Vascular access in haemodialysis patients: a modifiable risk factor for bacteraemia and death

BACKGROUND

Bacteraemia and the development of sepsis syndrome is second only to cardiovascular disease as the leading cause of death in patients on renal replacement therapy.

AIM

To determine the contributions of laboratory and clinical variables to the risk of bacteraemia and death in haemodialysis patients.

DESIGN

Retrospective analysis.

METHODS

We analysed all patients receiving haemodialysis in our renal unit at the beginning of January 2004 (n=263), recording clinical and laboratory variables for each patient at study entry. Bacteraemia and mortality were recorded for the subsequent 18-month period. Multivariate analysis using a Cox proportional hazards model was used to test for independent associations between variables and outcomes.

RESULTS

During the study period, 45 patients (17.1%) developed bacteraemia and 65 (24.7%) died. Under multivariate analysis, use of dialysis catheters at study entry was a major factor in the development of bacteraemia and death with hazard ratios (HR) of 5.4 (p<0.001) and 2.8 (p=0.012), respectively, for tunnelled central venous catheters vs. arteriovenous fistulas (AVFs) and 3.1 (p=0.01) and 3.4 (p=0.001), respectively, for non-tunnelled central venous catheters vs. AVFs. Elevated CRP at study entry was independently associated with bacteraemia (HR 1.5 per unit log-CRP, p=0.006). Low serum albumin (HR 0.92, p=0.005) was independently associated with death.

DISCUSSION

Use of synthetic vascular access catheters and heightened inflammatory state both have strong independent associations with subsequent bacteraemia and death. Bacteraemia surveillance strategies should be developed, with consideration of vascular access type and baseline inflammatory state as key components.

Treatment and outcome of adult patients with primary focal segmental glomerulosclerosis in five UK renal units

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is the least studied of the causes of idiopathic nephrotic syndrome, and there are few specific guidelines for treatment.

AIM

To review data from five UK renal units to investigate whether adult patients with FSGS were treated uniformly, and to examine the effect of treatment on proteinuria and survival.

DESIGN

Retrospective record review.

METHODS

We examined electronic records of patients with idiopathic FSGS for information on baseline clinical parameters, treatment regimens and outcomes.

RESULTS

Of 136 patients with primary FSGS and nephrotic range proteinuria, 76 (56%) were treated with prednisolone and of this group, 59% were treated with additional immunosuppression. Among the treated patients, the total remission rate (complete and partial) was 67%, and one hospital achieved a remission rate of 80%. Treated patients had a significantly higher remission rate than those who were not treated. Remission was associated with a 5-year survival off dialysis of 94%, compared with 53% if remission was not achieved. Baseline serum creatinine and remission were independently associated with survival off dialysis in a multivariate Cox proportional hazards model.

DISCUSSION

Patients with primary FSGS and nephrotic range proteinuria, who are treated with corticosteroids, are more likely to enter remission than those who are not treated. Remission rates of up to 80% can be achieved with prolonged treatment, and remission is an independent predictor of survival off dialysis. Patients who do not achieve remission have a poor prognosis. Further clarification of optimal treatment regimens requires additional, prospective studies.

Growth, photosynthetic performance and shade adaptation of rubber (Hevea brasiliensis) grown in natural shade

