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Stewart H Lambie

Publications and source records attributed to Stewart H Lambie.

10 recordsLinked to original sources
PubMed2006

Occurrence of regional left ventricular dysfunction in patients undergoing standard and biofeedback dialysis.

BACKGROUND: Cardiac failure and cardiovascular death are extremely prevalent in dialysis patients. Recurrent subclinical myocardial ischemia is important in the genesis of heart failure in nondialysis patients. We examined whether this phenomenon occurs in response to the stress of hemodialysis (HD). METHODS: Eight patients prone to intradialytic hypotension were recruited for a randomized crossover study to compare the development of left ventricular regional wall motion abnormalities during standard (HD) and biofeedback dialysis. Patients underwent serial echocardiography with quantitative analysis to assess ejection fraction and regional left ventricular systolic function during both types of dialysis. Blood pressure and hemodynamic variables also were measured by using continuous pulse wave analysis. RESULTS: Forty-two new regional wall motion abnormalities developed in all 8 patients during HD compared with 23 regional wall motion abnormalities that developed in 7 patients during biofeedback dialysis (odds ratio, 1.8; 95% confidence interval, 1.1 to 3.0). The majority of regional wall motion abnormalities showed improvement in function by 30 minutes postdialysis. Overall mean regional function was significantly more impaired during HD (P = 0.022). At peak stress, ejection fraction (measured by percentage of change from baseline) was significantly lower during HD (P = 0.043). Blood pressure was higher during biofeedback dialysis, with significantly fewer episodes of hypotension (odds ratio, 2.0; 95% confidence interval, 1.01 to 4.4). Significantly smaller decreases in stroke volume and cardiac output and a greater increment in pulse rate were observed during biofeedback dialysis. CONCLUSION: This study shows that reversible left ventricular wall motion abnormalities develop during dialysis with ultrafiltration. We also show that this phenomenon can be ameliorated by the improved hemodynamic stability of biofeedback dialysis and therefore is a potential target for intervention.

Aged↗
PubMed2006

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.

Adult↗
PubMed2005

Online measurement of haemoglobin concentration.

BACKGROUND: Regular monitoring of haemoglobin in chronic haemodialysis patients is essential to ensure that targets for anaemia management are consistently achieved. Repeated blood sampling can be time consuming, invasive and, for pragmatic reasons, only infrequently performed, often delaying therapeutic change. On-line optical continuous monitoring of the haemoglobin concentration would allow non-invasive assessment of haemoglobin, and immediate therapeutic changes could be implemented, thereby improving the efficiency of anaemia management. This study aimed to evaluate the use of on-line haemoglobin concentration measurement. METHODS: Eleven dialysis monitors (Integra Hospal) were calibrated using at least five haemoglobin samples spread over at least 4 g/dl. Optical measurement of haemoglobin concentration is already incorporated into the dialysis monitor to allow the study of relative blood volume. Fifteen patients were studied with paired haemoglobin measurements (i.e. dialysis monitor value and conventional laboratory assessment) taken at intervals over 7 months (mean 11.0+/-0.28 g/dl, range 7.5-14.8). RESULTS: Haemoglobin measured by Hemoscan correlated well with the laboratory measurements (r2 = 0.83, P<0.0001), indicating that the machine values are broadly comparable with laboratory figures. There was a mean underestimate of haemoglobin by Hemoscan of 0.34%. There was no significant deterioration in the quality of this correlation over the study period (r2>0.8). CONCLUSION: The ability of the dialysis monitor to measure the optical concentration of haemoglobin compared with conventional laboratory assessment is both precise and accurate. Regular on-line assessment of haemoglobin may allow more proactive micromanagement of renal anaemia, with a reduction in the time taken to achieve clinically important targets and give early warning of suboptimal response to treatment.

Aged↗
PubMed2004

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↗
PubMed2003

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↗
PubMed2003

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↗
PubMedDate not supplied

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↗