Population pharmacokinetics of daptomycin in critically ill patients.

Daptomycin has shown activity against a wide range of Gram-positive bacteria; however, the approved dosages usually seem insufficient for critically ill patients. The aim of this study was to develop a population pharmacokinetic model for daptomycin in critically ill patients and to estimate the success of the therapy by applying pharmacokinetic/pharmacodynamic (PK/PD) criteria. Sixteen intensive care unit patients were included, four of whom underwent continuous renal replacement therapies (CRRT). Blood and, when necessary, effluent samples were drawn after daptomycin administration at previously defined time points. A population approach using NONMEM 7.3 was performed to analyse data. Monte Carlo simulations were executed to evaluate the suitability of different dosage regimens. The probabilities of achieving the PK/PD target value associated with treatment success (ratio of the area under the plasma concentration-time curve over 24 h divided by the minimum inhibitory concentration (AUC24/MIC ≥ 666)) and to reach daptomycin concentrations linked to toxicity (minimum concentration at steady-state (Cminss) ≥ 24.3 mg/L) were calculated. The pharmacokinetics of daptomycin was best described by a one-compartment model. Elimination was conditioned by the creatinine clearance (Clcr) and also by the extra-corporeal clearance when patients were subjected to continuous renal replacement therapy (CRRT). The PK/PD analysis confirmed that 280- and 420-mg/d dosages would not be enough to achieve high probabilities of target attainment for MIC values ≥ 1 mg/L in patients with Clcr ≥ 60 mL/min or in subjects with lower Clcrs but receiving CRRT. In these patients, higher dosages (560-840 mg/d) should be needed. When treating infections due to MIC values ≥ 4 mg/L, even the highest dose would be insufficient.

[Hemodynamic monitoring in the critically patient. Recomendations of the Cardiological Intensive Care and CPR Working Group of the Spanish Society of Intensive Care and Coronary Units]. / Monitorización hemodinámica en el paciente crítico. Recomendaciones del Grupo de Trabajo de Cuidados Intensivos Cardiológicos y RCP de la Sociedad Española de Medicina Intensiva, Crítica y Unidades Coronarias.

Hemodynamic monitoring offers valuable information on cardiovascular performance in the critically ill, and has become a fundamental tool in the diagnostic approach and in the therapy guidance of those patients presenting with tissue hypoperfusion. From introduction of the pulmonary artery catheter to the latest less invasive technologies, hemodynamic monitoring has been surrounded by many questions regarding its usefulness and its ultimate impact on patient prognosis. The Cardiological Intensive Care and CPR Working Group (GTCIC-RCP) of the Spanish Society of Intensive Care and Coronary Units (SEMICYUC) has recently impulsed the development of an updating series in hemodynamic monitoring. Now, a final series of recommendations are presented in order to analyze essential issues in hemodynamics, with the purpose of becoming a useful tool for residents and critical care practitioners involved in the daily management of critically ill patients.

Effects of regular and abusive intake of alcohol at weekends on physiological parameters in Spanish young.

OBJECTIVES: The aim of this study was to evaluate the effects of excessive intake at weekends, on different parameters in young university students. STUDY DESIGN: Cross sectional, descriptive study. METHODS: A group of 180 subjects were selected (young males between 18 and 22 years old) and were classified into three groups by their alcohol consumption habits: The control group of non-drinkers (ND; n = 60), the group of one day/weekend drinkers (1D/W, n = 60) and the group of two day/weekend drinkers (2D/W, n = 60). An evaluation of the body composition, a spirometry test (FVC, PEF and MVV), a maximal cycle ergometer test (Heart rate, blood pressure, VO2 max, total watts and time test until exhaustion), a blood sample (GOT, Triglycerides, Total Cholesterol, HDL cholesterol, LDL cholesterol and Glucose) were performed. RESULTS: It was observed that 2D/W group presented significantly higher levels than ND in the following parameters: total cholesterol [185.66 (16.06) compared to 154.28 (25.53) mg/dl]; triglycerides [113.66 (22.47) compared to 45.75 (12.76) mg/dl]; systolic blood pressure [130 (9.50) compared to 115 (5.77) mmHg] and waist to hip ratio [0.92 (0.08) compared to 0.84 (0.05)], and 1D/W group also showed significantly higher levels of triglycerides [71.04 (24.31) compared to 45.75 (12.76) mg/dl] than ND. Moreover, it was confirmed that the accumulation of triglycerides in weekend drinkers is influenced by smoking and the lack of physical activity, and that the relationship between alcohol drinking and systolic blood pressure could be modified by smoking. CONCLUSIONS: Young people's abusive intake of alcohol at weekends can cause negative changes in various health parameters, similar to those observed in alcoholics that drink regularly during the week.

