Factors determining a low dose of haemodialysis as measured by ionic dialysance in critical patients with acute kidney injury.

BACKGROUND: Estimating the dialysis dose is a requirement commonly used to assess the quality of renal replacement therapy (RRT) in patients with chronic kidney disease (CKD). In patients with acute kidney injury (AKI), this value is not always evaluated and it has been estimated that the prescribed dose is seldom obtained. Reports addressing this issue in AKI individuals are scarce and most have not included an adequate number of patients or treatments, nor were patients treated with extended therapies. Kt values obtained by the ionic dialysance method have been validated for the evaluation of the dialysis dose and it has also been shown that, compared with Kt/V, this is the most sensitive strategy for revealing inadequate dialysis treatment in critically ill AKI individuals. The main aim of this study was to assess the difference between the prescribed and the administered dialysis dose in critically ill AKI patients, and to evaluate what factors determine this gap using Kt values assessed through ionic dialisance. MATERIAL AND METHOD: Data from 394 sessions of renal replacement therapy in 105 adult haemodialysis (HD) patients with oliguric acute kidney injury and admitted to ICU were included in this analysis. RRT was carried out with Fresenius 4008E dialysis machines equipped with on-line clearance monitoring (OCM® Fresenius), which use non-invasive techniques to monitor the effective ionic dialysance, equivalent to urea clearance. The baseline characteristics of the study population as well as the prescription and outcome of RRT were analysed. These variables were included in a multivariate model in which the dependent variable was the failure to obtain the threshold dose (TD). RESULTS: The main baseline characteristics of the study population/treatments were: age 66 ± 15 years, 37% female, most frequent cause of AKI: sepsis (70%). Low BP and/or vasoactive drug requirement (71%), mechanical ventilation (70%) and average individual severity index: 0.7 ± 0.26. Two hundred and one intermittent HD (IHD) and 193 extended HD (EHD) sessions were performed; the most frequently used temporary vascular access was the femoral vein catheter (79%). Prescribed Kt was 53.5 ± 14L and 21% of prescriptions fell below the TD. Sixty-one percent of treatments did not fulfill the TD (31 ± 8L) compared with 56 ± 12L obtained in the subgroup that achieved the target. Compared to IHD, EHD provided a significantly larger Kt (46 ± 16L vs 33L ± 9L). Univariate analysis showed that inadequate compliance was associated with age (>65y), male gender, intra-dialytic hypotension, low Qb, catheter line reversal, and IHD. The same variables with the exception of age and gender were independently associated in the multivariate analysis. CONCLUSIONS: The dialysis dose obtained was significantly lower than that prescribed. EHD achieved values closer to the prescribed KT and significantly higher than in IHD. Ionic Kt measurement facilitates monitoring and allows HD treatments to be extended based upon a previously established TD. Besides the chosen strategy to dispense the dose of dialysis, a well-functioning vascular access allowing for optimal blood flow and other approaches aimed at avoiding hemodynamic instability during RRT are the most important factors to achieve TD, mainly in elderly male patients. The dialysis dose should be prescribed and monitored for all critically ill AKI patients.

Calculation of Kt/V in haemodialysis: a comparison between the formulas.

INTRODUCTION: The quality of delivered dialysis can be measured by the Kt/V ratio, which can be calculated in various ways. OBJECTIVE: To compare the Kt/V ratio obtained with the formulas of Lowrie (L) and Daugirdas (D) with the results measured by an Online Clearance Monitor (OCM). METHOD: Observational, cross-sectional study of 59 patients on hemodialysis (HD). Data were collected in the same dialysis session (predialysis and postdialysis urea) and Kt/V was calculated by the OCM of the Fresenius 4008S machine (Fresenius Medical Care AG, Bad Homburg, Germany). RESULTS: A total of 95 sessions were assessed, with a predominance of males 56% (33), and a sample mean age of 57 + 14 years. Hypertension (42%; n = 25), diabetes (12%; n = 7) and glomerulonephritides (8%; n = 5) were the most frequent causes of chronic kidney disease (CKD). Mean Kt/V values obtained with the L and D formulas and the OCM were 1.31, 1.41 and 1.32, respectively. Comparison between the L and D formulas showed a statistically significant difference (p = 0.008), with a Pearson's correlation of 0.950. The difference between the D formula and the OCM was also significant (p = 0.011 and r = 0.346), probably due to convective loss, estimated by the D formula but not by the OCM and L formula. The difference between the L formula and the OCM was not significant (p = 0.999 and r = 0.577). CONCLUSION: These data suggest that the OCM can be used as a guide to the real-time adjustment of the dialysis dose.