We compared growth, photosynthetic performance and shade adaptation of rubber (Hevea brasiliensis Muell. Arg.) plants growing in natural shade (33, 55 and 77% reduction in incoming radiation) to control plants growing in full sunlight. Stem diameter and plant height, measured over a 15-month period, were greatest in plants grown in full sunlight, and both parameters decreased with increasing shade. At 7 and 14 months after planting (MAP), total plant dry mass was highest in control plants and lowest in plants in 77% shade. Expansion of the fourth leaf whorl, monitored at 5-6 MAP, was slowest in plants in 77% shade and fastest in unshaded plants, which had more leaves and higher leaf areas and inter-whorl shoot lengths. In response to increasing shade, specific leaf area increased, whereas leaf weight ratio and relative growth rate decreased. Chlorophyll a/b ratio decreased with increasing shade, indicating shade-induced partitioning of chlorophyll into light-harvesting complexes. Compared to the response in unshaded plants, CO2 assimilation saturated at lower photosynthetic photon flux densities in plants in 77% shade, with a lower upper-asymptote to the light response curve. Chlorophyll fluorescence revealed no evidence of sustained photoinhibitory damage in unshaded plants. Dynamic photoinhibition decreased with increasing shade, with the greatest depression in the ratio of variable to maximal fluorescence around midday. We conclude that shade adaptation and shade-induced reductions in dynamic photoinhibition account for the enhanced early growth of rubber in light shade.

Serum creatinine can predict adequacy of peritoneal dialysis--preliminary report

AIM

To determine the value of creatinine clearance, estimated using the Cockcroft and Gault formula, in assessing adequacy of peritoneal dialysis.

METHODS

We undertook a retrospective analysis of creatinine clearance results derived from a conventional 24-hour collection in 35 stable outpatients on peritoneal dialysis and compared them with those calculated from the corresponding serum creatinine using the Cockcroft and Gault formula.

RESULTS

There was a strong correlation between the 2 methods (r = 0.82, p < 0.0001), although the formula tended to over-estimate clearances. The formula had a positive predictive value of 88% and a negative predictive value of 86% for detecting inadequate dialysis.

CONCLUSION

The creatinine clearance calculated using the Cockcroft and Gault formula can be used in patients on peritoneal dialysis to estimate adequacy of dialysis. We believe that this method, which is far less expensive and time-consuming, deserves further testing in a larger population in order to define more accurately its role in the management of PD patients.

Architectural and physiological heterogeneity within the synflorescence of the pseudoviviparous grass Poa alpina var. vivipara L

Many biotypes of the northern-hemisphere Arctic-Alpine grass Poa alpina L. reproduce asexually via prolification of the spikelet axis to produce dehiscing shoots. Although capable of photosynthesis, the source-sink characteristics of these synflorescence systems are unknown, including the degree to which plantlets from different regions of the synflorescence are capable of providing for their own carbon requirements, or contributing to other sinks. Photosynthetic rates within the paracladial zone, as determined by infrared gas analysis (IRGA), exceeded respiratory rates by 3-4-fold. (14)CO(2) tracer studies determined that the paracladial zone was not only as efficient at fixing carbon as the youngest fully expanded leaf (per unit dry weight), but that both organs exported carbon mainly basipetally (cf. extensive acropetal export from this leaf in seminiferous grasses). Distal plantlets of the paracladial zone fixed approximately 20% more (14)CO(2) than did proximal plantlets. This was by virtue of their greater dry weight. At dehiscence, 'distal' plantlets were more likely to become established, and possessed relative growth rates more than 10 times those of 'proximal' plantlets. Paracladial heterogeneity was also apparent as an increased proportion of aborted spikelets on proximal paracladia. The possible causes of this heterogeneity are discussed.

The influence of secondary senescence processes within the culm of a pseudoviviparous grass (Poa alpina var. vivipara L.) on the supply of water to propagules

An anatomical investigation of the culm of pseudoviviparous alpine meadow grass (Poa alpina var. vivipara L.) revealed that transpiration flow, as delimited by Lucifer Yellow tracer dye, was maintained despite advanced senescence (as evidenced by loss of chlorophyll and chloroplasts), with leafy spikelets driving transpiration flow. Transpiration flow was not hindered by cavitation or tylosis in older culms, the low frequencies of these senescence processes being bypassed via nodal plexi. Despite this, water content of plantlets declined over time and water stress became apparent, suggesting that water supply via the determinate culm was not sufficient for the increasing transpirational demand of indeterminate plantlets. The implications of declining water content on the biomechanical properties of the culm, and concomitant limitations on the pseudoviviparous reproductive strategy, are discussed. Nomenclature of grass follows Hubbard.