Valoración de la precarga y la respuesta cardiovascular al aporte de volumen / Assessment of cardiovascular preload and response to volume expansion

El aporte de volumen es de especial interés en los pacientes ingresados en cuidados intensivos con inestabilidad hemodinámica en los que buscamos optimizar el gasto cardiaco .La predicción de la respuesta a esta expansión de volumen, evaluando el grado de precarga dependencia nos permitiría realizar una reanimación guiada evitando los efectos deletéreos del volumen. Actualmente, disponemos de parámetros tanto estáticos como dinámicos que identifican esta precarga-dependencia en diferentes escenarios. En este capítulo definiremos los conceptos de precarga y precarga-dependencia para luego describir cada uno de los parámetros hemodinámicos conocidos para poder predecir la respuesta a volumen, tanto en pacientes con ventilación mecánica como en respiración espontánea (AU)

Volume expansion is used in patients with hemodynamic insufficiency in an attempt to improve cardiac output. Finding criteria to predict fluid responsiveness would be helpful to guide resuscitation and to avoid excessive volume effects. Static and dynamic indicators have been described to predict fluid responsiveness under certain conditions. In this review we define preload and preload-responsiveness concepts. A description is made of the characteristics of each indicator in patients subjected to mechanical ventilation or with spontaneous breathing (AU)

Effects of aerobic exercise on urinary estrogens and progestagens in pre and postmenopausal women.

The purpose of this study was to elucidate the effect of 6 months of aerobic exercise on urinary excretion of female steroid hormones in pre and postmenopausal women and to check the basal values of urinary steroid. To this end, 20 premenopausal (age 45.56 ± 4.06 years) and 20 postmenopausal (age 52.27 ± 3.80 years) women, all sedentary, were studied before and after a supervised 6-month exercise training program (at 60-70% of maximal heart rate, 60 min/day, 3 days/week), based on aerobic dance. The exercise included standing on one leg, squatting, walking, and touching their heels. Before and after the program, anthropometric data and VO(2max) were measured and urine samples were collected and analyzed by gas chromatography/mass spectrometry (GC/Q-MS). Both, pre and postmenopausal women, improved their VO(2max) after the aerobic exercise program. Regarding the urinary steroids, on the one hand, important differences were observed between urinary estrogens and progestagens in pre and postmenopausal women in basal values. Estrone (P < 0.05), pregnanediol (P < 0.01), pregnanetriol (P < 0.05), and estriol (P < 0.01) levels were lower in postmenopausal women than in premenopausal women. On the other hand, the aerobic exercise program did not affect postmenopausal women in the same way as premenopausal women. After the exercise program, no changes in urinary steroid levels were observed in premenopausal women. However, the aerobic exercise program caused an increase in urinary excretion of pregnanediol (P < 0.05) and pregnanetriol (P < 0.05) in postmenopausal women.

[Assessment of cardiovascular preload and response to volume expansion]. / Valoración de la precarga y la respuesta cardiovascular al aporte de volumen.

Volume expansion is used in patients with hemodynamic insufficiency in an attempt to improve cardiac output. Finding criteria to predict fluid responsiveness would be helpful to guide resuscitation and to avoid excessive volume effects. Static and dynamic indicators have been described to predict fluid responsiveness under certain conditions. In this review we define preload and preload-responsiveness concepts. A description is made of the characteristics of each indicator in patients subjected to mechanical ventilation or with spontaneous breathing.