Cálculo de Kt/V em hemodiálise: comparação entre fórmulas / Calculation of Kt/V in haemodialysis: a comparison between the formulas

INTRODUÇÃO: A qualidade da diálise oferecida aos pacientes em diálise pode ser mensurada pelo Kt/V, o qual pode ser calculado de diversas maneiras. OBJETIVO: Comparar os resultados de Kt/V obtidos por meio das fórmulas de Lowrie (L) e de Daugirdas (D) com os resultados mensurados pelo monitor de clearence on-line - Online Clearence Monitor (OCM). MÉTODO: Estudo observacional transversal com 59 pacientes em hemodiálise (HD). Os dados foram coletados na mesma sessão de diálise: (ureia pré-diálise e pós-diálise) e o resultado de Kt/V foi obtido pelo OCM da máquina Fresenius 4008S (Fresenius Medical Care AG, Bad Homburg, Alemanha). RESULTADO: Foram analisadas 95 sessões, em que prevaleceu o sexo masculino, 56% (33), com idade média de 57 + 14 anos. A hipertensão arterial com 42% (25), diabetes com 12% (7) e glomerulonefrite com 8% (5) foram as causas mais frequentes da doença renal crônica (DRC). O Kt/V médio obtido pela fórmula de L, de D e pelo OCM foi de 1,31; 1,41 e 1,32, respectivamente. A comparação entre as fórmulas de L e D mostra que há diferença estatística p = 0,008 com a correlação de Pearson de 0,950. Entre D e OCM a diferença também é significativa: p = 0,011 e r = 0,346, provavelmente devido a perda convectiva, avaliada pela equação de D e não observadas por OCM e L. A comparação entre L e OCM não foi significativa p = 0,999 e r = 0,577. CONCLUSÃO: Os dados sugerem que o OCM pode ser utilizado como um norteador para ajuste da dose de diálise em tempo real.

INTRODUCTION: The quality of delivered dialysis can be measured by the Kt/V ratio, which can be calculated in various ways. OBJECTIVE: To compare the Kt/V ratio obtained with the formulas of Lowrie (L) and Daugirdas (D) with the results measured by an Online Clearance Monitor (OCM). Method: Observational, cross-sectional study of 59 patients on hemodialysis (HD). Data were collected in the same dialysis session (predialysis and postdialysis urea) and Kt/V was calculated by the OCM of the Fresenius 4008S machine (Fresenius Medical Care AG, Bad Homburg, Germany). RESULTS: A total of 95 sessions were assessed, with a predominance of males 56% (33), and a sample mean age of 57 + 14 years. Hypertension (42%; n = 25), diabetes (12%; n = 7) and glomerulonephritides (8%; n = 5) were the most frequent causes of chronic kidney disease (CKD). Mean Kt/V values obtained with the L and D formulas and the OCM were 1.31, 1.41 and 1.32, respectively. Comparison between the L and D formulas showed a statistically significant difference (p = 0.008), with a Pearson's correlation of 0.950. The difference between the D formula and the OCM was also significant (p = 0.011 and r = 0.346), probably due to convective loss, estimated by the D formula but not by the OCM and L formula. The difference between the L formula and the OCM was not significant (p = 0.999 and r = 0.577). CONCLUSION: These data suggest that the OCM can be used as a guide to the real-time adjustment of the dialysis dose.

