An unusual case of severe high anion gap metabolic acidosis

We present a case of high anion gap metabolic acidosis with an unusual aetiology in a 75-year-old lady with hypoglycaemia, encephalopathy and relatively preserved renal function. Full toxicology and biochemical analysis suggested that she had an inborn error of metabolism, riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency that can predispose to severe acidosis in situations where calorific intake is reduced. We believe this to be one of the few published cases and is remarkable for the presentation in late adulthood in addition to the requirement for emergency haemodialysis due to the severity of the metabolic disturbance.

Tissue-advanced glycation end product concentration in dialysis patients

BACKGROUND AND OBJECTIVES

Tissue-advanced glycation end products (AGE) are a measure of cumulative metabolic stress. Assessment of tissue AGE by skin autofluoresence (AF) correlates well with cardiovascular outcomes in hemodialysis (HD) patients. This study aimed to measure and compare tissue AGE levels in HD and peritoneal dialysis (PD) patients and to evaluate the impact of systemic PD glucose exposure.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Tissue AGE were measured in 115 established dialysis patients (62 HD and 53 PD) using a cutaneous AF device (AGE Reader; DiagnOptics). Values were compared with an age-matched non-chronic kidney disease database. Review of all previous PD solution delivery/prescription data determined PD glucose exposure.

RESULTS

PD patients were similar in age to HD patients but had a shorter dialysis vintage. There were no differences in ischemic heart disease or smoking history, statin or angiotensin-converting enzyme inhibitor (ACEi) use, lipids, biochemistry, or prevalence of diabetes. More than 90% of both groups had met current dialysis adequacy targets. Skin AF values in PD and HD patients were similar and strongly correlated with historical PD glucose exposure. Skin AF correlated with age in both groups but with dialysis vintage only in PD patients

CONCLUSIONS

Cumulative metabolic stress and transient hyperglycemia results in grossly elevated levels of tissue AGE in dialysis patients. In PD patients, this high level of AGE deposition is associated with historical glucose exposure. This observation provides a previously unappreciated potential link between PD exposure to glucose and systemic cardiovascular disease.

Renal infarction in patients presenting with suspected renal colic

Acute renal infarction is a serious medical emergency. The diagnosis is often delayed or missed as it is not common. Hence, the exact incidence of acute renal infarction is not known. Failure to consider renal infarction in the initial differential diagnosis results in a delay in diagnosis and treatment, which in turn leads to permanent loss of renal function. We present two cases of acute kidney infarction that were initially treated as renal colic. In addition, we present a third case when a kidney was saved with reperfusion therapy.

A meta-analysis of hemodialysis catheter locking solutions in the prevention of catheter-related infection

BACKGROUND

Catheter-related infection (CRI) is associated with increased all-cause mortality and morbidity in hemodialysis patients and may be reduced by using antimicrobial lock solutions (ALSs).

STUDY DESIGN

We performed a meta-analysis of studies identified from a search conducted in February 2007 of the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature, databases of ongoing trials, major renal journals, and reference lists of relevant reports.

SETTING & POPULATION

Patients receiving acute or long-term hemodialysis through a tunneled or nontunneled central venous catheter.

SELECTION CRITERIA FOR STUDIES

We included all prospective randomized studies that compared ALS with heparin.

INTERVENTION

Administration of antibiotic and/or antimicrobial catheter locking solution.

OUTCOME MEASURES

Primary outcome was CRI rate in patients using ALSs compared with those using heparin alone. We also examined effects of ALS use on mortality, adverse events, and catheter thrombosis.

RESULTS

7 studies were identified with a total of 624 patients and 819 catheters (448 tunneled, 371 nontunneled). CRI was 7.72 (95% confidence interval, 5.11 to 10.33) times less likely when using ALS. There were no consistent suggestions of adverse outcomes with ALS use; in particular, rates of catheter thrombosis did not increase. There was no evidence of antibiotic resistance developing during a maximum follow-up of 12 months.

LIMITATIONS

The major limitation of this review is the relatively short duration of follow-up of the included studies, which does not allow complete reassurance regarding the development of antibiotic resistance. Lack of direct comparisons means that determination of the most efficient ALS is not possible.