Estimación del gasto cardíaco. Utilidad en la práctica clínica. Monitorización disponible invasiva y no invasiva / Estimating cardiac output. Utility in the clinical practice. Available invasive and non-invasive monitoring

Esta revisión pretende profundizar en el conocimiento del gasto cardíaco, sus variables y sus condicionantes, así como repasar exhaustivamente las diferentes técnicas disponibles para su monitorización y establecer las situaciones en que el conocimiento del gasto cardíaco nos aporta una información fundamental en el manejo del paciente crítico. La técnica de Fick, utilizada en los inicios para calcular el gasto cardíaco de los pacientes, ha sido sustituida hoy en día en la práctica clínica por los métodos de termodilución (transcardíacao transpulmonar), litiodilución, biorreactancia, la tecnología basada en el efecto Doppler ola ecocardiografía. El análisis de la onda de pulso ha permitido la obtención de una medida continua y mínimamente invasiva del gasto cardíaco. Otros métodos, como la biorrectancia,el Doppler o la ecocardiografía nos permiten, en la actualidad, obtener medidas del gastocardíaco de forma no invasiva, rápida y fiable (AU)

This aim of this review is to provide a detailed review of the physiologic conditions and variables of the cardiac output, as well as review the different techniques available for its measurement. We also want to establish the clinical situations in which the measurement of cardiac output can add valuable information for the management of critically ill patients. The Fick technique, used in the beginning to calculate cardiac output, has been replaced today by thermodilution techniques (transcardiac or transpulmonary), lithium dilution, bioreactance, Doppler technique or echocardiography. Pulse wave analysis allows a continuous minimally invasive cardiac output measurement. Other methods, such bioreactance, Doppler technique or echocardiography currently provide a valid, fast and non-invasive measurement of cardiac output (AU)

[Estimating cardiac output. Utility in the clinical practice. Available invasive and non-invasive monitoring]. / Estimación del gasto cardíaco. Utilidad en la práctica clínica. Monitorización disponible invasiva y no invasiva.

This aim of this review is to provide a detailed review of the physiologic conditions and variables of the cardiac output, as well as review the different techniques available for its measurement. We also want to establish the clinical situations in which the measurement of cardiac output can add valuable information for the management of critically ill patients. The Fick technique, used in the beginning to calculate cardiac output, has been replaced today by thermodilution techniques (transcardiac or transpulmonary), lithium dilution, bioreactance, Doppler technique or echocardiography. Pulse wave analysis allows a continuous minimally invasive cardiac output measurement. Other methods, such bioreactance, Doppler technique or echocardiography currently provide a valid, fast and non-invasive measurement of cardiac output.

Donantes a corazón parado tipo III de Maastricht: una opción real / Non-beating heart donors - Maastricht type III: A real option

No disponible

The effect of high level tennis matches on urine steroid profiles in professional tennis players.

AIM: Modern day, tennis matches are characterized by shorter and more intense efforts with players enduring great physical and psychological stress. The aim of this study was to evaluate acute changes in the urinary steroid profile of elite tennis players following professional tournament matches. METHODS: Eight professional male tennis players participated in this study. Urine samples were collected before and after tennis matches corresponding to the quarter finals of the Spanish Tennis Masters. RESULTS: After the match, there was a significant fall (P<0.05) in testosterone, androsterone, etiocholanolone, and dehydroepiandrosterone (DHEA). Cortisone increased whereas tetrahydrocortisone (THE) decreased. The anabolic/catabolic hormone ratio also decreased, although only the fall in total suprarenal androgen (TSA)/total corticosteroid (TC) and DHEA/(THE+THF) ratios had a significant decrease (P<0.05). CONCLUSION: These results indicate that a professional tennis match modifies the urine steroid profiles of players, increasing corticosteroid and decreasing androgen excretion in urine, suggesting an important adrenal activation.

Evaluation of urinary steroid profile in highly trained cyclists.

