Optimization of levetiracetam dosing regimen in critically ill patients with augmented renal clearance: a Monte Carlo simulation study

Background

Levetiracetam pharmacokinetics is extensively altered in critically ill patients with augmented renal clearance (ARC). Consequently, the dosage regimens commonly used in clinical practice may not be sufficient to achieve target plasma concentrations. The aim of this study is to propose alternative dosage regimens able to achieve target concentrations in this population. Furthermore, the feasibility of the proposed dosing regimens will be discussed from a clinical point of view.

Methods

Different dosage regimens for levetiracetam were evaluated in critically ill patients with ARC. Monte Carlo simulations were conducted with extended or continuous infusions and/or high drug doses using a previously developed population pharmacokinetic model. To assess the clinical feasibility of the proposed dosages, we carried out a literature search to evaluate the information on toxicity and efficacy of continuous administration or high doses, as well as the post-dilution stability of levetiracetam.

Results

According to the simulations, target concentrations in patients with CrCl of 160 or 200 mL/min can be achieved with the 3000 mg daily dose by prolonging the infusion time of levetiracetam. For patients with CrCl of 240 mL/min, it would be necessary to administer doses higher than the maximum recommended. Available evidence suggests that levetiracetam administration in continuous infusion or at higher doses than those approved seems to be safe. It would be desirable to re-examinate the current recommendations about drug stability and to achieve a consensus in this issue.

Conclusions

Conventional dosage regimens of levetiracetam (500–1500 mg twice daily in a short infusion) do not allow obtaining drug plasma concentrations among the defined target in critically ill patients with ARC. Therefore, new dosing guidelines with specific recommendations for patients in this subpopulation are needed. This study proposes new dosages for levetiracetam, including extended (4 or 6 h) infusions, continuous infusions or the administration of doses higher than the recommended in the summary of product characteristics (> 3000 mg). These new dosage recommendations take into account biopharmaceutical and pharmacokinetic aspects and meet feasibility criteria, which allow them to be transferred to the clinical environment with safety and efficacy. Nevertheless, further clinical studies are needed to confirm these results.

Quantification of Ceftaroline in Human Plasma Using High-Performance Liquid Chromatography with Ultraviolet Detection: Application to Pharmacokinetic Studies

This study was conducted to develop a rapid, simple and reproducible method for the quantification of ceftaroline in plasma samples by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Sample processing consisted of methanol precipitation and then, after centrifugation, the supernatant was injected into the HPLC system, working in isocratic mode. Ceftaroline was detected at 238 nm at a short acquisition time (less than 5 min). The calibration curve was linear over the concentration range from 0.25 to 40 µg/mL, and the method appeared to be selective, precise and accurate. Ceftaroline in plasma samples was stable at -80 °C for at least 3 months. The method was successfully applied to characterize the pharmacokinetic profile of ceftaroline in two critically ill patients and to evaluate whether the pharmacokinetic/pharmacodynamic (PK/PD) target was reached or not with the dose regimen administered.

Pharmacokinetic/pharmacodynamic evaluation of the antimicrobial therapy of pneumococcal invasive disease in adults in post-PCV13 vaccine period in Madrid, Spain

The objective of our study was to evaluate by pharmacokinetic/pharmacodynamic (PK/PD) analysis, if the antimicrobials used for the treatment of invasive pneumococcal disease (IPD) in adults, including meningitis, are adequate considering the susceptibility profile of S. pneumoniae in Spain after the implantation of PVC13 vaccine. Pharmacokinetic parameters of benzylpenicillin and cefotaxime were obtained from the literature, and susceptibility data of invasive S. pneumoniae strains recovered in 2017 (post-PCV13 vaccination period) were provided by the Public Health Regional Laboratory of Madrid. We have also studied levofloxacin because it is used to treat pneumococcal pneumonia previously to be diagnosed as bacteremic pneumonia. Monte Carlo simulation was used to estimate the probability of target attainment (PTA) and the cumulative fraction of response (CFR). All doses of benzylpenicillin except 2 mU q6h provide a high probability of treatment success for MIC values ≤ 1 mg/L; 4 mU q4h is even useful for MIC values up to 4 mg/L. This high dose, used for the treatment of meningitis, also provides high probability of treatment success for MIC ≤ 0.5 mg/L. At the susceptibility EUCAST breakpoint (≤ 0.5 mg/L), cefotaxime provides a high rate of PD target achievement, even at the lowest dose (1 g q8h). For meningitis, 2 g q6h ensures probabilities of target attainment ≥90% for MIC up to 1 mg/L. Our study confirms that after the implementation of PCV13 vaccine, the treatment with benzylpenicillin and cefotaxime provides high probability of the therapy success of IPD, including meningitis.

[Non-functioning pituitary adenomas: epidemiology, clinical and postoperative outcome]

INTRODUCTION

Non-functioning pituitary adenomas are the most frequent tumor group in the sellar region. They are usually benign neoplasms diagnosed after visual or hormonal symptoms, although it is not uncommon to detect them as a casual finding.

AIM

To analyze the clinical aspects found in this disease and its response after surgical treatment.

PATIENTS AND METHODS

In a series of 100 cases, epidemiological, clinical, endocrinological, visual and radiological data were analyzed before and after surgical treatment, as well as the complications related to surgery and long-term follow-up.

RESULTS

The most frequent symptom at the time of diagnosis was visual field involvement (62%), and only the 7% of adenomas were a casual finding. The most common hormonal deficit was hypogonadotropic hypogonadism (48%). After surgery, complete recovery of the visual field defect was observed in 54.8% of the patients, only 1% worsening after surgery, and the incidence of diabetes insipidus was 4%. The resection was superior to 95% in 63% of cases, although the percentage of adenomas with invasion of the cavernous sinus in Knosp grades 3 and 4 it was high (45%).

CONCLUSIONS

Although the most frequent symptom of non-functioning pituitary adenomas is campimetric involvement, it has an excellent response to surgery if it is performed within the appropriate time. The grade of invasion of the cavernous sinus is the most limiting factor for a complete surgical resection.

