Dialysis Pro · Prescription
Prescription
The parameters to set for a maintenance HD session — flow rates, dialysate composition, membrane and dialyzer selection, and circuit anticoagulation. Dialysate calcium and magnesium shown in both mmol/L and mEq/L.
⚠️ Clinical reference only. Adult parameters; confirm against local protocol and individual labs. Anticoagulation doses must be confirmed with pharmacy. Developed by Dr. Abbas Deeb. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.
Prescription Overview
What you set for each session
A maintenance HD prescription specifies the clearance parameters (blood & dialysate flow, dialyzer, time), the dialysate composition (Na, K, bicarbonate, Ca, Mg), the fluid target (UF goal), and circuit anticoagulation. Dose adequacy targets (Kt/V, URR, UFR limits) live in the KPI / Adequacy tile; off-target management is in Dose Adjustment.
| Parameter group | Set |
|---|---|
| Clearance | Blood flow, dialysate flow, dialyzer (KoA/surface area), session time |
| Dialysate composition | Sodium, potassium, bicarbonate, calcium, magnesium (glucose typically included) |
| Fluid | Ultrafiltration goal (target weight) — see KPI tile for UFR limits |
| Circuit | Anticoagulation strategy based on bleeding risk |
Typical starting prescription
An orientation anchor — not a recommendation. A common adult thrice-weekly starting point, then individualise to labs, volume status, and tolerance:
| Blood flow (BFR) | 350–400 mL/min |
| Dialysate flow (DFR) | 600–700 mL/min |
| Time | 4 h, thrice weekly |
| Dialysate sodium | 138–140 mEq/L |
| Dialysate potassium | 2–3 mEq/L |
| Dialysate bicarbonate | 32–35 mEq/L |
| Dialysate calcium | 1.25–1.50 mmol/L (2.5–3.0 mEq/L) |
| Dialysate magnesium | 0.5 mmol/L (1.0 mEq/L) |
| Membrane | High-flux |
| Anticoagulation | UFH standard (adjust by bleeding risk) |
When a parameter is off-target, adjust elsewhere: hypotension → Complications (IDH) — lower UF rate, review target weight; hyperkalemia → Dose Adjustment (Hyperkalemia) — dialysate K⁺ / binder; high PTH or calcium → Dose Adjustment (PTH & Calcium) — dialysate Ca; recurrent clotting → Vascular Access + anticoagulation review.
Source: UpToDate "Overview of the hemodialysis apparatus"; "Prescribing and assessing adequate hemodialysis."
Blood & Dialysate Flow
Countercurrent · DFR set to 1.5–2× BFR
Blood flow (BFR)
300–500
mL/min
Dialysate flow (DFR)
500–800
mL/min (1.5–2× BFR)
Countercurrent flow (blood and dialysate in opposite directions) maximises diffusive clearance by maintaining a concentration gradient along the entire fibre length. Concurrent flow would equilibrate and abolish the gradient.
| Mechanism | How it works |
|---|---|
| Diffusion | Primary waste removal; solute moves down concentration gradient blood↔dialysate. Greatest flow-dependence for small solutes (urea, electrolytes). |
| Convection | Solute dragged with ultrafiltered fluid; matters most for larger solutes. Quantified by the sieving coefficient (1 = passes freely, 0 = fully rejected). |
BFR raises clearance more than DFR. Clearance rises with flow until a plateau; small solutes plateau at higher flows. For large/slow solutes, the concentration gradient persists — so treatment time becomes the major determinant of their removal.
Source: UpToDate "Overview of the hemodialysis apparatus."
Dialysate Sodium
Most use 138–140 mEq/L
Typical
138–140
mEq/L (= mmol/L)
Historical range
135–149
mEq/L
Sodium is monovalent, so mEq/L and mmol/L are numerically identical (138 mEq/L = 138 mmol/L). The optimal concentration remains uncertain and is often individualised to minimise the plasma–dialysate sodium gradient.