AIM: A regular and intense physical exercise significantly modifies hormonal metabolism and there are many reports of a change in urine steroid levels accompanying the practice of sport. The aim of this study was to compare the urinary steroid profile between highly trained cyclists and untrained subjects. METHODS: Urine levels of testosterone (T), epitestosterone (Epit), androstenedione, dehydroepiandrosterone (DHEA), androsterone (A), etiocholanolone (E), beta-estradiol (E2), estrone (E1) and the most abundant urine metabolites of cortisol and cortisone, tetrahydrocortisone (THE) and tetrahydrocortisol (THF) were determined by gas chromatography-mass spectrometry in urine samples from a group of professional cyclists (n=15) submitted to maximum level training for several years and compared with urine samples from sedentary subjects (n=15). The relationships between T/Epit, A+E/ THE, A+E/ THF, DHEA/THE and DHEA/THF were also studied. RESULTS: Cyclists showed lower urine levels of T, A, E and E2 and higher urine levels of androstenedione and E1 than sedentary individuals. A+E/THE and A+E/ THF ratios were higher in sedentary subjects than in cyclists. CONCLUSION: We conclude that cyclists showed a urinary steroid profile different from sedentary individuals, probably due to an adaptation to regular and intense physical training .

MARS, diálisis con albúmina y otros sistemas bioartificiales / MARS, albumin dialysis and other bioartificial systems

Dado que la albúmina participa en el transporte de bilirrubina, aminoácidos aromáticos, cobre o ácidos biliares, el añadir albúmina al dializador permite eliminar los compuestos adheridos a la albúmina del paciente (diálisis con albúmina de un solo paso). Existen dos variantes de este tratamiento que aumentan su eficacia y disminuyen su coste. Por una parte, el sistema «Molecular Adsorbent Recuirculating System » (MARS®) realiza el reciclado de la albúmina y disminuye su consumo. Por otra, el sistema Prometeus separa la albúmina del paciente y realiza la adsorción directamente sobre esta. Los resultados publicados apuntan a una mayor eficacia en la eliminación mediante el sistema Prometeus sobre el MARS pero con un posible menor impacto sobre la hemodinámica del paciente. Estos sistemas son útiles para eliminar bilirrubina y sales biliares (Recomendación Grado B). Su uso produce una mejoría significativa sobre la hemodinámica (Evidencia Grado C), el síndrome hepatorrenal (Evidencia Grado B) y la encefalopatía hepática (Evidencia Grado B) tanto en pacientes con insuficiencia hepática aguda como aguda sobre crónica. No se puede actualmente aconsejar un tratamiento de preferencia sobre los demás (Recomendación Grado C). Los efectos adversos esperables son los mismos que los descritos para las TDE y, salvo por una trombopenia sin trascendencia clínica, el tratamiento es seguro y bien tolerado (Evidencia Grado B). No existe suficiente evidencia para la generalización de su uso en niños (Sin Recomendación)

Serum albumin is a transporter for bilirubin, aminoacids or biliary salts. Adding albumin to a dialyser improves its capability for clearing these molecules (single pass albumin dialysis). Two systems has been developed for reducing the cost of this technique: the Molecular Adsorbent Recirculating System (MARS®) regenerates albumin reducing the final amount used and the Prometheus system separates serum albumin and performs direct adsorption on it. Results point to higher efficiency on clearance for Prometheus but higher impact on hemodynamics for MARS. These treatments are indicated for clearing bilirubin or biliary salts (recommendation B) and improve hemodynamics (evidence C), hepatorenal syndrome (evidence B) and hepatic encephalopathy (evidence B) in acute as well as acute on chronic patients, but we can not recommend a specific technique (recommendation C). Adverse affects are the same that in other extracorporeal techniques. Apart from clinically irrelevant lowering of platelets the treatment is safe and well tolerated (evidence B). Acute liver failure: It has been useful in cases of viral or toxic hepatitis, primary graph dysfunction after liver transplant or extensive liver surgery when hyperbilirubinemia, hepatic encephalopathy or high intracranial pressure are present. Two RCT show a possible effect on outcome for MARS treatment (recommendation C). Acute decompensation of chronic hepatopathy: It has been useful for liver cirrhosis, primary biliary cirrhosis or agudization of viral or alcoholic hepatitis. The clinical effect is more evident in the most severely ill patients (i.e. MELD > 20). Two RCT show a positive effect on survival but a third study did not show positive results. A meta-analysis of these data did not reach statistical significance (recommendation B). Pruritus: The effect of these treatments is intense but of limited duration. Subsequent treatments lose efficacy. It has been used as an effective rescue therapy for refractory pruritus but at this point a specific dosage or protocol has not jet been defined (recommendation C). Bioartificial systems: Cell based systems (bioreactors) have been recently introduced and a recent RCT with a low number of patients has been published but this study did not show a clear effect on outcome even though a positive effect on acute failure has been suggested (no recommendation). A preliminary study has been presented with the use of a circuit based on human tubular cells but more studies are needed before this system is introduced in the clinical practice (no recommendation)

