***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: In a double-blind cross-over trial , 22 stable end-stage renal failure patients on maintenance haemodialysis were subjected to conventional dialysis with dialysate containing 137 mEq/l sodium and constant ultrafiltration ( UF ) and to a different dialysis therapy , in which , by linear sodium modelling , the dialysate sodium was reduced from 137 to 128 mEq/l . A computerized UF program was used to gradually reduce the UF to a minimum towards the end of the session . Severity of thirst , interdialytic weight gain and intradialytic complications were less with low sodium dialysate . It allowed adequate UF with absolute hemodynamic stability . The reduced incidence of complication with low sodium dialysate therapy was probably because they required less UF The new population on dialysis  today consists mainly of high risk patients ( the elderly , diabetics , etc . ) with high cardiovascular scores , and such vascular pathology is the most important predisposing factor for the occurrence of a frequent intradialytic clinical complication , vascular instability syndrome , which covers a range of clinical problems . Recently a new dialysis technique , profiled hemodialysis ( PHD ) , has been set up and proposed for routine use . PHD consists of the clinical use of preestablished individual dialysis profiles aim ed at antagonizing the changes in intradialytic plasma osmolarity by continuous modulation of dialysate sodium concentration throughout the whole extracorporeal session . In particular , PHD aims at reducing the fall of plasma osmolarity in the first half of the session ( when it is higher ) by reducing the sodium removal rate through increasing its dialysate concentration while taking into account the desired individual sodium balance to be reached at the end of the session . In this work , we report clinical experience with PHD compared to st and ard hemodialysis with constant sodium dialysate ( SHD ) in terms of its efficacy to maintain a more stable intradialytic blood volume ( BV ) and more stable hemodynamics . The PHD used in this work has been implemented by a mathematical model for computing the individual dialysate sodium profile which we have recently vali date d ( Ursino M , Coli L , La Manna G , Grilli Cicilioni M , Dalmastri V , Guidicissi A , Masotti P , Avanzolini G , Stefani S , Bonomini V. A simple mathematical model of intradialytic sodium kinetics : " in vivo " validation during hemodialysis with constant or variable sodium . Int J Artif Organs 1996;19:393 - 403 . ) . Eleven uremic patients affected by hypotension at the beginning of dialysis treatment were studied . Each patient first underwent an SHD treatment and 1 week later a PHD treatment . The 2 extracorporeal sessions ( one on SHD and the other on PHD ) were performed in each individual patient under identical operative conditions including the sodium mass removal by the end of the session and the ultrafiltration rate . The crit line and Doppler echocardiography were used to determine BV , cardiac output ( CO ) , and stroke volume ( SV ) throughout the sessions . The mean blood pressure ( MBP ) and heart rate ( HR ) were simultaneously monitored . PHD was associated with a more stable intradialytic BV and more stable hemodynamics compared to SHD . The higher stability of BV and cardiac function ( in terms of SV and CO maintenance ) which was obtained above all in the first half of the PHD session was associated with a higher stability of the MBP and the HR . This result ed in an enhancement in cardiovascular tolerance to ultrafiltration throughout the session in all tested patients . In contrast , SHD in the same patients was characterized by early significant changes in BV and cardiovascular parameters result ing in a significant decrease of the MBP and a significant increase of the HR throughout the session and also 1 h after the end of dialysis . Our results indicate that PHD may represent an efficient approach for the treatment of patients suffering from intradialytic vascular instability . If long-term clinical practice confirms the efficacy of PHD in controlling dialysis intolerance symptoms , it will have great scope as a routine procedure OBJECTIVES To evaluate the effectiveness of sodium ramping ( profiling ) in reducing hypotensive episodes and symptoms during  haemodialysis .  