Effect of chloride dialysate concentration on metabolic acidosis in aintenance hemodialysis patients

Hyperchloremia is one of the multiple etiologies of metabolic acidosis in hemodialysis (HD) patients. The aim of the present study was to determine the influence of chloride dialysate on metabolic acidosis control in this population. We enrolled 30 patients in maintenance HD program with a standard base excess (SBE) ≤2 mEq/L and urine output of less than 100 mL/24 h. The patients underwent dialysis three times per week with a chloride dialysate concentration of 111 mEq/L for 4 weeks, and thereafter with a chloride dialysate concentration of 107 mEq/L for the next 4 weeks. Arterial blood was drawn immediately before the second dialysis session of the week at the end of each phase, and the Stewart physicochemical approach was applied. The strong ion gap (SIG) decreased (from 7.5 ± 2.0 to 6.2 ± 1.9 mEq/L, P = 0.006) and the standard base excess (SBE) increased after the use of 107 mEq/L chloride dialysate (from -6.64 ± 1.7 to -4.73 ± 1.9 mEq/L, P < 0.0001). ∆SBE was inversely correlated with ∆SIG during the phases of the study (Pearson r = -0.684, P < 0.0001) and there was no correlation with ∆chloride. When we applied the Stewart model, we demonstrated that the lower concentration of chloride dialysate interfered with the control of metabolic acidosis in HD patients, surprisingly, through the effect on unmeasured anions.

Effect of chloride dialysate concentration on metabolic acidosis in maintenance hemodialysis patients.

Hyperchloremia is one of the multiple etiologies of metabolic acidosis in hemodialysis (HD) patients. The aim of the present study was to determine the influence of chloride dialysate on metabolic acidosis control in this population. We enrolled 30 patients in maintenance HD program with a standard base excess (SBE) ≤2 mEq/L and urine output of less than 100 mL/24 h. The patients underwent dialysis three times per week with a chloride dialysate concentration of 111 mEq/L for 4 weeks, and thereafter with a chloride dialysate concentration of 107 mEq/L for the next 4 weeks. Arterial blood was drawn immediately before the second dialysis session of the week at the end of each phase, and the Stewart physicochemical approach was applied. The strong ion gap (SIG) decreased (from 7.5 ± 2.0 to 6.2 ± 1.9 mEq/L, P = 0.006) and the standard base excess (SBE) increased after the use of 107 mEq/L chloride dialysate (from -6.64 ± 1.7 to -4.73 ± 1.9 mEq/L, P < 0.0001). ∆SBE was inversely correlated with ∆SIG during the phases of the study (Pearson r = -0.684, P < 0.0001) and there was no correlation with ∆chloride. When we applied the Stewart model, we demonstrated that the lower concentration of chloride dialysate interfered with the control of metabolic acidosis in HD patients, surprisingly, through the effect on unmeasured anions.

Efeito benéfico da correção da acidose metabólica no estado nutricional de pacientes em hemodiálise / Beneficial effects of metabolic acidosis correction in hemodialysis patients

Objetivo: Avaliar o efeito da correção da acidose metabólica no estado nutricional de pacientes em hemodiálise. Métodos: Foram estudados, durante seis meses, 20 pacientes com acidose metabólica, definida pela média de tr~es mensurações de bicarbonato sérico pré-diálise <22 mEq/L. os pacientes dialisavam há, pelo menos, seis meses, utilizando bicarbonato de 35 mEq/L no dialisato. A correção da acidose metabólica foi feita mediante elevação do bicarbonato no dialisato para valores que não ultrapassaram 40 mEq/L, objetivando um bicarbonato sérico entre 22-26 mEq/L. Foram avaliados no início e no final do estudo: avaliação antropométrica, dietética, bioquímica e Avaliação subjetiva Global (ASG). Resultados: A avaliação nutricional na fase inicial do estudo demonstrou índice de massa corporal normal (24,23 +- 3,83 Kg/m²). A circunferência muscular do braço, a prega cutânea tricipital e a ASG classificaram homens e mulheres como desnutridos. Os consumos de calorias e proteínas foram 29,7 +- 10,1 Kcal?kg/dia e 1,31 +- 0,35 g/Kg/dia, respectivamente. A avaliação bioquímica observou albumina sérica normal e colesterol reduzido. Após correção, bicarbonato sérico e pH aumentaram de 18,2 +- 1,64 para 22 +- 1,70 (p<0,001), e de 7,32+- 0,45 para 7,37 +-0,41 (p<0,001), respectivamente. Houve melhora da ASG (21,7 +- 6,4 versus 16,8 +-6,6, p<0,0001) e aumento na ingestão calórica (1.892,61 +-454,30 versus 2.110,30 +-869,24, p<0,05). Conclusão: A suplementação de bicarbonato na solução de hemodiálise foi método efetivo para a correção da acidose metabólica, determinando aumento da ingestão calórica e melhora nos escores da ASG.

