Sivakumar Sridharan

A self-report comorbidity questionnaire for haemodialysis patients

BackgroundPatients with end-stage renal disease (ESRD) have multiple comorbid conditions. Obtaining comorbidity data from medical records is cumbersome. A self-report comorbidity questionnaire is a useful alternative. Our aim in this study was to examine the predictive value of a self-report comorbidity questionnaire in terms of survival in ESRD patients.MethodsWe studied a prospective cross-sectional cohort of 282 haemodialysis (HD) patients in a single centre. Participants were administered the self-report questionnaire during an HD session. Information on their comorbidities was subsequently obtained from an examination of the patient’s medical records. Levels of agreement between parameters derived from the questionnaire, and from the medical records, were examined. Participants were followed-up for 18 months to collect survival data. The influence on survival of comorbidity scores derived from the self-report data (the Composite Self-report Comorbidity Score [CSCS]) and from medical records data - the Charlson Comorbidity Index [CCI] were compared.ResultsThe level of agreement between the self-report items and those obtained from medical records was almost perfect with respect the presence of diabetes (Kappa score κ 0.97), substantial for heart disease and cancer (κ 0.62 and κ 0.72 respectively), moderate for liver disease (κ 0.51), only fair for lung disease, arthritis, cerebrovascular disease, and depression (κ 0.34, 0.35, 0.34 and 0.29 respectively). The CSCS was strongly predictive of survival in regression models (Nagelkerke R2 value 0.202), with a predictive power similar to that of the CCI (Nagelkerke R2 value 0.211). The influences of these two parameters were additive in the models – suggesting that these parameters make different contributions to the assessment of comorbidity.ConclusionThis self-report comorbidity questionnaire is a viable tool to collect comorbidity data and may have a role in the prediction of short-term survival in patients with end-stage renal disease on haemodialysis. Further work is required in this setting to refine the tool and define its role.

Scaling Hemodialysis Target Dose to Reflect Body Surface Area, Metabolic Activity, and Protein Catabolic Rate: A Prospective, Cross-sectional Study

BACKGROUND Women and small men treated by hemodialysis (HD) have reduced survival. This may be due to use of total-body water (V) as the normalizing factor for dialysis dosing. In this study, we explored the equivalent dialysis dose that would be delivered using alternative scaling parameters matching the current recommended minimum Kt/V target of 1.2. STUDY DESIGN Prospective cross-sectional study. SETTING & PARTICIPANTS 1,500 HD patients on a thrice-weekly schedule, recruited across 5 different centers. PREDICTORS Age, sex, weight, race/ethnicity, comorbid condition level, and employment status. OUTCOMES Kt was estimated by multiplying V by 1.2. Kt/body surface area (BSA), Kt/resting energy expenditure (REE), Kt/total energy expenditure (TEE) and Kt/normalized protein catabolic rate (nPCR) equivalent to a target Kt/V of 1.2 were then estimated by dividing Kt by the respective parameters. MEASUREMENTS Anthropometry, HD adequacy details, and BSA were obtained by standard procedures. REE was estimated using a novel validated equation. TEE was calculated from physical activity data obtained using the Recent Physical Activity Questionnaire. nPCR was estimated using a standard formula. RESULTS Mean BSA was 1.87m2; mean REE, 1,545kcal/d; mean TEE, 1,841kcal/d; and mean nPCR, 1.03g/kg/d. For Kt/V of 1.2, there was a wide range of equivalent doses expressed as Kt/BSA, Kt/REE, Kt/TEE, and Kt/nPCR. The mean equivalent dose was lower in women for all 4 parameters (P<0.001). Small men would also receive lower doses compared with larger men. Younger patients, those with low comorbidity, those employed, and those of South Asian race/ethnicity would receive significantly lower dialysis doses with current practice. LIMITATIONS Cross-sectional study; physical activity data collected by an activity questionnaire. CONCLUSIONS Current dosing practices may risk underdialysis in women, men of smaller body size, and specific subgroups of patients. Using BSA-, REE-, or TEE-based dialysis prescription would result in higher dose delivery in these patients.