Impact of augmented renal clearance on the pharmacokinetics of linezolid: Advantages of continuous infusion from a pharmacokinetic/pharmacodynamic perspective

OBJECTIVES

The aim of this study was to assess the influence of renal function, in particular the presence of augmented renal clearance (ARC), on the pharmacokinetics of linezolid in critically ill patients. The effect of continuous infusion on the probability of therapeutic success from a pharmacokinetic/pharmacodynamic (PK/PD) perspective was also evaluated.

METHODS

Seventeen patients received linezolid (600 mg every 12 h) as a 30-min infusion and 26 as a continuous infusion (50 mg/h). The PK parameters were calculated and the probability of PK/PD target attainment (PTA) was estimated by Monte Carlo simulation (MCS) for different doses administered by intermittent (600 mg every 12 h or 600 mg every 8 h) or continuous infusion (50 mg/h or 75 mg/h).

RESULTS

In patients without ARC, the standard dose was adequate to attain the PK/PD target. However, linezolid clearance was significantly higher in ARC patients, leading to sub-therapeutic concentrations. Continuous infusion (50 mg/h) provided concentrations ≥2 mg/l in 70% of the ARC patients. MCS revealed that concentrations ≥2 mg/l would be reached in >90% of patients receiving 75 mg/h.

CONCLUSIONS

ARC increases linezolid clearance and leads to a high risk of underexposure with the standard dose. Continuous infusion increases the PTA, but an infusion rate of 75 mg/h should be considered to ensure concentrations ≥2 mg/ml.

Novel Population Pharmacokinetic Model for Linezolid in Critically Ill Patients and Evaluation of the Adequacy of the Current Dosing Recommendation

Antimicrobial treatment in critically ill patients remains challenging. The aim of this study was to develop a population pharmacokinetic model for linezolid in critically ill patients and to evaluate the adequacy of current dosing recommendation (600 mg/12 h). Forty inpatients were included, 23 of whom were subjected to continuous renal replacement therapies (CRRT). Blood and effluent samples were drawn after linezolid administration at defined time points, and linezolid levels were measured. A population pharmacokinetic model was developed, using NONMEM 7.3. The percentage of patients that achieved the pharmacokinetic/pharmacodynamic (PK/PD) targets was calculated (AUC₂₄/MIC > 80 and 100% T_>MIC). A two-compartment model best described the pharmacokinetics of linezolid. Elimination was conditioned by the creatinine clearance and by the extra-corporeal clearance if the patient was subjected to CRRT. For most patients, the standard dose of linezolid did not cover infections caused by pathogens with MIC ≥ 2 mg/L. Continuous infusion may be an alternative, especially when renal function is preserved.

Pharmacokinetics of linezolid in critically ill patients on continuous renal replacement therapy: Influence of residual renal function on PK/PD target attainment

PURPOSE

To assess the pharmacokinetics of linezolid in septic patients undergoing continuous renal replacement therapy (CRRT) and investigate whether residual renal function affects the probability of attaining the pharmacokinetic/pharmacodynamic (PK/PD) target.

MATERIAL AND METHODS

Prospective study conducted in three Spanish hospitals. Linezolid concentrations were measured in plasma and effluent samples and pharmacokinetic parameters were calculated. The probability of target attainment (PTA) and the cumulative fraction of response (CFR) were calculated considering AUC₂₄/MIC>80 and %T_>MIC > 85% as the PK/PD indexes related to efficacy.

RESULTS

In anuric patients (CrCl<10 mL/min), the contribution of extracorporeal Cl to total Cl was higher (47% vs 16%) than in patients with residual renal function (CrCl≥10 mL/min). For an MIC of 2 mg/L, AUC₂₄/MIC>80 was achieved in >85% of the anuric patients, but in <15% of the patients with residual renal function.

CONCLUSIONS

The standard dose (600 mg q12h) ensures a moderately high probability of treatment success in anuric patients when the infection is due to microorganisms with MIC≤2 mg/L; although higher doses increase the probability of treatment success, the safety is compromised. In patients with residual renal function, the standard dose is insufficient, but 900 mg q8h provide higher probability of treatment success without compromising the safety.

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 (Cmin_ss) ≥ 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.

Search and analysis of genes involved in antibiotic resistance in Chilean strains of Piscirickettsia salmonis

Piscirickettsia salmonis is the pathogen causing Piscirickettsiosis. For treatment, the industry mainly uses oxytetracycline and florfenicol, so it is essential to understand the degree of susceptibility of this pathogen to these drugs. But this is still unknown for a large number of P. salmonis strains, as are the molecular mechanisms responsible for greater or lesser susceptibility. However, genes that confer resistance to these antimicrobials have been reported and characterized for this and other bacterial species, among which are membrane proteins that take out the drug. Our results identified differences in the degree of susceptibility to both antibiotics among different Chilean isolated of these bacteria. We analysed 10 available genomes in our laboratory and identified ~140 genes likely to be involved in antibiotic resistance. We analysed six specific genes, which suggests that some of them would eventually be relevant in conferring resistance to both antibiotics, as they encode for specific transporter proteins, which increase the number of transcripts when grown in media with these antibiotics. Our results were corroborated with EtBr permeability analysis, which revealed that the LF-89 strain accumulates this compound and has a reduced capacity to expulse it compared with the field strains.

Hiccups in Parkinson's disease: an analysis of cases reported in the European pharmacovigilance database and a review of the literature

BACKGROUND

Some reports have suggested an association between dopamine agonists and hiccups, involuntary contractions that merit full clinical attention because they can be very debilitating. Many drugs frequently used to treat hiccups are formally contraindicated in Parkinson's disease due to their liability to worsen motor symptoms, making the treatment of hiccups problematic in this disease. The objective of the present study was to analyze all spontaneous reports of hiccups from the European Pharmacovigilance Database in patients with Parkinson's disease and/or on dopaminergic drugs. Finally, we sought to identify evidence-based recommendations on the management of hiccups in Parkinson's disease.