Objective: To evaluate the effect of correction of metabolic acidosis on nutritional status of hemodialysis patients. Methods: We studied for six months, 20 patients with metabolic acidosis, defined as the average of tr ~ s measurements of predialysis serum bicarbonate <22 mEq / L. patients receiving dialysis treatment for at least six months, using bicarbonate of 35 mEq / L in the dialysate. The correction of metabolic acidosis was observed in the high bicarbonate dialysate for values that exceeded 40 mEq / L, aiming for a serum bicarbonate between 22-26 mEq / L. Were assessed at baseline and at the end of the study: anthropometric, dietary, biochemical and Subjective Global Assessment (SGA). Results: The nutritional assessment in the initial phase of the study showed normal BMI (24.23 + - 3.83 kg / m²). The arm muscle circumference, triceps skinfold and the ASG men and women classified as malnourished. The intake of calories and protein were 29.7 + - 10.1 Kcal? Kg / day and 1.31 + - 0.35 g / kg / day, respectively. The biochemical evaluation showed normal serum albumin and low cholesterol. After correction, serum bicarbonate and pH increased from 18.2 + - 1.64 for 22 + - 1.70 (p <0.001), and 7.32 + - 0.45 to 7.37 + -0.41 ( p <0.001), respectively. There was improvement in ASG (21.7 + - 6.4 versus 16.8 + -6.6, p <0.0001) and increased caloric intake (1892.61 + -454.30 vs 2110.30 + -869 , 24, p <0.05). Conclusion: Supplementation of bicarbonate in the dialysis solution was an effective method for correction of metabolic acidosis, determining increased caloric intake and improvement in the scores of the ASG.

Obstructive sleep apnea in patients on conventional and short daily hemodialysis.

Obstructive sleep apnea (OSA) is common among patients on maintenance hemodialysis. However, the factors associated with the origin of OSA as well as the cardiovascular consequences in this population are not completely understood. We evaluated, by standard overnight polysomnography, 24-hour ambulatory blood pressure (BP) monitoring and echocardiography in 30 patients (14 males, age 34 +/- 11 years, BMI 23.2 +/- 5.2) - 15 on short daily hemodialysis (SDH) and 15 matched patients on conventional hemodialysis (CHD). The hemodialysis dose (standard Kt/V) was higher in patients on SDH than on CHD (p = 0.001). OSA (apnea-hypopnea index >5 events/h) was present in 13 patients (43%). Patients with OSA were predominantly males (77 vs. 44%), presented a higher BMI (25.5 +/- 6.2 vs. 21.5 +/- 3.6), a larger neck circumference (38 +/- 1 vs. 34 +/- 1 cm) and a lower Kt/V (2.6 +/- 0.3 vs. 2.2 +/- 0.1) than patients with no OSA (p < 0.05). Neck circumference and lower Kt/V were independently associated with OSA on multivariate analysis. No patient with Kt/V >2.5 (n = 10) presented OSA. On the other hand, hypertensive patients with OSA needed more BP control pills (p = 0.03). Despite similar BP control, patients with OSA presented a higher interventricular septum thickness (11.5 +/- 0.5 vs. 9.9 +/- 0.3 mm; p = 0.011). In conclusion, among patients on maintenance hemodialysis, the traditional risk factors for OSA are present and interact with hemodialysis efficiency. Among these patients, OSA is associated with difficult BP control and heart remodeling suggesting that OSA may contribute to poor cardiovascular outcome.

Dosis de diálisis, nutrición y crecimiento en diálisis peritoneal pediátrica / Dialysis dose, nutrition and growth among pediatric patients on peritoneal dialysis