Low-sodium tradeoff: dialysate Na <138 reduces interdialytic weight gain and BP but increases intradialytic hypotension. Observational data have linked dialysate Na ≤138 mEq/L with higher mortality (adjusted HR 1.57), though causality remains uncertain. Higher Na transiently raises plasma Na and provokes thirst → more interdialytic gain.
Sodium ramping (e.g. decrementing 155 → 140 during the session) is generally not advocated — it tends to worsen interdialytic thirst and weight gain. Some advocate individualising toward a near-zero plasma–dialysate sodium gradient.
Source: UpToDate "Overview of the hemodialysis apparatus."
Dialysate Potassium
≥2 mEq/L · avoid <2
Common
≥2
mEq/L (= mmol/L)
Moderate hyperK approach
3
mEq/L + oral binder
Avoid dialysate K⁺ <2 mEq/L — fallen out of favour even for very high predialysis potassium, because of sudden-cardiac-death risk from a rapid fall in plasma potassium. Potassium is monovalent (mEq/L = mmol/L).
For moderate hyperkalemia, some use a higher dialysate K⁺ (e.g. 3 mEq/L) combined with an oral potassium-lowering agent on non-dialysis days. The optimal approach is unknown. At the bedside, avoiding a large serum-to-dialysate potassium gradient helps limit the rapid plasma-potassium fall that drives arrhythmia risk. High dialysate bicarbonate can further accelerate intradialytic potassium shifts → cardiac irritability.
Source: UpToDate "Overview of the hemodialysis apparatus." See also Dose Adjustment → Hyperkalemia.
Dialysate Bicarbonate
30–35 mEq/L · replaced acetate
Typical
30–35
mEq/L (individualised)
Bicarbonate replaced acetate as the standard buffer (acetate was associated with hemodynamic instability). The concentration is dictated by individual lab values. Total buffer = prescribed bicarbonate + acetate contained in the acid concentrate of the product used — buffering capacity varies between products.
High dialysate bicarbonate can accelerate potassium lowering and cause rapid intradialytic shifts in potassium and calcium → cardiac irritability and, rarely, fatal arrhythmias. Always account for total buffer delivery (bicarbonate + acetate in the acid concentrate), which varies by dialysate product.
Source: UpToDate "Overview of the hemodialysis apparatus."
Dialysate Calcium & Magnesium
Divalent — shown in both mmol/L and mEq/L
Calcium and magnesium are divalent, so the two unit systems differ by a factor of 2. Many countries prescribe dialysate calcium in mmol/L (1.25 / 1.50 / 1.75); US apparatus is often labelled in mEq/L (2.5 / 2.25). Both are shown below.
Why the factor of 2? The conversion factor is the ionic charge (valence), because an equivalent is one mole of charge: mEq/L = mmol/L × charge. So it is ×1 for Na⁺, K⁺, and HCO₃⁻ (numbers identical in both units) and ×2 for Ca²⁺ and Mg²⁺ (numbers differ twofold).
Dialysate Calcium
| mmol/L | mEq/L | Note |
|---|---|---|
| 1.25 | 2.5 | Standard (low) — KDIGO lower bound |
| 1.50 | 3.0 | Standard (higher end) — KDIGO upper bound |
| 1.13 | 2.25 | US low-calcium apparatus option |
| 1.75 | 3.5 | Older high concentration — largely abandoned |
Convert: mEq/L = mmol/L × 2 · mmol/L = mEq/L ÷ 2 (divalent ion)
e.g. 1.25 mmol/L × 2 = 2.5 mEq/L | 3.0 mEq/L ÷ 2 = 1.50 mmol/L
e.g. 1.25 mmol/L × 2 = 2.5 mEq/L | 3.0 mEq/L ÷ 2 = 1.50 mmol/L
KDIGO 2017 recommends dialysate calcium 1.25–1.50 mmol/L (2.5–3.0 mEq/L). The 3.5 mEq/L (1.75 mmol/L) concentration has largely been replaced because of hypercalcemia risk with concurrent oral calcium binders and calcitriol. US units commonly use 2.5 or 2.25 mEq/L. See Dose Adjustment → PTH & Calcium for the CKD-MBD logic.
