The Impact of Peritoneal Permeability and Residual Renal Function on Pd Prescription

Our objective was to evaluate the impact of peritoneal transport characteristics and residual renal function on peritoneal clearance and to determine the dialysis volume required to achieve targets for KT/V and weekly creatinine clearance (WCC) in patients with differing weights, renal function, and transport status.

Retrospective analysis and mathematical model simulation of urea and creatinine clearance were used.

This review demonstrates the important contribution of both residual renal function and peritoneal transport in attaining target values for KT/V and WCC. The limitations of a standard 4 x 2 L dialysis prescription are highlighted in anuric patients and those with low peritoneal transport. In addition, the limitations of short dwell, rapid exchange dialysis modalities are emphasized, especially in patients with low and low average peritoneal transport where daily clearance is demonstrated to be considerably less than conventional continuous ambulatory peritoneal dialysis (CAPD).

Attainment of proposed targets for KT/V (1.7) and WCC (50 L) is greatly dependent on residual renal function. In CAPD, peritoneal transport characteristics determine urea clearance through an effect on ultrafiltrate. Thus low transporters of identical weight will have greater values for peritoneal dialysis KT/V. Creatinine clearance is considerably influenced by transport status. The majority of low and low average groups will need some degree of renal function to achieve currently proposed targets. In these patients, conversion to high volume, short dwell modalities will further compromise small solute clearance unless daytime long dwells or tidal dialysis is instigated.

Tenckhoff Peritoneal Dialysis Catheter Insertion in a Northern Ireland District General Hospital

INTRODUCTION

Chronic kidney disease (CKD) affects approximately 5% of the population. Based on 2014 data, peritoneal dialysis (PD) is underutilised in Northern Ireland with a prevalence of only 11% in patients requiring renal replacement therapy (RRT). Recent National Institute of Clinical Excellence (NICE) guidelines aim to increase the rate of PD utilisation to 39% amongst patients requiring RRT. In order to implement these guidelines, nephrologists must have access to a reliable, effective PD catheter insertion service. The aim of this study was to assess the outcomes of PD catheter insertions and incident rates of PD use in a single centre in anticipation of a potential increased uptake.

METHODS

A retrospective analysis was conducted of all patients who underwent PD catheter insertion between April 2003 and October 2011. Case notes were reviewed for demographic information, complications, need for re-intervention, and primary catheter patency at 12 months. The UK Renal Registry annual reports were also reviewed for data on annual uptake of PD in our institution.

RESULTS

Fifty-four patients underwent PD catheter insertion between 2005 and 2011; 61% were male with a median age of 58 (range 21-82) years. Early complications (≤30 days) included bowel perforation (n=1) and wound infection (n=2). During this study period 17 (31%) patients required manipulation or reinsertion for catheter obstruction/migration. The primary catheter patency at 12 months was 76%. The average uptake of PD as the first treatment modality (incident use) was 21.3% compared to a Northern Ireland (NI) average of 12.4%.

CONCLUSION

Complication rates were comparable to the International Society of Peritoneal Dialysis (ISPD) guidelines in this case series and PD uptake was higher than the NI average. Therefore, local provision of an expert surgical PD catheter insertion service may potentially facilitate an increased uptake of this modality amongst RRT patients but further research is warranted.

Protective and non-protective CD8 T cell responses against Plasmodium infection (MPF2P.760)

Despite decades of research, malaria remains a global health crisis. Currently, subunit vaccine approaches do not provide long-term, sterilizing immunity against Plasmodium infection. Conversely, immunization using whole parasites can confer protection in rodents through eliciting protective CD8 T cell responses, likely against a broad spectrum of Plasmodium antigens. However, it is unknown whether all of these CD8 T cell specificities contribute to protection. Recently, four novel H-2b-restricted Plasmodium-specific CD8 T cell epitopes were described from the following antigens: GAP50, PbT, S20, and TRAP. Here, we show that priming with peptide-loaded mature dendritic cells followed by boosting with recombinant L. monocytogenes expressing these epitopes results in memory antigen-specific CD8 T cell responses constituting 5-40% of the CD8 T cell compartment. To date, only TRAP-specific CD8 T cells generated through this vaccination approach can provide sterilizing immunity following a sporozoite challenge. This result occurs despite similar numbers, function and phenotype for each of the memory CD8 T cell populations. These data suggest that timing of antigen presentation during liver-stage infection coupled with a requirement for direct MHC presentation predicts the protective capacity of a CD8 T cell specificity. These data may aid in identifying novel target antigens to elicit sterilizing protection against Plasmodium infection.

The timing of stimulation and IL-2 signaling regulate secondary CD8 T cell responses (LYM5P.701)

Memory CD8 T cells provide protection to immune hosts by eliminating pathogen-infected cells during re-infection. While parameters influencing the generation of primary (1o) CD8 T cells are well established, the factors controlling the development of secondary (2o) CD8 T cell responses remain largely unknown. Here, we explored the mechanisms involved in the generation and development of 2o memory (M) CD8 T cells. We observed that the time at which 1o M CD8 T cells recognize Ag and become activated impacts their fate and differentiation into 2o M CD8 T cells. Late-entry of 1o M CD8 T cells into an immune response not only facilitated the expression of transcription factors associated with memory formation in 2o effector CD8 T cells, but also influenced the ability of 2o M CD8 T cells to localize within the LN, produce IL-2, and undergo Ag-driven proliferation. The timing of stimulation of 1o M CD8 T cells also impacted the duration of expression of the high-affinity IL-2 receptor (CD25) on 2o effector CD8 T cells and their sensitivity to IL-2 signaling. Importantly, by blocking or enhancing IL-2 signaling in developing 2o CD8 T cells, we confirmed the role of IL-2 in controlling the differentiation of 2o CD8 T cell responses. Thus, our data suggest that the process of 1o M to 2o M CD8 T cell differentiation is not fixed and can be manipulated, a notion with relevance for the design of future prime-boost vaccination approaches.