Sistemas adsorbente y mixtos: su papel en la sepsis / Adsorbent and mixed systems: their role in sepsis

La hemoperfusión a través de cartuchos con polymyxina inmovilizada y la plasmafiltración acoplada con adsorción son tratamientos adicionales en el manejo de pacientes críticos con sepsis grave que cuentan con una escasa penetración en la práctica clínica habitual. Sólo Japón cuenta con una amplia experiencia en un tratamiento relativamente sencillo como es la hemoperfusión a través de polymyxina en el manejo de pacientes críticos con sepsis grave por gram negativos. Esta amplia experiencia contrasta con la escasez de pruebas científicas, 2 estudios randomizados y uno casirandomizado junto a series de casos con controles históricos. De estas pruebas se puede extraer que es un tratamiento adicional en pacientes con sepsis por gram negativos: • Eficaz en la eliminación de endotoxina (Grado de recomendación A). • Relativamente seguro, con único problema derivado del empleo de la anticoagulación y de una posible asociación con disminución del recuento de plaquetas (Grado de recomendación B). • Con un posible impacto favorable en la mortalidad (Grado de recomendación B). La plasmafiltración acoplada con adsorción (CPFA) cuenta con menos difusión en la práctica clínica y con una mayor complejidad en el tratamiento, que implica disponer de equipos especiales (HF 440® Infomed Co. o Linda® Soria Co.) Sus bases científicas se han edificado desde estudios animales de elegante diseño pero las pruebas a nivel de ensayos clínicos no son definitivas. La plasmafiltración acoplada en pacientes sépticos con un Grado de recomendación C: • Es un tratamiento seguro. • Restaura la respuesta celular a la administración de LPS. • Mejora la supervivencia en estudios animales. • Mejoría hemodinámica en estudios clínicos

Hemoperfusion using immobilised polymyxin membranes or coupled plasma filtration with adsorption are new treatments aimed for the critically ill patient with severe sepsis that are still scarcely used. Only Japan counts on a wide experience with the use of hemoperfusion over polymyxin membrane, a simple technique indicated for the management of gram negative sepsis, and only 2 RCT and one study with historic controls have been published. From these experiences we can conclude that it is: • Useful for eliminating endotoxins (recommendation A). • Safe, the only reported problems being those derivates from anticoagulation and a lowering of serum platelets (recommendation B). • With a positive impact on outcome (recommendation B). Coupled plasma filtration with adsorption (CPFA) is a newer technique, more complex and one needing specific monitors (HF 440® Infomed Co. o Linda® Soria Co.) It’s usefulness has been proved in clinical models but human clinical studies are jet scarce. We can consider that this therapy for septic patients (recommendation C): • Is safe. • Restores cellular response to LPS administration. • Improves survival in animal studies. • Improves haemodynamics in human studies

Concepto de aclaramiento extracorpóreo y fracción de aclaramiento extracorpóreo: conceptos farmacocinéticos y ajuste de dosis en técnicas continuas / The concept of extracorporeal clearance and extracorporeal clearance fraction: pharmacokinetic concepts and dose adjustment with continuous techniques