Dialysate Magnesium
| mEq/L | mmol/L | Note |
|---|---|---|
| 1.0 | 0.5 | Typical standardised concentration |
Convert: mmol/L = mEq/L ÷ 2 · mEq/L = mmol/L × 2 (divalent ion)
e.g. 1.0 mEq/L ÷ 2 = 0.5 mmol/L
e.g. 1.0 mEq/L ÷ 2 = 0.5 mmol/L
Both high and low serum magnesium are associated with excess mortality, and magnesium can potentiate potassium shifts — hence standardised dialysate magnesium, typically 1.0 mEq/L (0.5 mmol/L).
Source: UpToDate "Overview of the hemodialysis apparatus"; KDIGO 2017 CKD-MBD (dialysate Ca 1.25–1.50 mmol/L).
Membrane & Flux
Flux defined by β2-microglobulin clearance
Low flux
<10
β2M mL/min
Mid flux
10–20
β2M mL/min
High flux
>20
β2M mL/min · US default
Flux = membrane permeability, defined by β2-microglobulin clearance (mL/min). High-flux membranes have larger pores and greater permeability to larger molecules; virtually all patients in resource-abundant countries use high-flux. (Japan also has super-high-flux, 50–70 / >70 mL/min.)
| Membrane class | Examples / status |
|---|---|
| Unmodified cellulose (cuprophane) | Most bioincompatible — effectively obsolete in high-resource settings |
| Substituted cellulose | e.g. cellulose acetate — more biocompatible |
| Cellulosynthetic | e.g. hemophane — synthetic material added to cellulose |
| Synthetic (noncellulose) | PAN, polysulfone, polycarbonate, polyamide, PMMA — most biocompatible, higher permeability |
MCO (medium cutoff) dialyzers have larger pores for better middle-molecule clearance without albumin loss — outcome benefit not yet established. HCO (high cutoff) dialyzers pass 25–50 kDa proteins; used for light-chain removal in myeloma, not conventional HD. Biocompatibility advantage on hard outcomes (incl. HEMO study) was not demonstrated.
Source: UpToDate "Overview of the hemodialysis apparatus."
Dialyzer Selection
KoA drives clearance — more than surface area
KoA (mass transfer-area coefficient) — urea KoA 200–1100 mL/min
| KoA band | Use |
|---|---|
| <300 | Small patients & AKI (gradual solute removal desirable — reduces disequilibrium risk), then advance |
| 300–600 | Chronic maintenance hemodialysis |
| >600 | High-efficiency dialysis — larger patients |
Surface area
0.8–2.1
m²
Priming volume
160–270
mL total (dialyzer + lines)
KUf (ultrafiltration coefficient) = mL/h transferred per mmHg of transmembrane pressure; UF rate = KUf × TMP. Higher-KUf dialyzers achieve target UF at lower TMP. KoA (not surface area alone) is the primary determinant of diffusive clearance — surface area correlates with KoA but is not interchangeable with it. Priming volume: dialyzer 60–120 mL + lines 100–150 mL = 160–270 mL total; lower is better hemodynamically.
Hollow-fibre (capillary) dialyzers are standard; parallel-plate are obsolete. Report KoA at a blood flow of 300–400 mL/min. Most dialyzers are ethylene-oxide sterilised; reuse is now rare in the US.
Source: UpToDate "Overview of the hemodialysis apparatus."
Anticoagulation
Start with bleeding-risk assessment
Circuit clotting loses ~180–200 mL blood and reduces clearance, so anticoagulation (usually UFH) is standard — but the decision begins with bleeding risk. Modern biocompatible circuits need far less heparin than older equipment.