Highly focused TCR Vβ repertoire is associated with a large number of naive precursors and robust CD8 T cell responses specific for a Plasmodium antigen (IRM14P.450)

Here we describe, to our knowledge, the most TCRβ focused CD8 T cell response to date. This TCR is specific for a conserved Plasmodium-derived epitope in mice (GAP5041-48), presented by H-2Db. After various immunization regimens, >99% of epitope-specific CD8 T cells detected by tetramer staining expressed TCR Vβ8.1 (TRB). Interestingly, priming with dendritic cells coated with GAP5041-48 peptide resulted in the same TCR Vβ distribution, suggesting that the observed bias does not evolve with multiple antigen exposures. Additionally, DC-priming induced exceptionally strong responses only 4 days post-immunization (~20% of total CD8 T cells were tetramer positive), suggesting an unusually large antigen-specific naïve CD8 T cell repertoire. Currently, the upper limit for the size of antigen-specific naive CD8 T cell repertoire ranges from 600-1500 cells (VacV B8R, MCMV M45). We show that GAP5041-48-specific naïve CD8 T cell repertoire, with its size of ~2,200 cells, extends this upper limit by more than 40%. Finally, classical Ala-substitution screening of the peptide (SQLLNAKYL), showed that amino acids (aa) at positions 6 and 7 are critical for TCR recognition. This epitope could be used as a valuable tool for better understanding the relation between a TCR structure and thymic selection. Moreover, the unique property of GAP5041-48-specific response make it a powerful tool to study fundamental processes underlying CD8 T cell activation upon Plasmodium infection.

Characterization of comorbid factors in hip fracture related in-hospital mortality

It is important to delineate factors which influence in-hospital mortality rates following a hip fracture. The current study aimed to identify the nature and frequency of comorbidities prevalent in this patient cohort. A retrospective chart review of cases of in-patient mortality following admission for a hip fracture was performed. These cases (n=127) were characterized for comorbidities, complications, medical status indicators, and other contributory factors. Cardiovascular 104 (81.9%), respiratory 66 (52.0%), genitourinary 41 (32.3%), psychiatric 41 (32.3%), vascular 40 (31.5%), and gastrointestinal 40 (31.5%), are the physiological systems, most commonly associated with comorbidity amongst hip fracture patients who succumb to in-hospital mortality. Renal failure, pneumonia, sepsis, myocardial infarction, congestive cardiac failure (CCF), respiratory failure, and Clostridium difficile infection are conditions which are associated with postoperative complications leading to in-patient mortality. Analysis of medical status indicators illustrated an inverse correlation between ASA scores and postoperative survival time, in this cohort-of hip fracture patients (R2 = 0.9485).

Protective capacity of CD8 T cells targeting a spectrum of Plasmodium-specific epitopes (MPF6P.735)

Despite decades of research, malaria remains a global health crisis. Currently, the most advanced anti-malarial vaccine in human clinical trials (RTS,S) does not provide long-term, sterilizing immunity against Plasmodium infection. Plasmodium-specific CD8 T cells can provide sterilizing immunity to Plasmodium infection in rodent models. However, the numerical requirements for memory CD8 T cell protection against a defined epitope, P. berghei CS252-260 (a CSP epitope) exceeds 1% of peripheral blood lymphocytes - a 103-104 fold higher number than required for protection against some bacterial or viral infections. Recently, three novel H-2b-restricted Plasmodium-specific CD8 T cell epitopes were described from the following antigens: GAP50, S20, and TRAP. Priming with peptide-loaded mature dendritic cells followed by boosting with recombinant L. monocytogenes expressing these epitopes results in antigen-specific CD8 T cell responses constituting 0.3-6% of the PBL in CB6.F1 mice. The capacity of these single CD8 T cell responses to provide protective immunity in a stringent model of liver stage infection with P. berghei will be described. Moreover, we are determining whether combining multiple epitope-specific responses can reduce the total numerical requirement for CD8 T cell-mediated protection. These studies may aid in the preclinical design of a sterilizing CD8 T cell based anti-Plasmodium subunit human vaccine containing multiple CD8 T cell epitopes.

Tim-3 enhances CD8 T cell responses to acute listeria monocytogenes infection (IRC9P.711)

Tim-3 is a cell surface molecule expressed on multiple immune cell populations that can mediate both stimulatory and inhibitory effects. Tim-3 has been previously shown to enforce CD8 T cell exhaustion, a dysfunctional state associated with chronic stimulation. In contrast, the role of Tim-3 in the regulation of CD8 T cell responses to acute infection remains undefined. To address this knowledge gap, we examined how Tim-3 affects CD8 T cell responses to acute Listeria monocytogenes (LM) infection. Analysis of wild-type (WT) mice infected with LM showed that Tim-3 was transiently expressed by activated CD8 T cells and was associated with acquisition of an effector CD8 T cell phenotype. Comparison of responses to LM by WT and Tim-3 KO mice showed that the absence of Tim-3 significantly reduced the magnitudes of both primary and secondary CD8 T cell responses, which correlated with decreased IFN-γ production and degranulation by Tim-3 KO cells. To address the T cell-intrinsic role of Tim-3, we analyzed responses to LM infection by WT and Tim-3 KO TCR-transgenic CD8 T cells following adoptive transfer into a shared WT host. In this setting, the generation of cytokine-producing cells and proliferation by Tim-3 KO cells were significantly reduced, demonstrating that Tim-3 has a direct effect on CD8 T cell function. Our results suggest that Tim-3 can mediate a stimulatory effect on CD8 T cell responses during an acute infection.