METHODS

We searched for all reports of hiccups in the European Pharmacovigilance Database (EudraVigilance) and calculated proportional reporting ratios for dopamine agonists and hiccups. We reviewed the literature on Parkinson's disease, dopamine agonists, and hiccups, searching for specific treatment recommendations for hiccups in this disease.

RESULTS

Both rotigotine and pramipexole fulfilled the criteria to generate a safety signal. We found 32 and 13 cases of hiccups associated with dopamine agonists in EudraVigilance and the literature, respectively. There were no specific recommendations for the management of hiccups in Parkinson's disease in the clinical guidelines consulted.

CONCLUSIONS

We have found evidence that rotigotine and pramipexole are associated with the appearance of hiccups and that this adverse reaction occurs predominantly in males. Given the scarce information available, specific recommendations are needed in clinical guidelines for the adequate management of hiccups in Parkinson's disease.

Immunostimulatory effect of salmon prolactin on expression of Toll-like receptors in Oncorhynchus mykiss infected with Piscirickettsia salmonis

In aquaculture, antibiotics are the traditional treatment used against bacterial infections. However, their use has increasingly come into question given their effects on fish and, possibly, on human health. Consequently, there is interest in developing alternative treatments aimed at stimulating the innate immune response of fish, which is the first line of defense against pathogens. In relation to this, the Toll-like receptors (TLR) aid in the selective identification of pathogens. The present study evaluated immunostimulatory activity of prolactin (PRL) hormone on expression levels of TLR1, 9, and 22, MyD88, and IL-1β during in vitro infection with the fish pathogen Piscirickettsia salmonis, in primary cultures of Oncorhynchus mykiss head kidney cells. Results indicated that PRL increased expression of TLRs and MyD88 during the first hours of bacterial infection, while a constant increase in expression was found for IL-1β. These findings suggest that PRL indirectly modulates expression of TLRs by activating expression of suppressors of cytokine signaling, thereby regulating immune response over long periods of time during bacterial infection.

Immunostimulatory effects of prolactin on TLR1 and TLR5M in SHK-1 cells infected with Piscirickettsia salmonis

The innate immune system is the first line of defense against infection by pathogens. It consists of various elements, including Toll-like receptors (TLRs), which recognize molecular patterns associated with pathogens and trigger the immune response, through activation of important transcription factors such as NF-κB, which are usually found sequestered in the cytoplasm by IκBα until it receives the release signal. Piscirickettsia salmonis causes piscirickettsiosis or salmonid rickettsial septicemia, a disease of great importance in Chile, representing 79.4% of the secondary mortality in important species such as Salmo salar, which is reflected in the Chilean economy. Prolactin (PRL) is a peptide hormone which has immunomodulating functions in mammals and some fish. Olavarría et al. (2010, J Immunol 185:3873-3883) determined its ability to increase the respiratory burst, its relationship with the JAK/STAT pathway, and the expression of interleukin IL-1β in Sparus aurata. Therefore, the present study was intended to establish a possible correlation and modulation between the signal transduction pathway of PRL (JAK/STAT), the pathways of NF-κB, and TLRs, in an infection caused by P. salmonis in salmon head kidney (SHK‑1) cells of S. salar. Stimulus with native PRL from S. salar was performed, and gene expression was analyzed for IL-1β, IκBα, TLR1, and TLR5M (membrane-bound form). In addition, the effect of PRL in the nuclear translocation of the transcription factor NF-κB and the possible involvement of JAK2 were analyzed by using a pharmacological inhibitor of this kinase. The results show a positive modulation of PRL in all analyzed genes and a significant increase in the translocation of NF-κB, recording a maximum at 2 h post-treatment, supporting the stimulatory hypothesis of PRL.

Vaginal gene therapy

In the last years, vaginal gene therapy has gained increasing attention mainly for the treatment and control of sexually transmitted infections. DNA delivery has been also suggested to improve reproductive outcomes for women with deficiencies in the female reproductive tract. Although no product has reached clinical phase, preclinical investigations reveal the potential of the vaginal tract as an effective administration route for gene delivery. This review focuses on the main advantages and challenges of vaginal gene therapy, and on the most used nucleic acid delivery systems, including viral and non-viral vectors. Additionally, the advances in the application of vaginal gene therapy for the treatment and/or prevention of infectious diseases such as the human immunodeficiency virus (HIV), the human papillomavirus (HPV) or the herpes simplex virus (HSV) are presented.

Anticholinergic burden in Parkinson's disease inpatients

PURPOSE

Anticholinergic toxicity can arise as a result of the cumulative burden of multiple medications and metabolites rather than be caused by a single compound. In this sense, prescribing drugs with anticholinergic properties to Parkinson's disease (PD) patients could contribute to aggravate some frequent problems of the disease, like dementia, urinary retention, falls, or constipation, among others. The main purpose of this article is to measure the total anticholinergic burden in a group of PD inpatients.

METHOD

We analyzed information from different administrative Basque Country's healthcare databases using encrypted unique identifiers in order to detect PD patients admitted to public acute care hospital during 2011-2012. Subsequently, anticholinergic burden was measured using Duran et al.'s list. Secondarily, total anticholinergic load was assessed with the Anticholinergic Drug Scale, the Anticholinergic Risk Score, and the Anticholinergic Burden Scale. A logistic regression model was performed to study association of predictive variables with anticholinergic use.

RESULTS

A high proportion of PD patients were prescribed anticholinergic drugs, with 53.6% of admissions receiving at least one drug from Duran et al.'s "low-risk" and 10% at least "high-risk" drug. Drugs used for non-motor symptoms and other comorbidities other than PD itself contributed significantly to anticholinergic burden, namely antidepressants, antipsychotics, urological drugs, analgesics, and antihistamines, among others. The total number of drugs and cholinesterase inhibitors were independently associated with anticholinergic drug use.

