Hemodialysis Parameters and Target Values

Dialysis Adequacy Parameters

• The American Journal of Kidney Diseases recommends a target single pool Kt/V (spKt/V) of 1.4 per hemodialysis session for patients treated thrice weekly 1, 2
• The minimum delivered spKt/V should be 1.2, and should never fall below this threshold 1, 2
• For schedules other than thrice weekly, the target standard Kt/V is 2.3 volumes per week with a minimum delivered dose of 2.1 1, 2
• Kt/V represents fractional urea clearance and is the most precise measure of dialyzer effect on patient survival 2

Blood Urea Nitrogen (BUN) Sampling

• Proper BUN sampling techniques are crucial for accurate Kt/V calculation, according to the American Journal of Kidney Diseases 3, 4
• Common sampling errors to avoid include dilution of predialysis sample with saline, drawing predialysis sample after dialysis start, drawing postdialysis sample before dialysis end or more than 5 minutes after dialysis, and laboratory calibration errors 4

Treatment Schedule Parameters

• The standard schedule for hemodialysis is three times weekly, as recommended by the American Journal of Kidney Diseases 1, 2
• Treatment time should be sufficient to achieve adequate fluid removal without excessive ultrafiltration rates, according to the American Journal of Kidney Diseases 5

Residual Kidney Function (RKF)

• In patients with significant residual native kidney function (Kru), dialysis dose may be reduced, as recommended by the American Journal of Kidney Diseases 1, 2
• Regular measurement of Kru is essential to avoid inadequate dialysis, according to the American Journal of Kidney Diseases 1, 2
• RKF contributes to total clearance and should be included in calculations for non-standard schedules, as recommended by the American Journal of Kidney Diseases 2

Fluid and Electrolyte Parameters

• Ultrafiltration rate should be monitored to avoid rapid fluid removal, according to the American Journal of Kidney Diseases 5
• Excessive ultrafiltration can lead to intradialytic hypotension and increased mortality, as reported by the American Journal of Kidney Diseases 5
• Fluid removal should be individualized based on interdialytic weight gain and cardiovascular stability, as recommended by the American Journal of Kidney Diseases 5
• The target sodium intake is 1.8-2.5 g/day, according to Clinical Nutrition 6
• The target potassium intake is 2000-2500 mg/day, as recommended by Clinical Nutrition 6
• The target phosphate intake is 800-1000 mg/day, according to Clinical Nutrition 6
• The target fluid intake is 1000 ml plus urine volume, as recommended by Clinical Nutrition 6

Nutritional Parameters

• The recommended protein intake is 1.2-1.4 g/kg body weight/day (≥50% high biological value), according to Clinical Nutrition 6
• The recommended energy intake is 35 kcal/kg body weight/day for patients <60 years and 30 kcal/kg body weight/day for patients >60 years, as recommended by Clinical Nutrition 6
• Nutritional status is an independent determinant of morbidity and mortality in hemodialysis patients, according to Clinical Nutrition 6

Monitoring Frequency

• Delivered dose of hemodialysis should be measured at least once monthly in all patients, as recommended by the American Journal of Kidney Diseases 4
• Increase measurement frequency when patients are non-compliant with prescriptions, frequent problems in delivery of prescribed dose occur, wide variability in urea kinetic modeling results is observed, or hemodialysis prescription is modified, according to the American Journal of Kidney Diseases 4

Common Pitfalls and How to Avoid Them

• Targeting minimum values as goals can result in many sessions falling below the threshold; always target higher (1.4), as recommended by the American Journal of Kidney Diseases 4
• Ignoring residual kidney function can lead to over-dialysis; measure periodically, according to the American Journal of Kidney Diseases 1, 2
• Inadequate sampling techniques can lead to inaccurate Kt/V calculations; follow standardized protocols, as recommended by the American Journal of Kidney Diseases 4
• Focusing solely on small-solute clearance can overlook other critical aspects like fluid balance, blood pressure control, and nutritional status, according to the American Journal of Kidney Diseases 7