The antigen sensitivity of effector but not memory CD4 T cells is regulated by the pathogen-induced inflammatory milieu. (IRM6P.712)

CD4 T cells play an important role in orchestrating immune responses following recognition of antigens through their T cell receptor (TCR). As such, their sensitivity for cognate antigen is likely to be tightly regulated. Previously, we demonstrated that the antigen sensitivity of CD8 T cells was tuned by inflammatory cytokines. Whether inflammatory cytokines also tune the antigen sensitivity of CD4 T cells remains unknown. Herein, we demonstrate that the antigen sensitivity of effector CD4 T cells is tuned by the inflammatory milieu. Mechanistically, we demonstrate that, in contrast to CD8 T cells, increased antigen sensitivity is not linked to enhanced TCR signal transduction capacity. In addition, tuning of the antigen sensitivity of CD4 T cells by inflammatory cytokines is independent of their role in the polarization of these cells towards a Th1 phenotype. Further, we demonstrate that, unlike CD8 T cells, inflammatory cytokines do not regulate the antigen sensitivity of memory CD4 T cells. Taken together, these data demonstrate that while inflammatory cytokines tune the antigen sensitivity of both CD4 and CD8 T cells, they do so through distinct mechanisms. Understanding the regulation of the antigen sensitivity of T cells can yield important insight leading to potential therapeutic avenues aimed at manipulating the antigen sensitivity of T cells. These approaches may be useful to prevent chronic viral infections, allow for clearance of tumors and prevent autoimmunity.

Manipulating number and function of effector CD8 T cells (IRC9P.710)

In response to infection or vaccination, CD8 T cells undergo massive proliferative expansion in numbers followed by a contraction phase where 90-95% of the expanded population is eliminated through apoptosis, with the remaining cells initiating the memory pool. Although basic CD8 T cell kinetics in response to infection and immunization have been described, the mechanisms regulating how memory CD8 T cell numbers are determined remain unknown. The current paradigm regarding memory CD8 T cell numbers states that the size of the memory pool is dictated primarily by the peak numbers achieved after infection or immunization. However, our data directly challenge this paradigm. Here, we demonstrate that DC-immunization and infection models, coupled with stimulatory IL-2/Ab complex treatment, can increase peak effector CD8 T cell numbers over 100-fold with no concurrent increase in memory CD8 T cell numbers post-contraction. Additionally, IL-2/Ab complex treatment not only increases effector CD8 T cell numbers, but also enhances and sustains expression of cytolytic molecules such as granzyme B, 4-1BB, and GITR. Thus, our data dissociate the magnitude of effector CD8 T cell expansion from memory set point, as well as highlight how IL-2/Ab complexes can enhance effector CD8 T cell function. Our findings suggest that IL-2/Ab complex therapy may be useful in short-term elevation of effector CD8 T cell numbers and function for tumor immunotherapy or during infectious disease outbreaks.

Inflammatory cytokines extend the division of activated CD8 T cells in vivo by maintaining high affinity IL-2 signaling (P6050)

Activation of naïve CD8 T cells requires several signals including TCR ligation and costimulation. Although these signals induce division, accumulation of activated CD8 T cells is dependent on a third signal provided by inflammatory cytokines. In vitro studies suggest that “signal 3”specifically enhances survival; however, the mechanisms for optimal accumulation of activated CD8 T cells in vivo is unknown. To explore these mechanisms, we transfer ~600 OT-I tg-CD8 T cells into congenic hosts and immunize hosts with OVA257-coated dendritic cells in the absence (DC) or presence of inflammation (CpG; DC+CpG). OT-I numbers were similar in DC and DC+CpG recipients at day 5 p.i. However, the presence of inflammation during immunization increased accumulation and extended division of OT-I at day 6-7 p.i. while not altering survival. Extended division of DC+CpG OT-I depended on the maintenance of IL-2/PI3K signaling that was regulated by early/direct IL-12 signaling. These findings indicate that "signal 3" enhances accumulation by maintaining division (not survival) of activated CD8 T cells in a manner dependent on a temporally orchestrated sequence of cytokine signals.

