic by noncompetitive antagonism of the N-methyl- d -aspartate receptor. However, the induction of unusual and substantial changes in perception and emotion (psychedelic effects) made ketamine a drug of abuse, used in a wide range of public and private settings with increasing consume all over the world. This pharmaceutical product displays a wide safety margin, but toxicological and adverse effects may occur. In that sense, increasing reports have shown cognitive impairment, hepatotoxicity, urological, and gastrointestinal toxicity associated with the recreational use of ketamine. Also, as ketamine abusers increase, concerns over its physical and psychological consequences have been raised despite the difficulty in determining its prevalence. Notwithstanding its adverse effects, the psychedelic effects of ketamine have been appointed as a promising therapy for the treatment of heroin addiction and alcoholism. Thus, further investigation should be conducted to clarify the severity of the pathophysiological conditions associated with nonmedical ketamine use in order to minimize risks.

Tempo até a morte após fratura do fêmur proximal: uma coorte prospectiva de 252 doentes tratados no segundo maior hospital em Portugal

Los objetivos del estudio fueron analizar la supervivencia tras un ano y los factores asociados para enfermos con fractura de la cadera (bajo impacto). Fue constituida una cohorte con todos los enfermos hospitalizados en el servicio de ortopedia del segundo mayor hospital de Portugal (mayo/2008 – abril/2009). La supervivencia fue evaluada a los 3, 6, 9 y 12 meses tras la fractura y relacionada con factores demograficos, estilo de vida, historia clinica y factores medicos (tipo de fractura, fecha de la cirugia, tratamiento y riesgo preoperatorio). De los 340 enfermos hospitalizados, 252 (78,9% mujeres) fueron incluidos. La mortalidad a los 3, 6, 8 y 12 meses de seguimiento fue de un 21,2%, 20%, 28,8%, 34,6% en hombres y un 7,8%, 13,5%, 19,2%, 21,4% en mujeres. Los factores asociados con la mortalidad fueron: sexo masculino (HR = 2,54; IC95%: 1,40-4,58), ASA puntuacion mas elevada, III/IV vs. I/II (HR = 1,95; IC95%: 1,10-3,47), edad (HR = 1,06; IC95%: 1,03-1,10) y dias de retraso en la cirugia (HR = 1,07; IC95%: 1,03-1,12). Los factores estan en su mayoria relacionados con las caracteristicas del enfermo en la admision.

Tiempo transcurrido hasta la muerte después de una fractura de cadera: una cohorte prospectiva de 252 pacientes del segundo mayor hospital de Portugal

Los objetivos del estudio fueron analizar la supervivencia tras un ano y los factores asociados para enfermos con fractura de la cadera (bajo impacto). Fue constituida una cohorte con todos los enfermos hospitalizados en el servicio de ortopedia del segundo mayor hospital de Portugal (mayo/2008 – abril/2009). La supervivencia fue evaluada a los 3, 6, 9 y 12 meses tras la fractura y relacionada con factores demograficos, estilo de vida, historia clinica y factores medicos (tipo de fractura, fecha de la cirugia, tratamiento y riesgo preoperatorio). De los 340 enfermos hospitalizados, 252 (78,9% mujeres) fueron incluidos. La mortalidad a los 3, 6, 8 y 12 meses de seguimiento fue de un 21,2%, 20%, 28,8%, 34,6% en hombres y un 7,8%, 13,5%, 19,2%, 21,4% en mujeres. Los factores asociados con la mortalidad fueron: sexo masculino (HR = 2,54; IC95%: 1,40-4,58), ASA puntuacion mas elevada, III/IV vs. I/II (HR = 1,95; IC95%: 1,10-3,47), edad (HR = 1,06; IC95%: 1,03-1,10) y dias de retraso en la cirugia (HR = 1,07; IC95%: 1,03-1,12). Los factores estan en su mayoria relacionados con las caracteristicas del enfermo en la admision.