CONCLUSIONS

Anticholinergic burden in PD patients is significant, and is caused mostly by drugs not used for PD motor symptoms. Polypharmacy and cholinesterase inhibitors were independently associated with anticholinergic drug prescriptions.

Pharmacokinetic/pharmacodynamic analysis to evaluate ceftaroline fosamil dosing regimens for the treatment of community-acquired bacterial pneumonia and complicated skin and skin-structure infections in patients with normal and impaired renal function

In this study, the probability of pharmacokinetic/pharmacodynamic target attainment (PTA) of ceftaroline against clinical isolates causing community-acquired bacterial pneumonia (CABP) and complicated skin and skin-structure infection (cSSSI) in Europe was evaluated. Three dosing regimens were assessed: 600 mg every 12 h (q12 h) as a 1-h infusion (standard dose) or 600 mg every 8 h (q8 h) as a 2-h infusion in virtual patients with normal renal function; and 400 mg q12 h as a 1-h infusion in patients with moderate renal impairment. Pharmacokinetic and microbiological data were obtained from the literature. The PTA and the cumulative fraction of response (CFR) were calculated by Monte Carlo simulation. In patients with normal renal function, the ceftaroline standard dose (600 mg q12 h as a 1-h infusion) can be sufficient to treat CABP due to ceftazidime-susceptible (CAZ-S) Escherichia coli, CAZ-S Klebsiella pneumoniae, meticillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis (CFR>90%). However, against meticillin-resistant S. aureus (MRSA), the CFR was 72%. In cSSSI, the CFR was also <80% for MRSA. Administration of ceftaroline 600 mg q8 h as a 2-h infusion or 400 mg q12 h as a 1-h infusion in patients with moderate renal insufficiency provided a high probability of treatment success (CFR ca. 100%) for most micro-organisms causing CABP and cSSSI, including MRSA and penicillin-non-susceptible S. pneumoniae. These results suggest that in patients with normal renal function, ceftaroline 600 mg q8 h as a 2-h infusion may be a better option than the standard dose, especially if the MRSA rate is high.

Applications of the pharmacokinetic/pharmacodynamic (PK/PD) analysis of antimicrobial agents

The alarming increase of resistance against multiple currently available antibiotics is leading to a rapid lose of treatment options against infectious diseases. Since the antibiotic resistance is partially due to a misuse or abuse of the antibiotics, this situation can be reverted when improving their use. One strategy is the optimization of the antimicrobial dosing regimens. In fact, inappropriate drug choice and suboptimal dosing are two major factors that should be considered because they lead to the emergence of drug resistance and consequently, poorer clinical outcomes. Pharmacokinetic/pharmacodynamic (PK/PD) analysis in combination with Monte Carlo simulation allows to optimize dosing regimens of the antibiotic agents in order to conserve their therapeutic value. Therefore, the aim of this review is to explain the basis of the PK/PD analysis and associated techniques, and provide a brief revision of the applications of PK/PD analysis from a therapeutic point-of-view. The establishment and reevaluation of clinical breakpoints is the sticking point in antibiotic therapy as the clinical use of the antibiotics depends on them. Two methodologies are described to establish the PK/PD breakpoints, which are a big part of the clinical breakpoint setting machine. Furthermore, the main subpopulations of patients with altered characteristics that can condition the PK/PD behavior (such as critically ill, elderly, pediatric or obese patients) and therefore, the outcome of the antibiotic therapy, are reviewed. Finally, some recommendations are provided from a PK/PD point of view to enhance the efficacy of prophylaxis protocols used in surgery.

Identification of the clpB and bipA genes and an evaluation of their expression as related to intracellular survival for the bacterial pathogen Piscirickettsia salmonis

Piscirickettsia salmonis is the pathogen responsible for salmonid rickettsial septicemia (SRS), a disease that affects a wide variety of marine cultivated fish species and causes economic losses for the aquaculture industry worldwide. Many in vitro studies have reported on the capacity of this microorganism to replicate in the interior of cytoplasmic vesicles from varied fish cell lines. However, the mechanisms used by this bacteria to survive, replicate, and propagate in cell lines, especially in macrophages and monocytes, are unknown. A number of studies have described the diverse proteins in pathogens such as Legionella pneumophila, Coxiella burnetii, and Francisella tularensis which allow these to evade the cellular immune response and replicate in the interior of macrophages in different hosts. Some of these proteins are the virulence factor BipA/TypA and the heat shock protein ClpB, both of which have been widely characterized. The results of the current study present the complete coding sequence of the genes clpB and bipA from the P. salmonis genome. Moreover, the experimental results suggest that during the infectious process of the SHK-1 cellular line in P. salmonis, the pathogen significantly increases the expression of proteins ClpB and BipA. This would permit the pathogen to adapt to the hostile conditions produced by the macrophage and thus evade mechanisms of cellular degradation while facilitating replication in the interior of this salmon cell line.

Population pharmacokinetics of piperacillin and tazobactam in critically ill patients undergoing continuous renal replacement therapy: application to pharmacokinetic/pharmacodynamic analysis

OBJECTIVES

To evaluate the pharmacokinetics of piperacillin/tazobactam in critically ill patients undergoing continuous renal replacement therapy (CRRT) and to assess the success of the therapy against susceptible bacteria.

PATIENTS AND METHODS

Sixteen patients undergoing CRRT with different degrees of renal function were included in the study. Blood and ultrafiltrate samples were drawn after administration of piperacillin/tazobactam (4/0.5 g) every 4, 6 or 8 h. The data were analysed by a population approach using NONMEM 7.2. The probability of target attainment (PTA) of maintaining free piperacillin levels above the MIC during the entire dosing interval was estimated by simulation of intermittent and continuous infusions.