Perforin expression is required for fatal blood-brain barrier disruption in the Plasmodium berghei ANKA model of cerebral malaria (P3061)

The most severe clinical complication of Plasmodium falciparum infection is cerebral malaria (CM). Plasmodium berghei ANKA (PbA) infection of C57BL/6 mice is an established model of CM. Previous work has implied a role for CD8 T cells and perforin expression in fatal stages of PbA infection. We therefore infected C57BL/6 and C57BL/6 Perforin-/- mice with PbA and assessed the CNS for cerebral endothelial cell blood-brain barrier (BBB) disruption using FITC albumin leakage into tissue, confocal microscopy and 3D volumetric T2 and T1 gadolinium enhanced MRI. PbA infected C57BL/6 mice: 1.) had extensive disruption of BBB tight junction proteins Occludin and Claudin 5, 2.) developed severe CNS vascular permeability of FITC albumin and gadolinium leakage, and 3.) became moribund. We also observed increased VEGF cytokine expression coinciding with CNS vascular permeability in these animals. Despite having similar CD8 T cell infiltration into the brain, PbA infected C57BL/6 Perforin-/- mice had intact BBB tight junction, were devoid of CNS vascular permeability, presented with normal brain MRI, and had normal behavioral scores on the rotarod assay. This study is therefore the first to demonstrate the critical importance of perforin expression in promoting BBB tight junction alteration during PbA infection. Therefore, development of therapies to block factors related perforin mediated delivery could have significant benefit to the treatment of CM.

IL-12 inhibits memory CD8+ T cells localization to the respiratory tract and reduces protection against Influenza A virus. (P5093)

Memory CD8 T-cells specific for conserved antigens from Influenza A virus (IAV), like nucleoprotein (NP), may provide an important line of defense when neutralizing antibodies are absent (e.g. IAV pandemic). Here we show, through local CD8 T-cell depletions, that NP specific memory CD8 T-cells have superior protective capacity against IAV when they are localized inside the respiratory tract (BAL fluid). Expression of the chemokine receptor CXCR3 on memory CD8 T-cells was essential for the maintenance of a local memory population in the respiratory tract. Interestingly, the inflammatory milieu during immunization seems critical for the ability of memory CD8 T-cells to express CXCR3. Exposure to interleukin 12 (IL-12), but not other signal 3 cytokines, led to reduced expression of CXCR3 on memory CD8 T-cells, through a STAT4 and T-bet dependant pathway. Neutralization of IL-12 during priming or selection of adjuvants that induce little IL-12, significantly increases CXCR3 expression on memory CD8 T-cells, enhances their numbers in the respiratory tract and provides superior protection against IAV challenge. Thus, CXCR3+ memory CD8 T-cells have a superior protective capacity against IAV, due to their capacity to populate the respiratory tract and IL-12 is a key regulator for the establishment of CD8 T-cell memory inside the respiratory tract.

Memory CD8 T cells are programmed to rapidly synthesize core 2 O-glycans for tissue-specific trafficking in response to inflammatory cues (P5112)

Immune cell trafficking from the circulation into peripheral tissues is a highly orchestrated process involving a number of receptor-ligand interactions. Previously, it has been demonstrated that memory CD8 T cells localize to areas of infection/inflammation in an antigen-independent manner and that these recruited CD8 T cells are highly cytolytic, thus providing rapid protection against pathogens expressing cognate antigen. However, the molecular mechanisms regulating memory T cell recruitment to inflamed tissue remain ill defined. Herein, we demonstrate that memory CD8 T cells utilize core 2 O-glycans, which mediate interactions with P- and E-selectin, for trafficking to inflamed tissues. Following infection, antigen-specific effector CD8 T-cells strongly express core 2 O-glycans, but this glycosylation pattern is lost by almost all memory CD8 T cells. However, following an inflammatory challenge, de novo generation of core 2 O-glycans occurs on memory, but importantly, not naïve CD8 T cells. Mechanistically, memory and naive CD8 T-cells exhibit the opposite pattern of histone H3 modifications at the Gcnt1 locus, a critical enzyme for core 2 O-glycan synthesis and its expression is regulated by IL-15. Thus, initial antigen encounter epigenetically programs memory CD8 T cells to rapidly generate functional selectin ligands in response to inflammatory cues, a previously unknown mechanism controlling differential localization of naïve and memory CD8 T cells.

The expression of FcγRIIB by effector and memory CD8 T cells (46.14)

In response to infection, antigen-specific naïve CD8 T cells proliferate and differentiate, eventually becoming long-lived memory cell populations. It has been well documented that throughout this process, CD8 T cells undergo both phenotypic and functional changes. However, the expression of FcγRIIB (CD32) by effector or memory CD8 T cells has not been reported at the molecular level. Using OT-I TCR-tg cells and OVA expressing attenuated L. monocytogenes (LM) infections, we found that CD32 mRNA was increased in memory relative to naïve populations. Surface expression of CD32 is undetectable on naive CD8 T cells, but can be observed at effector and memory time points in endogenous populations following either LM or LCMV Arm-infection. At memory, CD32+ antigen-specific CD8 T cells are CD127hiCD122hi and undergo more homeostatic proliferation relative to CD32- cells. CD32 KO antigen-specific CD8 T cells expand similarly to WT following LM challenge. However, CD32 KO cells undergo a higher degree of contraction and, thereafter, undergo less homeostatic proliferation than WT cells. These data suggest that the expression of CD32 positively correlates with the maintenance of CD8 T cells from effector to memory differentiation.

NFIL3/E4BP4 is a key transcription factor for CD8α+ dendritic cell development (153.47)

Antigen presentation by mature dendritic cells (DCs) is the first step for initiating adaptive immune responses. DCs are comprised of heterogeneous functional subsets. However, the molecular mechanisms regulating differentiation of specific DC subsets are not understood. Here, we report that the basic leucine zipper transcription factor NFIL3/E4BP4 is essential for the development of CD8α+ conventional DC (cDC). Nfil3-/- mice specifically lack CD8α+ cDCs but not CD8α- cDCs or plasmacytoid DCs in lymphoid tissues. Flt3 ligand-dependent generation of CD8α+ cDCs in lymphoid tissues and CD8α+-equivalent cDCs from Nfil3-/- bone marrow cells was also impaired. NFIL3 regulates CD8α+ cDC development in part throuth Batf3 expression. Importantly, Nfil3-/- mice exhibit impaired cross-priming of CD8+ T cells against cell-associated antigen, a process normally carried out by CD8α+ cDCs, and failed to produce IL-12 after TLR3 stimulation. Thus, NFIL3 plays an essential role in the development of CD8α+ cDCs.

