Stewart H. Lambie

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.

Myocardial contractile function and intradialytic hypotension

Dialysis‐induced hypotension remains a significant problem in hemodialysis (HD) patients. Numerous factors result in dysregulation of blood pressure control and impaired myocardial reserve in response to HD‐induced cardiovascular stress. Episodic intradialytic hypotension may be involved in the pathogenesis of evolving myocardial injury. We performed an initial pilot investigation of cardiovascular functional response to pharmacological cardiovascular stress in hypotension‐resistant (HR) and hypotension‐prone (HP) HD patients. We studied 10 matched chronic HD patients (5 HP, 5 HR). Dobutamine‐atropine stress (DAS) was performed on a nondialysis short interval day, with noninvasive pulse‐wave analysis using the Finometer® to continuously measure hemodynamic variables. Baroreflex sensitivity was assessed at rest and during DAS. Baseline hemodynamic variables were not significantly different. The groups had differing hemodynamic responses to DAS. The Mean arterial pressure was unchanged in the HR group but decreased in HP patients (−13.6 ± 3.5 mmHg; P<0.001). This was associated with failure to significantly increase cardiac output in the HP group (cf. increase in cardiac output in the HR group of +33.4 ± 6%; P<0.05), and a reduced response in total peripheral resistance (HP −10.3 ± 6.8%, HR −22.7 ± 2.9%, P=NS). Baroreflex sensitivity was not significantly different between groups at baseline or within groups with increasing levels of DAS; however, the mean baroreflex sensitivity was higher in HR cf. HP subjects throughout pharmacological stress (P<0.05). Hypotension‐prone patients appear to have an impaired cardiovascular response to DAS. The most significant abnormality is an impaired myocardial contractile reserve. Early identification of these patients would allow utilization of therapeutic strategies to improve intradialytic tolerability, potentially abrogating aggravation of myocardial injury.

Buttonhole needling of ateriovenous fistulae: a randomized controlled trial.

Buttonhole needling of arteriovenous fistulae (AVFs) was first described 30 years ago, but little evidence has been reported to show how it might differ from the standard rope-ladder technique. We carried out a randomized control trial comparing these two techniques. All suitable patients within the region were considered for recruitment. Patients were then randomized to continue with traditional rope-ladder needling or changed to buttonhole needling. A mean of 13.7 (median, 11) sharp needles were required to create a track. Nine of 22 patients in the buttonhole group reduced or stopped local anesthetic (LA) for needle insertion compared with one of 25 in the traditional group. The diameter of the buttonhole AVFs remained unchanged, whereas the control group increased in size by 30% ± 7% (p < 0.01), equivalent to an absolute increase of 5 mm. There was no difference in bleeding times, but there was a preference for the buttonhole technique with 21 of the 22 patients and 15 of 23 nurses preferring buttonhole needling. Buttonhole needling is preferred by both patients and staff, reduces discomfort during needling and reduces AVF enlargement. There is a low level of complication.

Use of online conductivity monitoring to study sodium mass balance in chronic haemodialysis patients: prospects for treatment individualisation.

Background: Failure to achieve isonatric haemodialysis (HD) drives an expansion of extracellular volume leading to increased interdialytic weight gain (IDWG). This may be a causative factor in the development of HD-induced cardiac injury. We examined total and diffusive sodium mass balance during HD. Methods: 24 chronic HD patients using a fixed 140 mmol/l sodium concentration were studied over 4 weeks. Dialysate and plasma conductivity and ionic mass balance (IMB) were recorded. IMB estimates total ionic transfer across the HD membrane. Results: Mean total IMB was 338 mmol indicating net sodium removal. Intrapatient variability was less than interpatient variability (coefficient of variation = 42 vs. 26%, respectively). The diffusive component of ionic mass balance (IMBdiff) was 97 ± 18 mmol approximating 29% (±22–36) of total sodium removal. IMBdiff also correlated with both plasma conductivity and predialysis plasma sodium (r2 = 0.82 and 0.6, respectively; p < 0.0001) as well as the reduction in plasma conductivity and plasma sodium during HD (r2 = 0.7 and 0.5, respectively; p < 0.0001). Conclusion: HD against a fixed dialysate sodium concentration of 140 mmol/l results in a wide range of sodium removal with a mean of 29% removed by diffusion. Online conductivity monitoring can be utilized as part of a variety of strategies to enable the delivery of individualised and isonatric HD. Further study is required to explore the utility of such strategies which may be crucial in reducing IDWG and HD-induced cardiac injury.

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/VID) 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/VID. Predicted treatment time required to achieve a Kt/VID≥1.1 (equivalent to a urea‐based method of 1.2) was calculated from the delivered Kt/VID 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/VID of ≥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/VID (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/VID appears both practicable and effective at ensuring consistently delivered adequate dialysis.

Czech Society News

Nephrology has a long tradition in the Czech Republic. The first acute dialysis was performed in 1955, a chronic dialysis programme started in the early 60ies, and a transplantation programme in 1966. This was reflected by many important international meetings held in Prague: The 2nd Congress of the International Society of Nephrology (1963), 17th Congress of the European Dialysis and Transplantation Association (1980) and the 15th Congress of the European Society of Artificial Organs (1988). More recently, the 17th and 25th meetings of the International Society of Blood Purification (1999 and 2007), 11th ANCA and Vasculitis Workshop (2003), 7th European Peritoneal Dialysis Meeting (2005), 13th Congress of the European Society of Organ Transplantation (2007) and finally, this year, the 48th Congress of ERA-EDTA.