El concepto de aclaramiento (Cl) no difiere se trate de productos finales del metabolismo celular o de fármacos. Cuando la vía de interés es la extracorpórea, ocurre de igual forma. Para calcular la cantidad de suero que limpiamos de una determinada molécula, en este caso fármaco, tendremos que conocer la concentración de la molécula en fluido que eliminamos, compararla con la plasmática, multiplicarla por el volumen obtenido de ese fluido y finalmente relacionarlo con la unidad de tiempo deseada. Así obtendremos el aclaramiento de cualquier molécula, generalmente expresado como mL/min, ya que las unidades de la magnitud concentración se eliminan de numerador y denominador. Clx = [x]efluente x Volumenefluente / [x]plasma x tiempo La mayoría de los fármacos se eliminan en mayor o menor medida mediante los tratamientos de depuración extracorpórea (TDE). La clave es saber si esa eliminación es significativa o no. Dicho de otra forma, saber si para obtener el objetivo terapéutico debemos reponer esa eliminación extraordinaria o no. Los trabajos basados en farmacodinamia relacionada con TDE son escasos. Son más abundantes los trabajos que intentan filiar la farmacocinética de diferentes moléculas cuando se añade una nueva vía de eliminación de moléculas. Por consenso se ha fijado que esta nueva vía de eliminación debe ser considerada como significativa cuando la eliminación mediante TDE suponga más del 25% del aclaramiento en condiciones normales. Los limitantes principales para que ese aclaramiento se alcance son: El tamaño: la molécula debe ser inferior al punto de corte que supone el poro de las membranas (normalmente hasta 50.000 Daltons). Pocos son los fármacos que no cumplen este requisito. Fracción no unida a proteínas: es la única que atraviesa la membrana, ya que las proteínas no pasan el punto de corte, y por tanto la única que se puede eliminar. A mayor fracción libre, mayor posibilidad de aclaramiento extracorpóreo. Volumen de distribución: habla de la cantidad total de molécula presente en el organismo, por lo que a mayor volumen de distribución menor impacto. Aclaramiento residual: el aclaramiento extracorpóreo significa una nueva vía de limpieza. Su importancia será mayor cuando las otras vías sean de escasa importancia o estén anuladas. La relevancia final de estos principios se ve reflejada por el concepto de fracción de aclaramiento (FCl), que relaciona lo que se produce mediante TDE con el aclaramiento en condiciones normales (Clnormal)

Clearance, as a concept, reflects the amount of water cleaned of a substance in a time fraction. Extracorporeal way is one more. To know the amount of fluid cleaned, we need to assess the molecule concentration in the effluent, to compare it with plasmatic one and multiply it with the total effluent volume in a time unit. Clx = [x]effluent x Volume/[x]plasma x time (mL/min) Most of drugs are eliminated in any quantity through extracorporeal purification techniques (EPT). The clue is to know if this elimination has significant value, and implies reposition to ensure an appropriate treatment. It is accepted that a value of 25% of the overall elimination, imply a supplementation in drug doses. Molecular size and protein binding are the most important characteristics to limit the transport through the membrane. There are only few drugs with size over the cut off of the membrane (40-50 KD). Then protein binding is the major limitation for most of drugs. Unbound fraction (a) is the only one allowed. Coexisting clearance ways are other factor to qualify the importance of the extracorporeal one. With other ways open, EPT could be less important than if there is no other. The concept is reflected in the extracorporeal clearance fraction. When it is over 25% the EPT imply a significant elimination of drug. In an ideal scenery we must calculate doses based on plasma levels. X Dose = ([X]target - [X]actual) x Distribution Volume x kg When these levels are not available we can apply the equation Dose= Dnormal x FCl In no toxic molecules, a 25% correction over the result is recommended to ensure appropriate treatment. Grade of Recommendation C. The great variability in patients and in treatments makes plasma levels the gold standard

Elimination of piperacillin and tazobactam by renal replacement therapies with AN69 and polysulfone hemofilters: evaluation of the sieving coefficient.