CONCLUSIONS

This review confirms that antibiotic locking solutions reduce the frequency of CRI without significant side effects.

Progressive vascular calcification over 2 years is associated with arterial stiffening and increased mortality in patients with stages 4 and 5 chronic kidney disease

BACKGROUND AND OBJECTIVES

Vascular calcification is increasingly recognized as an important component of cardiovascular disease in chronic kidney disease. The objective of this study was to investigate prospectively the determinants, cardiovascular functional consequences, and survival associated with vascular calcification over 24 mo.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 134 patients (60 on hemodialysis, 28 on peritoneal dialysis, and 46 with stage 4 chronic kidney disease) were studied. Vascular calcification of the superficial femoral artery was assessed using multislice spiral computed tomography; pulse wave velocity; all medications and time-averaged biochemical parameters were recorded at baseline and 12 and 24 mo.

RESULTS

A total of 101 patients remained at 24 mo. Progressive calcification was seen in 58 of 101 patients. Most (31 of 46) patients with an initial calcification score of zero did not develop calcification. The hemodialysis group demonstrated a greater degree of progression than patients who were on peritoneal dialysis or had stage 4 chronic kidney disease. Progressive calcification was associated with age, male gender, serum alkaline phosphatase, beta blockers, and lipid-lowering agents. Increases in vascular calcification correlated with increased arterial stiffness. Vascular calcification was present in 20 of 21 patients who died. Cox proportional hazard analysis identified change in calcification score, calcium intake from phosphate binders, and low albumin as risk factors for death.

CONCLUSIONS

Patients with stages 4 and 5 chronic kidney disease and preexisting vascular calcification exhibit significantly increased calcification over 24 mo. Rapid progression of calcification is associated with arterial stiffness and mortality.

Comparison of Progressive Conductivity Reduction with Diacontrol and Standard Dialysis

We examined whether progressive reduction of dialysate sodium with Diacontrol (DC, plasma conductivity targeted feedback system) confers any clinical benefit over a similar strategy using dialysis with fixed dialysate conductivity (HD). Ten stable patients entered a randomized crossover study conducted over 360 dialysis sessions. Sodium balance, blood pressure (BP), intradialytic hypotension rates (IDH), thirst score, and extracellular water (ECW) were recorded. Interdialytic ambulatory BP was measured at the highest and lowest conductivities. BP, interdialytic weight gains and thirst scores were low at the outset and were not altered significantly by conductivity reduction. The lowest fixed dialysate setting of 13.2 mS/cm resulted in greater sodium depuration than the lowest conductivity setting allowable with DC, as reflected by lower post dialysis plasma conductivity (13.4 +/- 0.14 mS/cm versus 13.5 +/- 0.04 mS/cm, p < 0.001). Predialysis ECW fell from 0.22 +/- 0.04 l/kg to 0.21 +/- 0.09 l/kg as conductivity reduced with HD (p < 0.05), but did not change significantly with DC. When HD and DC were matched for end-dialysis plasma conductivity, there were no differences in BP, IDH frequency, or dialysis tolerability even at the lowest conductivity settings. In a setting of dialysate sodium reduction, DC did not appear to have any short-term clinical advantage over standard dialysis, and its range is limited at the lower conductivity settings.

Continuous online monitoring of ionic dialysance allows modification of delivered hemodialysis treatment time