The relevance of non-human primate and rodent malaria models for humans

At the 2010 Keystone Symposium on "Malaria: new approaches to understanding Host-Parasite interactions", an extra scientific session to discuss animal models in malaria research was convened at the request of participants. This was prompted by the concern of investigators that skepticism in the malaria community about the use and relevance of animal models, particularly rodent models of severe malaria, has impacted on funding decisions and publication of research using animal models. Several speakers took the opportunity to demonstrate the similarities between findings in rodent models and human severe disease, as well as points of difference. The variety of malaria presentations in the different experimental models parallels the wide diversity of human malaria disease and, therefore, might be viewed as a strength. Many of the key features of human malaria can be replicated in a variety of nonhuman primate models, which are very under-utilized. The importance of animal models in the discovery of new anti-malarial drugs was emphasized. The major conclusions of the session were that experimental and human studies should be more closely linked so that they inform each other, and that there should be wider access to relevant clinical material.

Self-reported complication rates following primary total hip arthroplasty in Ireland: fact or fiction

BACKGROUND

There are little data available on complication rates following primary total hip arthroplasty (THA) surgery in Ireland.

AIMS

To determine self-reported complication rates and national data for primary THA.

METHODS

A postal questionnaire surveyed Irish orthopaedic association consultant members. Additional data were obtained from the economic and social research institute (ESRI).

RESULTS

We achieved an 83% response rate. 5,424 THAs were self-reported. Mean dislocation rates were 1%, but higher using a posterior surgical approach (p < 0.05). Mean deep infection rates were 0.4%. 29% were MRSA. No reduction was reported from additional barrier prophylaxes. Mean venous thrombo-embolism (VTE) rates were 3.5%. No reduction was reported from commencing prophylaxis preoperatively or extending treatment duration. National rates for dislocation, deep infection and VTE were 25.7, 0.87, and <0.1%, respectively.

CONCLUSIONS

The creation of a National Hip Register is strongly recommended. A register would improve surgical practices and patient outcomes, and provide significant healthcare savings.

Molecular profiling of memory CD8 T cells after repeated antigen stimulations (39.5)

Repetitive antigen stimulation by prime-boost vaccination or pathogen re-encounter increases memory CD8 T cell numbers, however the impact on memory T cell differentiation is unknown. Here we show that repetitive antigen stimulations induce the selective accumulation of CD8 T cells with a uniform effector memory phenotype. In contrast to this, genome-wide microarray analysis reveals that each additional antigen challenge results in the differential regulation of several hundred genes in memory CD8 T cells and therefore in stepwise diversification of T cell transcriptomes. As a consequence, repeatedly stimulated memory CD8 T cells and primary memory CD8 T cells differ significantly in their molecular signature and share expression of only a small but preserved group of memory signature genes. Our results provide new insight into the complex regulation of memory CD8 T cell differentiation and identify potential new molecular targets to dissect and manipulate the function of memory T cells in human diseases.

Predicting mortality and uptake of renal replacement therapy in patients with stage 4 chronic kidney disease

BACKGROUND

Novel strategies are required to efficiently manage the increasing number of patients diagnosed with chronic kidney disease (CKD). We sought to identify factors predicting outcome in patients with stage 4 CKD and to determine whether low-risk patients could be managed in primary care.

METHODS

We performed a two-centre, retrospective cohort study including 396 patients with stage 4 CKD referred to nephrology clinics from 1998 to 2002. We utilized electronic databases to determine the incidence of renal replacement therapy (RRT) and mortality and the rate of deterioration in estimated glomerular filtration rate (eGFR) to the year end 2005.

RESULTS

This was an elderly cohort, with 71.7% of patients aged > or =65 years. The risk of surviving to require dialysis fell with increasing age (HR 0.44; 95% CI: 0.23-0.84 for those >74 years verses those <65 years), in part due to the slower rate of decline in renal function in older patients (median fall in eGFR was -2.25, -1.38 and -0.86 ml/ min/1.73 m(2)/year in those aged <65 years, 65-74 years and >74 years, respectively, P < 0.0001). Additional independent risk factors predicting RRT included: high baseline proteinuria (HR 6.26; 95% CI: 2.74-14.23 for >3 g/24 h versus <0.3 g/24 h), greater early decline in renal function (HR 3.86; 95% CI: 2.34-6.38 for > or =4 ml/min/1.73 m(2)/year versus <4 ml/min/1.73 m(2)/year), low baseline eGFR (HR 2.92; 95% CI: 1.61-5.30 for 15-19 versus 25-29 ml/min/1.73 m(2)) and low haemoglobin (HR 3.16; 95% CI: 1.64-6.08 for <10 versus >12 g/dl). The 98 (24.7%) patients discharged to primary care had more stable renal function than those remaining under nephrology care (median change in eGFR of +0.20 versus -1.88 ml/ min/1.73 m(2)/year, P = 0.0001).