Comparison of energy estimates in chronic kidney disease using doubly-labelled water

BACKGROUND Total energy expenditure (TEE) is estimated in clinical practice as a combined measure of resting energy expenditure and physical activity level. Commonly available questionnaires to estimate physical activity level have not been validated in patients with kidney disease using the doubly-labelled water method. METHODS This prospective, cross-sectional study was conducted on 40 patients with chronic kidney disease stages 1-5 with the objective of validating two physical activity questionnaires: the Recent Physical Activity Questionnaire (RPAQ) and the Stanford 7-day recall questionnaire. TEE was measured using doubly-labelled water technique. TEE was also estimated using predicted resting energy expenditure and estimated physical activity measures from the questionnaires. RESULTS Measured TEE correlated better with TEE estimated from RPAQ compared to that from the Stanford questionnaire. In Bland-Altman analysis, TEE estimated from RPAQ had the least bias and narrower limits of agreement compared to the measured TEE. A metabolic equivalent of task value of 1.3 for the unaccounted time in RPAQ provided the best approximation of estimated TEE to the measured TEE. CONCLUSIONS RPAQ is an acceptable questionnaire tool for assessing physical activity level in patients with chronic kidney disease.

Dalteparin dosing in high-flux haemodialysis and haemodiafiltration.

Background: Low-molecular-weight heparins are being increasingly used as an alternative to unfractionated heparin for anticoagulation of the haemodialysis (HD) circuit. Data on dalteparin use in high-flux HD and haemodiafiltration (HDF) are limited. We examined the safety and efficacy of dalteparin in this setting to enable recommendations on the optimal dose range. Methods: This prospective study was conducted in a single dialysis unit. Subjects who had been receiving dalteparin for at least 10 HD sessions were studied. Anti-Xa activity was measured for all subjects at the start of the HD session, at 60 min into HD and at the end of dialysis. Results: 55 subjects were studied. None had detectable anti-Xa activity at the start of the session. Using adequacy criteria based on target anti-Xa activity >0.4 IU/ml at 1 h and <0.4 IU/ml at the end of dialysis, 39 (71%) patients had adequate anticoagulation, 12 (22%) patients were under-anticoagulated and 4 (7%) were over-anticoagulated. The mean dose in the adequately anticoagulated group was 60.7 ± 11.7 IU/kg, in the under-anticoagulated group 39.3 ± 9.6 IU/kg and in the over-anticoagulated group 70.1 ± 14.6 IU/kg. The optimal dose of dalteparin appears to be 60 ± 10 IU/kg, which facilitates the achievement of the target anti-Xa activity in the range of 0.4-0.75 IU/ml at 1 h and <0.4 IU/ml at the session end. Conclusion: Dalteparin is a safe and effective anticoagulant for patients on high-flux HD and HDF. The optimal dose appears to be 60 ± 10 IU/kg. The desirable target range of anti-Xa activity is 0.4-0.75 at 1 h and <0.4 IU/ml at the session end.

Energy metabolism, body composition, and urea generation rate in hemodialysis patients

Hemodialysis (HD) adequacy is currently assessed using normalized urea clearance (Kt/V), although scaling based on Watson volume (V) may disadvantage women and men with low body weight. Alternative scaling factors such as resting energy expenditure and high metabolic rate organ mass have been suggested. The relationship between such factors and uremic toxin generation has not been established. We aimed to study the relationship between body size, energy metabolism, and urea generation rate. A cross‐sectional cohort of 166 HD patients was studied. Anthropometric measurements were carried on all. Resting energy expenditure was measured by indirect calorimetry, fat‐free mass by bio‐impedance and total energy expenditure by combining resting energy expenditure with a questionnaire‐derived physical activity data. High metabolic rate organ mass was calculated using a published equation and urea generation rate using formal urea kinetic modeling. Metabolic factors including resting energy expenditure, total energy expenditure and fat‐free mass correlated better with urea generation rate than did Watson volume. Total energy expenditure and fat‐free mass (but not Watson Volume) were independent predictors of urea generation rate, the model explaining 42% of its variation. Small women (

Comparison of resting energy equations and total energy expenditure in haemodialysis patients and body composition measured by multi-frequency bioimpedance

Waste products of metabolism are retained in haemodialysis (HD) patients. Cellular metabolism generates energy, and patients with greater energy expenditure may therefore require more dialysis. The aim of the present study was to determine the amount of dialysis required, to determine equations estimating the required resting and total energy expenditure (REE, TEE).