Considerable intrinsic intrapatient variability influences the actual delivery of Kt/V. The aim of this study is to examine the feasibility of using continuous online assessment of ionic dialysance measurements (Kt/V(ID)) to allow dialysis sessions to be altered on an individual basis. Ten well-established chronic hemodialysis (HD) patients without significant residual renal function were studied (mean age 65+/-4.3 [38-81] years, mean length of time on dialysis 66+/-18 [14-189] months). These patients had all been receiving thrice-weekly 4-hr dialysis using Integra dialysis monitors. Dialysis monitors were equipped with Diascan modules permitting measurement of Kt/V(ID). Predicted treatment time required to achieve a Kt/V(ID) > or = 1.1 (equivalent to a urea-based method of 1.2) was calculated from the delivered Kt/V(ID) at 60 and 120 min. Treatment time was reprogrammed at 2 hr (ensuring all planned ultrafiltration would be accommodated into the new modified session duration). Owing to practical issues, and to avoid excessively short dialysis times, these changes were censored at no more than+/-10% of the usual 240-min treatment time (210-265 min). Data were collected from a total of 50 dialysis sessions. Almost all sessions (47/50) required modification of the standard treatment time: 13/50 sessions were lengthened and 34/50 shortened (mean length of session 232.2+/-2.5 [210-265] min). A Kt/V(ID) of > or = 1.1 was achieved in 39/50 sessions. The difference in mean urea-based Kt/V poststudy (1.3+/-0.05 [1.1-1.6]) and mean achieved Kt/V(ID) (1.16+/-0.02 [0.7-1.37]) was significant (p = 0.002). The use of individualized variable dialysis treatment time using online ionic dialysance measurements of Kt/V(ID) appears both practicable and effective at ensuring consistently delivered adequate dialysis.

Predicting initiation and progression of chronic kidney disease: Developing renal risk scores

Epidemiological studies have raised awareness of the problem of undiagnosed chronic kidney disease (CKD) and suggest that early identification and treatment will reduce the global burden of patients requiring dialysis. This has highlighted the twin problems of how to identify subjects for screening and target intervention to those with CKD most likely to progress to end-stage renal disease. Prospective studies have identified risk factors for CKD in the general population as well as risk factors for progression in patients with established CKD. Risk factors may thus be divided into initiating factors and perpetuating factors, with some overlap between the groups. In this paper, we review current data regarding CKD risk factors and illustrate how each may impact upon the mechanisms underlying CKD progression to accelerate loss of renal function. We propose that these risk factors should be used as a basis for developing a renal risk score, analogous to the Framingham risk score for ischemic heart disease, which will allow accurate determination of renal risk in the general population and among CKD patients.

Automated peritoneal dialysis has significant effects on systemic hemodynamics

OBJECTIVES

Maintenance of residual renal function (RRF) is an important determinant of outcome in peritoneal dialysis patients. It remains contentious as to whether automated peritoneal dialysis (APD) leads to an increased rate of decline of RRF compared with continuous ambulatory peritoneal dialysis (CAPD). We studied whether APD was associated with significant systemic hemodynamic changes that may play a role in the accelerated loss of RRF.

METHODS

As a follow-on from a previous study, 8 well-established CAPD patients underwent a 4-hour APD treatment consisting of 3 drain/fill cycles using 2 x 2.5 L 1.36% glucose and 1 x 3.86% glucose dialysate. Each dwell phase lasted 76 minutes. Blood pressure (BP) and a full range of hemodynamic variables, including pulse (HR), stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR), were measured noninvasively using continuous arterial pulse wave analysis.

RESULTS

BP fell during 2 of the 3 drain/fill periods when dialysate was drained from the peritoneal cavity, but then rose upon instillation of dialysate fluid. The fall in BP was associated with a fall in TPR, matched by an inadequate rise in SV and CO. Over the entire study period, TPR progressively rose to +53.4% above baseline (p = 0.032). Both SV and CO fell over the same period, to -21.1% (p = 0.060) and -22.4% from baseline (p = 0.037) respectively. This did not result in any significant difference between start and end BP.

CONCLUSIONS

This study demonstrates that APD is associated with significant systemic hemodynamic effects. The increased number of drain/fill cycles compared to CAPD, or the progressive rise in TPR and reduction in CO (possibly due to a cooling effect), may potentially be factors that adversely affect RRF in APD patients.