BACKGROUND/AIM: Piperacillin-tazobactam is commonly used to treat infections in ICU patients. Controversial data have been published about the sieving/saturation coefficient (Sc/Sa) of piperacillin during continuous renal replacement therapies (CRRT). The objective was to evaluate the Sc/Sa of piperacillin-tazobactam during continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodialysis (CVVHD) using AN69 and polysulfone. METHODS: Ringer lactate, BSA-containing Ringer lactate and plasma were circulated at 150 ml/min. The ultrafiltrate/dialysis flow was kept at 1,500 ml/min. A bolus was injected and samples were taken. Drugs were measured using HPLC. Sc/Sa was calculated according to standard formula. RESULTS: Free passage of drugs through the membranes was reported with protein free solutions. In the presence of proteins the Sc/Sa lowered and correlated to protein free fraction. Polysulfone had a significantly higher permeability than AN69 during CVVH. CONCLUSION: Drug binding to albumin contributes to the decrease of the Sc/Sa of piperacillin but it does not completely justify the in vivo value obtained by some authors.

Determination of ceftazidime and cefepime in plasma and dialysate-ultrafiltrate from patients undergoing continuous veno-venous hemodiafiltration by HPLC.

We have developed and validated a new, rapid and reproducible HPLC method for the determination of cefepime and ceftazidime in plasma and dialysate-ultrafiltrate samples obtained from intensive care unit (ICU) patients undergoing continuous veno-venous hemodiafiltration (CVVHDF). The method for plasma samples involved protein precipitation with acetonitrile, followed by washing with dichloromethane to remove apolar lipophilic compounds. Dialysate-ultrafiltrate samples did not require any preparation. Separation was performed on a muBondapak C18 (30 cm x 3.9 mm x 10 microm) with UV detection. The mobile phase contained acetate buffer: ACN and was delivered at 2 ml/min. The coefficients of determination of the calibration curves were always > or = 0.998 and R.S.D.% of the response factors <10%. The intra and inter-assay precision and accuracy of the quality controls (QC) and limit of quantification (LOQ) were satisfactory in all cases. Plasma and dialysate-ultrafiltrate samples were stable at -20 and -80 degrees C for 2 months and also after three freeze/thaw cycles. Dialysate-ultrafiltrate samples were stable in the chromatographic rack for 24h at room temperature, but we recommend storing processed plasma samples at 4 degrees C until the analysis. The described method has proved to be useful to give accurate measurements of ceftazidime and cefepime in samples obtained from patients undergoing CVVHDF.

Quantitation and stability of piperacillin and tazobactam in plasma and ultrafiltrate from patients undergoing continuous venovenous hemofiltration by HPLC.

Simple and reproducible HPLC methods for the determination of piperacillin and tazobactam have been developed and a complete stability study carried out. The method for piperacillin plasma samples consisted of protein precipitation with methanol using penicillin G as internal standard. No sample preparation was needed for ultrafiltrate samples. Tazobactam sample preparation involved protein precipitation with acetonitrile and the removal of lipids with dichloromethane. Piperacillin separation was performed on a microBondapack C(18) column (300 x 3.9, 10 microm) and tazobactam on a Novapack C(18) column (150 x 3.9, 4 microm) with UV detection set at 229 and 225 nm, respectively. The mobile phase consisted of phosphate buffer-acetonitrile, delivered at 1.5 mL[sol ]min. Calibration curves determination coefficients were >or=0.999 and response factors CV% < 5%. Intra- and inter-assay precision and accuracy of the quality control and limit of quantification were satisfactory. Plasma and ultrafiltrate samples were stable at -20 and -80 degrees C for 2 months and after three freeze-thaw cycles. In the chromatographic rack, tazobactam ultrafiltrate samples were stable for 24 h and plasma samples for 12 h, piperacillin ultrafiltrate samples for 8 h, but plasma samples for only 4 h. Storage of piperacillin samples at 4 degrees C until analysis is recommended. Piperacillin was stable in the presence of tazobactam.