DESIGN Prospect i ve study . SETTING Regional hospital , Hong Kong . PATIENTS Thirteen patients who experienced frequent episodes of hypotension and /or symptoms such as cramps , dizziness , chest pain , nausea , vomiting , and headache during haemodialysis in the preceding 4 weeks . INTERVENTIONS Each patient was switched from st and ard haemodialysis with a constant dialysate sodium concentration of 135 to 140 mmol/L to a ramped sodium haemodialysis for a period of 4 weeks . During this time the dialysate sodium concentration was ramped linearly downwards from 150 mmol/L at the beginning of dialysis to 140 mmol/L at the end of dialysis . MAIN OUTCOME MEASURES Intradialytic hypotensive episodes , intradialytic symptoms , nursing interventions , systolic and diastolic blood pressures , and interdialytic weight gain . RESULTS A total of 248 haemodialysis sessions undertaken by 13 patients were analysed . Switching from constant sodium haemodialysis to ramped sodium haemodialysis result ed in a significant reduction in the number of intradialytic hypotensive episodes from 5.8 ( st and ard deviation , 6.4 ) to 2.2 ( 3.3 ) [ P<0.05 ] , the total number of intradialytic symptoms from 7.1 ( 3.4 ) to 0.9 ( 1.3 ) [ P<0.01 ] , and nursing interventions from 11.3 ( 6.3 ) to 1.7 ( 3.9 ) [ P<0.01 ] . Post-dialysis systolic and diastolic blood pressures were higher during ramped sodium haemodialysis compared with constant sodium haemodialysis ( systolic blood pressure , 139 [ st and ard deviation , 23 ] vs 133 [ 22 ] mm Hg , P<0.001 ; diastolic blood pressure , 77 [ 11 ] vs 74 [ 13 ] mm Hg , P<0.01 ) , and there was a trend towards a smaller drop in blood pressure after dialysis . The interdialytic weight gain with sodium ramping haemodialysis was greater compared with constant sodium haemodialysis ( 3.1 [ st and ard deviation , 1.0 ] vs 2.7 [ 1.1 ] kg , P<0.001 ) . CONCLUSION Sodium ramping during haemodialysis effectively reduces hypotensive episodes and intradialytic symptoms . Post-dialysis blood pressure is better maintained . A side-effect of sodium ramping is a greater interdialytic weight gain An important factor in the development of hypotension during  hemodialysis ( HD )  is a decrease in blood volume , due to ultrafiltration ( UF ) and an insufficient refill of the intravascular compartment . This insufficient refill might be caused by a transcellular fluid shift from the extracellular to the intracellular compartment . We studied the influence of dialysate sodium concentration and UF rate on the refill rate , blood volume , intracellular ( ICV ) and extracellular fluid volume ( ECV ) . Three different HD strategies were studied in 15 patients : ( A ) conventional HD ( dialysate sodium 140 mmol/L ) ; ( B ) HD with a sodium profile ( 140–148 mmol/L ) ; and ( C ) HD with a sodium profile and a variable UF rate ( high-low UF rate ) . ICV and ECV were measured by non-invasive conductivity measurements , blood volume was calculated from erythrocyte counts before and after treatment . Blood volume decrease was most pronounced during conventional HD , due to insufficient refilling without a detectable transcellular fluid shift . The sum of the decrease in ICV and ECV was less than during ( B ) and ( C ) . The insufficient refill led to a higher prevalence of hypotension and cramps . The strategies ( B ) and ( C ) led to an significant and comparable transcellular fluid shift to the extracellular compartment . Thus , the use of a sodium profile led to a better intravascular refill and clinical tolerance of HD . Addition of a UF profile did not improve this any further One important pathogenic factor in dialysis hypotension is the drop in plasma osmolality . Increasing the dialysate Na+ concentration decreases hypotensive episodes . The authors studied 39 patients being treated with high flux dialysis .  During a 9 week period , the patients were on a st and ard Na+ dialysate ( Na+ = 140 meq/L ) basal period ( B ) ; 9 % ( Na+ = 149 meq/L ) linear ( L ) ; step drop ( S ) ; and exponential drop ( E ) . The Na+ program was changed weekly at r and om . The results obtained with the three Na+ modeling programs were similar . We compared the periods with and without Na+ modeling : no differences were found in weight gained interdialysis , mean blood pressure predialysis and postdialysis , and hemoconcentration . Serum Na+ levels were significantly higher predialysis and postdialysis for those patients on Na+ modeling .  