Effects of acetate-free double-chamber hemodiafiltration and standard dialysis on systemic hemodynamics and troponin T levels

Using acetate as a buffer during hemodialysis is recognized to predispose to intradialytic hypotension; however, bicarbonate-based dialysis is not acetate free. Paired hemodiafiltration (PHF) is a novel online acetate-free technique. We investigated whether PHF is capable of abrogating the changes in systemic hemodynamics and troponin T (cTnT) seen with conventional hemodialysis. Twelve patients entered a randomized crossover study. Blood pressure (BP) and a full range of hemodynamic variables were measured throughout PHF and standard dialysis using continuous pulse wave analysis. We also measured predialysis cTnT in 54 stable and unstable dialysis patients. BP was lower during PHF but without increased instability. Stoke volume and cardiac output declined progressively during both treatments but to a much lesser extent during PHF (p = 0.003, p < 0.0001 respectively), whereas peripheral resistance rose to a larger degree during hemodialysis (p < 0.0001). cTnT levels were lower before PHF as compared with hemodialysis (p = 0.023), with levels falling after PHF and rising after hemodialysis (p < 0.0001). In the supplementary patient group, predialysis median serum cTnT was higher in the unstable patients (p = 0.0001). This study demonstrates that PHF (without exposure to acetate) is associated with less deterioration in systemic hemodynamics, maintenance of BP, and less suppression of myocardial contractility as compared with bicarbonate dialysis.

Hypertonic glucose-based peritoneal dialysate is associated with higher blood pressure and adverse haemodynamics as compared with icodextrin

BACKGROUND

Little is known about the haemodynamic effects of continuous ambulatory peritoneal dialysis (CAPD) despite its widespread use in the management of end-stage renal failure. We undertook a study to delineate the haemodynamic effects of CAPD using glucose-containing fluids (1.36 and 3.86% glucose) and icodextrin.

METHODS

Eight CAPD patients were recruited for a prospective crossover study. Patients attended for two investigatory days (in random order). CAPD was carried out using 1.36% followed by 3.86% glucose (buffered with lactate/bicarbonate, Physioneal) on one study day and 1.36% glucose followed by 7.5% icodextrin (Extraneal) on the other day. Dwell times were 150 min. Blood pressure (BP) and a full range of haemodynamic variables including pulse (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were measured non-invasively using continuous arterial pulse wave analysis.

RESULTS

BP was significantly higher during 3.86% glucose dwells as compared with 1.36% glucose or icodextrin dwells (P<0.0001). TPR during all three dwells was similar; the higher blood pressure was due to an increased HR, SV and, therefore, CO during 3.86% glucose dwells. The higher blood pressure during the 3.86% glucose dwells was present despite the highest ultrafiltration volume and sodium removal.

CONCLUSION

This study demonstrates large magnitude haemodynamic changes in response to CAPD. In addition to the well-recognized adverse effects on blood glucose and long-term peritoneal membrane viability, CAPD fluids containing high glucose concentrations may also exert undesirable effects on systemic haemodynamics, with potential long-term consequences for patient outcomes.

Length of interdialytic interval influences serum calcium and phosphorus concentrations

BACKGROUND

Higher levels of serum phosphorus and calcium are associated with increased haemodialysis (HD) patient mortality. Both of these factors act synergistically to promote vascular smooth muscle differentiation to an osteoblast-like phenotype and subsequent vascular calcification. The aim of this study was to investigate the influence of interdialytic interval on serum levels, as well as the influence of oral calcium-based phosphate binder load on the magnitude of the observed differences.

METHODS

We studied 100 patients undergoing HD three times per week, over a 2 week period. Haemoglobin, albumin, calcium and phosphate were measured pre-dialysis before each HD session. Oral phosphate binder usage was recorded. All patients were treated with dialysate containing 1.25 mEq/l calcium.

RESULTS

Both mean serum phosphate and calcium were higher after the long interdialytic interval (1.59+/-0.05 vs 1.45+/-0.04 mmol/l, P = 0.0005, and 2.46+/-0.03 vs 2.4+/-0.02 mmol/l, P = 0.001, for serum phosphate and uncorrected calcium, respectively). There were no significant differences in haemoglobin or serum albumin, indicating that variable dilution from an increased hydration status in the long interdialytic interval was unlikely to contribute to these observed differences. A total of 74 patients were treated with calcium-containing binders and 26 patients with sevelamer. Patients on sevelamer did not exhibit the observed cyclical increase in serum calcium seen in patients on calcium-containing binders (mean difference in serum calcium 0.09+/-0.01 mmol/l in the calcium-treated group vs 0.01+/-0.01 mmol/l in the sevelamer-treated patients, P = 0.0004). The increase in serum calcium after the long interval as compared with the short interval was proportional to the daily amount of the oral calcium-containing binder load ingested (r = 0.63, P<0.0001).