Effects of elevated CO2 and temperature on growth and allometry of five native fast-growing annual species

Whereas much is known of the short-term growth response to elevated atmospheric CO₂ concentrations, [CO₂ ]_elev , there is relatively little information on how the response of native species is modified by temperature, despite the fact that an increase in global mean temperature is expected to accompany the rise in [CO₂ ]. In this study, five functionally related annual native species were exposed to different combinations of ambient and elevated [CO₂ ] and temperatures in order to assess their response in terms of growth and allometry. Fast-growing annuals were selected for the study because their growth responses could be assessed over a major portion of the plant's life cycle and in as short a period as 8 wk. Plants were grown in eight hemi-spherical glasshouses, programmed to track outside ambient conditions and provide a replicated experimental design. Treatments comprised (i) current ambient [CO₂ ] and temperature, (ii) elevated [CO₂ ] (ambient+34 kPa), and ambient temperature (iii) ambient [CO₂ ] and elevated temperature (ambient+3°C) and (iv) elevated [CO₂ ] and elevated temperature (T°C_elev ). All five species responded positively to [CO₂ ]_elev , although the response was statistically significant for only one, Poa annua L. Averaged over all five species, [CO₂ ]_elev increased total plant biomass by 25% (P=0·005) at 56 d, reflecting a proportionally greater increase in leaf and stem mass relative to root weight. Elevated [CO₂ ] had no effect on leaf area, either at the individual species level or overall. Elevated T°C, by contrast, had little effect on shoot growth but increased root mass on average by 43% and leaf area by 22%. Few interactions between elevated [CO₂ ] and T°C were observed, with the CO₂ response generally greater at elevated than ambient T°C. Both [CO₂ ]_elev and T°C_elev resulted in a transient increase in relative growth rate, (rgr), during the first 14 d exposure and a 3°C increase in temperature had no effect on the duration of the response. CO₂ stimulation of growth operated through a sustained increase in net assimilation rate. (nar), although the potential benefit to rgr was offset by a concurrent decline in leaf area ratio (lar), as a result of a decrease in leaf area per unit leaf mass (sla). The response to T°C_elev was generally opposite of that to [CO₂ ]_elev . For example, T°C_elev increased lar through an increase in sla and this, rather than any effect on nar, was the major factor responsible for the stimulation of rgr. Allometric analysis of CO₂ effects revealed that changes in allocation observed at individual harvests were due solely to changes associated with plant size. Elevated T°C, by contrast, had a direct effect on allocation patterns to leaves, with an increase in leaf area expansion relative to whole plant mass during the initial stages of growth and subsequent increased allocation of biomass away from leaves to other regions of the plant. No change in the allometric relation between roots and shoots were observed at either elevated [CO₂ ] or T°C. We conclude, therefore, that allocation of biomass and morphological characteristics such as sla, are relatively insensitive to [CO₂ ], at least when analysed at the whole-plant level, and where changes have been observed, these are the product of comparing plants of the same age but different size.

Immunosuppression and outcome in idiopathic membranous nephropathy

From 1986 to 1996, 53 patients with idiopathic membranous nephropathy (IMN) presented to the Glasgow Royal Infirmary renal unit: 19 (36%) were treated because of progressive disease. We compared outcomes of treated and untreated patients with 37 historical and untreated controls. Five- and 10-year survival rates off dialysis were 83.5 and 53.5%, respectively. At the end of a mean observation period of 5.9 years, 47% of patients were in remission, 13% had reached end-stage renal failure, 15% had died, 13% had persistent proteinuria but stable renal function, and 11% had declining renal function. These results are better than those in historical controls, with a reduction in the number of patients reaching ESRF (13% vs. 22%), a larger proportion of patients achieving remission (47% vs. 30%) and smaller numbers of patients with declining renal function (11% vs. 19%) at the end of a similar follow-up period. These data suggest that the use of immunosuppression in selected patients with IMN improves prognosis, although the results did not achieve statistical significance.