CONCLUSIONS

Most patients with stage 4 CKD, in particular the elderly, die without commencing RRT. Patients at low risk of progression can be identified and discharged safely to primary care with an active management plan.

Hydrogen peroxide as an irrigation solution in arthroplasty – A potential contributing factor to the development of aseptic loosening

The reason for revision of primary total hip arthroplasty is quoted as aseptic loosening in 60.6% of cases between 1979 and 2003 in the Swedish National Hip Arthroplasty Registry. Much research effort has been directed toward enhancing the bone-cement interface of total joint arthroplasties, in an attempt to reduce this complication. Haemostatic agents have been popularized as effective means of retarding the development of potentially harmful debris interposition adjacent to, and blood lamination patterns within, the methylmethacrylate. Such agents include hydrogen peroxide (H(2)O(2)), local freezing saline, saline at room temperature and adrenaline solution. One main concern with the use of hydrogen peroxide is whether it affects the material properties of bone cement such that in the long term it contributes to aseptic loosening. This would have enormous clinical consequences. Preliminary studies indicate that porosity increases and that the tensile strength and yield stresses are reduced by up to a factor of 10 by contaminating samples with increasing concentrations of hydrogen peroxide. We postulate that the current use of hydrogen peroxide as an irrigation solution in arthroplasty contributes to the development of aseptic loosening.

Use of cardiac troponin T in diagnosis and prognosis of cardiac events in patients on chronic haemodialysis

BACKGROUND

Patients undergoing chronic haemodialysis frequently have elevated serum cardiac troponin T (cTnT) levels resulting in difficulty in diagnosing acute coronary syndromes (ACS) in these patients. We sought to determine whether: (i) cTnT concentrations were consistent over time; (ii) intradialytic changes in cTnT levels were due to haemoconcentration; (iii) baseline cTnT levels predicted subsequent mortality or ACS.

METHODS

We measured serial pre- and post-dialysis cTnT concentrations in 75 asymptomatic patients undergoing chronic haemodialysis at baseline, and at 48 h, 8 months and 15 months. At 15 months, we also measured pre- and post-dialysis haematocrit levels in order to adjust the post-dialysis cTnT concentration for the effect of ultrafiltration. Kaplan-Meier survival curves, log-rank tests and Cox models were employed to determine whether baseline cTnT levels predicted death or ACS within 18 months.

RESULTS

Thirty-five (47%) patients had a baseline pre-dialysis cTnT concentration in the diagnostic range for an ACS (cTnT > or = 0.03 microg/l). There was a strong correlation between serial cTnT concentrations in individual patients (P<0.0001 for each time point). The median cTnT concentration was significantly greater post- than pre-dialysis (P<0.01 for each serial analysis); however, there was no significant difference following correction of post-dialysis cTnT levels for the effect of haemoconcentration (P = 0.48). Elevated baseline cTnT levels were associated with an increased risk of mortality or ACS at 18 months (P = 0.0015).

CONCLUSION

In asymptomatic patients on haemodialysis, serum cTnT concentrations are frequently elevated, and they rise during dialysis due to haemoconcentration. cTnT levels fluctuate minimally in individual patients in the medium term, therefore annual measurements may be useful reference points in the diagnosis of chest pain and in the prediction of ACS and mortality.

Primary total hip replacement--a survey of current practice and identifying changing trends

Primary total hip replacement (THR) surgery is the most commonly performed and successful reconstructive procedure in orthopaedic surgery. We performed a survey of Irish Orthopaedic consultants to elucidate current practices of primary THR in elderly and young patients and identify changing trends. There was an 83% response rate. Most respondents use a cemented THR in elderly patients. 69% use a different THR in younger patients compared to older patients. 9% refer younger patients to hip replacement specialist consultant colleagues. 70% report changing to a new implant or new technique in younger patients and 45% use a hybrid THR, 15% an uncemented THR, 15% perform hip resurfacing and 47% use different bearing surfaces. Only 17% use the Charnley hip prosthesis in younger patients. Young and active patients will place high demands on a new THR and newer techniques, implants and bearing surfaces are being adopted in the hope of better outcomes.

In vitro effects of soy phytoestrogens on rat L6 skeletal muscle cells

Soy isoflavones display estrogenic activity in humans and animals, and thus are referred to as phytoestrogens. This study was performed to observe the effects of the soy isoflavones genistein, daidzein, and glycitein on cell cultures of rat skeletal muscles. [3H]Thymidine incorporation was used to determine cell proliferation, while protein synthesis and degradation were determined by tracking radiolabeled leucine. For the proliferation studies, insulin, estradiol, genistein, daidzein, or glycitein was supplemented at 0, 0.04, 0.08, 0.16, 0.31, 0.63, 1.25, 2.5, 5, 10, or 20 microM, respectively, or in combinations with final concentrations of 0, 0.1, 1, or 10 microM. Genistein reacted most similarly to estradiol, inhibiting proliferation at > or = 1 microM (P < .001). A combination of phytoestrogens resulted in significant inhibition of cell proliferation, but not to the extent observed with genistein alone. For the protein synthesis and degradation experiments, treatments of 0.1 microM dexamethasone or 1 microM concentrations of insulin, genistein, daidzein, or glycitein were used. Phytoestrogens did not inhibit or stimulate protein degradation or synthesis (P > .05). A one-tailed univariate analysis of variance revealed a trend (P < or = .1) in protein stimulation with genistein and glycitein treatments. These results suggest that the tyrosine kinase inhibiting activity of genistein may be affecting phosphorylation of the mitosis-promoting factor, preventing the advancement of the mitotic cell cycle. In addition, at higher total combined concentrations, daidzein and glycitein may be able to outcompete genistein for receptor sites. These results suggest that soy isoflavones in the diet may potentially modulate normal growth and development in humans and animals that ingest soy-based products.

