Care trajectories of patients initiating dialysis as planned versus emergency procedure

Background

Emergency dialysis is defined as a first dialysis session performed within 24 hours after the nephrologist’s assessment due to a life-threatening risk. Starting dialysis in emergency (ES) is associated with poorer outcomes compared to a planned start (PS). The aim of this study was to compare the pre-dialysis care trajectory between ES and PS patients.

Methods

Patients ≥ 18 years old who started dialysis in 2015 in France were included. Data from REIN were linked with the French national health database (SNDS). Individual characteristics at dialysis initiation, inpatient stays (number, duration and diagnosis), and consultations with general practitioners (GP) and nephrologists during the year before dialysis start were compared between ES and PS patients, as well as with national clinical practice guidelines.

Results

Among 8964 patients included, 30.6% started dialysis in emergency. These patients had more comorbidities than PS patients (19% of ES patients had 3 or more cardiovascular diseases versus 12.6% of PS patients, p < 0.001). In the year before dialysis start, ES patients had a lower median number of inpatient stays (1 versus 2 for PS patients, p = 0.001) but had a longer mean duration of hospital stay (8.1 days versus 5.8 days for PS patients, p < 0.001). ES patients had less consultations with a nephrologist (2.5 versus 4.5 for PS patients, p < 0.001). However, the number of GP consultations was not different between the two groups (9.7 versus 9.4 for PS patients, p < 0.064).

Conclusions

Nearly 1 in 3 patients started dialysis in emergency with more comorbidities at baseline than PS patients. Their one year pre-dialysis care trajectory was characterized by less frequent nephrological follow-up and a similar GP follow up, compared with PS patients. These results raise questions regarding access to coordinated care associating GPs and nephrologists. This issue of coordination will be investigated using qualitative methods.

Apoptosis and necrosis in toxicology: a continuum or distinct modes of cell death?

Mounting evidence indicates that apoptosis rather than necrosis predominates in many cytolethal toxic injuries. Associated cell death models of apoptosis and necrosis are either: (1) totally separate death modes, (2) a continuum whereby they are extremes of biochemically overlapping death pathways, or (3) essentially distinct processes with only limited molecular and cell biology overlap. We conclude that the current balance of evidence favours the third of these options. The established axiom that, even when considering the same toxicant, injury amplitude (dose) is a primary determinant of whether cells die via active cell death (apoptosis) or failure of homeostasis (necrosis) remains valid. Tissue selectivity of toxicants can stem from the apoptotic or necrotic thresholds at which different cells die, as well as targeting factors such as toxicokinetics, receptor recognition, bioactivation, and cell-specific lesions.

Thymocyte apoptosis as a mechanism for tributyltin-induced thymic atrophy in vivo

Tributyltin (TBT) immunotoxicity in rodent species is primarily characterised by T-lymphocyte deficiency resulting from a depletion of cortical thymocytes. In this study, bis(tri-n-butyltin) oxide (TBTO) was administered to male rats as a single oral dose of 30 or 60 mg/kg, and assessments were made of thymic cytopathology and the integrity of cellular DNA. TBTO treatment did not cause severe toxicity or overt clinical signs; however, by 48 h post-dosing relative thymus weights at 30 and 60 mg/kg were reduced to 66 and 43%, respectively, of control values. Increased DNA fragmentation was evident in thymic cell isolates (principally thymocytes) obtained from treated animals during the period of thymic involution. When DNA purified from these cells was visualised by agarose gel electrophoresis a multimeric internucleosomal fragmentation pattern, indicative of supra-physiological levels of apoptosis, was detected. Although unassociated apoptotic or necrotic thymocytes were essentially absent in cell preparations from TBTO-treated rats, significantly increased numbers of mononuclear phagocytic cells were observed. Many of these cells contained either apoptotic thymocytes, with nuclear morphologies exhibiting chromatin condensation, or cell remnants which were characterised as apoptotic bodies. Dibutyltin, which is a major metabolic dealkylation product of tributyltin, failed to significantly stimulate apoptosis when added to isolated thymocytes in vitro. Collectively, these findings suggest that activation of apoptosis contributes to TBT-induced thymocyte depletion in vivo, and indicate that it is unlikely that the metabolite dibutyltin is responsible for this effect.

Apoptosis as a mechanism of tributyltin cytotoxicity to thymocytes: relationship of apoptotic markers to biochemical and cellular effects

Recent in vitro studies have suggested that activation of apoptosis could account for the profound depletion of cortical thymocytes, which characterizes tributyltin (TBT) immunotoxicity. However, it has also been shown that TBT disrupts macromolecular synthesis and cellular energetics to an extent that might be expected to interfere with the initiation of apoptosis. The purpose of these studies was to further evaluate the morphological and biochemical characteristics of thymocyte killing by TBT and to relate this to key cellular processes. Ex vivo thymocyte cultures from immature rats were treated with bis(tri-n-butyltin) oxide (TBTO) at concentrations ranging from those which rapidly produced necrosis (5-10 microM), down to cytotoxic but subnecrotic concentrations (0.1-2 microM). In cells exposed to TBTO concentrations that caused a rapid and near maximal inhibition of protein synthesis, it remained possible to demonstrate the stereotypic internucleosomal DNA cleavage and morphological changes indicative of apoptosis. Further confirmation that apoptosis was occurring independently from protein synthesis was provided by the absence of a protective effect following cycloheximide pretreatment. Apoptosis still occurred in TBTO-treated thymocytes although intracellular ATP levels were depressed to 20% or less of control values. Cytoprotective effects were noted with the intracellular Ca2+ chelators BAPTA-AM and Quin-2 AM, and also with zinc. Cell killing by TBTO occurred without overt disturbance of thymocyte cell cycle parameters. These results indicate that thymocyte apoptosis stimulated by TBT exposure occurs independently of a requirement for protein synthesis and does not require fully conserved cellular energetics.

Bis(tri-n-butyltin)oxide induces programmed cell death (apoptosis) in immature rat thymocytes

In order to characterise the mechanism of cytotoxicity of the immunotoxic organotin compound bis(tri-n-butyltin)oxide (TBTO) to lymphoid cells, isolated thymocytes from immature rats were exposed to TBTO (0.1-5 microM) for up to 6 h. At lower TBTO concentrations (0.1 and 1 microM) vital staining showed that only marginal loss of viability occurred, although morphological studies demonstrated increased numbers of cells with abnormal features indicative of programmed cell death (apoptosis). These changes included nuclear chromatin condensation (which was associated with increased DNA fragmentation), cytoplasmic contraction and formation of membrane bound apoptotic bodies. When visualised by agarose gel electrophoresis, genomic DNA appeared as a series of fragments with a repeat multiple of 180-200 base pairs. Comparable morphological changes and cleavage of DNA into oligonucleosomal fragments were evident in thymocytes incubated with 10 microM methyl prednisolone hemisuccinate (MPS); a glucocorticoid hormone known to induce programmed cell death in thymocytes. Marked cytotoxicity associated with degenerative changes indicative of necrosis was observed in thymocytes incubated with 5 microM TBTO. These findings indicate that, at levels which are not overtly cytotoxic, TBTO is capable of inducing programmed cell death in rat thymocytes. This suggests a possible mechanism for the T-cell immunodeficiency previously reported for TBTO in vivo.