Changes in the photosynthetic light response curve during leaf development of field grown maize with implications for modelling canopy photosynthesis

Changes in the photosynthetic light-response curve during leaf development were determined for the fourth leaf of maize crops sown on 23 April and 10 June. Temperatures were unusually mild during late spring/early summer and neither crop experienced chilling damage. The concept of thermal time was used to take into account the effects of different temperature regimes on developmental stage, thereby enabling photosynthetic light-response data to be combined for both crops to describe the general response. Large variations in the upper asymptote (Asat) and convexity (Θ) of the light-response curve occurred during leaf development, but the maximum quantum yield of CO2 assimilation remained relatively constant throughout. Dark respiration rates showed a small but significant decrease with leaf age and generally ranged between 5 and 10% of Asat. A simple mathematical model was developed to assess the sensitivity of daily leaf photosynthesis (AL) to reductions in the Asat, Θ and the initial slope (Φ) of the light-response curve at different stages of leaf development. On bright sunny days, and at all developmental stages, AL was ca. twice as sensitive to reductions in Asat than to reductions in Φ and Θ. In overcast conditions, however, all three parameters contributed significantly to reductions in leaf photosynthesis, although the contribution of Φ was greatest during early leaf growth, while older leaves were most sensitive to depressions in Asat. The implications of these results for modelling the sensitivity of canopy photosynthesis to chill-induced photoinhibition of the light-response curve are discussed.

Chilling and photosynthetic productivity of field grown maize (Zea mays); changes in the parameters of the light-response curve, canopy leaf CO2 assimilation rate and crop radiation-use efficiency

The effect of growth temperatures on the photosynthetic performance of field grown maize (Zea mays cv. LG11) was examined for crops sown on 1 May and 28 June 1991. During the period of growth, 2 May to 10 August, the early-sown crop experienced temperatures below 10 °C on 33 occasions compared with only one for the crop sown on 28 June. The prolonged period of low temperatures throughout May and beginning of June were associated with a marked depression in CO2 assimilation rates at all light levels in the early-sown treatment. Chill-induced depression of the photosynthetic light-response curve reflected a sustained reduction in canopy leaf photosynthesis and crop radiation-use efficiency (RUE). During the early stages of growth, RUE was 65% lower in the early- than late-sown treatment, with no marked recovery observed in the former treatment until approximately three weeks after chilling conditions had ceased. Data show a close correlation between chill-induced depression of quantum yield (Φ) and RUE, with corresponding reductions in the light-saturated rates of CO2 assimilation (Pmax). The convexity of the light-response curve recovered most rapidly from chilling temperatures, and at least three weeks before any improvement in RUE. It is concluded that photosynthetic productivity of immature maize stands is less sensitive to changes in the convexity of the light response, than to changes in either Φ or Pmax.

The effect of timing of shade on development, dry matter production and light-use efficiency in groundnut (Arachis hypogaea L.) under field conditions

During the rainy season in India, bamboo screens intercepting approximately 46% of the incident light were used to simulate the effect of shading by a cereal grown as an intercrop with groundnut (Arachis hypogaea L.). The treatments comprised an unshaded control and two durations of shading extending from peg initiation (T1) and the onset of pod filling (T2) to final harvest. Plant height was greatest in the T1 crop, but the maximum rates of leaf development on the main stem, leaf area expansion and pod production were similar in all crops. Shading appeared to reduce the rate of the linear growth phase because the reduced light interception was not entirely offset by an increase in light-use efficiency. Premature senescence in the shaded crops coincided with the virtual cessation of pod production, although continued allocation of dry matter to reproductive structures in the T1 crop resulted in a greater proportion of pods being filled at final harvest than in the other treatments. The responses of groundnut to timing of shade are discussed in terms of their implications for the selection of improved crop combinations for intercropping.