RESULTS

The pharmacokinetics of piperacillin and tazobactam were best described by two-compartment models where the elimination of both drugs was conditioned by renal [dependent on creatinine clearance (CLCR)], non-renal and extracorporeal clearances. A 20 min infusion of piperacillin/tazobactam administered every 6 h provided high PTAs against MICs ≤ 32 mg/L in patients with severe renal failure. In patients with normal or moderate renal function PTAs ≥ 90% were only obtained up to MICs ≤ 8 mg/L with short infusions. However, simulating continuous infusion, higher probabilities of success were obtained against MICs of 32 and 16 mg/L when CLCR was 50 and 100 mL/min, respectively.

CONCLUSIONS

Population pharmacokinetic models have been developed and validated for piperacillin and tazobactam. Based on the pharmacokinetic/pharmacodynamic analysis, dosing recommendations are given considering the residual renal function of the patient and the MIC for the isolated bacteria.

Evaluation of Antimicrobial Treatments in Children with Acute Otitis Media in Spain: A Pharmacokinetic-Pharmacodynamic (PK/PD) Approach

Pharmacokinetic/pharmacodynamic (PK/PD) principles are priceless tools for evaluating the effectiveness of different antimicrobial treatments for different infections. However, very few studies deal with pediatric dosages and take into account the unbound drug serum levels. Our study is focused on the most frequent antibiotic dosing schedules used in Spain for the treatment of acute otitis media (AOM) in children, where high rates of penicillin and macrolide resistance exist among pneumococcal isolates. Pharmacokinetic parameters of antibiotics in children where obtained from the literature. The minimum inhibitory concentrations (MIC90) of antibiotics for pediatric strains of Streptococcus pneumoniae and Haemophilus influenzae were obtained from the SAUCE 2 project. Only ceftriaxone (50 mg/kg single intramuscular dose) and high doses of co-amoxiclav (27-33 mg/kg q8h) provided adequate efficacy indexes (tss(%)>MIC) for both S. pneumoniae and H. influenzae in AOM in children. These results are consistent with MEF (medium ear fluid) levels obtained from the literature. Our results confirm the utility of serum unbound levels to predict efficacy of antibiotics in children with AOM.

Influence of Renal Function on the Pharmacokinetics of Piperacillin/Tazobactam in Intensive Care Unit Patients During Continuous Venovenous Hemofiltration

The pharmacokinetics of piperacillin/tazobactam (4 g/0.5 g every 6 or 8 hours, by 20-minute intravenous infusion) were studied in 14 patients with acute renal failure who underwent continuous venovenous hemofiltration with AN69 membranes. Patients were grouped according to severity (CL(CR) < or =10 mL/min, 10 < CL(CR) < or =50 mL/min, and CL(CR) > 50 mL/min). A noncompartmental analysis was performed. The sieving coefficient (0.78 +/- 0.28) was similar to the unbound fraction (0.65 +/- 0.24) for tazobactam, but it was significantly different (0.34 +/- 0.25) from the unbound fraction (0.78 +/- 0.14) for piperacillin. Extracorporeal clearance was 37.0% +/- 28.8%, 12.7% +/- 12.6%, and 2.8% +/- 3.2% for piperacillin in each group and 62.5% +/- 44.9%, 35.4% +/- 17.0%, and 13.1% +/- 8.0% for tazobactam. No patients presented tazobactam accumulation. In patients with CL(CR) < 50 mL/min, t(%)ss >MIC90 values were 100% for a panel of 19 pathogens, but in those with CL(CR) > 50 mL/min, t(%)ss >MIC90 indexes were 55.5% and 16.6% for pathogens with MIC90 values of 32 and 64. The extracorporeal clearance of piperacillin/tazobactam is clinically significant in patients with CL(CR) > 50 mL/min, in which the risk of underdosing and clinical failure is important and extra doses are required.

Comparison of antimicrobial pharmacokinetic/pharmacodynamic breakpoints with EUCAST and CLSI clinical breakpoints for Gram-positive bacteria

This study compared the susceptibility breakpoints based on pharmacokinetic/pharmacodynamic (PK/PD) models and Monte Carlo simulation with those defined by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for antibiotics used for the treatment of infections caused by Gram-positive bacteria. A secondary objective was to evaluate the probability of achieving the PK/PD target associated with the success of antimicrobial therapy. A 10,000-subject Monte Carlo simulation was executed to evaluate 13 antimicrobials (47 intravenous dosing regimens). Susceptibility data were extracted from the British Society for Antimicrobial Chemotherapy database for bacteraemia isolates. The probability of target attainment and the cumulative fraction of response (CFR) were calculated. No antibiotic was predicted to be effective (CFR≥90%) against all microorganisms. The PK/PD susceptibility breakpoints were also estimated and were compared with CLSI and EUCAST breakpoints. The percentages of strains affected by breakpoint discrepancies were calculated. In the case of β-lactams, breakpoint discrepancies affected <15% of strains. However, higher differences were detected for low doses of vancomycin, daptomycin and linezolid, with PK/PD breakpoints being lower than those defined by the CLSI and EUCAST. If this occurs, an isolate will be considered susceptible based on CLSI and EUCAST breakpoints although the PK/PD analysis predicts failure, which may explain treatment failures reported in the literature. This study reinforces the idea of considering not only the antimicrobial activity but also the dosing regimen to increase the probability of clinical success of an antimicrobial treatment.

Pharmacokinetic/pharmacodynamic evaluation of amoxicillin, amoxicillin/clavulanate and ceftriaxone in the treatment of paediatric acute otitis media in Spain

INTRODUCTION

Acute otitis media is the most common respiratory tract infection in infancy and early childhood that is managed with antimicrobial agents. Ninety-three per cent of the cases diagnosed in Spain are treated with antibiotics, and Streptococcus pneumoniae and untypeable Haemophilus influenzae are the most frequently isolated pathogens. The aim of this work was to evaluate the usefulness of amoxicillin, amoxicillin/clavulanate and ceftriaxone for the empirical treatment of acute otitis media, looking at the pharmacokinetic variability and the antimicrobial susceptibility of paediatric strains of the two main pathogens responsible for AOM in Spain, Streptococcus pneumoniae and Haemophilus influenzae.