The effect of leg length discrepancy on foot loading patterns and contact times

The effect of a simulated leg length discrepancy on foot loading patterns and gait cycle times in normal individuals was investigated. Thirty feet of 15 normal volunteers were evaluated. Leg length discrepancy was simulated using flexible polyurethane soles. As leg length discrepancy increased, the total loading increased from 35.31 to 37.99 kg/cm2/sec, forefoot loading increased from 15.58 to 19 kg/cm2/sec, hindfoot loading remained the same. All subjects, except females with middle loading patterns, demonstrated increased hallux loading. The contact phase of gait decreased from 22% to 13%, the midstance phase remained the same, the propulsion phase increased from 44% to 50%. All findings were statistically significant. Leg length discrepancy has significant effects on the foot. Different adaptive loading patterns amongst subsets of individuals are seen.

Right-sided non-bacterial thrombotic endocarditis in a chronic hemodialysis patient with Muir-Torre syndrome

Endocarditis is a recognised complication ofhemodialysis. This is generally only thought of in terms of infective vegetations. We present a case of right-sided NBTE in a patient with an indwelling venous catheter who also had advanced pelvic malignancy. The unusual side of this patient's endocarditic lesions implicates a role for the venous catheter in determining the site of non-bacterial thrombus formation. It is also a reminder that endocarditis is always a risk when using central venous catheters, even after appropriate sterile precautions have been taken.

Impact of increasing dialysis volume on adequacy targets: a prospective study

Failure to achieve target values for both urea (Kt/V) and creatinine clearance has been associated with increased morbidity and mortality in continuous ambulatory peritoneal dialysis patients. The conventional continuous ambulatory peritoneal dialysis regimen, which uses four 2-L exchanges per day, has resulted in up to 40% of such patients failing to achieve proposed targets for weekly Kt/V of 1.7 and weekly creatinine clearance (WCC) of 50 L. In a prospective study, the impact of increasing prescribed volumes by 0.5 L per exchange was evaluated on attaining urea and creatinine clearance targets over a 1-yr period. At 1 yr, 17 patients remaining on the increased dialysis prescription were compared with 18 patients remaining on an unchanged regimen. The mean increase in daily prescribed volume was 1.5 L (22%). This resulted in a significant increase in both peritoneal dialysis Kt/V (1.59 to 1.78 L = 12%) and peritoneal dialysis WCC (45.8 to 50.1 L = 10%) by 1 yr. Because of loss of renal function, there was no significant increase in total clearance at 1 yr, but this loss of renal clearance was offset by the gain in peritoneal clearance. Residual renal function fell at a similar rate in both the increased dialysis and control groups. In the latter, although peritoneal clearance remained stable over the 1-yr period, loss of renal function resulted in reductions in both total Kt/V and WCC. In conclusion, exchange volume can be increased to compensate for loss of renal function over a 1-yr period. Progressive loss of renal clearance resulted in only a modest gain in total solute clearance. It was the larger patients who tolerated the increase in exchange volumes. However, such patients (by virtue of their size) tended not to achieve target values for solute clearance, and the modest gain in peritoneal clearance was insufficient to increase the number of patients in this group achieving such targets for dialysis adequacy.

The influence of small solute clearance on dietary protein intake in continuous ambulatory peritoneal dialysis patients: a methodologic analysis based on cross-sectional and prospective studies

The statistical relationship between solute clearance (expressed as Kt/V) and dietary protein intake (DPI; estimated from the normalized protein catabolic rate [NPCR]) has led to the assumption that dialysis dose is one of the most important determinants of DPI in continuous ambulatory peritoneal dialysis patients. However, there is increasing concern about the clinical value of such a correlation between variables that contain common components. We have investigated the statistical nature of the cross-sectional correlation between Kt/V and NPCR using mathematical modelling. In addition, in a prospective study, the impact of increasing Kt/V on protein intake estimated from the NPCR and from 3-day food diaries (DPI) was evaluated in 59 patients over a 1-year period. Two thousand sets of random numbers were generated for the components, from which Kt/V and NPCR were calculated. The subsequent cross-sectional correlation between the randomly generated Kt/V and NPCR was highly significant (r = 0.64 to 0.74). In contrast, there was a much weaker cross-sectional correlation between relatively independent measures of dialysis dose (urea clearance) and protein intake measured from food diaries (r = 0.36). Analysis of the prospective relationship revealed a significant correlation with a decrease in urea clearance (due to loss of renal function) accompanied by a decrease in both PCR (r = -0.80) and DPI (r = -0.51). In contrast, when Kt/V was increased (by larger volume exchanges) there was no significant increase in protein intake. This study has demonstrated that the strength of the cross-sectional relationship between Kt/V and NPCR is due to mathematical coupling of "like with like," and this correlation cannot be used to substantiate a link between dialysis dose and nutrition. Prospective analysis does show a dependence of protein intake on urea clearance. However, this dependence is only seen in those patients undergoing a reduction in clearance due to loss of renal function. Increasing exchange volume to offset such losses was not accompanied by improvements in protein intake.

