Obstructive uropathy associated with endovascular repair of an inflammatory abdominal aortic aneurysm.
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Biomedical subjects
Christopher W McIntyre
Publications and source records attributed to Christopher W McIntyre.
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.
Adult↗
Imaging and assessment of vascular calcification in chronic kidney disease patients.
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Arteries↗
Locking of tunneled hemodialysis catheters with gentamicin and heparin.
INTRODUCTION: Catheter-related infection (CRI) is a major cause of morbidity and mortality in patients receiving hemodialysis. Antibiotic locking of these catheters has been shown to increase both the success of systemic antibiotic treatment in line sepsis, and to reduce the incidence of sepsis. We have studied the use of gentamicin locking of catheters (in combination with standard heparin rather than previously reported citrate) to reduce CRI rates. Furthermore, we have investigated the effects of this strategy on epoetin requirements and vascular access function. METHODS: Fifty patients were studied. Patients were randomized to catheter-restricted filling with either standard heparin (5000 IU/mL) alone, or gentamicin and heparin (5 mg/mL). Epoetin requirements and hemoglobin response were monitored over the study period. RESULTS: The gentamicin-locked group suffered only one infective episode (0.3/1000 catheter days) compared to 10 episodes in six patients in the heparin alone group (4/1000 catheter days, P= 0.02). The isolated organisms were equally split between Staphylococcal species and coliforms. There were no statistically significant differences in delivered dialysis dose (Kt/V) or QA between the two groups. Use of antibiotic locking was associated with both a higher mean hemoglobin (10.1 +/-0.14 g/dL vs. 9.2 +/- 0.17 g/dL in the heparin group, P= 0.003) and a lower mean epoetin dose (9000 +/- 734 IU/week vs. 10790 +/-615 IU/week in the heparin group, P= 0.04). CONCLUSION: The practice of locking newly inserted tunneled central venous catheters with gentamicin and heparin is an effective strategy to reduce line sepsis rates, and is associated with beneficial effects on epoetin requirements.
Adult↗
Glycemic control in diabetic CAPD patients assessed by continuous glucose monitoring system (CGMS).
INTRODUCTION: From 20% to 40% of all patients commencing dialysis are diabetic. The quality of glycemic control is an important determinant of outcome. The aims of this study were to investigate the use of the continuous glucose monitoring system (CGMS) to assess overall 24-hour glycemic control and the effects of both nonglucose containing and more biocompatible alternative peritoneal dialysis solutions in insulin-treated continuous ambulatory peritoneal dialysis (CAPD) patients. METHODS: We studied 8 insulin treated diabetic CAPD patients. A CGMS probe was inserted [allowing automatic measurement of interstitial fluid (ISF) glucose every 5 minutes, for a 72-hour period]. The patients were then allowed home with CGMS monitoring to assess the effect on glycemic control of three differing peritoneal dialysis regimes. Phase 1 consisted of three exchanges of 1.36% glucose and one of 3.86% glucose, utilizing a lactate/bicarbonate buffer. Phase 2 was identical but used lactate-buffered fluid alone. Phase 3 utilized a minimally glycemic combination of one amino acid, one icodextrin, and two 1.36% glucose lactate/bicarbonate-containing exchanges. RESULTS: ISF glucose measured by CGMS correlated well with venous glucose measurements (r2 = 0.82, P < 0.0001). There was a statistically significant difference in the mean ISF glucose between all three phases (P < 0.0001). The variation in glycemic control was tighter during phase 3 [mean coefficient of variation (CV) 0.21 +/- 0.03]. CONCLUSION: CGMS appears to be a clinically useful tool to gain additional insights into the glycemic control of diabetic CAPD patients. More biocompatible and nonglucose-containing dialysis fluids seem to be associated with improvements in glycemic control in this group of patients.
Adult↗
Adherence of tunnelled haemodialysis catheter to superior vena caval stent: successful percutaneous removal.
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Adult↗
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.
Adult↗
Developments in online monitoring of haemodialysis patients: towards global assessment of dialysis adequacy.
PURPOSE OF REVIEW: Online monitoring of haemodialysis provides more detailed and more immediate measurement of parameters currently assessed during haemodialysis. It can also assess novel variables that are not routinely measured and could intensively monitor the haemodynamic response to dialysis. In an era of expanding numbers of increasingly dependent patients on dialysis, the ability to provide intensive and extensive monitoring of haemodialysis is a boon. The technology available to do this is rapidly becoming more sophisticated, more widely available and more diverse than ever before. RECENT FINDINGS: Adequacy of urea removal is of crucial importance to mortality on haemodialysis, and online monitoring of urea removal is now achievable using a number of different methods. Some of these methods also measure sodium flux, allowing precise monitoring of sodium balance. Haemodynamic disturbance can be assessed using relative blood volume monitoring equipment, or more directly with non-invasive pulse-wave analysis giving a continuous blood pressure reading. The attributes of each of the separate technologies involved are examined. SUMMARY: Online monitoring of a variety of pertinent parameters during haemodialysis provides an array of tools that are steadily being incorporated into routine clinical practice. Research is also benefiting from novel insights into the process of haemodialysis provided by this technology.
Forecasting↗
Use of albumin dialysis in the treatment of hepatic and renal dysfunction due to paracetamol intoxication.