METHODS

Free-drug plasma concentrations were simulated and the probability of target attainment at each minimum inhibitory concentration and the cumulative fraction of response (CFR) were determined. Microbiological susceptibility information was extracted from SAUCE 3 surveillance.

RESULTS

CFR with amoxicillin varied from 83% to 96% against S. pneumoniae and from 78% to 86% against H. influenzae. CFR was always >85% with amoxicillin/clavulanate. With the 3-day ceftriaxone regimen, the probability of achieving free concentrations above MIC at 72 hours significantly increased compared to the single dose, with which CFR ranged from 70% to 84%.

CONCLUSIONS

High-dose amoxicillin (at least 80 mg/kg/day) should be the first-line therapy in uncomplicated infections, whereas amoxicillin/clavulanate (40 mg/kg/day) should be the choice when additional coverage for H. influenzae is desired. Administration of 3 daily doses of ceftriaxone increases bacteriological eradication probability when compared with one-day regimen, although additional clinical evaluations are necessary to establish the best target attainment with ceftriaxone.

Impact of acute otitis media pathogen shifts on the clinical efficacy of several antibiotics: a therapeutic outcomes model

The aim of this study was to predict the clinical efficacy of different antimicrobials in the treatment of patients with acute otitis media (AOM), before and after the change in the proportion of middle ear pathogens observed after the introduction of the new conjugated heptavalent penumococcal vaccine (pPCV-7). The therapeutic Outcomes model was used to predict the likelihood of clinical success. According to this mathematical model the obtained rank order of predicted clinical efficacy was similar in the pre-PVC7 period and the post-PVC period. The results suggest that ceftriaxone and amoxicillin/clavulanate are the antibiotics with the highest predicted clinical efficacy, whereas cefaclor, azithromycin, erythromycin and clarithromycin are those with the lowest predicted clinical efficacy. The differences between antibiotics with good and those with low antibacterial activity were greater when only cases of bacterial AOM were considered. Antibiotics for which the highest clinical efficacy was predicted should maximize the likelihood of cure in outpatient antibiotic treatment of AOM.

[Identification of genetic alterations by multiple ligation-dependent probe amplification (MLPA) analysis in oligodendrogliomas]

Concurrent deletion at 1p/19q is a common signature of oligodendrogliomas, and it may be identified in low-grade tumours (grade II) suggesting it represents an early event in the development of these brain neoplasms. Additional non-random changes primarily involve CDKN2A, PTEN and EGFR. Identification of all of these genetic changes has become an additional parameter in the evaluation of the clinical patients' prognosis, including good response to conventional chemotherapy. Multiple ligation-dependent probe amplification (MLPA) analysis is a new methodology that allows an easy identification of the oligodendrogliomas' abnormalities in a single step. No need of the respective constitutional DNA from each patient is another advantage of this method. We used MLPA kits P088 and P105 to determine the molecular characteristics of a series of 40 oligodendrogliomas. Deletions at l p and 19q were identified in 45% and 65% of cases, respectively. Alterations of EGFR, CDKN2A, ERBB2, PTEN and TP53 were also identified in variable frequencies among 7% to 35% of tumours. These findings demonstrate that MLPA is a reliable technique to the detection of molecular genetic changes in oligodendrogliomas.

Laparoscopic management of insulinomas

BACKGROUND

Conventional surgical management of insulinomas involves an open technique. The laparoscopic approach has advantages in terms of improved postoperative pain and recovery time. This retrospective study evaluated the laparoscopic management of pancreatic insulinomas.

METHODS

Between December 2000 and March 2007, 23 patients were referred for consideration of laparoscopic insulinoma resection. Two patients were not deemed appropriate for the laparoscopic approach and were managed with open surgery. All surgery was performed by one experienced pancreatic surgeon. Laparoscopic intraoperative ultrasonography was not available for the first six procedures, but was used thereafter.

RESULTS

Twenty-one patients (five men and 16 women, median age 46 (range 22-70) years) had a successful resection. All had single tumours, five in the head, nine in the body and seven in the tail of the pancreas. One conversion to open operation was performed in a patient with an insulinoma in the head of the pancreas who had dense adhesions resulting from pancreatitis. Three patients developed a postoperative pancreatic fistula. There has been no recurrence of symptoms in any patient.

CONCLUSION

Laparoscopic management of insulinomas is feasible and safe. Laparoscopic intraoperative ultrasonography is a promising adjunct to the procedure, even after accurate preoperative localization.

[Antibiotic therapy in odontogenic infections in children and adolescents: pharmacokinetic/pharmacodynamic analysis]

INTRODUCTION

The objective of this study was to evaluate the efficacy of the most commonly used antimicrobial treatments in odontogenic infections in children and adolescents on the basis of pharmacokinetic/ pharmacodynamic (PK/PD) criteria.

METHODS

Unbound drug plasma concentration-time curves were simulated with mean population pharmacokinetic parameters of amoxicillin, co-amoxiclav, cefuroxime axetil, spiramycin, clindamycin, azithromycin, and metronidazole. For drugs showing time-dependent antibacterial killing, the time above MIC90 of the pathogens studied was calculated (T>MIC). For drugs with concentration-dependent bactericidal activity, the area under the concentration-time curve (AUC)/MIC90 ratio was calculated.

RESULTS

Adequate efficacy indexes (T>MIC>40%) against all the microorganisms examined with the exception of Veillonella spp. were obtained with co-amoxiclav (80 mg/kg/day). Clindamycin (40 mg/kg/day) obtained adequate PK/PD indexes except for Lactobacillus, Actinobacillus actinomycetemcomitans, penicillin-resistant Peptostreptococcus, and Eikenella corrodens. High-dose amoxicillin yielded unsatisfactory results against many bacterial species. Azithromycin and metronidazole showed inadequate efficacy indexes against the majority of pathogens studied (AUC/MIC90<25).