CONCLUSION

Cyclical differences in interdialytic interval and overall exposure to both dietary phosphate and oral calcium load influence serum levels. This may have consequences for registry reporting, therapy modulation and potentially the pathogenesis of accelerated vascular calcification seen in HD patients.

Reduced baroreflex sensitivity is associated with increased vascular calcification and arterial stiffness

INTRODUCTION

Vascular calcification is a critical determinant of cardiovascular morbidity and mortality in chronic haemodialysis (HD) patients. The pathophysiology underlying this observation remains obscure. Baroreceptor sensitivity (BRS) is important in the maintenance of an appropriate cardiovascular status both at rest and under the physiological stress of HD. BRS is determined by both the mechanical properties of the vascular wall, mediating the transfer of transmural pressure, and afferent and efferent autonomic function. We aimed to study the association between arterial structure, function and BRS in chronic HD patients.

METHODS

We studied 40 chronic HD patients mean age 62+/-2 (26-86) years who had received HD for a mean 40+/-4 (9-101) months. Spontaneous BRS was assessed using software studying the relationship between inter-beat variability and beat to beat changes in systolic blood pressure. Functional characteristics of conduit arteries (pulse wave analysis) were studied with applanation tonometry at the radial artery. Arterial calcification was assessed in lower limbs using reconstructed multi-slice computed tomography and quantified with volume-corrected calcification scores within the superficial femoral artery.

RESULTS

Mean BRS was 4.43+/-0.44 ms/mmHg, with a wide range from 1.0 to 11.5 ms/mmHg. This correlated with arterial stiffness as measured by time to shoulder calculated from the central pulse wave analysis (r = 0.4, P = 0.01). BRS was also associated with vascular calcification (P = 0.01) but not by other factors such as dialysis vintage, age or pre-dialysis systolic/diastolic blood pressure.

CONCLUSION

The reduction in BRS and the resulting aberrant blood pressure response to the physiological stress and volume changes of HD may be important in the further understanding of the pathophysiology of the increased mortality in HD patients with vascular calcification.

Online Conductivity Monitoring: Validation and Usefulness in a Clinical Trial of Reduced Dialysate Conductivity

Relatively low dialysate conductivity (Cndi) may improve outcomes by reducing the overall sodium burden in dialysis patients. Excess sodium removal, however, could lead to hemodynamic instability. We performed a randomized controlled trial of reduction of Cndi. For the study, 28 patients were randomized to maintenance of Cndi at 13.6 mS/cm (equivalent to 135 mmol/L of Na+) or serial reduction of Cndi in steps of 0.2 mS/cm, guided by symptoms and blood pressure. Sodium removal estimated from pre- and postplasma concentrations correlated well with removal measured by conductivity monitoring as ionic mass balance (R2 0.66, p < 0.0001). Of the 16 patients randomized to reduction of Cndi, 6 achieved Cndi 13.4 mS/cm, 6 achieved 13.2 mS/cm, and 4 achieved 13.0 mS/cm. No episodes of disequilibrium occurred. Interdialytic weight gain was reduced from 2.34 +/- 0.10 kg to 1.57 +/- 0.11 kg (p < 0.0001). Predialysis systolic blood pressure fell from 144 +/- 3 mm Hg to 137 +/- 4 mm Hg (p < 0.05). The reduction in convective sodium removal was balanced by an increase in diffusive sodium removal (95 +/- 9 mmol cf. 175 +/- 14 mmol, p < 0.0001). Reduction in Cndi monitored by IMB is safe and practical and leads to improved interdialytic weight gains and blood pressure control, while avoiding excessive sodium removal.