Key Parameters in Hemodialysis

Introduction to Hemodialysis Parameters

• The American Journal of Kidney Diseases recommends that blood flow rate (BFR) is limited by vascular access function and patient tolerance 8
• Inadequate BFR can significantly reduce delivered dialysis dose and contribute to treatment failure, according to the American Journal of Kidney Diseases 9
• Inadequate dialysate flow can reduce effective clearance and contribute to underdialysis, as stated by the American Journal of Kidney Diseases 8
• Treatment time must accurately reflect the exact amount of time during which diffusion occurred at the prescribed blood and dialysate flow rates, as recommended by the American Journal of Kidney Diseases 8
• Interruptions during treatment reduce actual dialysis time, according to the American Journal of Kidney Diseases 8
• Heparin prevents clotting of the dialyzer during treatment, which would otherwise reduce effective dialyzer surface area, as stated by the American Journal of Kidney Diseases 8
• Inadequate anticoagulation can lead to dialyzer clotting and reduced clearance, according to the American Journal of Kidney Diseases 10
• UF volume is determined by interdialytic weight gain and target dry weight, as reported by Kidney International 11
• Monthly measurement of delivered dose is recommended to ensure adequacy, as suggested by the American Journal of Kidney Diseases 12
• Inadequate blood sampling techniques can lead to inaccurate Kt/V calculations, according to the American Journal of Kidney Diseases 12
• Ignoring treatment time reductions due to late starts or early terminations can affect dialysis efficacy, as stated by the American Journal of Kidney Diseases 8
• Failing to account for access recirculation reduces effective clearance, according to the American Journal of Kidney Diseases 9
• Proper BUN sampling techniques are crucial for accurate Kt/V calculation, as recommended by the American Journal of Kidney Diseases 12

Adjusting Hemodialysis Order to Target 2.5L Ultrafiltration

Introduction to Hemodialysis Targets

• The American Journal of Kidney Diseases recommends modifying the Net UF order from "2 L as tolerated" to "2.5 L as tolerated" to match the consultant's target 13, 14

Specific Hemodialysis Orders

• The dialysis order should include a treatment duration of 6 hours 13
• The ultrafiltration rate for 2.5 L over 6 hours equals 417 mL/hour, which is generally well-tolerated for most patients 13, 14

Communication and Monitoring

• The National Kidney Foundation's KDOQI guidelines emphasize balancing euvolemia achievement against hemodynamic instability, making the "as tolerated" qualifier essential 13, 14
• Monitor mean arterial pressure (MAP) every 30 minutes during the first session, as hypotension is a common risk with initiation 14

Critical Considerations for First HD Session

• KDOQI guidelines recommend prescribing an ultrafiltration rate that allows optimal balance among achieving euvolemia, adequate blood pressure control, and solute clearance while minimizing hemodynamic instability 13, 14
• For patients with large weight gains or difficulty achieving dry weight, longer treatment times or adjusted UF targets are appropriate 13, 14
• The 6-hour treatment time provides adequate duration to achieve 2.5 L removal at a moderate rate, reducing risk of intradialytic hypotension 13, 14

Common Pitfalls to Avoid

• Do not attempt aggressive UF (>2.5 L) on the first session without assessing hemodynamic tolerance, as this increases risk of hypotension and potential access complications 13, 14
• Avoid excessive saline boluses, as this defeats the purpose of fluid removal 13, 14
• Do not ignore intradialytic symptoms - cramping, nausea, or dizziness indicate the UF rate may be too aggressive 14

Documentation Requirements

• Document blood pressure readings every 30 minutes to establish this patient's tolerance pattern 13, 14

Ideal Blood Flow Rate and Dialysate Flow Rate for Hemodialysis Patients with Heart Failure

Blood Flow Rate Recommendations

• The American Journal of Kidney Diseases recommends a blood flow rate of 300-400 mL/min for hemodialysis patients with heart failure, with 400 mL/min preferred when hemodynamically tolerated, as higher BFRs maintain better blood pressure stability during dialysis 15
• A minimum blood flow rate of 300 mL/min is required to achieve adequate dialysis dose (spKt/V ≥1.2) in hemodialysis patients with heart failure, and failure to maintain this threshold results in underdialysis and increased morbidity 15, 16
• Higher blood flow rates (400 mL/min) are associated with better hemodynamic stability compared to lower rates in hemodialysis patients with heart failure 15

Dialysate Flow Rate Recommendations

• The American Journal of Kidney Diseases recommends a standard dialysate flow rate of 500-800 mL/min for conventional thrice-weekly hemodialysis in heart failure patients, with rates typically set at 700-800 mL/min to optimize small solute clearance 16
• The FHN Daily Trial demonstrated improved outcomes in patients with cardiovascular disease using mean dialysate flow rates of 747 ± 68 mL/min for frequent hemodialysis and 710 ± 106 mL/min for conventional hemodialysis 16

Ultrafiltration Rate Management

• The Kidney International recommends ultrafiltration rates be kept below 10 mL/h/kg in heart failure patients to minimize cardiovascular mortality risk, requiring longer or more frequent dialysis sessions to achieve adequate fluid removal 17
• Extended treatment time allows achievement of adequate fluid removal at moderate ultrafiltration rates, reducing risk of intradialytic hypotension and end-organ ischemia in heart failure patients 17

Monitoring and Adjustment

• Prepump arterial pressure monitoring is essential to ensure valid blood flows in hemodialysis patients with heart failure, as the criterion for adequate BFR (>300 mL/min) must be qualified by prepump arterial pressure 15
• Intradialytic blood pressure should be monitored every 30 minutes and ultrafiltration rate adjusted if systolic blood pressure drops >30 mmHg or mean arterial pressure falls <65 mmHg in heart failure patients 17