Hypotensive episodes and cramps decreased 50 % with Na+ modeling . The amount of hypertonic and normal saline given during dialysis was markedly reduced . Na+ modeling should always be used in patients being maintained on high flux dialysis Low dialysate sodium concentrations can reduce postdialysis thirst and serum sodium activity , but patients typically experience dialysis hypotension , fatigue , disequilibrium , and cramps .  " High-sodium " hemodialysis minimizes dialysis disequilibrium but increases the serum sodium activity of most patients . Programmed " variable-sodium " dialysis can minimize dialysis discomfort but may also alter the sodium kinetics from those of " high-sodium " dialysis . We design ed a cross-over study with r and om order assignment to determine whether a " variable-sodium " dialysis program could reduce the blood pressure of dialysis patients without increasing dialysis morbidity .  Dialysis with a dialysate sodium of 140 mEq/L was compared with dialysis with a programmed exponential decrease of dialysate sodium from 155 mEq/L to 135 mEq/L. Dialysate sodium was then held constant at 135 mEq/L for the final half hour of dialysis .  Eighteen patients completed the 7-month study , each receiving 3.5 months of experimental and 3.5 months of st and ard therapy . Programmed " variable-sodium " dialysis result ed in a reduction in antihypertensive drug use without alterations in predialysis blood pressure , interdialytic weight gain , ultrafiltration tolerance , or the frequency of symptomatic dialysis cramps or hypotension . Patients did , however , have lower postdialysis st and ing blood pressures and higher postdialysis target weights during programmed " variable-sodium " dialysis BACKGROUND Modern haemodialysis monitors offer computerised ultrafiltration and sodium concentration profiles which promise better dialysis tolerance . This presumption was tested in chronic haemodialysis patients . METHODS Using Fresenius MC 4008S monitors  a group of nine patients were dialysed with a given ultrafiltration profile comparing sessions with decreasing sodium concentration ( 145 to 133 mmol/L ) to sessions with constant sodium concentration ( 138 mmol/L ) in r and om order . The built-in blood volume monitor recorded changes in haematocrit and blood volume during each dialysis . The analyses included dialytic weight loss , interdialytic weight gain and adverse symptoms ( hypotensive episodes and muscle cramps ) . RESULTS 321 dialysis sessions , 160 with and 161 without sodium profile , were available for analysis . No significant differences could be detected regarding changes in haematocrit , blood volume and weight in relation to sodium profiling . No significant difference in the incidence of hypotension or muscle cramping was observed with 55 symptomatic dialyses of 160 with sodium profile , compared to 52 symptomatic dialyses of 161 without sodium profile . Interdialytic weight gain and consequent weight loss during dialysis was higher in symptomatic dialyses both with sodium profile or without sodium profile . The same was true of increase in haematocrit and decrease in blood volume , which were greater for symptomatic versus symptom-free dialyses irrespective of sodium profiling . CONCLUSIONS Sodium balance-neutral sodium profiling failed to improve dialysis tolerance in a group of stable chronic haemodialysis patients . This may be explained by the fact that vascular refilling as deduced from changes in haematocrit was uninfluenced by sodium profiling Inadequate plasma refilling is an important determinant of vascular instability during hemodialysis .  Hypotension is more frequent toward the end of dialysis , as the patient reaches dry weight . This study compared plasma volume changes in 12 patients dialyzed with constant ultrafiltration and a constant dialysate Na of 140 mEq/L ( Group A ) , sequentially decreasing ultrafiltration ( 50 % in first hour , 30 % in the second hour , and 20 % in the third hour ) using constant dialysate Na ( Group B ) , and sequentially decreasing ultrafiltration with sequentially decreasing dialysate Na from 150 to 140 mEq/L ( Group 
    Output:
    
CONCLUSION This evaluative review could not provide evidence to support the clinical use of sodium profiling in the population of patients on hemodialysis who are symptomatic .