Venography at insertion of tunnelled internal jugular vein dialysis catheters reveals significant occult stenosis

BACKGROUND

Tunnelled catheters are widely used to provide vascular access for haemodialysis. Percutaneous insertion of these catheters requires large calibre tissue dilators with the potential to cause trauma to central veins, particularly if anatomical abnormalities are present.

METHODS

We evaluated the use of venography to identify central vein anatomical abnormalities in 69 consecutive patients undergoing percutaneous placement of tunnelled right internal jugular vein catheters. The internal jugular vein was entered under ultrasound guidance and venography was performed prior to insertion of a guide-wire. Images were evaluated on-screen by the operator and a decision made regarding the need for additional fluoroscopy during insertion of the catheter.

RESULTS

In 29 cases (42%), venography showed evidence of unexpected stenosis and/or angulation of the central veins of sufficient severity to warrant additional fluoroscopy during insertion of the dilators, or abandonment of the procedure. Patients who had previously had tunnelled internal jugular catheters had more than double the incidence of such abnormalities than those who had not [15/23 (65%) vs 14/46 (30%); P = 0.009]. In two patients the procedure was abandoned due to severe stenosis. No patient suffered central vein trauma or pneumothorax. There were no adverse reactions to contrast injection.

CONCLUSIONS

Venography performed immediately prior to tunnelled internal jugular dialysis catheter insertion detects unexpected, clinically significant anatomical abnormalities of the central veins in a substantial proportion of patients, particularly those with a history of previous tunnelled catheter insertion. We suggest that the use of venography may help to minimize the risk of complications from this procedure.

Venography at insertion of tunnelled internal jugular vein dialysis catheters reveals significant occult stenosis

BACKGROUND

Tunnelled catheters are widely used to provide vascular access for haemodialysis. Percutaneous insertion of these catheters requires large calibre tissue dilators with the potential to cause trauma to central veins, particularly if anatomical abnormalities are present.

METHODS

We evaluated the use of venography to identify central vein anatomical abnormalities in 69 consecutive patients undergoing percutaneous placement of tunnelled right internal jugular vein catheters. The internal jugular vein was entered under ultrasound guidance and venography was performed prior to insertion of a guide-wire. Images were evaluated on-screen by the operator and a decision made regarding the need for additional fluoroscopy during insertion of the catheter.

RESULTS

In 29 cases (42%), venography showed evidence of unexpected stenosis and/or angulation of the central veins of sufficient severity to warrant additional fluoroscopy during insertion of the dilators, or abandonment of the procedure. Patients who had previously had tunnelled internal jugular catheters had more than double the incidence of such abnormalities than those who had not [15/23 (65%) vs 14/46 (30%); P = 0.009]. In two patients the procedure was abandoned due to severe stenosis. No patient suffered central vein trauma or pneumothorax. There were no adverse reactions to contrast injection.

CONCLUSIONS

Venography performed immediately prior to tunnelled internal jugular dialysis catheter insertion detects unexpected, clinically significant anatomical abnormalities of the central veins in a substantial proportion of patients, particularly those with a history of previous tunnelled catheter insertion. We suggest that the use of venography may help to minimize the risk of complications from this procedure.

Analysis of factors associated with variability in haemodialysis adequacy

BACKGROUND

Delivered dialysis dose measured as Kt/V is widely accepted as an important factor affecting mortality on haemodialysis. It is currently measured relatively infrequently in most units for pragmatic reasons. We have previously shown that significant variation occurs within individuals which often makes the difference between dialysis that would be considered adequate, and inadequate. The aim of this study is to delineate which factors are responsible for the observed variation.

METHODS

We studied 1109 treatments in 109 patients, mean age 59.9 years, mean dry weight 71.8 kg. Depurated volume (Kt) was measured by ionic dialysance for each treatment. Kt and other relevant treatment-related variables were automatically recorded on a central server. Multivariate analysis using mixed models with backwards elimination was used to analyse the determinants of Kt. Kt/V was not used, in order to avoid introducing error in the determination of V.

RESULTS

The analysis indicated that the following were independent determinants of Kt: blood pump speed, time, minimum and mean arterial line pressure, both maximum and minimum venous line pressures and total ionic mass balance.