CONCLUSION

When antibiotic therapy is needed for odontogenic infections in children and adolescents, the most active empirical therapeutic choice is co-amoxiclav with high doses of amoxicillin. Clindamycin can be used as an alternative option. These results should be confirmed in clinical trials, in which the PK/PD approach could be useful for the design and assessment of results.

[Protective effects of the growth hormone (GH) on the irradiated spinal cord in rats]

Radiotherapy or irradiation of SNC AVM's or tumors also presents a high risk for provoking lesions in adjacent surrounding tissue. The objective of our study is to demonstrate radiotherapy induced alterations in a rat spinal cord model and evaluate the protective effect of Growth Hormone (GH) on rats exposed to high radiotherapy doses. The experimental study employed two groups of Wistar rats: Group A (control group):10 rats, which received 30 Gy at the spinal cord . Group B: 10 rats, these animals received 30 Gy and dose of 2mg/kg/day GH. Growth hormone administration was begun three days before radiotherapy and continued until two days after radiotherapy for a total of six days. At 14 days postradiotherapy, all the rats were sacrificed and the spinal cord extracted immediately. Hematoxyline-eosine histologic studies showed that control animals only exposed to radiotherapy had severe alterations with hemorrhage and vacuolisation of the entire irradiated segment while these alterations were much less severe in the GH-treated group. In conclusion, 30 Gy irradiation produced morphological changes including vascular endothelial oedema, necrosis, hemorrhage, and inflammatory exudates. A 2 mg/kg/day dose of GH protected the rat spinal cord against the noxious effects of the radiotherapy, decreasing the clinical, macro and microscopic damage in the treated animals.

In vitro AN69 and Polysulphone Membrane Permeability to Ceftazidime and in vivo Pharmacokinetics during Continuous Renal Replacement Therapies

BACKGROUND

Ceftazidime is a third-generation cephalosporin almost entirely eliminated by glomerular filtration and dose reductions are essential in patients with renal impairment. The physicochemical and pharmacokinetic properties of ceftazidime make it susceptible to be eliminated by continuous renal replacement therapies (CRRT), but there is little clinical information to guide the correct administration in patients undergoing these techniques.

METHODS

In vitro procedures were carried out in three different fluids, using AN69 or polysulphone membranes. Four patients entered the in vivo study. Two patients received 1,000 mg every 6 h and the other two 2,000 mg every 6 h. Concentrations of ceftazidime were measured by high-performance liquid chromatography.

RESULTS

No differences were detected in thesieving coefficients (Sc) or saturation coefficients (Sa)between membranes during continuous venovenous hemofiltration (CVVH) or continuous venovenous hemodiafiltration (CVVHD). Sc-Sa values were close to 1 when Ringer's lactate was used as ceftazidime vehicle, but were lower in plasma samples (p < 0.05). In patients, the Sc-Sa was 0.93 +/- 0.06 and correlated well with the unbound fraction (0.86 +/- 0.08). The contribution of CRRT to ceftazidime clearance was higher in anuric patients than in nonanuric patients.

CONCLUSIONS

No differences were shown in vitro in the Sc obtained with both membranes during CVVH or the Sa obtained during CVVHD. The contribution of clearance by CRRT to total clearance is clearly dependent on the renal function. The administration of ceftazidime every 6 h could be associated with unnecessarily high trough levels which increase the risk of drug nephrotoxicity. Nonanuric patients undergoing CRRT need higher ceftazidime doses to reach adequate plasma concentrations against pathogens isolated in the critically ill.

DAPK1 promoter hypermethylaiton in brain metastases and peripheral blood

The DAPK1 gene works as a regulator of apoptosis and is frequently inactivated in cancer by aberrant promoter hypermethylation. Loss of DAPK1 expression is associated with a selective advantage for tumor cells to resist apoptotic stimuli, allowing them to separate from the original tumor; from this point of view, DAPK1 could be considered a tumor metastases inhibitor gene. To verify the participation of DAPK1 silencing in cerebral invasion, we analyzed its promoter methylation status in a series of 28 samples from cerebral metastases using MSP and sequencing of the MSP-product. We have found hypermethylation in 53.6% (15/28) metastatic tumor samples as well as in 27.8% (5/18) of its peripheral blood samples. Our data suggest an important role of DAPK1 for silencing through promoter CpG island hypermethylation in the development of brain metastases from solid tumors. The detection of aberrant hypermethylation on DAPK1 promoter from peripheral blood samples has potential clinical implications as a tumor prognosis marker.

In vitro and in vivo evaluation of enoxaparin removal by continuous renal replacement therapies with acrylonitrile and polysulfone membranes

BACKGROUND

Enoxaparin is a low-molecular-weight heparin for which the degree of elimination through hemofilters during continuous renal replacement therapy (CRRT) is not well established.

OBJECTIVE

The elimination of enoxaparin by CRRT, using acrylonitrile (AN69) or polysulfone (PS) membranes, was studied in vitro and among critically ill patients.

METHODS

In vitro procedures were carried out using Ringer's lactate, bovine albumin-containing Ringer's lactate, or fresh human plasma as enoxaparin vehicle, using AN69 or PS membranes, and following continuous veno-venous hemofiltration (CVVH) or continuous veno-venous hemodialysis (CVVHD). Prefilter and ultrafiltrate samples were collected over 60 minutes. All procedures were carried out in triplicate. Patients undergoing CRRT entered the in vivo study. Enoxaparin was administered subcutaneously once daily. The sieving coefficient (Sc) and saturation coefficient (Sa) were calculated as the relation between anti-factor Xa activity in simultaneously collected dialysate/ultrafiltrate samples and plasma samples.