1
Assess bleeding risk
High risk if: platelets <20,000/µL, active bleeding, major surgery <72 h (esp. intraocular/spinal), active intracranial/extradural hemorrhage, systemic anticoagulants, uremic pericarditis, factor VII or VIII deficiency.
NOT high-risk: antiplatelet agents alone (even aspirin + clopidogrel at standard doses); deficiency of factors IX, XI, or XII (circuit clotting is factor VII–driven). Hemophilia A (factor VIII) may need recombinant factor VIII before needle removal.
2
Standard-risk — UFH or LMWH (equally acceptable)
UFH (North America)
2000 unit bolus → 500 units/h infusion, off 60 min before end (30 min if clotting). Europe often 1000 unit bolus.
Weight-based UFH bolus <50 kg → 500 IU · 50–100 kg → 1000 IU · >100 kg → 2000 IU
LMWH (Europe/Asia/Australia) Tinzaparin 2500 anti-Xa units, or enoxaparin 20 mg, for a 4-h session. Give in arterial limb ~2–3 min after starting. Short-acting agents may need a second bolus beyond 4 h.
Weight-based UFH bolus <50 kg → 500 IU · 50–100 kg → 1000 IU · >100 kg → 2000 IU
LMWH (Europe/Asia/Australia) Tinzaparin 2500 anti-Xa units, or enoxaparin 20 mg, for a 4-h session. Give in arterial limb ~2–3 min after starting. Short-acting agents may need a second bolus beyond 4 h.
3
Titrate for clotting or bleeding
| Problem | Adjustment |
|---|---|
| Clotting — first half | ↑ UFH bolus by 500 IU increments per treatment, max 4000 IU |
| Clotting — second half | ↑ UFH infusion by 100 IU/h per treatment, max 1000 IU/h |
| Bleeding >7 min at needle sites | Lengthen infusion off-time in 10-min increments until bleeding ≤7 min |
| Recurrent filter clotting | Evaluate access for inflow/outflow stenosis |
4
High bleeding risk — heparin-free strategies
No-heparin method: saline prime + flush the arterial limb with 200 mL isotonic saline every hour (factor into UF goal); vigilant monitoring for clots/pressure alarms. Alternatives: heparinised solution rinse or heparin-bonded dialyzer; predilution HDF. Switch back to heparin once bleeding risk resolves.
Recurrent thrombosis escalation: maximise BFR/needle gauge → more frequent flushes (q30 min) → tight-heparin (1000 IU bolus) → mini-heparin (1000 IU bolus + 500 IU/h) → citrate dialysate or HDF + epoprostenol regional anticoagulation 4–8 ng/kg/min (start 0.5, double q2 min). Citrate dialysate needs Ca/Mg monitoring (hospital setting).
5
Heparin-induced thrombocytopenia (HIT)
Type I — mild, transient, self-limited drop in first 2 days; no change to anticoagulation needed. Type II — immune (PF4/heparin antibodies), causes thrombosis + thrombocytopenia; stop all UFH and LMWH, use a non-heparin strategy, flag the chart to prevent inadvertent heparin lock, and co-manage with hematology.
Inpatient notes: for AKI inpatients, the no-heparin method is typical (escalate to UFH/LMWH if recurrent clotting). For chronic HD inpatients, mirror the outpatient regimen — unless admitted for bleeding or a major procedure, then reassess bleeding risk.
Source: UpToDate "Anticoagulation for the hemodialysis procedure."
Dialysis Pro — Prescription · Sourced from UpToDate "Overview of the hemodialysis apparatus," "Anticoagulation for the hemodialysis procedure," and KDIGO 2017 CKD-MBD (dialysate calcium). Literature current through 2026.
Developed by Dr. Abbas Deeb. For clinical reference only. Adult parameters; confirm dialysate composition against local apparatus and individual labs, and all anticoagulation doses with pharmacy. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.
Developed by Dr. Abbas Deeb. For clinical reference only. Adult parameters; confirm dialysate composition against local apparatus and individual labs, and all anticoagulation doses with pharmacy. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.