Stunting is common among pediatric patients on peritoneal dialysis. Aim: To stablish the best profile for urea kinetic variables associated to growth inchildren on chronic peritoneal dialysis (PD). Patients and Methods: Twenty patients, aged 1 month to 14 years, 13 males, were followed for 6-12 months, with monthly measurements of weight/age and height/age Z score; plasma creatinine, BUN, protein and albumin and urine and dialysate urea nitrogen, creatinine, protein and albumin. Minimum total Kt/V was 2.1. Dialysis dose (Kt/V), Protein Equivalent of Urea Nitrogen Appearence (PNA), Protein Catabolic Rate (PCR) and Nitrogen Balance (NB) were calculated. To identify the variable(s) associated to growth, the Tree Classification Model (CART) Enterprise Miner 8.1 was applied. Results: Mean total/residual Kt/V: 3.4±1.3/1.69±1.27; Daily Protein Intake (DPI) was 3.25±1.27 g/kg/day. nPNA, PCR and NB were 1.37±0.44, 0.84±0.33 and 1.86±1.25 g/kg/day, respectively. Mean heigth/age Z score was -2.3±1.19. Eleven patients showed a positive height/age delta Z (mean 0.55±0.38) and nine showed a negative growth (mean -0.50±0.42). The main variable explaining the positive growth was a Nitrogen Balance between 0.54 and 2.37 g/kg/ day, mean 1.55±0.21 (p <0.001). The second associated variable to growth was a residual Kt/V between 0.43 and 4.6 (2.02±0.49) (p <0.05). Kt/V and nPNA showed a significant correlation, but no correlation could be found between Kt/V and NB. Conclusions: Nitrogen Balance was the main variable associated to growth in pediatric PD, with values between 0.53 to 2.38 g/kg/day. The second variable was a residual Kt/V between 0.43 and 4.6. Therapy should be reassessed with NB values less than 0.54 or above 2.37 g/kg/day....

[Dialysis dose, nutrition and growth among pediatric patients on peritoneal dialysis]. / Dosis de diálisis, nutrición y crecimiento en diálisis peritoneal pediátrica.

BACKGROUND: Stunting is common among pediatric patients on peritoneal dialysis. AIM: To establish the best profile for urea kinetic variables associated to growth in children on chronic peritoneal dialysis (PD). PATIENTS AND METHODS: Twenty patients, aged 1 month to 14 years, 13 males, were followed for 6-12 months, with monthly measurements of weight/age and height/age Z score; plasma creatinine, BUN, protein and albumin and urine and dialysate urea nitrogen, creatinine, protein and albumin. Minimum total Kt/V was 2.1. Dialysis dose (Kt/V), Protein Equivalent of Urea Nitrogen Appearance (PNA), Protein Catabolic Rate (PCR) and Nitrogen Balance (NB) were calculated. To identify the variable(s) associated to growth, the Tree Classification Model (CART) Enterprise Miner 8.1 was applied. RESULTS: Mean total/residual Kt/V: 3.4+/-1.3/1.69+/-1.27; Daily Protein Intake (DPI) was 3.25+/-1.27 g/kg/day. nPNA, PCR and NB were 1.37+/-0.44, 0.84+/-0.33 and 1.86+/-1.25 g/kg/day, respectively. Mean height/age Z score was -2.3+/-1.19. Eleven patients showed a positive height/age delta Z (mean 0.55+/-0.38) and nine showed a negative growth (mean -0.50+/-0.42). The main variable explaining the positive growth was a Nitrogen Balance between 0.54 and 2.37 g/kg/day, mean 1.55+/-0.21 (p <0.001). The second associated variable to growth was a residual Kt/V between 0.43 and 4.6 (2.02+/-0.49) (p <0.05). Kt/V and nPNA showed a significant correlation, but no correlation could be found between Kt/V and NB. CONCLUSIONS: Nitrogen Balance was the main variable associated to growth in pediatric PD, with values between 0.53 to 2.38 g/kg/day. The second variable was a residual Kt/V between 0.43 and 4.6. Therapy should be reassessed with NB values less than 0.54 or above 2.37 g/kg/day.

Clinical consequences of an individualized dialysate sodium prescription in hemodialysis patients.