RESULTS

Mean Sc (for CVVH) or Sa (for CVVHD) values in the in vitro procedures ranged from 0.16 to 0.57. Sc values during CVVH were significantly higher than Sa values during CVVHD in the Ringer's lactate procedures for both membranes (AN69 membrane, P = 0.014; PS membrane, P < 0.001) and in the plasma procedures with the PS membrane (P < 0.001). Six male and 2 female patients (all white) participated in the in vivo study. Their mean body weight ranged from 55 to 80 kg, and their age ranged from 71 to 82 years. In patients, Sc or Sa achieved values between 0.26 and 0.67. No significant differences were found in vivo in the permeability of the 2 membranes to enoxaparin.

CONCLUSIONS

In these studies, the Sc and Sa values suggested that enoxaparin passed through AN69 and PS membranes during CRRT. Further pharmacokinetic and clinical studies are needed to determine whether a dose adjustment for enoxaparin is needed for patients undergoing CRRT.

[Causes of reoperations in patients with lumbar spinal stenosis treated with instrumentations]

OBJECTIVE

In present study we analyze the causes leading to reoperation patients treated for lumbar spinal stenosis with laminectomy and lumbar instrumentation.

MATERIAL AND METHODS

74 patients operated between January of 1996 and December of 2000 with a minimum 4 year follow-up were seleted for the study.

RESULTS

16 patients (21.1%) underwent a new surgical intervention. The main cause for reoperation was stenosis of the adjacent level superiorly to the instrumentation (in 50%). Other causes were radicular fibrosis, persistence of stenosis after the surgery, neuropatic pain, failure of the instrumentation system, transpedicular screws misplacement and break of screws.

CONCLUSIONS

Complications related with the initial surgical procedure are low, as half of the reoperations were due to stenosis of the segment superior to the fixation.

Anatomical and functional connectivity of the transected ulnar nerve after accessory nerve neurotization in the cat

AIM

The objective of this experimental study was to test the capacity of accessory nerve motoneurons to innervate muscles of the ulnar nerve territory after direct anastomosis.

METHODS

This study used 22 cats in two groups: experimental group (15 cats) and control group (7 cats). The first one was followed during twelve months using electromyographic records every two months postsurgery; muscle and nerve histological assessment and counting horseradish peroxidase-labeled motoneurons.

RESULTS

Our results showed that reinnervation was achieved in 12/15 nerves. The number of HRP labelled medullar motoneurons after anastomosis showed a significant statistic difference with a simple ulnar nerve transection; there was no significant statistic difference in labelling between the group with an anastomosis and the one with a simple accessory nerve transection.

CONCLUSIONS

Direct anastomosis between the spinal accessory nerve and the ulnar nerve is achievable and thus, the accessory spinal nerve is another possible choice for correcting the motor deficit arising from lower brachial plexus avulsion, but the limited number of motoneurons would only allow partial reinnervation..

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.

Meropenem and continuous renal replacement therapy: in vitro permeability of 2 continuous renal replacement therapy membranes and influence of patient renal function on the pharmacokinetics in critically ill patients

The pharmacokinetics of meropenem were characterized in 20 patients with different degrees of renal function who underwent continuous renal replacement therapy. Previously, no differences were detected in vitro in the removal of meropenem by continuous venovenous hemofiltration or continuous venovenous hemodialysis or when AN69 or polysulfone membranes were compared. In patients, no significant differences in the sieving coefficient or the saturation coefficient with the renal function were found, and the mean sieving coefficient/saturation coefficient value (0.80 +/- 0.12) was similar to the unbound fraction (0.79 +/- 0.08). An increase in total clearance and a decrease in elimination half-life were observed to the extent that the patient's creatinine clearance was higher. Likewise, the contribution of continuous renal replacement therapy to total clearance diminished in patients with less renal impairment. The results suggest that the renal function of the patient may influence meropenem pharmacokinetics during continuous renal replacement therapy. The lower trough plasma levels observed in nonrenal patients would not lead to adequate time during which serum drug concentrations are above the minimum inhibitory concentration values in many infections.

Laparoscopy for abdominal emergencies

BACKGROUND

Emergency laparoscopic exploration can be used to identify the causative pathology of acute abdominal pain. Laparoscopic surgery also allows treatment of many intraabdominal disorders. This report was prepared to describe the effectiveness of laparoscopic surgery compared to laparotomy or nonoperative treatment.

METHODS

A panel of European experts in abdominal and gynecological surgery was assembled and participated in a consensus conference using Delphi methods. The aim was to develop evidence-based recommendations for the most common diseases that may cause acute abdominal pain.

RECOMMENDATIONS

Laparoscopic surgery was found to be clearly superior for patients with a presumable diagnosis of perforated peptic ulcer, acute cholecystitis, appendicitis, or pelvic inflammatory disease. In the emergency setting, laparoscopy is of unclear or limited value if adhesive bowel obstruction, acute diverticulitis, nonbiliary pancreatitis, hernia incarceration, or mesenteric ischemia are suspected. In stable patients with acute abdominal pain, noninvasive diagnostics should be fully exhausted before considering explorative surgery. However, diagnostic laparoscopy may be useful if no diagnosis can be found by conventional diagnostics. More clinical data are needed on the use of laparoscopy after blunt or penetrating trauma of the abdomen.

CONCLUSIONS

Due to diagnostic and therapeutic advantages, laparoscopic surgery is useful for the majority of conditions underlying acute abdominal pain, but noninvasive diagnostic aids should be exhausted first. Depending on symptom severity, laparoscopy should be advocated if routine diagnostic procedures have failed to yield results.

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.

[Intramedullary spinal cord metastasis as the first manifestation of a renal carcinoma]

We present the case of a 69 year-old male without known antecedente who presented a clinical loss of distal force in his lower limbs during the last two months. Magnetic resonance imaging (MRI) showed an intramedullary spinal cord mass at the level of the medullaris cone. The patient was operated on; the histological diagnosis was clear cells carcinoma suggestive of metastasis from an unsuspected renal tumor that was later confirmed with an abdominal CT. When the patient's state is good, surgery can correct the neurological deficit produced by an intramedullary spinal cord lesion. The neurological state of our patient improved after the intervention, and 14 months after surgery, he has no neurological deficit in the lower limbs.