Energy metabolism during CAPD: a controlled study

Abnormalities of energy metabolism may exacerbate the high prevalence of protein-calorie malnutrition and inadequate calorie intake in continuous ambulatory peritoneal dialysis (CAPD) patients, leading to further nutritional depletion. In a controlled study, using indirect calorimetry, we evaluated oxygen consumption (VO2), CO2 production, resting energy expenditure, and respiratory exchange ratio (RER) in 12 CAPD patients at rest and during a standard CAPD exchange and in 11 healthy nonuremic control patients. In addition, we investigated the influence of nutritional status and dialysis adequacy on energy metabolism in the CAPD group. There was no significant difference in resting energy parameters between the two groups. Unlike the control group, blood glucose and RER were maintained during prolonged fasting in the CAPD patients. This observation indicates that all the absorbed glucose was used as a metabolic fuel preventing fat oxidation. There was no significant relationship between energy expenditure and dialysis adequacy. There was no significant relationship between nutritional state (including energy intake) and energy expenditure despite evidence of malnutrition in 41% of the patients. If maintenance of "normal levels" of energy expenditure occurs in dialysis patients with suboptimal calorie intake (especially with evidence of protein-calorie malnutrition), this inability to conserve energy may act as an additional risk factor for ongoing malnutrition.

Limitations of kinetic models as predictors of nutritional and dialysis adequacy in continuous ambulatory peritoneal dialysis patients

Nutrition has been shown to predict clinical outcome in continuous ambulatory peritoneal dialysis (CAPD) patients. However, despite the positive relationship between KT/V (urea) and the normalised protein catabolic rate, the ability of urea kinetic modelling to predict clinical outcome or nutrition remains inconclusive. We have evaluated the relationship between nutrition and achieved dialysis in a cross-sectional study of 147 stable CAPD patients on dialysis for a mean period of 22 months. Protein-energy malnutrition was present in 22-32% of the study population. 39 and 41% of the population failed to achieve suggested adequacy targets of 50 liters/week for total creatinine clearance and a weekly KT/V (urea) of 1.7, respectively. Severely malnourished patients had significantly greater normalised clearance and adequacy values than well-nourished patients. Intrinsic actual peritoneal clearance bore no relation to patient size. The subsequent normalisation of this value by a component of patient mass results in a mathematical bias against well-nourished or obese patients. This may explain the failure of such adequacy values to reflect outcome and argues against accepting such values as measures of dialysis well-being.

Preliminary vascular control for renal trauma

Preliminary control of the renal vascular pedicle prior to opening Gerota's fascia is advocated as the standard approach for decreasing the rate of nephrectomy from trauma. This method, however, has not been studied widely. Previous reports failed to grade the severity of the renal injury and involved small patient series and historic control for comparison of nephrectomy rates. We studied 297 patients with renal trauma during a ten year period. Sixty-three of 75 patients with penetrating injuries and 12 of 222 patients with blunt injuries underwent renal exploration. We obtained vascular control prior to opening Gerota's fascia in 32 patients; it was obtained in 43 patients after opening Gerota's fascia. The nephrectomy rate depended on the degree of injury rather than on the type of renal vascular control obtained. Obtaining vascular control after opening Gerota's fascia did not increase the nephrectomy rate and shortened operative time by an average of 58 minutes. We recommend vascular control after opening Gerota's fascia when there is a large hematoma crossing the midline, a rapidly expanding renal hematoma, if the patient is unstable, or if Gerota's fascia has already been opened by the injury.

Polyclonal B cell activation of IgG2a and IgG2b production by infection of mice with lactate dehydrogenase-elevating virus is partly dependent on CD4+ lymphocytes

Concentrations of IgM and IgG isotypes were determined by capture ELISA in plasma of Swiss, BALB/c and C58/M mice. Plasma IgG isotype concentrations, especially of IgM, IgG1 and IgG2a, varied considerably between mouse strains, batches of mice of the same strain and individual mice and as a function of age. Infection of the mice with LDV, which is known to replicate primarily in a subpopulation of macrophages, consistently resulted in a rapid elevation of plasma IgG2a (or of IgG2b in some Swiss nu/+ mice), but no plasma IgG increases were observed in mice immunized with inactivated LDV. Plasma IgG2a elevation after LDV infection was greatly delayed and reduced by depletion of the mice of CD4+, but not of CD8+, T cells by administration of protein-G-purified anti-CD4 or anti-CD8 mAbs, and completely inhibited by repeated treatment of the mice with cyclophosphamide. Treatment with anti-CD4 mAbs, or cyclophosphamide also greatly reduced the production of anti-LDV antibodies, while not significantly affecting the replication of LDV in these mice. Nude Swiss mice also failed to produce anti-LDV antibodies, though supporting normal LDV replication. Plasma IgM, IgG1, IgG2a and IgG2b levels increased in LDV-infected nu/nu mice, but similar changes were observed in uninfected mice. The results indicate that the LDV-induced polyclonal activation of B cells requires productive LDV infection of mice and is, at least partly, dependent on functioning CD4+ cells. They suggest that productive infection of the LDV-permissive subpopulation of macrophages leads to the activation of CD4+ T lymphocytes of subset 1 and their Spleen cells from 5-day LDV-infected BALB/c mice incorporated [3H]thymidine 2-3 times more rapidly in vitro than spleen cells from companion uninfected mice, whereas their responses to concanavalin A and lipopolysaccharide were reduced 60-70%.