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Acetaminophen↗
A prospective study of combination therapy for hyperphosphataemia with calcium-containing phosphate binders and sevelamer in hypercalcaemic haemodialysis patients.
INTRODUCTION: Hyperphosphataemia is predictive of death, in haemodialysis (HD) patients. Sevelamer is a mineral-free phosphate binder not limited by the hypercalcaemia often encountered when utilizing calcium-containing phosphate binders. Highly positive calcium balance is associated with ectopic calcification and potentially accelerated vascular disease. Unfortunately, exclusive use of sevelamer entails a large cost differential, limiting its use in many centres. We report on a strategy of partial replacement of calcium with sevelamer for the management of hyperphosphataemia in hypercalcaemic chronic HD patients. METHODS: We identified 23 HD patients with serum calcium >2.6 mmol/l. Dietary phosphate and calcium intake were assessed and baseline serum calcium, phosphate and 1alpha calcidol and elemental calcium dose recorded. Fifty per cent of this initial calcium dose was exchanged for sevelamer. Vitamin D doses were left unchanged. If serum calcium was still >2.6 mmol/l after 4 weeks a further 50% of calcium was exchanged. If serum phosphate was >2 mmol/l the sevelamer dose was increased by 25%. The patients were followed up for a further 4 weeks. RESULTS: Seven patients complained of gastrointestinal intolerance of sevelamer. Serum calcium fell from a mean value of 2.8+/-0.04 (2.64-3.54) mmol/l to 2.56+/-0.03 (2.4-2.9) mmol/l, P<0.0005. The hypercalcaemic percentage of patients fell from 100 to 26%. Mean serum phosphate was not significantly changed, 1.59+/-0.1 (0.57-2.6) mmol/l to 1.63+/-0.11 (0.55-2.68) mmol/l, 17-22% of patients having serum phosphate >2 mmol/l. Serum intact parathyroid hormone increased from 166+/-47 (12-933) ng/l to 276+/-104 (20-1013) ng/l, P=0.02. Mean sevelamer dose was 2.77+/-0.36 (0-5.6) g per day. Elemental calcium dose fell from 2.05+/-0.23 (0.5-4.5) g to 1.03+/-0.1 (0.5-2.5) g, P<0.0001. CONCLUSION: A regimen based on the combination of sevelamer and calcium is capable of effectively managing hyperphosphataemia, without hypercalcaemia, in the majority of hypercalcaemic HD patients. Such a minimally calcaemic approach might reduce the financial burden of sevelamer therapy, and enable a wider range of patients to be treated.
Calcium↗
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.
Blood Pressure↗
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.
Acetates↗
Bimodal dialysis: an integrated approach to renal replacement therapy.
BACKGROUND: Peritoneal dialysis (PD) and hemodialysis (HD) are both widely used as sole therapies for end-stage renal disease (ESRD). There is still controversy over which (if either) is superior in terms of patient outcomes. Peritoneal dialysis offers the advantages of long, slow, continuous ultrafiltration and potentially enhanced protection of residual renal function (RRF). In contrast, HD offers superior solute removal at the cost of undesirable cardiovascular tolerance of high rates of sodium and water removal. The aim of this study was to investigate the clinical feasibility of offering a combined treatment of both modalities [bimodal dialysis (BMD)] to incident patients reaching ESRD. We set out to investigate if it might be possible to utilize the intrinsic advantages of both modalities within a setting of good patient acceptability. METHODS: We prospectively studied 8 patients. They were recruited in the pre-ESRD phase from a specialist low clearance clinic. An arteriovenous fistula was formed and peritoneal catheters were inserted. The BMD consisted of 2, 3-hour, high efficiency, euvolemic HD sessions per week in combination with 2 PD exchanges per day to provide a degree of solute clearance and all of the ultrafiltration. Adequacy was measured independently for each modality. Patients were followed using the standard range of evaluations in addition to RRF (by creatinine clearance and EDTA clearance), echocardiography (left ventricular mass and ventricular performance), treatment outcomes, patient symptoms, and complications. RESULTS: Mean time on BMD was 346 +/- 74.9 (range 245 - 431) days. Peritonitis rate was 21 months per episode (mean 0.6 +/- 0.9, 0 - 2 episodes per patient). Mean peritoneal ultrafiltration volume was 1.58 +/- 0.32 (1.3 - 2.1) L per day. Delivered Kt/V and weekly PD Kt/V did not change significantly. Patients' RRF was maintained over the study period, as were serum albumin and control of serum phosphorus. Blood pressure was controlled with a reduction in the number of antihypertensive agents. Left ventricular mass index reduced over the treatment period, from a mean of 194 +/- 31.2 (161 - 265) to 156 +/- 21.2 (138 - 189) g/m2 (p = 0.05). Ventricular performance remained unchanged over the study [ejection fraction 50.4 +/- 11.1 (38 - 67) % to 48 +/- 8.0 (48 - 67) %]. Mean time during BMD spent on HD alone was 4.2 +/- 6.9 (0 - 16) days, and on PD alone 9.2 +/- 10.6 (0 - 25) days. CONCLUSION: This study suggests that BMD is a feasible treatment for ESRD. It is associated with adequate solute removal and good hemodynamic/volume control, and allows increased treatment flexibility for coping with complications normally requiring recourse to unplanned HD with temporary central venous access.
Antihypertensive Agents↗
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.
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