Comparison of estimates of resting energy expenditure equations in haemodialysis patients

Purpose Waste products of metabolism accumulate in patients with chronic kidney disease, and require clearance by haemodialysis (HD). We wished to determine whether there was an association between resting energy expenditure (REE) and total energy expenditure (TEE) in HD patients and body composition. Subjects/Methods We determined REE by recently validated equations (CKD equation) and compared REE with that estimated by standard equations for REE, and TEE calculated from patient reported physical activity, in HD patients with corresponding body composition measured by dual energy X-ray absorptiometry (DEXA) scanning. Results We studied 107 patients, 69 male (64.5%), mean age 62.7 ± 15.1 years. The CKD equation REE was 72.5 ± 13.3 watts (W) and TEE 83.2 ± 9.7 W There was a strong association between REE with body surface area (BSA) (r2 = 0.80), total soft lean and fat lean tissue mass (r2 = 0.69), body mass index (BMI) (r2 = 0.34), all p<0.001. REE estimated using the modified Harris Benedict, Mifflin St. Jeor, Katch McArdle, Bernstein and Robertson equations underestimated REE compared to the CKD equation. TEE was more strongly associated with BSA (r2 = 0.51), appendicular muscle mass (r2 = 0.42), than BMI (r2 = 0.15) all p<0.001. TEE was greater for those employed (104.9 ± 10.7 vs. 83.1 ± 12.3 W, p<0.001), and with no co-morbidity (88.7 ± 14.8 vs. 82.7 ± 12.3 W, P<0.05). Conclusions Standard equations underestimate REE in HD patients compared to the CKD equation. TEE was greater in those with more skeletal muscle mass, in those who were employed and in those with the least comorbidity. More metabolically active patients may well require greater dialytic clearances.

Indexing dialysis dose for gender, body size and physical activity: Impact on survival

Current practice basing dialysis dose on urea distribution volume (V) has been questioned. We explored the impact on survival of scaling dialysis dose (Kt) to parameters reflective of metabolic activity. In a multicentre prospective cohort study of 1500 patients on thrice-weekly haemodialysis, body surface area (BSA) and resting energy expenditure (REE) were estimated using validated equations and physical activity by the Recent Physical Activity Questionnaire. Total energy expenditure (TEE) was estimated from REE and physical activity data. Kt was calculated from delivered (single-pool Kt/V)*Watson V. Kt/BSA, Kt/REE and Kt/TEE were then calculated at baseline and 6 monthly during follow-up for 2 years. In adjusted Cox models Kt/TEE, Kt/BSA, Kt/REE, in that order, had lower hazard ratios for death than single-pool Kt/V. On the basis of adjusted survival differences, putative minimum target doses were estimated for Kt/BSA as 27119 ml/m2 and Kt/TEE as 25.79 ml/kcal. We identified spKt/V values equivalent to these estimated targets, ranging from 1.4 to 1.8 in patient groups based on gender, body size and physical activity. For sedentary patients, the minimum target dose was 1.4 for large males, 1.5 for small males and 1.7 for women. For active patients the target was 1.8 irrespective of gender and body-weight. Patients achieving these individualised minimum targets had greater adjusted two-year survival compared to those achieving conventional minimum targets. Metabolic activity related parameters, such as Kt/TEE and Kt/BSA, may have a clinically important role in scaling haemodialysis dose. Using such parameters or their spKt/V equivalents to adjust minimum target doses based on gender, body size and habitual physical activity may have a positive impact on survival.

Exploring the uncharted territory of social media: the next frontier of medical education in nephrology

Abstract Social media is gaining popularity amongst both medical educators and life-long learners. One of the most popular social media platforms used by the medical community is Twitter, which is popular amongst physicians, students and patients, and particularly in medical societies. Major international and regional societies commonly use Twitter to amplify their reach beyond what their live annual meetings can achieve. There has been a unique and notable effort by Nephrology societies to craft a structured social media strategy that results in the broadest reach to the community of nephrology providers. We report on the first three such experiments performed by three separate nephrology organizations.