BACKGROUND: Predialysis plasma sodium (Na(+)) concentration is relatively constant in hemodialysis (HD) patients, and a higher dialysate Na(+) concentration can promote an increase in the interdialytic fluid ingestion to achieve an individual's osmolar set point, and individualization of dialysate Na(+) concentration may improve interdialytic weight gain (IDWG), blood pressure (BP), and HD-related symptoms. METHODS: Twenty-seven nondiabetic, non-hypotension prone HD patients were enrolled in a single-blind crossover study. Subjects underwent nine consecutive HD sessions with the dialysate Na(+) concentration set to 138 mEq/L (standard Na(+) HD), followed by nine sessions wherein the dialysate Na(+) was set to match the patients average pre-HD plasma Na(+) measured three times during the standard Na(+) phase multiplied by 0.95 (individualized dialysate Na(+) HD). Dry weight, dialysis prescription, and medications were not modified during the six weeks of the study. RESULTS: Pre-HD Na(+) was similar in both periods of the study (standard Na(+) HD, 134.0 +/- 1.4 mEq/L; individualized Na(+) HD, 134.0 +/- 1.5 mEq/L; P= 0.735). There was a significant decrease in interdialytic weight gain (2.91 +/- 0.87 kg vs. 2.29 +/- 0.65 kg; P< 0.001), interdialytic thirst scores, and episodes of intradialytic hypotension in the individualized Na(+) period compared with the standard phase. Pre-HD BP was lower in individualized Na(+) HD in patients with uncontrolled BP at baseline (N= 15), but not in those with controlled BP at baseline (N= 12) (DeltaBP -15.6/-6.5 mm Hg in uncontrolled vs. DeltaBP +6.4/+4.5 mm Hg in controlled, P= <0.001 for systolic BP and P= <0.001 for diastolic BP). CONCLUSION: An individualized Na(+) dialysate based on predialysis plasma Na(+) levels decreases thirst, IDWG, HD-related symptoms, and pre-HD BP (in patients with uncontrolled BP at baseline).

Relationship between fill volume, intraperitoneal pressure, body size, and subjective discomfort perception in CAPD patients. Mexican Nephrology Collaborative Study Group.

OBJECTIVE: To determine changes in intraperitoneal pressure (IPP) when dialysate fill volume is increased from 2.0 L to 2.5 L to 3.0 L per exchange, and to evaluate the relationship with subjective discomfort perception. DESIGN: Cross-sectional survey. SETTING: Seven Mexican hospital-based dialysis centers. PATIENTS: Eighty-one adult patients on continuous ambulatory peritoneal dialysis (CAPD) without restriction criteria for age, gender, or time on dialysis, were studied. Patients seropositive for HIV or hepatitis B, and those with cancer or receiving immunosuppressive drugs were excluded. Participants were studied as outpatients. MAIN MEASURES: Blindly and in random order, 2.0-, 2.5-, and 3.0-L volumes of dialysate were infused consecutively. Body surface area (BSA) was calculated from patient height and weight. IPP was assessed with the patient lying supine, measuring the height of the dialysate column inside the peritoneal dialysis bag tubing. Blood pressure and subjective discomfort perception (using a visual analog scale of 0-100 mm) were also evaluated and registered after each of the three exchanges. RESULTS: The IPP rose with each increase of dialysate volume and was higher in males than in females for each fill volume level. For males IPP was 18.9 +/- 6.9, 20.8 +/- 7.1, and 22.9 +/- 7.5 cm H2O; and for females it was 16.5 +/- 5.7, 18.4 +/- 5.5, and 19.7 +/- 6.2 cm H2O for 2.0-, 2.5-, and 3.0-L fill volumes respectively (p < 0.01 among fill volumes and between genders). Intraperitoneal pressure showed significant negative correlation with the fill volume corrected for patient body size as reflected by the dialysate volume/ BSA ratio (r= -0.393, p < 0.01; r= 0.319, p < 0.01; and r= -0.274, p < 0.02 for 2.0-, 2.5-, and 3.0-L fill volumes respectively). Discomfort score rose as fill volume rose, with a median of 0, 2.5, and 13.0 for 2.0-, 2.5-, and 3.0-L fill volumes respectively (p< 0.001). It is interesting, however, that with 2.5-L and 3.0-L dialysate infusion volumes, 64% and 44% of the patients, respectively, had no discomfort at all. CONCLUSION: Dialysate volume increase is associated with higher IPP, which is modulated by the gender and body size of the patients. Although the mean discomfort score was higher with larger dialysate volumes, there was no significant correlation between discomfort and IPP or the dialysate volume/BSA ratio. Many patients had no discomfort with 2.5-L or even with 3.0-L dialysate infusions; theoretically, they can be treated with larger volumes.