CONCLUSION

This analysis suggests that the variation in adequacy that occurs within an individual is multifactorial. It confirms the importance of effective vascular access, prescription of and adherence to adequate time on dialysis, and reinforces the impact of degree of sodium removal. In clinical practice absolute control of these variables is not possible in every dialysis session and some degree of variability in Kt is therefore inevitable. Monitoring of adequacy thus requires more frequent assessment of Kt than is currently performed. Online monitoring of ionic dialysance achieves this.

Slowing the Progression of Adult Chronic Kidney Disease

When kidney disease of any aetiology results in substantial loss of nephrons, a common clinical syndrome, characterised by hypertension, proteinuria and a progressive decline in renal function, ensues. This observation suggests that common mechanisms may contribute to progressive renal injury and that therapeutic interventions that inhibit these common pathways may afford renal protection. Research to date has identified several mechanisms that may contribute to progressive renal injury including glomerular haemodynamic changes, multiple effects of angiotensin II and detrimental effects of excessive filtration of plasma proteins by injured glomeruli. Clinical trials over the past decade have identified several interventions that are effective in slowing the rate of progression of chronic kidney disease (CKD). The use of ACE inhibitors, angiotensin receptor antagonists or a combination of the two should be regarded as fundamental to any therapy for slowing the rate of CKD progression. Hypertension should be treated aggressively to achieve a blood pressure target of < 130/80 mm Hg. Reduction of proteinuria to < 0.5 g/day should be regarded as an independent therapeutic goal. Although inconclusive, there is some evidence to support moderate dietary protein restriction to 0.6 g/kg/day in appropriate patients. Hyperlipidaemia may contribute to CKD progression and should be treated to reduce cardiovascular risk and potentially improve renal protection. Smoking cessation should be encouraged and, where necessary, assisted. Among diabetic patients tight glycaemic control should be achieved (glycosylated haemoglobin < 7%). These interventions are simple and relatively inexpensive. If applied to all patients with CKD they will result in substantial slowing of renal function decline in many patients and thereby reduce the number who progress to end-stage renal disease and require renal replacement therapy.

Assessment of haemodialysis adequacy by ionic dialysance: intra-patient variability of delivered treatment

INTRODUCTION

Adequate delivered dose of solute removal (as assessed by urea reduction and calculation of Kt/V) is an important determinant of clinical outcome in chronic haemodialysis (HD) patients. The requirement for multiple blood sampling and efforts taken to minimize the effects of rebound on post-treatment samples ensure Kt/V is measured only intermittently. On-line conductivity monitoring (using sodium flux as a surrogate for urea) allows the repeated non-invasive measurement of Kt/V on each HD treatment. We have studied the accuracy of this method of measuring Kt/V, and the variability of treatment dose delivered to individual patients.

METHODS

We prospectively studied 26 established chronic HD patients over 4 weeks (316 treatments). Patients were dialysed using Hospal Integra dialysis monitors, equipped with Diascan modules to measure Kt/V. Data were downloaded automatically to a central computer server. Urea reduction was measured (once a week) by a two-pool calculation using 30 min post-treatment sampling.

RESULTS

Treatment time, Q(B) and modality were fully delivered in all treatments analysed (97% of total). Kt/V measured by ionic dialysance (Kt/V(ID)) correlated highly with that derived from measurement of urea reduction (R(2)=0.92, P<0.0001). Kt/V(ID) underestimated urea-based Kt/V by a mean of only 1.5% (95% CI 0.18-2.9%). Kt/V(ID) varied greatly within individual patients with a mean CV of 0.13+/-0.10 (95% CI 0.05-0.3). If a Kt/V(ID) of 1.0 is considered 'adequate', 55% of the patients had variations that would have potentially altered their status as being adequately or inadequately dialysed, as the range of Kt/V readings cross that point during the study period.

CONCLUSION

In conclusion, Kt/V(ID) seems to be an accurate and readily obtained measure of adequacy. Substantial variation in Kt/V implies repeated measures (ideally for all treatments) are necessary to gain a true picture of the mean treatment dose being delivered to patients.